Arachnoid cyst
Introduction
Introduction to arachnoid cyst Arachnoid cysts, which are congenital benign brain cyst lesions, are caused by abnormal arachnoid division during development. The wall of the capsule is mostly arachnoid, glial and pia mater, and there is cerebrospinal fluid-like cyst fluid in the capsule. The cyst is located on the surface of the brain, in the brain and in the cerebral cistern, and does not involve the brain parenchyma. Mostly single, a few more. The disease is asymptomatic, and the large volume can simultaneously compress the brain tissue and the skull, which can produce neurological symptoms and changes in skull development. The disease is more common in children and adolescents, more males, more common on the left side than on the right side. Arachnoid cysts can be divided into congenital and secondary (traumatic and post-infection) according to different causes. Congenital arachnoid cyst is a bag-like structure formed by the cerebrospinal fluid enclosed in the arachnoid membrane and does not communicate with the subarachnoid space. Secondary patients develop cysts in the subarachnoid space due to arachnoid adhesions, which contain cerebrospinal fluid. According to different parts, it can be divided into two types: intracranial and spinal. The intracranial type is mostly located in the relevant brain pool of the brain. The spinal cord type can be located in the epidural, intradural or nerve sheath, causing related radiculopathy symptoms and signs. basic knowledge The proportion of illness: 0.0032% Susceptible people: no specific population Mode of infection: non-infectious Complications: epilepsy
Cause
Arachnoid cyst etiology
Congenital factors (35%)
Congenital arachnoid cysts are a common type, and the cause of the disease is not fully understood. The following hypothesis: 1 The cause of this disease may be due to the development of small arachnoids falling into the subarachnoid space during embryonic development. That is, the cyst is located in the arachnoid. Under the microscope, the arachnoid is divided into two layers around the cyst. The outer layer constitutes the surface part of the cyst, and the inner layer forms the bottom of the capsule. There is still a subarachnoid space between the pia mater and the fundus. 2 Some people think that during embryonic development, due to the pulsation of the choroid plexus, the cerebrospinal fluid can be pumped, and the loose periprosthetic network around the nerve tissue can be separated to form the subarachnoid space. If the early cerebrospinal fluid flows abnormally, it can be in the periarticular cavity. A cyst is formed in the mesh. 3 Because this disease is often accompanied by other congenital anomalies, such as ectopic choroid plexus in the cyst, local cerebral palsy, and loss of the epiphyseal plate, temporal lobe and internal carotid artery, etc., all confirmed that the basic cause of this disease is brain hypoplasia. To. There is no consensus on the reason for the increase of arachnoid cysts. It may be: 1The small wall of the cyst has a small hole communicating with the subarachnoid space. The cerebrospinal fluid continuously flows into the capsule from the hole, and the small hole acts as a flap. Beating, the cysts gradually increase. It is also possible that some factors cause the small holes to clog and cause an increase in intracranial pressure. 2 There is an ectopic choroid plexus in the sac, which secretes excessive cerebrospinal fluid and cannot be absorbed. 3 In some cases, the cyst is not connected to the subarachnoid space, the protein in the cyst fluid is increased, and the difference in osmotic pressure between the capsule and the outside causes the cyst to gradually increase. 4 venous hemorrhage in the capsule or on the wall of the capsule, so that the capsule cavity increases rapidly.
Infection (30%)
After meningitis, a cyst is formed due to local adhesion of the arachnoid, and the capsule is filled with cerebrospinal fluid. Mostly multiple. More common in children. Common in the optic chiasm, basal pool, cisterna magna, ring pool and so on. The cerebrospinal fluid circulation pathway is blocked.
Injury (20%)
Soft meningeal cyst. The mechanism of the injury is a linear fracture of the skull with a dural tear defect, and there is hemorrhage in the subarachnoid space or adhesion at the peripheral edge of the arachnoid, causing local cerebrospinal fluid circulation disorder, causing local arachnoid to dura mater and fracture. In the line, under the continuous impact of the brain beat, the cyst is gradually formed, and the edge of the fracture is continuously enlarged, which is called a growth fracture. The cyst can protrude under the scalp and can also compress the underlying cortex. The capsule is filled with clear liquid and has scar tissue around it. If the pia mater is damaged during trauma, the brain tissue may also break into the fracture, and the ipsilateral ventricle expands, and even forms a brain penetrating malformation. This disease is more common in infants and young children.
Prevention
Arachnoid cyst prevention
1, congenital diseases are difficult to prevent, but the mother's good father's good habits can reduce the incidence of fetal diseases.
2. Arachnoid cysts caused by other factors should be prevented from the cause.
Complication
Arachnoid cyst complications Complications, epilepsy, hemiplegia
The common arachnoid cyst after injury is a linear fracture of the parietal bone. The scalp can be ruptured without injury, and the scalp is locally bulged. After 2 to 3 years, the fracture at the fracture line is enlarged. The bone edge is lifted outwards like a fish lip, and the cyst compresses the brain tissue to produce epilepsy, hemiplegic and other neurological symptoms.
Symptom
Arachnoid cyst symptoms Common symptoms Increased intracranial pressure hydrocephalus epileptic headache
Congenital arachnoid cysts are common in the lateral fissure, cerebral longitudinal fissure, brain surface or bottom, cerebellum, etc., and can also be found in the saddle area, optic nerve, quadrilateral region, slope, cerebellopontine angle and so on. Infant patients often have ankle cranial bulge, squamous squamous bones and increased intracranial pressure, but most of them do not attract attention, most of them produce symptoms until adulthood. Symptoms are related to cyst size and growth site. Small cysts can be found without any symptoms, even found in autopsy.
symptom
The disease is insidious onset and more asymptomatic. Some large arachnoid cysts may have clinical manifestations similar to intracranial lesions.
