Neurinoma is a benign neoplasm arising from the myelin sheath of the nerve trunk. It causes irritation and dysfunction of the affected nerve, compression of adjacent tissues. Clinical manifestations correspond to the location of the tumor. The most common are neurinomas of the auditory nerve. Diagnosis is carried out comprehensively according to the results of neurological examination, ultrasound, MRI, CT of the affected area, electroneuromyography, histological examination. The treatment is surgical, according to the indications, open or radiosurgical removal of the neoplasm is performed.
ICD 10
D36.1 Peripheral nerves and autonomic nervous system
General information
The neurinoma originates from the Schwann cells of the nerve sheath (neurilemma). The term was introduced in 1910 and is widely used in the literature on clinical neurology. However, taking into account the histological characteristics, it is more correct to call this neoplasia schwannoma, neurilemma. Neurinoma can occur in patients of any age category, it is more often diagnosed in women. Among cerebral tumors it is 8-10%, among neoplasms of the spinal cord — 20%, among neoplasms of peripheral nerves — 50%. Most often, the vestibular cochlear nerve and spinal roots are affected, less often – other cranial nerves (trigeminal, facial, lingopharyngeal, vagus), peripheral nerve trunks of the extremities, nerves of the pharynx, stomach, intestines.
Causes
Schwannoma is formed due to excessive reproduction of Schwann cells in the neurilemma. The reasons for the process of enhanced division remain unknown. Significant factors are considered to be:
- ionizing radiation
- poor environmental situation
- exposure to carcinogens entering the body with food, inhaled air.
Hereditary determinism of the development of neurinomas is assumed. The tendency to their formation is noted in patients with neurofibromatosis. The occurrence of pharyngeal neurinomas is caused by the chronic harmful effects of various chemical agents, dust, frequent and prolonged inflammatory processes in chronic tonsillitis, pharyngitis, nasopharyngitis.
Pathogenesis
Macroscopically, a neurinoma is enclosed in a capsule, delimited by a rounded formation with a bumpy surface. On the incision, the tumor has a light gray or brownish-brown color, numerous fibrosed areas filled with brown cyst fluid are determined. As the neoplasia grows, it begins to squeeze the nerve fibers and the tissues surrounding the nerve, which causes the occurrence of the main clinical manifestations – disorders of the function of the nerve and adjacent structures. The severity of symptoms is determined by the localization of schwannoma. When located in a narrow framework of the bridge-cerebellar angle, the musculoskeletal canal, symptoms appear early, even with small sizes of the formation.
Microscopically, a neurinoma is a parallel series of cells with rod-shaped nuclei interspersed with fibrous structures. The peripheral areas of the tumor are surrounded by a vascular network, the central ones are poor in vessels. Due to insufficient blood supply, dystrophic changes occur in the central departments. As a result of the latter, the neurinoma undergoes various morphological transformations, according to which three main histological types of neoplasia are distinguished: epithelioid, angiomatous, xanthomatous. This classification has no clinical significance.
Symptoms
Schwannoma is characterized by slow development of symptoms, can remain unnoticed for a long time. Signs of neoplasia depend on its location, include two main components – symptoms of dysfunction of the affected nerve and manifestations caused by compression of nearby tissues. With neurinoma of the auditory nerve, progressive hearing loss is noted. Since the tumor is one-sided, the patient does not immediately notice the development of hearing loss. When the vestibular portion is involved, dizziness with nausea and vomiting, vestibular ataxia appear.
Trigeminal neurinoma manifests itself with prosopalgia, hypesthesia of half of the face, sometimes with taste hallucinations. The lesion of the facial nerve is characterized by weakness of the facial muscles. In some cases, trigeminal and facial symptoms are provoked by compression of the roots of the corresponding cranial nerves by an increasing vestibulocochlear schwannoma.
Spinal root neurinoma occurs with the classic radiculopathy: pain, sensitivity disorder, muscle hypotension, weakness, atrophy in the innervation zone of the affected root. Peripheral nerve neurinoma is manifested by similar disorders in the innervated area. Over time, trophic disorders develop in the denervated tissues. Pharyngeal neurinoma causes a feeling of discomfort, causes dysphagia, difficulty in nasal breathing.
