Widening of the Sylvian fissure. Arachnoid cyst

Congenital arachnoid cysts are also called leptomeningeal cysts. This term does not include either secondary “arachnoid” cysts (for example, post-traumatic, post-infectious, etc.) or glioepindemal cysts lined with glial tissue and epithelial cells.

Definition and etiology. Congenital arachnoid cysts are a developmental anomaly resulting from division or duplication of the arachnoid membrane (thus, they are actually intraarachnoid cysts).

The etiology of these lesions has long been the subject of debate. The most common theory is that they develop due to a slight developmental abnormality of the arachnoid membrane around the 15th week of gestation, when cerebrospinal fluid (CSF) begins to be produced to gradually replace the extracellular substance between the outer and inner arachnoid membranes (endomenings).

The developmental anomaly hypothesis is confirmed by the usual location of arachnoid cysts at the level of normal arachnoid cisterns, their random appearance in siblings, the presence of concomitant anomalies of vein architecture (for example, the absence of the Sylvian vein) and the presence of other congenital anomalies (agenesis of the corpus callosum and Marfan syndrome).

It is still unclear why arachnoid cysts tend to expand. Electron microscopy and ultracytochemical analysis showed increased activity of the Na + and K + pump in the cyst wall compared with the normal arachnoid, supporting the theory of active production of cerebrospinal fluid by the membrane lining the cyst, which has morphological similarities with the subdural neuroepithelium and the neuroepithelial lining of the arachnoid granulation. On the other hand, cine-MPT and live endoscopic video have shown that some arachnoid cysts may enlarge when CSF is trapped by the valve mechanism.

The pressure gradient for the movement of cerebrospinal fluid into the arachnoid cyst will be provided by a transient increase in cerebrospinal fluid pressure caused by the systolic oscillation of the cerebral arteries or the transmitting pulsation of the veins.

Specific problems in determining pathogenesis concern intraventricular cysts. Some authors present them as a kind of “internal” meningocele; according to others, they are formed from the arachnoid layer and are transported along with the choroid plexus when it protrudes through the choroidal fissure.

Anatomical classification and topographic distribution of intracranial arachnoid cysts.

I. Intracranial arachnoid cysts:

A) Frequency of occurrence. Congenital arachnoid cysts are reported to account for approximately 1% of nontraumatic intracranial mass lesions. This rather old indicator was obtained by correlating clinical experience in the pre-CT/MRI era (0.7-2% of mass lesions) and autopsy data (0.1-0.5% of incidental findings at autopsy); In recent years, an increase in the incidence of these formations has been described. Intracranial arachnoid cysts are almost always solitary and sporadic.

They occur 2-3 times more often in men than in women, and 3-4 times more often on the left side of the brain than on the right. The appearance of bilateral, more or less symmetrical cysts has been described in healthy children, as well as in children with neurological disorders, although this is rare. In the latter case, especially in patients with bitemporal cysts, the differential diagnosis should be made with damage resulting from perinatal hypoxia.

Based on information provided from large mixed series (including both children and adults), it appears that the largest proportion of childhood cases occurs in the first two years of life.

b) Anatomical distribution. The typical localization of arachnoid cysts is within the middle cranial fossa, where 30-50% of the damage was found. Another 10% occurs in the medullary convex, 9-15% are found in the suprasellar region, 5-10% in the quadrimenal plate cistern, 10% in the cerebellopontine angle, and 10% in the midline of the posterior fossa. The anatomical classification and topographic distribution of the different types of arachnoid cysts are given in the table below.

II. Supratentorial arachnodal cysts:

A) Sylvian fissure cysts. Lateral sulcus cysts account for about half of all cases in adults and a third of cases in children. Galassi et al. divided Sylvian fissure cysts into three types depending on their size and relationship (CT with metrizamide) with normal cerebrospinal fluid spaces:

- Type I: cysts are small, biconvex or semicircular, freely communicating with adjacent cisterns.

- Type II: medium-sized cysts, rectangular in shape, associated with the anterior and middle parts of the temporal fossa with a moderate mass effect; they communicate or do not communicate with adjacent tanks.

- Type III: cysts are large, round or oval, occupying the middle cranial fossa almost completely, causing constant and severe compression of adjacent nerve structures, resulting in displacement of the ventricles and midline; connections with the subarachnoid space are absent or non-functional.

Lateral sulcus cysts can present clinically at any age, but are more likely to become symptomatic in childhood and adolescence than in adulthood, and in most studies, infants and toddlers account for about 1/4 of the cases.

The diagnosis is often made by chance. Symptoms that occur are often nonspecific, with headache being the most common complaint. Among the focal symptoms in advanced cases, slight proptosis and contralateral paresis of the central type are possible. Seizures and signs of increased intracranial pressure represent the clinical onset in approximately 20-35% of patients. When signs of increased intracranial pressure appear acutely, they are usually the result of a sharp increase in cyst volume due to subdural or intracystic hemorrhage.

Mental disturbances are found in only 10% of cases, but developmental delay and behavioral disturbances are common in children with large cysts and are almost constant and severe in patients with bilateral cysts.

Local convexity of the skull and/or asymmetrical macrocrania are characteristic signs observed in half of the patients. CT scan in such cases reveals outward protrusion, thinning of the temporal scales and anterior displacement of the lesser and greater wings of the sphenoid bone. Cysts appear as clear formations between the dura mater and the malformed brain with cerebrospinal fluid density and no contrast enhancement. The ventricles of the brain are usually of normal size or slightly dilated. MRI reveals T1-hypointense and T2-hyperintense formations.

Vascular examination is useful to determine the relationship of arteries and veins to the cyst wall. In order to determine the presence or absence of communication between the cyst and the subarachnoid space, flow cine sequences have recently been used, which can replace CT with metrizamide. This may be especially important in asymptomatic patients and in patients with nonspecific clinical symptoms. In this regard, additional information that may indicate the need for surgical intervention can be obtained by monitoring ICP. Perfusion MRI and SPECT are also used, the latter helping to assess cerebral perfusion around the cyst wall.

