Epidermal cyst

Introduction to epidermal cyst The epidermal cyst was officially named by Critchey in 1928. It is different from middle ear cholesteatoma, not due to epithelial shedding caused by repeated inflammation, but innate ectopic. If the ectopic tissue occurs in the early stage of the embryo (ie, when the nerve groove is closed), the cyst is mostly located in the midline, and if it occurs in the late stage (second cerebral vesicle formation), the cyst is mostly located laterally. A small number of epidermoid cysts can be caused by trauma. For example, epithelial tissue can be implanted into the brain through experimental injury to form epidermoid cysts. basic knowledge The proportion of sickness: 0.01% Susceptible people: no specific people Mode of infection: non-infectious Complications: hydrocephalus meningitis arachnoiditis ventriculitis epidermoid cyst

Epidermal cyst cause

Cause of the disease (70%)

The epidermal cyst originates from the ectodermal tissue of the residual tissue of the ectopic embryo. It is the result of the introduction of the surface in the late embryonic stage when the secondary brain cells are formed. In 1954, Choremis et al. noticed that the epidermoid cyst was produced after the lumbar puncture, thus supporting the epithelial cyst. The theory of the cause of trauma, in 1961, Blockey and Schorstein reviewed 8 cases of children's patients, most of them for the treatment of tuberculous meningitis after intrathecal injection, tumors can be multiple, ranging from a few millimeters to several centimeters in size, cysts lack blood vessels, in Injecting skin fragments directly into the spinal cord and forehead of the mouse during the experiment can repeatedly produce the same cyst.

Pathogenesis (10%)

Most of the cysts are single or multiple, and occasionally with dermoid cysts accompanied by congenital malformations or abnormalities, such as sinus sinus, spina bifida, etc., intracranial epidermoid cysts can be located outside the dura mater, subdural , subarachnoid space, brain parenchyma and intraventricular, etc., according to the origin of the site in the cerebellopontine angle, saddle area, cerebral hemisphere, ventricle, quadrilateral area, cerebellum, etc., about 25% of cysts can occur in In the skull barrier or in the spine, due to the biological characteristics of the cyst, it is not limited to one place. It often protrudes from the initial part of the cyst into the adjacent cerebral cistern, the groove is split, and even the brain parenchyma can be penetrated. It grows along the nerve cellulose, so it can sometimes grow widely from the posterior cranial fossa to the anterior cranial fossa.

Histologically, the specific form of epidermoid cyst is a round, nodular or elliptical mass with a pearly luster. The capsule is intact, can be calcified, has a smooth surface, and its wall is thin and translucent. The boundary is clear, the blood supply is not rich, and the size is different. The contents of the capsule are cheese-like substances, which are slightly greasy and are accumulated by exfoliated cells. Due to the large amount of cholesterol crystals, the contents have a special luster and are transparent and thin. The wall of the capsule has a special appearance, and the boundary between the tumor and the adjacent brain tissue is clear, but because the wall of the capsule is very thin, and it often extends into all corners and cerebral cisterns, the deep wall often has some large blood vessels and nerve adhesions. Or wrapping it inside the tumor, causing difficulties in total tumor resection.

Under the microscope, the tumor wall is composed of two layers of tissue, the outer layer is a thin layer of fibrous connective tissue, the inner layer is a stratified squamous epithelium, the epithelial layer faces the cystic cavity, and there are many keratinocytes on the surface, which continuously fall off to form a capsule. The contents and the tumors are constantly increasing. The arachnoid tissue adjacent to the tumor is fibroproliferative and hyalinized. Sometimes, ectopic macrophages, lymphocytes and histiocytes are infiltrated, and the contents of the capsule are tissue toxic. Excessive spillage into the subarachnoid space can cause a granulocyte-like inflammatory response, and the brain tissue adjacent to the sac can have gliosis.