Complications
Steadily increasing neurinoma of the bridge-cerebellar angle can lead to complete hearing loss, persistent hemiparesis of the face, intracranial hypertension, compression of stem structures with the development of bulbar syndrome, including swallowing disorders, speech, the appearance of double vision. Compression of the cerebellum causes the occurrence of cerebellar ataxia: unsteadiness of walking, discoordination, large-scale movements, chanted speech, nystagmus. Spinal neurinoma is complicated by compression of the spinal cord with the development of compression myelopathy, manifested by sensorimotor disorders below the lesion, disorders of pelvic functions. A complication of schwannoma of the branches of the vagus nerve is neuropathic laryngeal paresis.
Diagnostics
The clinical picture of neurinoma is in many ways similar to the lesion of the nerve trunk of inflammatory, compression, dysmetabolic etiology. Clinical symptoms, examination by a neurologist allow you to determine the level of lesion. Subsequent instrumental diagnostics is aimed at clarifying the morphological substrate that caused the lesion of the nerve trunk. The list of necessary examinations is determined by the location of neoplasia, includes:
- Cerebral neuroimaging. It is used for neoplasms of cranial nerves. Contrast CT of the brain is able to detect neurinomas larger than 1 cm. Brain MRI is more informative, it better visualizes the condition of the tissues surrounding the tumor.
- MRI. An isolated MRI of the affected spine is performed. The study makes it possible to detect neurinomas of the spinal roots, to determine the degree of spinal compression.
- Audiometry. Along with the consultation of an otorhinolaryngologist and a surdologist, audiometry is indicated for patients with hearing loss. The examination is carried out to assess the degree of hearing loss, to exclude other possible causes of hearing impairment.
- CT or MRI of the larynx and pharynx. It is prescribed for suspected pharyngeal neurinoma. It is performed after pharyngoscopy to clarify the diagnosis, localization and size of neoplasia.
- Sonography. Ultrasound of peripheral nerves is advisable when the nerve trunks of the extremities are affected. Makes it possible to determine the presence of a local thickening of the neurilemma. Local MRI of the soft tissues of the limb helps to visualize the formation more accurately.
- Electroneuromyography. ENMG is necessary to analyze the functional state of the nerve trunk affected by schwannoma. In the postoperative period, it is used to control recovery.
- Histological examination. The above-mentioned examinations allow us to determine the presence of a tumor formation, to assume its benign nature. Accurate verification of neoplasia is possible only based on the results of a study of the structure of its tissues. As a rule, a biopsy is not prescribed, the histology of the surgical material is carried out.
Differential diagnosis of schwann is performed with other tumor formations. Neurinoma of the bridge-cerebellar localization requires differentiation from meningiomas, astrocytomas, cerebellar tumors, spinal schwannoma — from other extramedullary tumors. Peripheral nerve neurinomas differentiate from compression-ischemic, inflammatory neuropathy.
Treatment
The only effective way to treat schwann is to remove them. The choice of therapeutic tactics is carried out by a neurosurgeon, depends on the localization of neoplasia, the age and state of health of the patient. Two main techniques are used:
- Surgical excision. It requires the release of nerve fibers from tumor tissues, which is associated with a high risk of injury, the probability of preservation of individual tumor particles, which in the future may cause a relapse. Microsurgical techniques are used to reduce the risk of these complications. With intracranial localization, the operation is performed by trepanation of the skull, with spinal — with laminectomy.
- Radiosurgical removal. It is performed with intracranial and spinal localization of schwannoma. Directed radiation exposure causes the death of part of the tumor cells, the remaining cells lose their ability to reproduce. Radical radiosurgical surgery is possible with a neoplasia size of less than 30 mm, in other cases, the radiosurgical method is used as palliative treatment in order to reduce the size of the neoplasm in patients with contraindications to open surgery.
Prognosis and prevention
The outcome of the disease depends on the location of the tumor, the timeliness of diagnosis and treatment. In most cases, radical removal provides a favorable result. In some cases, there is a recurrence of the neoplasm. The lack of treatment leads to irreversible loss of function of the affected nerve trunk, the occurrence of complications. Specific prevention has not been developed, general preventive measures are reduced to preventing the effects of oncogenic factors, increasing antitumor immunity.