There are three surgical treatment options, used alone or in combination:
- Marsupialization by craniotomy
- Endoscopic cyst removal
- Cyst shunting

Open removal of the cyst is considered the optimal surgical procedure. Successful results range from 75 to 100%, and surgical mortality is almost zero. There are two issues to note regarding open surgery:
- Total removal of the arachnoid cyst is no longer considered advisable; large holes in the cyst wall are sufficient to ensure the passage of cerebrospinal fluid through the cyst cavity and reduce the risk of damage to adjacent brain structures. Moreover, partial opening of the cyst can also prevent the leakage of cerebrospinal fluid into the subdural space and the development of postoperative subdural hygromas.
- All vessels that cross the cyst cavity or lie on the cyst wall are normal and therefore should be preserved.

In recent years, endoscopic cyst removal has been proposed as an alternative to open surgery. Endoscopy is also used as an adjunct to open surgery to reduce the size of the surgical approach. Positive results of endoscopic techniques range from 45 to 100%.

Cyst bypass is clearly safer, but is accompanied by a high frequency of additional surgical procedures (about 30%) and lifelong dependence on the shunt.

Examples of arachnoid cysts of the Sylvian fissure according to Galassi.

b) Sellar cysts. Sellar cysts are the second most common supratentorial location among intracranial arachnoid cysts. There are slightly more men affected than women: the ratio is about 1.5/1. Cysts can be divided into two groups:
- Suprasellar cysts located above the diaphragm of the sella turcica.
- Intrasellar cysts located in the cavity of the sella turcica.

The latter are much less common and occur exclusively in children.

The term sella cysts does not include empty sella syndrome, intrasellar and/or suprasellar diverticula of the arachnoid membrane. Metrizamide CT or cine-MPT aids in the differential diagnosis by showing lack of contrast enhancement and absence of cerebrospinal fluid flow within a true cyst.

Intrasellar arachnoid cysts are asymptomatic in approximately half of the cases. Headache is the most common complaint in symptomatic patients, and endocrinological disturbances are often observed with this location of the cyst. Suprasellar cysts, on the contrary, most often present with headaches, visual disturbances and neuroendocrine symptoms are typical. Hydrocephalus typically occurs when cyst expansion obstructs the flow of cerebrospinal fluid from the foramina of Monro and/or basal cisterns. With large cysts, posterior dislocation of the brainstem may develop with secondary compression of the aqueduct of Sylvius, which can lead to dilatation of the ventricles.

This process occurs relatively slowly, for this reason, signs of intracranial hypertension (papilledema, optic nerve atrophy occur, although often, but relatively late.

Hypopituitarism is common, mostly with impaired metabolism of growth hormone and ACTH. Delayed menstruation may also be noted. A rare but typical manifestation of cysts above the sella turcica is the “doll's head” symptom, characterized by slow, rhythmic movements of the head in an anteroposterior direction.

In the pre- and neonatal period and early childhood, echoencephalography is a useful diagnostic tool to monitor the evolution of these types of lesions during the first months of life. If possible, an MRI should be performed to assess the multilevel connections between the cyst and the surrounding neural structures and ventricles, which is necessary for planning surgical treatment. MRI (or contrast-enhanced CT as an alternative) is also important for the differential diagnosis between supra sellar arachnoid cysts and other possible cystic lesions of the sellar region (eg, Rathke's pouch cyst, cystic craniopharyngioma, epidermoid cyst, etc.).

The rapid development of endoscopic technologies has significantly changed the treatment of sellar cysts. The endoscopic transnasal approach is ideal for intrasellar cysts, replacing the traditional microsurgical approach to these lesions. Cysts located above the sella turcica are treated only by opening the roof of the cyst (endoscopic transventricular vengriculocystostomy) compared to opening both the roof of the cyst and the bottom of the cyst (ventriculocisternostomy), the latter method is actually considered safer and, compared with ventriculocystostomy, is associated with lower relapse rate (5-10% versus 25-40%).

Shunt operations are practically not performed. Although relatively safe, they are associated with a surprisingly high rate of reoperation. Microsurgical excision, dissection, or marsupialization are reserved for cases where endoscopic techniques are not feasible or for patients with cysts extending beyond the ventricle (eg, suprasellar arachnoid cyst involving the medial temporal lobe).

It is important to remember that, regardless of surgical treatment, existing endocrinological disorders resolve in rare cases, which requires adequate drug therapy. Visual signs and symptoms of intracranial hypertension resolve after surgery.

V) Cerebral convex cysts. They are relatively rare (4-15% of all intracranial arachnoid cysts), and women are affected more often than men. We distinguish two main types of these cysts:
- Hemispherical cysts, huge accumulations of fluid extending over the entire or almost the entire surface of one hemisphere of the brain.
- Focal cysts are usually small formations associated with the cerebral surface of the hemispheres.

Hemispheric cysts are considered expanded lateral sulcus cysts, characterized by a compressed rather than enlarged lateral sulcus and the absence of temporal lobe aplasia. They are most often found in children with macrocrania, a prominent anterior fontanelle, and cranial asymmetry. CT and MRI in most cases allow a differential diagnosis with chronic fluid accumulation in the subdural space (subdural hygroma and hematoma).

Localized cranial protrusion usually suggests the presence of a solitary cyst. Children typically have no neurological symptoms, while adults often develop focal neurological deficits and/or seizures. Differential diagnosis is made from low-grade neuroglial tumors, usually using MRI.