Epidermal cysts occasionally have malignant changes, invasive growth, abominable squamous cell carcinoma, and some can be widely seeded and transferred with cerebrospinal fluid. Under the microscope, multilateral neoplasms are visible, the nucleus is pleomorphic, and the periphery is surrounded by necrosis. The cells are surrounded by sparse stromal cells and have cytoplasmic fibrils. Under the electron microscope, the nucleus of the sputum is different in shape and size, and has an irregular nuclear membrane. The cytoplasm often contains electron-intensive filamentous bundles, occasionally embedded in desmosomes. The desmosome junction is a large and distinct intraserosal fold, occasionally bundled.

At present, there is a relatively consistent view on the pathogenesis of epidermoid cysts. It is generally believed that inclusions containing epithelial components are retained in the neural tube during the embryonic stage 3 to 5 weeks, that is, when the neural tube is formed into a neural tube. The object becomes the pathological root of epidermoid cysts in the future. With the continuous keratinization and detachment, the tumor contents are gradually enlarged, and the clinical symptoms are caused. In addition, there are still some cases due to scalp trauma. Epithelial implantation and the onset of the disease.

Epidermal cyst prevention

Food diversification and rationalization: To ensure a balanced and comprehensive nutrition, daily food diversification is necessary, that is, according to the ratio of the five categories of food displayed by the Chinese residents' balanced diet pagoda.

A small amount of meals, eating light and digestible food: For patients after radiotherapy and chemotherapy and surgery, due to weakened digestive function, increasing the number of meals can reduce the burden on the digestive tract and increase the food intake.

It is not appropriate to avoid taboos: taboos should be decided according to the condition of the disease and the individual characteristics of different patients, and do not advocate excessive taboos. Common foods that need to be restricted or contraindicated are: high-temperature frying, smoked barbecue, spicy stimulation, greasy and hard food.

Choose foods with anti-cancer effects: fruits and vegetables (such as asparagus, carrots, spinach, tomatoes, broccoli, potatoes, kiwi, citrus), soybeans and their products, edible fungi, nuts, seaweed, glutinous rice kernels, milk , eggs, etc.

Epidermal cyst complications Complications hydrocephalus meningitis arachnoiditis ventriculitis epidermoid cyst

Postoperative complications are:

1. Aseptic meningitis and ventriculitis are the most common postoperative complications of epidermoid cysts, mainly due to the tumor contents entering the subarachnoid space or intraventricular stimulation of brain tissue, the incidence rate is 10% to 40 %, most patients occur within 1 to 2 weeks after surgery. Early surgery and microsurgery for total tumor resection are the basic measures to prevent this complication. Once a large dose of hormones and antibiotics can be used, and timely lumbar puncture The cerebrospinal fluid is continuously drained by liquid or lumbar puncture, and most patients can return to normal within 1 to 4 weeks after surgery.

2. The incidence of hydrocephalus is low, mainly due to repeated meningitis or ventriculitis, symptomatic treatment can be taken, and shunt can be considered after inflammation control.

3. Chronic granulomatous arachnoiditis is due to the repeated discharge of the contents of the capsule into the subarachnoid space, which stimulates the formation of chronic granuloma in the arachnoid, and can be treated with a large dose of hormones.

4. Secondary cranial nerve dysfunction, the contents of the capsule repeatedly overflow into the cranium, causing fibrosis around the cranial nerves, thus, compressing the nerve and causing neurological dysfunction.

5. Malignant lesions, the epidermoid cyst wall is a typical stratified squamous epithelium, under certain conditions can occur malignant transformation, become squamous epithelial cancer, repeated recurrence after multiple surgery can occur cancer, especially cerebellopontine angle epidermis a cyst.

When the epidermoid cyst is surgically removed, if the intended purpose is not achieved or the condition deteriorates rapidly, the epidermoid cyst should be considered. The postoperative CT scan shows tumor enhancement at the tumor site. The possibility of malignant transformation should also be considered. Postoperative radiotherapy, more than 20 cases of malignant changes have been documented in the literature.

