Cranial nerve neurinomas

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Neurinomas, also called Schwannomas, are tumours that affect cranial nerves and spinal nerves. They develop from Schwann cells, which form the myelin sheath covering peripheral nerves.

Neurinomas are characterised by their relatively slow growth, and they are usually benign, although they turn into malignant tumours in less than 1% of cases. In children, however, the percentage of neurogenic tumours of a malignant nature is significant, including neuroblastomas in particular. 

Neurinomas represent about 7% of primary central nervous system tumours and are divided into different types. The most common ones include:

• Facial nerve neurinoma (also called neurinoma of the seventh cranial nerve)
• Trigeminal neurinoma (also called neurinoma of the fifth cranial nerve)
• Acoustic neurinoma (also called neurinoma of the eighth cranial nerve)

The most frequently involved nerve is the auditory vestibular nerve (also called the eighth cranial nerve), that is, the one that regulates hearing and balance; therefore, acoustic neurinoma is the most common type of Schwannoma.

Neurinomas can occur both in single and multiple forms; in the latter, they can be traced back to multiple neurofibromatosis.

Causes of cranial nerve neurinomas

Although the causes of neurinomas are still unknown, it is not uncommon for this type of tumour to arise simultaneously with a faulty gene on chromosome 22. This means that neurinomas can arise more easily in the presence of other pathologies evaluated as a real risk factor, specifically:

• Von Recklinghausen disease
• Fibromatosis type I
• Neurofibromatosis type II

Symptoms of cranial nerve neurinomas

Cranial nerves are defined as mixed nerves in the sense that they contain both nerve fibres that control motor capacity and the end of the sensory sphere. As a result, a lesion to these nerves causes a series of problems that vary depending on the location of the tumour. 
In Cranial nerve neurinomas, the following symptoms can be found:

• Lack of balance
• Dizziness
• Hearing loss
• Buzzing in the ears and tinnitus
• Reduced tone of voice
• Problem swallowing
• Headaches
• Diplopia
• Facial nerve palsy
• Motor difficulties in the shoulders
• Nausea
• Vomiting
• Tingling
• Hypoesthesia

As previously mentioned, these symptoms appear depending on the location of the tumour.

Diagnosis of cranial nerve neurinomas

The test to get a clear diagnosis of cranial nerve neurinoma is a computed tomography (CT) scan. However, to be sure that the tumour has not extended to the spinal canal or brain too, a nuclear magnetic resonance (MRI) scan is also required.

Diagnosis can also be supplemented by some functional tests such as a vocal and tonal audiometry, aimed at assessing the extent of any lesions caused by the presence of the tumour.

Treatment of cranial nerve neurinomas

Even if most cases of benign tumours can be treated, to remove or reduce the mass is advisable to prevent the tumour from growing, even if slowly, as this may worsen the symptoms. The treatment of cranial nerve neurinomas depends on both location and size of the tumour. 

Given that the neurosurgeon must evaluate the correct treatment according to a series of factors that change from one patient to another, in general terms all neurinomas larger than 3 cm are treated with surgery, while masses with a smaller diameter are treated with radiosurgery.