The treatment of choice is microsurgical marsupialization. There is no need to remove the medial wall of the cyst, which is closely connected to the cerebral cortex. Shunt implantation is recommended only in cases of recurrence, although this method has also been proposed as a primary procedure in children with hemispheric cysts due to immature absorption capacity and the high risk of failure of open surgery. In such cases, it is recommended to install a shunt with a programmable valve to effectively control the pressure inside the cyst and favor the development of natural pathways for the outflow of cerebrospinal fluid.

G) Interhemispheric cysts. Interhemispheric cysts are quite rare, accounting for 5-8% of intracranial arachnoid cysts in all age groups. There are two main types:
- Interhemispheric cysts associated with partial or complete agenesis of the corpus callosum
- Parasagittal cysts not accompanied by defects in the formation of the corpus callosum

Macrocrania is observed in a large percentage of cases, and two-thirds of patients develop symptoms of intracranial hypertension. Localization: A bulging skull is the second most common manifestation. Hydrocephalus is mild or absent in patients with parasagittal cysts, but is relatively common in patients with interhemispheric cysts.

On MRI, interhemispheric arachnoid cysts are differentiated by a typically wedge-shaped appearance on coronal sections sharply separating the falx on one side. Primary agenesis of the corpus callosum and type IC holoprosencephaly may have a similar appearance on MRI; however, an interhemispheric cyst of the occipital horns of the lateral ventricles can be easily differentiated, since the occipital horns are displaced by the cyst, and the basal ganglia are normally divided.

The method of choice is craniotomy with removal of the cyst. This allows you to normalize intracranial pressure. Because of the significantly high complication rate, bypass procedures should only be considered as a second choice in complex cases.

d) Cysts of the quadrigeminal plate area. Cysts of the quadrigeminal plate region account for 5-10% of all intracranial arachnoid cysts. Most of them are diagnosed in children, with a higher frequency in girls than boys.

Clinical manifestations depend on the direction of cyst growth. Most of these cysts develop upward into the posterior part of the interhemispheric fissure or downward into the fossa of the superior cerebellar vermis, in some cases with the possibility of supratentorial infratentorial expansion. Because of their close location to the cerebrospinal fluid pathways, they are usually diagnosed in childhood due to secondary obstructive hydrocephalus. Abnormalities in pupil reaction or eye movement may be detected due to compression of the quadrigeminal plate or stretching of the trochlear nerve; however, impairment of upward gaze is relatively rarely diagnosed. When growth is directed to the lateral side and into the cisterns, hydrocephalus is usually absent, but focal symptoms are determined.

Sagittal and coronal MRI sections clearly show the connection of the cyst with the supratentorial and infratentorial structures and ventricles.

As with sella cysts, modern neuroendoscopic techniques have significantly changed the treatment tactics for these types of lesions, which were previously considered technically difficult. In case of small formations (< 1 см), вызывающих вторичную тривентрикулярную гидроцефалию, вентрикулостомию третьего желудочка следует рассматривать как необходимое хирургическое лечение. При крупных образованиях должна быть выполнена вентрикулоцистостомия, по возможности в сочетании с вентрикулостомией третьего желудочка у пациентов с гидроцефалией. Хотя на момент написания в литературе описаны небольшие серии наблюдений, исследователи однозначно пришли к выводу, что эндоскопическое удаление кист области четверохолмной пластины является безопасным и успешным практически во всех случаях.

III. Subtentorial arachnoid cysts. Cysts of the arachnoid membrane of the posterior cranial fossa are quite rare and account for about 15% of all intracranial cysts. It is necessary to distinguish them from other cystic malformations of the posterior fossa, namely Dandy-Walker malformation and cystic evagination of the choroidal plexus. The main differential features of these various pathological conditions are given in the table below.

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immaturity

Hello! Please tell me, my one month old baby is diagnosed with brain immaturity by ultrasound, here are the ultrasound results. Midline structures are not displaced, differentiated, the pattern of convolutions and sulci is N, the interhemispheric fissure is 1.9 mm, the subarachnoid space is not expanded, vascular pulsation is not strength, echogenicity of the brain parenchyma is not changed, the echo structure of the brain parenchyma is homogeneous, the echo structure of the thalami is not changed, the Sylvian fissure is U-shaped with D and S, the depth of the anterior horns is right 2.6 mm, left 2.4 mm, body depth - right 2.5 mm, left 2.4 mm, anterior horn index 26.5, width of the 3rd ventricle 2.2 mm, cavity of the transparent septum 5.3 mm, periventricular region: structure unchanged, choroid plexus: dimensions right - 5.2 left - 5.2, the contour is clear, even, the structure is homogeneous! The neurologist said that all the child’s reflexes are normal, he prescribed picamilon 0.02 1/4 2 times a day...

immaturity

Hello! Please tell me, my one month old baby is diagnosed with brain immaturity by ultrasound, here are the ultrasound results. Midline structures are not displaced, differentiated, the pattern of convolutions and sulci is N, the interhemispheric fissure is 1.9 mm, the subarachnoid space is not expanded, vascular pulsation is not strength, echogenicity of the brain parenchyma is not changed, the echo structure of the brain parenchyma is homogeneous, the echo structure of the thalami is not changed, the Sylvian fissure is U-shaped with D and S, the depth of the anterior horns is right 2.6 mm, left 2.4 mm, body depth - right 2.5 mm, left 2.4 mm, anterior horn index 26.5, width of the 3rd ventricle 2.2 mm, cavity of the transparent septum 5.3 mm, periventricular region: structure unchanged, choroid plexuses: dimensions right - 5.2 left - 5.2, the contour is clear, even, the structure is homogeneous! The neurologist said that all the child’s reflexes are normal, he prescribed picamilon 0.02 1/4 2 times a day...

What is an arachnoid cyst? How dangerous is it to human life? In the thickness of the membranes that cover the brain, a benign sphere is formed and filled with cerebrospinal fluid. This is an arachnoid cyst of the brain.