Symptoms of epidermal cysts Common symptoms Polyneodynia, dizziness, tinnitus, tinnitus, increased intracranial pressure, ataxia, polyuria edema, weakness, sensory disturbance

1. The course of the disease is many years to decades. The disease is slow due to its growth. Although the tumor is very large and even involves more than one cerebral lobe, the clinical symptoms can still be very mild. Therefore, in the past, the average time from symptom onset to visit was reported. For 16 years, in recent years, it has been reported that the average time is 5 years, and about 70% of patients have a disease duration of more than 3 years.

2. With malformation, the disease can be associated with skin fistula, spina bifida, syringomyelia, basement depression and so on.

3. Symptoms and signs: The clinical symptoms and signs of epidermoid cysts in different parts are also different. According to the relationship between the origin of intracranial epidermoid cysts and their relationship with skull blood vessels and choroid plexus, they are divided into three groups: 1 saddle Posterior or vertebral-basal artery group. 2 saddle, saddle or internal carotid artery group. 3 intraventricular or choroid plexus group. The symptoms and signs of epidermoid cysts in various parts are as follows:

(1) cerebellopontine angle epidermoid cyst: about 70% of patients with trigeminal neuralgia as the first symptom, a few with hemifacial spasm, facial sensation, tinnitus, deafness, signs including facial sensation, hearing loss, ataxia The posterior group of cranial nerve palsy can be expressed as cerebellopontine angle syndrome in the later stage. According to its clinical manifestations, it can be divided into the following three types.

1 simple trigeminal neuralgia type: accounting for about 42.9% of all intracranial epidermoid cysts. This type of tumor occurs mostly in the upper trigeminal nerve root of the pons cerebellum. It is characterized by episodic electric shock like severe pain in the affected trigeminal nerve distribution area. There are trigger points, most of which are not associated with other abnormal signs of the nervous system, and are easily misdiagnosed as primary trigeminal neuralgia. Therefore, young or middle-aged trigeminal neuralgia should be alert to the presence of epidermoid cysts.

2 cerebral cerebellopontine angle tumor type: about 18.1%, the tumor is located in the lower part of the cerebellopontine angle of the pons, mostly with tinnitus, dizziness, hemifacial spasm and VII, VIII cranial nerve involvement and other cerebellopontine angle syndrome as the main performance, individual cases may appear Tongue, vagus and accessory nerve damage, and cerebellar signs and signs of brain stem involvement, therefore, should be differentiated from acoustic neuroma, this type of impact on the auditory nerve, cochlear nerve and vestibular nerve is very inconsistent, it is worth noting.

3 Increased intracranial pressure: This type of tumor grows in the direction of the cerebral cistern, and the surrounding brain tissue is slightly compressed. When further developed, the hydrocephalus occurs in the cerebrospinal fluid circulation pathway and the intracranial pressure increases.

(2) Epidermoid cyst in the middle cranial fossa: The epidermoid cyst in the middle cranial fossa is located beside the trigeminal nerve, originating from the dura mater, invading the cranial fossa along the rock bone, located under the semilunar ganglion, first involving the trigeminal nerve, and then involving II, III, IV, VI, VII, VIII cranial nerves, 50% cross the rock bones to invade the cerebellopontine angle of the cerebral pons, forming a "riding-type" tumor that rides across the cranial fossa and posterior fossa. For trigeminal nerve paralysis symptoms, such as facial sensation loss, masticatory muscle weakness, etc., sometimes visual acuity, visual field impairment and eye movement disorders.

(3) Epidermoid cyst in the sellar region: accounting for about 3% of all epidermoid cysts, mainly for progressive visual acuity, visual field damage, optic atrophy in the late stage, endocrine disorders are rare, individual patients may have sexual dysfunction, more Drinking, polyuria, etc., to the frontal lobe development may appear frontal lobe mental symptoms, backward development can obstruct the third ventricle or interventricular pores and hydrocephalus, saddle epidermoid cysts generally do not involve the brain outside the eye, The lateral development of the para-sacral epidermoid cyst can cause the C. serrata syndrome. The patient presents with temporal lobe epilepsy with hemiplegia, and few cases have language problems.