(1) Skull dysplasia or giant cranial deformity, especially in children.
(2) The saddle-upper cyst in the child's period can be expressed as a head-head activity, that is, a doll head-like symptom.
(3) The left middle cranial cyst can be combined with attention deficit disorder (ADHD).
(4) Headache, but not all headache patients have arachnoid cysts.
(5) Epilepsy.
(6) Hydrocephalus (excessive accumulation of cerebrospinal fluid).
(7) Increased intracranial pressure.
(8) Stunting.
(9) Behavior changes.
(10) Disgusting.
(11) Hemiplegia (one limb is weak or paralyzed).
(12) Ataxia (uncoordinated muscle movement).
(13) Auditory hallucinations.
(14) Alzheimer's disease.
Elderly patients (>65 years old) symptoms
Older patients (>65 years old) Symptoms are similar to chronic subdural hematomas or normal pressure hydrocephalus:
(1) Dementia.
(2) Urinary incontinence.
(3) Hemiplegia.
(4) Headache.
(5) Epilepsy.
Site related symptoms
(1) The supratentorial cyst can be similar to the symptoms of Ménière's disease.
(2) Depression can occur in frontal lobe cysts.
(3) Left temporal lobe cysts may have psychiatric symptoms. Left frontal temporal lobe cysts are more often expressed as alexithymia.
(4) Cysts in the right lobes can cause new-onset schizophrenia around the age of 61.
(5) Left middle cranial cysts may have auditory hallucinations, migraine and episodic illusions.
(6) Most neurosurgeons believe that arachnoid cysts are associated with mental illness.
Examine
Examination of arachnoid cysts
Imaging findings: a clear, smooth cerebrospinal fluid density zone with a CT value of 0-20 Hu, with no enhanced performance. The lateral fissure pool and the cyst near the cranial sac are characterized by a linear shape on the inner edge, which can be square. Often causing absorption and bulging of adjacent skulls. The arachnoid cyst of the occipital cistern can shift the anterior chamber of the fourth ventricle, with the enlargement of the ventricles above the lesion.
Diagnosis
Diagnosis and differentiation of arachnoid cyst
Conventional CT and MRI examinations can generally be diagnosed. In a few cases, cranial fluid contrast agents or flow measurements are used for upper and lower cranial fossa lesions in the midline. For cognitive function, the Simple Mental Rating Scale (MMSE) can also be used for evaluation.
Clinical manifestations are similar to intracranial lesions. Some patients may have convulsions or seizures. There may also be local symptoms such as eyeball protrusion and head disregard.
According to the common parts of this disease, it is as follows:
1. Lateral arachnoid cyst: the most common. The lateral fissure is enlarged, sometimes accompanied by a anterior temporal lobe and a subfrontal gyrus. Common in men under the age of 20, often have headaches, seizures (can be limited or generalized epilepsy, psychomotor seizures), ankle bone bulge, a few have ipsilateral eyes, late can have papilledema Contralateral hemiplegic and other symptoms.
2. Arachnoid cysts in the brain: seen in infants or adults. Infants often have progressive head enlargement, bilateral asymmetry, light transmission test can see cyst boundaries, and sometimes seizures. Adults often have headaches, epilepsy, progressive contralateral hemiparesis, and papilledema.
3. Cervical longitudinal arachnoid cyst: often no clinical symptoms, about half of which are associated with corpus callosum dysplasia.
4. Saddle area arachnoid cyst: located on the saddle or inside the saddle. The saddle is rare and can occur at any age. The cyst can communicate or not communicate with the optic chiasm. Small cysts can be asymptomatic, the larger can destroy the sella, compress the pituitary, optic nerve and interventricular pores, resulting in visual impairment, hypopituitarism, obstructive hydrocephalus and so on. The cyst inside the saddle is asymptomatic and can be developed on the saddle through the enlarged saddle hole, similar to the empty sella syndrome.
5. Optic nerve arachnoid cyst: There may be two types of internal and intracranial segments. The former is located behind the eyeball, and has symptoms such as ipsilateral vision loss, papilledema, and ciliary venous engorgement. The intracranial segment can compress the optic nerve to produce visual impairment, visual field defects, etc. (Holt1966).
6. Quadrilateral arachnoid cyst: The cyst is connected or not connected to the quadruple pool. Early compressible aqueduct produced masculine hydrocephalus and increased intracranial pressure, and about 1/4 of Parinaud syndrome.
7. Arachnoid cysts in the cerebellopontine angle: early neurological deafness, corneal reflex, late cerebellar sign and increased intracranial pressure. Individuals may have peripheral facial paralysis and trigeminal neuralgia (Bengochea et al. 1955, Sumner et al. 1975).
8. Cerebellar arachnoid cyst: can be located in the cerebellar hemisphere, ankle or occipital pool. Clinical symptoms often increase intracranial pressure, and some cases have cerebellar signs.
Arachnoid cysts after infection can be clinically characterized by hydrocephalus and increased intracranial pressure. Visually intersecting pool cysts can cause visual impairment, and other parts can also produce localized symptoms. Children often have a head enlargement.
The common arachnoid cyst after injury is a linear fracture of the parietal bone. The scalp can be ruptured without injury, and the scalp is locally bulged. After 2 to 3 years, the fracture at the fracture line is enlarged. The bone edge is lifted outwards like a fish lip, and the cyst compresses the brain tissue to produce epilepsy, hemiplegic and other neurological symptoms.
Identification: ventricular system epithelioid cysts, cerebral hemisphere epithelioid cysts.