It is so called because of the dislocation of the sphere, since the accumulation of cerebrospinal fluid in it occurs between two layers of the thickened arachnoid membrane. The brain has only three of them. The arachnoid is located between the other two - hard superficial and soft deep.

Frequent locations of the cyst are the Sylvian fissure, the cerebellopontine angle or the area above the sella turcica and other areas. The development of the liquor sphere is more often observed in children and male adolescents.

In children, arachnoid cysts of the brain are predominantly congenital and form in the embryonic stage during the formation of the central nervous system. It accounts for 1% of volumetric neoplasms inside the skull due to disturbances in liquor circulation.

Small spheres may not appear during life. As the cyst grows after it begins to form, the flow of fluid through the brain is blocked and hydrocephalus develops. When compression (pressure) is applied to the cerebral cortex, clinical symptoms appear, hernias may form or sudden death may occur.

The ICD-10 code for arachnoid cyst (AC) is G93.0.

According to anatomical and topographical characteristics, cysts of the cerebral hemispheres include:

• AC of the lateral (Sylvian) fissure;
• parasagittal (parallel planes) AC;
• convexital medullary surface.

Mid-basal formations include cysts:

• arachnoid intrasellar and suprasellar;
• cisterns: covering and quadrigeminal;
• retrocerebellar arachnoid;
• arachnoid cerebellopontine angle.

Cysts are formed differently, so they are divided by type. There are AKs:

1. True or isolated.
2. Diverticular or communicating. Disturbed cerebrospinal fluid dynamics at the end of embryo development leads to the formation of cysts.
3. Valved or partially communicating. This development is associated with productive changes in the arachnoid membrane.

The generally accepted classification (according to E. Galassi - 1989) is also used to separate the most common ACs of the lateral fissure (LS);

• Small type 1 cysts are bilateral, located at the pole of the temporal lobe, and do not appear. CT cisternography with contrast agent shows that the cysts communicate with the subarachnoid space;
• Type 2 cysts are located in the proximal and middle parts of the thyroid gland and have an oval shape due to an incompletely closed contour. They partially communicate with the subarachnoid space, as can be seen on spiral computed tomography with contrast agent;
• Type 3 cysts are large and therefore located throughout the Sylvian fissure. This significantly shifts the midline, raises the lesser wing of the main bone and the scales of the temple bone. They communicate minimally with the cerebrospinal fluid system, as shown by CT cisternography with contrast.

There are two types of arachnoid cyst of the brain:

• primary (congenital) due to abnormal development of the meninges under the influence of drugs, radiation exposure, toxic agents and physical factors;
• secondary (acquired) in connection with various diseases: meningitis, agenesis of the corpus callosum. Or due to complications after injury: bruises, concussions, mechanical damage to the hard surface shell, including surgery.

Based on its composition, the cyst is divided into: simple, since it is formed from cerebrospinal fluid (CSF), and complex sphere, consisting of cerebrospinal fluid and various types of tissue.

AK forms on the head in the area:

• left or right temporal lobe;
• crown and forehead;
• cerebellum;
• spinal canal;
• posterior cranial fossa.

Perineural cysts are also found in the spine and in the lumbar region.

Symptoms

Asymptomatic small AKs are discovered incidentally during examination for another reason. Symptoms become more pronounced with growth and depending on the location of the cyst, compression of tissues and brain matter. The manifestation of focal symptoms occurs against the background of the formation of a hygroma or when the aortic valve ruptures.

As the formations progress, adults lose orientation and sleep. They complain of uncomfortable conditions in which muscle tone is disturbed, limbs twitch involuntarily and go numb, and lameness occurs. I regularly experience tinnitus, migraines, nausea with vomiting, and often feel dizzy and even lose consciousness. Also in patients:

• hearing and vision are impaired;
• hallucinations and convulsions occur;
• the psyche is upset;
• “bursting” inside the head and the pulse is felt;
• Pain under the skull intensifies when moving the head.

A secondary (acquired) cyst complements the clinical picture with manifestations of the underlying disease or injury.

This is the basis for a full examination of the baby at the medical center.

Diagnostics

When establishing a diagnosis, clinical, neuroimaging and neurophysiological data are compared. The child should be examined by a neurologist, ophthalmologist, pediatrician, and geneticist. The diagnosis is confirmed by the following clinical manifestations:

• local changes: bone deformation of the cranial vault, especially in infants under one year of age;
• symptoms indicating intracranial hypertension, in which the fontanelle is tense and bone sutures diverge in children under one year of age;
• lethargy, drowsiness, vomiting, headache, pyramidal symptoms;
• neuro-ophthalmological symptoms arising in connection with mechanocompression of the interpeduncular and chiasmatic cistern, compression of the optic nerves by the lateral fissure cyst;
• dysfunction of the oculomotor nerves, chiasmatic syndrome, decreased vision, atrophy and congestion in the fundus;
• neuroimaging signs: one or more ACs are found in the cerebrospinal fluid, causing pathosymptoms.

In newborn babies and infants, a screening method (NSG - neurosonography) of the brain is used. Spiral computed tomography (SCT) is also recommended. An MRI is mandatory, but if the data is questionable, it is double-checked with a contrast agent and the CISS test and heavily T2-weighted images are used for diagnosis.

MRI examines the craniovertebral region to exclude associated anomalies: Arnold-Chiari, hydromyelia. The anesthesiologist examines patients, preparing them for surgery and assessing the degree of risk of the operation. If the surgical and anesthetic risk is large, then methods of preoperative management of patients are being prepared. Examinations are carried out by related specialists to determine concomitant diseases and their degree of development. At the same time, existing violations are corrected and patients are additionally examined:

• Blood tests reveal (or exclude) viruses, infections, and autoimmune diseases. They also determine clotting and bad cholesterol;
• The Doppler method is used to detect obstructions in the patency of arteries, which leads to a lack of blood supply to the brain.