(4) Epidermoid cysts in the brain parenchyma: About 41% of patients with cerebral hemisphere have seizures, 50% have optic disc edema, and sometimes progressive hemiparesis. Cerebellar hemispheres may have ataxia and other symptoms of cerebellar damage. .

(5) intraventricular epidermoid cyst: the lateral ventricle epidermoid cyst is mostly located in the lateral ventricle triangle and body, early patients may have no obvious symptoms, with the increase of cysts, there may be volatility or paroxysmal headache attacks, When cerebrospinal fluid circulation pathway is blocked, symptoms of increased intracranial pressure may occur. Some patients show Brun sign and forced head position. Those who develop outside the brain may cause hemiparesis, hemianopia and partial sensory disturbance. The third ventricle is mainly characterized by Obstructive hydrocephalus, endocrine symptoms are not obvious, the fourth ventricle epidermoid cyst can still cause walking instability.

(6) Cerebral hemisphere epidermoid cyst: mostly located in the longitudinal fissure, lateral fissure, hemisphere surface, mainly manifested as epilepsy, hemiplegia, mental abnormalities and increased intracranial pressure. Tytus (1956) reported 143 cases of cerebral hemisphere epidermoid cyst In patients, 41% had seizures and 50% had optic disc edema. In addition, language disorders were still present.

(7) Skull stenosis epidermoid cyst: often manifested as a local enlargement of the scalp mass of the skull, more than no signs of the nervous system, inward development involving the intracranial can occur epilepsy or increased intracranial pressure.

(8) Epidermoid cysts in other parts: Epidermoid cysts in the cerebellum are mainly manifested by increased intracranial pressure and tonic ataxia, unstable walking, and epidermal-like cysts in the brainstem are characterized by brain stem damage and increased intracranial pressure. In the late stage of the epidermoid cyst in the pineal region, the main manifestations are increased intracranial pressure and difficulty in both eyes, pupils with light reflexes, and regulation of reflexes. Parinaud syndrome, scalp epidermoid cysts can only be expressed as scalp mass, and tough.

Examination of epidermal cysts

Cerebrospinal fluid examination brain pressure can be slightly increased, a small amount of cerebrospinal fluid protein content is mild, moderately elevated, most patients with normal cerebrospinal fluid test.

1. In addition to the manifestations of increased intracranial pressure, the X-ray film of the skull has its own changes in different parts. The epidermoid cyst of the cerebellopontine angle can be absorbed by the tip of the rock, and the shape of the internal auditory canal is normal. The cysts may be damaged by the rock bone tip or the rock bones; the saddle area has more normal saddle saddle, one side of the anterior bed or the posterior bed has bone changes, and there may be saddle enlargement and bone destruction, involving the sacral It can be seen that the supraorbital fissure, the optic nerve hole is enlarged, and the epidermoid cyst in the stenosis can be seen with limited circular or elliptical density or bone destruction, sharp edges, obvious bone density, and edge hardening zone. The damage is more serious than the outer plate, and calcified plaques can be seen in some cases.

2. The typical image features of CT epidermal cyst on CT is uniform low-density area, CT value is between -2~12Hu, lower than cerebrospinal fluid value, irregular shape, mostly isolated, and has a mass effect (Fig. 1). Intensive scans were generally not significantly enhanced. Nosaka (1979) reported a case of primary epithelial carcinoma of the right cerebral cerebellopontine angle, and reviewed 13 cases of literature, enhanced intensified scan images, and considered that the cerebellopontine angle is a common site for malignant transformation of epidermoid cysts. , accounting for 57.1%.

