Schwannoma

Schwann cells are present in the peripheral nervous system, which provide support to the nerves there and produce thick insulation called the myelin sheath around the nerves and the nerve roots to increase the rate of signal transmission. Schwannomas are a rare kind of tumour that arise from Schwann cells which are usually benign. 

What is Schwannoma?

Schwannoma refers to a rare type of tumour that occurs in the nervous system, arising from the Schwann cells. Schwann cells have a role in the development, maintenance, function and regeneration of the peripheral nervous system. Schwannomas are almost always non-cancerous but may become malignant as well. 

Vestibular Schwannomas or acoustic neuromas are tumours arising from the vestibulocochlear nerve or the cranial nerve VIII. This nerve connects the inner ear with the brain and is involved in transmitting the sounds and sending information for maintaining balance from the inner ear to the brain. 

These tumours account for 8% of all primary intracranial tumours. They usually occur in the late stages of life from the fourth to sixth decade of life at a median age of 50 years. These bilateral vestibular schwannomas are suggestive of Neurofibromatosis Type 2 and then individuals with type 2 neurofibromatosis tend to present the schwannomas earlier around the third decade of life. Acoustic neuromas are usually slow-growing tumours spread over years. They commonly result in neurological defects and hearing loss although they don’t invade the brain usually. If the tumours become large enough to compress the brain stem or the cerebellum, they may lead to life-threatening conditions. Apart from hearing losses, additional findings include ringing in the ears, dizziness and imbalance. Acoustic neuromas are usually not malignant. 

Types Of Acoustic Neuromas

There are two common types of acoustic neuromas, namely 

1. Sporadic acoustic neuromas
2. Neurofibromatosis Type 2 (NF2)

Sporadic form is the most common type, occurring to approximately 2500-3000 individuals in a year in the US. It typically affects only one ear. The NF2 associated neuroma is a rare one accounting for only 5 per cent of the acoustic neuromas. 

Causes

The cause of schwannoma in most cases is unknown. 

• As told above, it may occur with other underlying genetic disorders like Neurofibromatosis type 2, schwannomatosis, or the Carney complex
• This disease is inherited in an autosomal pattern, which means, a mutation in only one allele of the responsible gene, is enough to cause the disease
• The mutations can be both inherited as well as may occur de novo

Symptoms

Schwannomas may grow slowly without any symptoms with their presence for months and years. So some people never experience any symptoms while other people may experience immense pain, muscle weakness, tinglings and numbness sensation. These are the general symptoms and the specific symptoms may vary depending upon which cranial/peripheral nerve is affected.  For example- 

• Vestibular nerve- hearing loss, ringing/buzzing in the ear, disbalance
• Facial nerve- loss of sense/taste, facial paralysis, problem in swallowing, pain
• Spinal nerve root- muscle weakness, numbness, radiating pain in legs or arms
• arm/leg nerve- localised pain, carpal tunnel syndrome or tarsal tunnel syndrome, “pins and needles” sensation

Diagnosis 

Schwannomas are a little difficult to diagnose since depending on the location of the schwannoma, the symptoms may be similar to the symptoms caused by other health problems. To confirm the diagnosis, the following procedures may need to be performed:

• X-ray
• Ultrasound
• CT scan
• MRI
• Tumour biopsy

Treatment

Treatment depends on the location of the tumour, the severity of symptoms, and the malignancy or benign nature of the tumour. Surgical options involve removal of the tumour depending upon its location and can be stereotactic radiosurgery or microsurgery. 

Conclusion

Schwannomas can be of various types, one of which is Vestibular Schwannomas. These are also called acoustic neuroma and occur due to problems with the 8th cranial nerve. The symptoms, diagnosis, and treatment methods of schwannomas have been listed in the text. In conclusion, it can be said that schwannomas are rare tumours that occur due to random mutations in genes in Schwann cells. Schwannomas are very rare but can be fatal if they spread to the brain. These are usually non-cancerous but can become malignant too. Based on