The heart function is checked and blood pressure is measured throughout the day.

Treatment

According to the dynamics of development, cysts are frozen and progressive. Frozen cysts are not treated unless they cause pain or other uncomfortable symptoms. In these cases, underlying diseases are identified and treated, which stimulate the development of AK.

To eliminate the inflammatory process, normalize blood flow to the brain, restore damaged cells, cope with medium-sized cysts, you should be treated, for example, with means for:

• resorption of adhesions: “Longidaz”, “Karipatin”;
• activation of metabolic processes in tissues: “Actovegin”, “Gliatilin”;
• increasing immunity: “Viferon”, “Timogen”;
• getting rid of viruses: “Pyrogenal”, “Amiksin”.

Important. Treatment of an arachnoid cyst should only be carried out as prescribed by a doctor. You cannot exceed or reduce the dosage of medications or cancel treatment on your own, so as not to aggravate the inflammatory process and provoke cyst growth.

Surgical operations

Absolute indications for neurosurgical treatment for AK with cerebrospinal fluid or hydrocephalus include:

• hypertension syndrome (increased intracranial pressure);
• increasing neurological deficit.

Relative indications are:

• large asymptomatic AK, since it deforms the adjacent lobes of the brain;
• AK LSH with progressive growth and causing disruption of the circulation of cerebrospinal fluid due to deformation of its pathways.

Important. Surgical treatment is contraindicated in cases of decompensated state of vital functions (unstable hemodynamics, breathing), coma III, extreme exhaustion (cachexia), and active inflammatory process.

When using surgical treatment, craniocerebral disproportion is eliminated. For this purpose, liquor shunting, microsurgical, and endoscopic operations are used. Intraoperative ultrasound and neuronavigation are prescribed to achieve safe manipulation.

To determine the tactics of the operation, the shape and size of the AC, the estimated accessible area, the trajectory of movement, and possible complications are taken into account, since during the operation, neurovascular structures may be damaged, a hyperdrainage state may occur, an outpouring of blood and cerebrospinal fluid, and if the cyst ruptures, an infection can occur. A histological examination of the contents of the cyst and its walls is carried out.

When prescribing liquor shunt operations, for example, cystoperitoneal shunting, the surgeon achieves the goal of draining the cyst in a cavity outside the brain with minimal damage. However, it is necessary to implant an artificial drainage system, which is considered a disadvantage of this treatment method. If the circulation of cerebrospinal fluid is impaired, having a hypo- or aresorptive nature, it is combined or provoked by giant AKs. Then liquor shunt operations are the main methods of treatment.

Microsurgical surgery is used to eliminate type 2 AK. In this case, a large craniotomy is not performed. It is performed only on the temporal bone close to the base, that is, in the area of ​​the scales. If there is a convexital location - at its most protruding part. Ultrasound navigation is used to determine the area of ​​craniotomy.

Treatment with the endoscopic method is carried out for patients with the presence of symptoms of AK, especially types 2–3 LS. Endoscopic surgery is possible only if the clinic has a full set of rigid endoscopes with different viewing angles, illumination, a digital video camera, a saline irrigation system, bi- and monopolar coagulation.

Complications

After surgery, cerebrospinal fluid may leak, which is called liquorrhea. Necrosis of the edge of the skin flap and wound dehiscence after surgery are possible, so a revision of the incision is prescribed. If resorption is impaired, peritoneal shunting of the cyst is performed. Cysts and hydrocephalus of the brain are also corrected to ensure favorable treatment outcomes for patients, especially young children.

Surgical correction of hydrocephalus is performed before removal of cysts in cases of severe hydrocephalic-hypertensive syndrome: Evans index > 0.3, periventricular edema of the optic nerve, disturbance of consciousness and children under one year of age.

After the operation, patients are under medical supervision. In the presence of type 1 AK, children are monitored so as not to miss neurological and neuro-ophthalmological symptoms. SCT/MRI (spiral and magnetic resonance computed tomography) is monitored at least once a year for 3 years. Patients are examined by neurosurgeons, neuropsychologists, neurologists, pediatricians, ophthalmologists, and neurophysiologists.

Localization of the pathological focus with MRI of the brain begins with determining the location of the lesion in relation to the tentorium of the cerebellum. Therefore, formations above the tentorium are classified as supratentorial, and everything below is classified as infratentorial.

MRI of the brain. Midsagittal section. tentorium cerebellum (arrow).

Above the tentorium are the cerebral hemispheres. Each hemisphere of the brain consists of four lobes - frontal, parietal, occipital and temporal. If the pathology is located in the hemisphere, then it is necessary to decide which lobe it belongs to. To do this, you first need to find the grooves that serve as the boundaries of the lobes.
The central sulcus (sulc.centralis) is better visible in the sagittal plane. It is located in the middle between the parallel precentral and postcentral sulci. There are many options for the structure and course of the furrow. Usually it has a significant extent and goes in the anterior-inferior direction from the interhemispheric fissure to the Sylvian fissure, which it does not always reach. The lower end of the furrow either continues in its main direction or bends back. The central sulcus may be interrupted along the way. In the transverse plane on the upper sections, the groove has the greatest extent, reaching almost to the interhemispheric fissure. The lower the cut, the shorter the central groove on it. At the level of the lateral ventricles it is barely visible. The central sulcus separates the frontal and parietal lobes.

MRI of the brain. Lateral sagittal section. Central sulcus (arrow).

MRI of the brain. Axial slice. Central sulcus (arrows).

MRI of the brain. Axial section at the level of the roof of the lateral ventricles. Central sulcus (arrows).

MRI of the brain. Borders of the frontal and parietal lobes in the axial plane.

Another important groove is the Sylvian fissure (fissura cerebri lateralis). On sagittal sections it goes from bottom to top in the anteroposterior direction (Fig. 32). In the axial plane, the Sylvian fissure itself also deviates backward, while its branches are directed perpendicularly towards the interhemispheric fissure. The Sylvian fissure separates the frontal and parietal lobes from the temporal lobe.