3. MRI MRI is superior to CT in the diagnosis and detection of epidermoid cysts in the posterior cranial fossa, especially in the brainstem epidermoid cyst. It can show its occupancy effect, tumor extent, vascular displacement, etc. Most cases are long T1 and The long T2 has a low signal on the T1-weighted image and a high signal on the T2-weighted image. The unevenness of the tumor and the change in signal intensity are the MRI features.

Diagnosis and identification of epidermal cyst

Diagnostic criteria

According to the age of onset, clinical manifestations and auxiliary examination, qualitative diagnosis is not difficult, especially in young patients with trigeminal neuralgia, the cause is mostly epidermoid cyst. The clinical application of CT and MRI makes the epidermoid cyst of each site qualitative and localized. The diagnosis becomes fast, accurate, easy, and even unexpected lesions can be found. The diagnosis points of epidermoid cysts in common sites are as follows:

1. Cerebellar cerebellopontine epidermoid cyst

(1) The age of onset is relatively early and the course of disease is longer.

(2) Mainly manifested as trigeminal neuralgia, or manifested as cerebellopontine angle syndrome, but hearing and vestibular dysfunction is lighter.

(3) The protein content of cerebrospinal fluid is normal.

(4) The auditory canal is normal in the flat slice of the skull.

2. Saddle-like epidermoid cyst

(1) The medical history is long and the progress is slow.

(2) The appearance of optic nerve atrophy and bilateral sacral hemianopia.

(3) The pituitary function is normal.

(4) The size of the flat slice of the skull is normal, but the optic nerve hole, the chiasm can have localized damage.

3. Cranial fossa epidermoid cyst

(1) It is mainly caused by trigeminal nerve damage and has a long course of disease.

(2) Increased intracranial pressure may occur in some cases later.

(3) The skull base often shows a bone defect with a sharp edge at the tip of the rock.

(4) The protein content of cerebrospinal fluid is generally not high.

(5) When the sinus sinus appears in the skin before the ear, it is very helpful for qualitative diagnosis.

4. Lateral cerebral epidermoid cyst

(1) More common in young and middle-aged people.

(2) When the tumor does not cause ventricular internal obstruction or oppression, the important structure can be asymptomatic. When the intracranial pressure is increased, the tumor volume has grown larger, and there may be hemiparesis and partial sensation.

(3) The protein content of cerebrospinal fluid is generally normal.

(4) Images of CT and MRI visible point performance.

Differential diagnosis

Epidermal cysts in different parts need to be differentiated from different tumors.

1. Primary trigeminal neuralgia: cerebellopontine angle epidermoid cyst simple trigeminal neuralgia, need to be differentiated from primary trigeminal neuralgia, primary trigeminal neuralgia onset age, more no positive signs, pain episodes More typical, CT scans help to identify.

2. Other cerebellopontine angle tumors (acoustic neuroma, meningioma): Acoustic neuroma often uses hearing impairment as the first symptom, while meningioma is mainly characterized by increased intracranial pressure, but sometimes for cerebellopontine angle tumor or increased intracranial pressure Type epidermoid cysts are distinguished from cerebellopontine angle acoustic neuroma or meningioma. It is difficult to rely on clinical examination alone, and CT or MRI is needed.

3. Trigeminal semilunar schwannomas: The epithelioid cyst in the middle cranial fossa needs to be differentiated. The cranial sinus of the trigeminal semilunar schwannomas is enlarged, and the CT manifests as a uniform enhancement lesion.

4. Saddle area tumor: The epidermoid cyst in the sellar region needs to be differentiated from pituitary tumor, craniopharyngioma, saddle nodule meningioma, pituitary tumor with decreased vision, sputum hemianopia, endocrine disorder as the main manifestation, craniopharyngioma Endocrine disorders, developmental disorders are the main manifestations, and saddle nodule meningioma is normal.

5. Other cysts: CT showed low-density areas, but their CT values were different, and there were differences after enhancement. MRI was helpful for differential diagnosis.

In short, with neuroradiology, the differential diagnosis of epidermoid cysts is not difficult.

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