Neurofibromatosis Type 2 (NF2) – Causes and Treatment
Neurofibromatosis type 2 (NF2) is a rare genetic disorder that causes benign tumors to grow on the nervous system, most commonly on the hearing nerves.
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Neurofibromatosis type 2 (NF2) is a rare genetic disorder that causes benign tumors to grow on the nervous system, most commonly on the hearing nerves.
What is Neurofibromatosis Type 2?
Neurofibromatosis type 2 (NF2) is a rare, inherited condition caused by mutations in the NF2 gene located on chromosome 22. This gene encodes a protein called Merlin (also known as Schwannomin), which acts as a tumor suppressor. When Merlin is absent or non-functional, benign tumors -- particularly schwannomas and meningiomas -- can develop along the nervous system. NF2 affects approximately 1 in 25,000 to 33,000 people worldwide, making it significantly rarer than neurofibromatosis type 1.
Causes and Genetics
NF2 is caused by a mutation in the NF2 tumor suppressor gene on chromosome 22q12. The condition follows an autosomal dominant inheritance pattern, meaning that only one altered copy of the gene is sufficient to cause the disease. Approximately 50% of cases are inherited, while the remaining 50% arise from de novo mutations -- new mutations with no family history.
- Autosomal dominant inheritance pattern
- Mutation in the NF2 gene (chromosome 22q12)
- Loss of tumor-suppressing function of Merlin
- Approximately 50% of cases are de novo mutations
Symptoms
The hallmark feature of NF2 is the development of bilateral vestibular schwannomas (formerly called acoustic neuromas) -- benign tumors on both auditory nerves (vestibulocochlear nerve). These typically cause:
- Progressive hearing loss, often in both ears
- Tinnitus (ringing in the ears)
- Balance problems and dizziness
- Facial weakness or paralysis (if the facial nerve is involved)
Other common manifestations include:
- Meningiomas (tumors of the membranes surrounding the brain and spinal cord)
- Ependymomas of the spinal cord
- Peripheral schwannomas along other nerves
- Cataracts (lens opacities, often juvenile onset)
- Skin changes (less prominent than in NF1)
Diagnosis
Diagnosis of NF2 is based on clinical criteria together with imaging and genetic testing.
Clinical Diagnostic Criteria (Manchester Criteria)
- Bilateral vestibular schwannomas, or
- First-degree relative with NF2 and a unilateral vestibular schwannoma or two of the following: meningioma, schwannoma, glioma, neurofibroma, posterior subcapsular cataract
Diagnostic Procedures
- MRI (Magnetic Resonance Imaging) of the brain and spine with contrast -- the gold standard for tumor detection
- Audiometry to assess hearing function
- Genetic testing to identify NF2 gene mutations
- Ophthalmological examination (slit lamp) to detect cataracts
Treatment
There is currently no cure for NF2. Management is symptom-oriented and tumor-focused, requiring a multidisciplinary approach.
Surgical Treatment
Surgical removal of schwannomas and meningiomas is a primary treatment option, especially when tumors are growing or causing neurological deficits. In the case of vestibular schwannomas, the goal is to preserve hearing and facial nerve function as much as possible.
Radiation Therapy
Stereotactic radiosurgery (e.g., Gamma Knife) can be used to control tumor growth without open surgery and is particularly suitable for smaller tumors.
Medical Therapy
Bevacizumab, a VEGF inhibitor, has been used in some NF2 patients and may slow the growth of vestibular schwannomas while improving hearing function. Its use is considered on an individual basis and within the context of clinical trials.
Hearing Rehabilitation
- Hearing aids or cochlear implants for partial hearing loss
- Auditory brainstem implants (ABI) for patients with complete hearing loss
Regular Monitoring
Due to the progressive nature of NF2, regular MRI surveillance, audiological follow-up, and neurological monitoring are essential. Patients should ideally be managed at specialized NF2 centers with multidisciplinary expertise.
Prognosis
The prognosis of NF2 varies widely depending on the number, location, and growth rate of tumors. Many patients develop significant hearing loss over time. With appropriate medical care, life expectancy is not substantially reduced, but neurological complications can considerably impact quality of life.
References
- Evans DG. - Neurofibromatosis type 2. In: GeneReviews, NCBI Bookshelf, National Library of Medicine (2022).
- Plotkin SR et al. - Updated diagnostic criteria and nomenclature for neurofibromatosis type 2 and schwannomatosis. Genetics in Medicine, 2022; 24(9): 1967-1977.
- World Health Organization (WHO) - Classification of Tumours of the Central Nervous System, 5th Edition (2021).
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