MRI of the brain. Lateral sagittal section. Sylvian fissure (arrows).

MRI of the brain. Axial section at the level of the third ventricle. Sylvian fissure (arrows).

MRI of the brain. Borders of the frontal, parietal, temporal and occipital lobes on a sagittal section.

To delimit the parietal lobe, you also need to find the parieto-occipital sulcus (sulc. parietooccipitalis). This groove in the sagittal plane can be traced on the median and medial sections. It extends from the surface of the brain downwards, has a considerable extent and is often segmented. In the transverse plane, the parieto-occipital sulcus extends almost perpendicular to the interhemispheric fissure (Fig. 36) and gives off many small branches. Thus, the boundaries of the parietal lobe are the central sulcus with the frontal lobe, the parieto-occipital sulcus with the occipital lobe, the Sylvian fissure and the superior temporal sulcus (angular gyrus) with the temporal lobe.

MRI of the brain. Medial sagittal section. Parieto-occipital sulcus (arrow).

MRI of the brain. Axial slice. Parieto-occipital sulcus (arrow).

MRI of the brain. Borders of the parietal lobe on the medial sagittal section.

The next important dividing groove is the collateral groove (sulc.collateralis). On sagittal sections, it is visible as the inferolateral border of the parahippocampal gyrus, in the region of the pole of the temporal lobe (Fig. 38). It is easier to see in the axial plane in sections at the level of the midbrain (Fig. 39). When the axial plane of the slices is tilted backward, it is visible simultaneously with the temporo-occipital sulcus. The temporo-occipital groove (sulc. temporooccipitalis) on lateral sagittal sections runs sinuously backward along the border of the brain with the temporal bone and then bends upward (Fig. 40). On axial sections at the level of the Varoliev bridge, it is located in the anteroposterior direction. Thus, the border of the temporal lobe (Fig. 41) with the frontal and parietal lobes is the Sylvian fissure, with the occipital lobe - the temporo-occipital sulcus and the collateral sulcus.

MRI of the brain. Sagittal section. Collateral groove (arrow).

MRI of the brain. Axial slice. Collateral groove (arrows).

MRI of the brain. Axial section at the level of the Varoliev bridge. Temporo-occipital sulcus (arrows).

MRI of the brain. Axial section at the level of the cerebral peduncles. Borders of the temporal lobe.

To determine the boundaries of the occipital lobe, we already have all the landmarks. The border with the parietal lobe is the medially located parieto-occipital sulcus, and the border with the temporal lobe is the laterally located temporo-occipital sulcus.

MRI of the brain. Coronal section. Border sulci (SPO - parieto-occipital sulcus, STO - temporo-occipital sulcus, SCol - collateral sulcus).

MRI of the brain. Borders of the occipital lobe on the medial sagittal section.

Usually localization by lobes is sufficient to describe hemispheric pathologies. In some cases, when reference to gyri or functional areas is required, we recommend using the appropriate atlases (A.V. Kholin, 2005).
With centrally (axially) located space-occupying formations, the ventricles of the brain and the subcortical (basal) nuclei located around them may be involved. The optic thalamus, hypothalamus, subthalamus, and epithalamus belong to the diencephalon, a component of the brain stem.

MRI of the brain. Axial slice. Lateral ventricles and subcortical nuclei (NC - caudate nucleus, NL - lenticular nucleus, Th - thalamus optic). Parts of the brainstem (lower part of the midbrain, pons and medulla oblongata) and the cerebellum are located infratentorially.

The midbrain only partially occupies the supratentorial space; a significant part of it passes through the hole in the tentorium into the posterior cranium. hole. The paired legs of the brain and roof (tectum) are always clearly visible from behind. The roof of the midbrain lies posterior to the aqueduct and consists of the quadrigeminal plate.

MRI of the brain. Midsagittal section. Brain stem (V3 - third ventricle, V4 - fourth ventricle, Q - plate quadrigeminal, Mes - midbrain, P - pons, C - cerebellum, M - medulla oblongata).

The border between the midbrain and the pons is the superior sulcus, and the border with the medulla oblongata is the inferior sulcus of the pons. The bridge has a characteristic protruding front part. The posterior surface of the pons is a continuation of the medulla oblongata. At the upper border of the bridge between its abdomen and the middle cerebellar peduncle, the trigeminal nerves (n. trigeminus, V pair) begin. They are clearly visible on transverse MR sections, as they run horizontally forward and are about 5 mm thick. The trigeminal nerve is divided into 3 branches - optic (1), maxillary (2) and mandibular (3). They all go forward into Meckel's cavity to the trigeminal ganglion. From here, branch 3 goes down through the foramen ovale, and branches 1 and 2 go through the cavernous sinus, along its lateral wall. Then, branch 1 enters the orbit through the superior foramen, and branch 2 exits the cranial cavity through the foramen rotundum.
The III, IV and VI pairs of cranial nerves, which provide movement of the eyeball, are usually not visualized on MRI scans.

MRI of the brain. Axial slice. Trigeminal nerves (arrow).

The facial nerve (n. facialis, VII pair) and the vestibular-cochlear nerve (n. vestibulocochlearis, VIII pair) exit their trunk together, the facial nerve is slightly medial, and go in one bundle, crossing the pontocerebellar cistern, and go into the internal auditory opening temporal bone. In the internal auditory canal, the vestibular branch runs in the posterior superior and inferior quadrants, the cochlear branch in the inferior, and the facial nerve in the anterior superior. The VII nerve enters the labyrinth (labyrinthine segment), runs inside the temporal bone to the geniculate body, turns back and passes under the lateral semicircular canal (tympanic segment) and exits the temporal bone through the stylomastoid foramen (foramen stylomastoideum). Next, the nerve goes to the salivary gland, where it divides into terminal branches. On MRI scans in sections 3-5 mm thick, the VII and VIII nerves are not separated and are designated as the auditory nerve. With thinner sections, the course of each nerve can be visualized separately.

MRI of the brain. Axial slice. Auditory nerve.

The medulla oblongata begins from the lower border of the pons. At the level of the foramen magnum it passes into the spinal cord. From it depart from the IX to XII pairs of cranial nerves, of which the initial part of the hypoglossal nerve (n. hypoglossus, XII pair) and, in the form of a single complex, IX, X, XI pairs are sometimes visible on transverse MRI.
The IV ventricle runs from the aqueduct above to the foramen of Majendie below. It is located between the brainstem in front and the velum and cerebellar peduncles in the back.
The cerebellum is located posterior to the pons and medulla oblongata. It is connected to the brain stem by the superior, middle and inferior cerebellar peduncles. The cerebellum consists of a midline vermis and paired hemispheres.

MRI of the brain. Axial slice. Cerebellum (CV - cerebellar vermis, CH - cerebellar hemisphere).

MRI in St. Petersburg, carried out by us, always clearly indicates the localization of the lesion in the conclusion, which is necessary for comparison with the clinic and deciding on the possibility and scope of the operation.

If you are looking for information on the topic “cyst in the brain” or an answer to the question “what is a cyst in the brain?”, then this article is for you. A cyst in the brain, or more precisely, an arachnoid cerebrospinal fluid cyst, is a congenital formation that occurs during development as a result of splitting of the arachnoid (arachnoid) membrane of the brain. The cyst is filled with cerebrospinal fluid - a physiological fluid that washes the brain and spinal cord. True congenital arachnoid cysts should be distinguished from cysts that appear after damage to the brain due to traumatic brain injury, infection, or surgery.

Arachnoid cyst ICD10 code G93.0 (cerebral cyst), Q04.6 (congenital cerebral cysts).

Classification of arachnoid cerebrospinal fluid cyst.

By location:

1. Sylvian fissure arachnoid cyst 49% (the fissure formed by the frontal and temporal lobes of the brain), is sometimes called a temporal lobe arachnoid cyst.
2. Arachnoid cyst of the cerebellopontine angle 11%.
3. Arachnoid cyst of the craniovertebral junction 10% (junction between the skull and spine).
4. Arachnoid cyst of the cerebellar vermis (retrocerebellar) 9%.
5. Arachnoid cyst sellar and parasellar 9%.
6. Arachnoid cyst of the interhemispheric fissure 5%.
7. Arachnoid cyst of the convexital surface of the cerebral hemispheres 4%.
8. Arachnoid cyst of the clivus 3%.

Some retrocerebellar arachnoid cysts can mimic Dandy-Walker anomaly, but they do not have agenesis (a term meaning the complete absence) of the cerebellar vermis and the cyst does not drain into the fourth ventricle of the brain.

Classification of arachnoid cysts of the Sylvian fissure.

Type 1 arachnoid cyst of the Sylvian fissure, click on the picture to enlarge Type 2 arachnoid cyst of the Sylvian fissure, click on the picture to enlarge Type 3 arachnoid cyst of the Sylvian fissure

Type 1: a small arachnoid cyst in the region of the pole of the temporal lobe, does not cause mass effect, drains into the subarachnoid space.

Type 2: includes the proximal and middle parts of the Sylvian fissure, has an almost rectangular shape, and partially drains into the subarachnoid space.

Type 3: includes the entire Sylvian fissure; with such a cyst, bone protrusion is possible (external protrusion of the scales of the temporal bone), minimal drainage into the subarachnoid space, surgical treatment often does not lead to straightening of the brain (transition to type 2 is possible).

Certain types of congenital arachnoid cysts.

It is worth highlighting separately in this article such congenital cysts as the cyst of the septum pellucidum, the Verge's cyst and the cyst of the intermediate velum. There is no point in devoting a separate article to each of the cysts, since you can’t write much about them.

Click on the picture to enlarge CT scan of the brain in the axial plane. The red arrow indicates a septum pellucida cyst. Author Hellerhoff [CC BY-SA 3.0], from Wikimedia Commons, click on the image to enlarge MRI of the brain in the coronal plane. The red arrow indicates a septum pellucida cyst. By Hellerhoff [CC BY-SA 3.0 or GFDL], from Wikimedia Commons

A cyst of the septum pellucida or cavity of the septum pellucida is a slit-like space between the layers of the septum pellucidum, filled with fluid. It is a stage of normal development and does not persist for long after birth, so it is present in almost all premature babies. Found in approximately 10% of adults, it is a congenital asymptomatic developmental anomaly that does not require treatment. Sometimes it can communicate with the cavity of the third ventricle, so it is sometimes called the “fifth ventricle of the brain.” The transparent septum belongs to the midline structures of the brain and is located between the anterior horns of the lateral ventricles.

A Verge's cyst or Verge's cavity is located immediately posterior to the cavity of the septum pellucidum and often communicates with it. Very rare.

The cyst or cavity of the intermediate velum is formed between the thalamus above the third ventricle as a result of separation of the crura of the fornix; in other words, it is located in the midline structures of the brain above the third ventricle. Present in 60% of children under 1 year of age and 30% between 1 and 10 years of age. As a rule, it does not cause any changes in the clinical condition, but a large cyst can lead to obstructive hydrocephalus. In most cases, no treatment is required.

Clinical signs of an arachnoid cyst.

Clinical manifestations of arachnoid cysts usually occur in early childhood. In adults, symptoms appear much less frequently. They depend on the location of the arachnoid cyst. Often cysts are asymptomatic, are an incidental finding during examination and do not require treatment.

Typical clinical manifestations of an arachnoid cyst:

1. General cerebral symptoms due to increased intracranial pressure: headache, nausea, vomiting, drowsiness.
2. Epileptic seizures.
3. Protrusion of the skull bones (this happens rarely, I have never personally encountered it).
4. Focal symptoms: monoparesis (weakness in the arm or leg), hemiparesis (weakness in the arm and leg on one side), sensory disturbances of the mono- and hemitype, speech disorders in the form of sensory (lack of understanding of spoken speech), motor (inability to speak) or mixed (sensory-motor) aphasia, loss of visual fields, paresis of cranial nerves.
5. Sudden deterioration, which may be accompanied by depression of consciousness up to coma:

• Due to hemorrhage into the cyst;
• Due to cyst rupture.

Diagnosis of arachnoid cyst.

Neuroimaging methods are usually sufficient to diagnose an arachnoid cyst. These are computed tomography (CT) and magnetic resonance imaging (MRI).

Additional diagnostic methods are contrast studies of the cerebrospinal fluid pathways, such as cisternography and ventriculography. They are required occasionally, for example, when examining median suprasellar cysts and when affecting the posterior cranial fossa for the purpose of differential diagnosis with Dandy-Walker anomaly.

Examination of the fundus by an ophthalmologist for hypertension syndrome (intracranial hypertension).

Electroencephalography (EEG) in case there was an epileptic seizure, to determine whether it was really caused by a cyst.

Treatment of arachnoid cyst.

As I said above, most congenital arachnoid liquor cysts are asymptomatic and do not require any treatment. Sometimes a neurosurgeon may recommend dynamic monitoring of the size of the cyst; for this, it will be necessary to periodically perform computed tomography or magnetic resonance imaging.

In rare cases, when an arachnoid cyst is accompanied by the symptoms described above and has a mass effect, surgical treatment is resorted to.

In some cases with a sharp deterioration, due to rupture of the arachnoid cyst or hemorrhage into it, urgent surgical treatment is resorted to.

There is no standard size for an arachnoid cyst. Indications for surgery are determined taking into account the location and symptoms of the arachnoid cyst, and not just its size. This can only be determined by a neurosurgeon during an in-person examination.

Absolute indications for surgery:

1. intracranial hypertension syndrome caused by an arachnoid cyst or concomitant hydrocephalus;
2. the appearance and increase of neurological deficit.

Relative indications for surgery:

1. large “asymptomatic arachnoid cysts” that cause deformation of neighboring lobes of the brain;
2. progressive increase in cyst size;
3. deformation of the cerebrospinal fluid tract caused by the cyst, leading to disruption of the cerebrospinal fluid circulation.

Contraindications for surgery:

1. decompensated state of vital functions (unstable hemodynamics, breathing), terminal coma (coma III);
2. the presence of an active inflammatory process.

There are three possible options for surgical treatment of arachnoid cysts. Your treating neurosurgeon chooses the tactics, taking into account the size of the cyst, its location and your wishes. Not all three methods are suitable for all arachnoid cysts.

Evacuation of an arachnoid cyst through a burr hole in the skull using a navigation station. The advantage is simplicity and speed of implementation with minimal trauma to the patient. But there is a drawback - the high rate of cyst recurrence.

Open surgery, that is, craniotomy (cutting out a bone flap on the skull, which is placed in place at the end of the operation) with excision of the walls of the cyst and fenestration (drainage) into the basal cisterns (cerebrospinal fluid spaces at the base of the skull). This method has the advantage of allowing direct examination of the cystic cavity, avoiding a permanent shunt, and is more effective for the treatment of arachnoid cysts consisting of multiple cavities.

Shunt surgery with installation of a shunt from the cyst cavity into the abdominal cavity or superior vena cava near the right atrium through the common facial vein or internal jugular vein. Many foreign and domestic neurosurgeons consider shunting of an arachnoid cerebrospinal fluid cyst to be the best treatment method, but it is not suitable in all cases. The advantage is low mortality and low rates of cyst recurrence. The disadvantage is that the patient becomes dependent on the shunt, which is installed for life. If the shunt becomes blocked, it will have to be replaced.

Complications of the operation.

Early postoperative complications - liquorrhea, marginal necrosis of the skin flap with dehiscence of the surgical wound, meningitis and other infectious complications, hemorrhage into the cyst cavity.

Outcomes of treatment of arachnoid cyst.

Even after successful surgery, part of the cyst may remain, the brain may not fully expand, and the midline structures of the brain may remain displaced. It is also possible to develop hydrocephalus. As for focal neurological symptoms in the form of paresis and other things, the longer it exists, the less chance of its recovery.

Literature:

1. Neurosurgery / Mark S. Greenberg; lane from English - M.: MEDpress-inform, 2010. - 1008 p.: ill.
2. Practical neurosurgery: A guide for doctors / Ed. B.V. Gaidar. - St. Petersburg: Hippocrates, 2002. - 648 p.
3. Neurosurgery / Ed. HE. Drevalya. - T. 1. - M., 2012. - 592 p. (Guide for doctors). - T. 2. - 2013. - 864 p.
4. Ivakina N.I., Rostotskaya V.I., Ozerova V.I. and others. Classification of intracranial arachnoid cysts in children // Current issues of military medicine. Alma-Ata, 1994. Part 1.
5. Mukhametzhanov X., Ivakina N. I. Congenital intracranial arachnoid cysts in children. Almaty: Gylym, 1995.
6. K.A. Samochernykh, V.A. Khachatryan, A.V. Kim, I.V. Ivanov Features of surgical tactics for large arachnoid cysts. \\ Scientific and practical journal “Creative surgery and oncology” Academy of Sciences of the Republic of Belarus Media Group “Health”, Ufa, 2009
7. Huang Q, Wang D, Guo Y, Zhou X, Wang X, Li X. The diagnosis and neuroendoscopic treatment of noncommunicating intracranial arachnoid cysts. Surg Neurol 2007

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