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Neurofibromatosis type 2 (NF2)

Neurofibromatosis type 2 (NF2)



Overview

Neurofibromatosis type 2 (NF2), also known as NF2-related schwannomatosis, is a rare genetic disorder characterized by noncancerous (benign) tumors, particularly bilateral vestibular schwannomas affecting hearing and balance. Caused by a mutation in the NF2 gene on chromosome 22, it leads to tumors on cranial/spinal nerves (meningiomas, ependymomas). Symptoms typically appear in adolescence or early adulthood, including hearing loss, tinnitus, and balance issues

Symptoms

Primary Symptoms (Vestibular Schwannomas)

Hearing loss: Usually affects both ears and is often the first sign, starting early in life.

Tinnitus: A persistent ringing or buzzing sound in the ears.

Balance problems: Vertigo and instability, causing difficulty with balance or walking. 

Other Neurological and Physical Symptoms

Facial weakness/numbness: Caused by tumors pressing on facial nerves.

Headaches: Frequent headaches.

Muscle weakness/numbness: Weakness or numbness in the arms or legs.

Eye problems: Juvenile cataracts are a common early indicator.

Skin lesions/tumors: Less common than in NF1, but can include skin lesions or subcutaneous nodules (tumors on nerves).

Causes

Gene Mutation: NF2 is caused by a mutation in the NF2 gene, which is responsible for producing the protein merlin (also known as schwannomin). This protein suppresses tumors, and its loss causes cells to grow uncontrolled.

Autosomal Dominant Inheritance: The disorder is inherited in an autosomal dominant fashion, meaning only one copy of the altered gene is needed to inherit the condition.

"Two-Hit" Hypothesis: While inherited, tumor formation requires a "two-hit" mechanism. Individuals are born with one mutated copy of the gene, and a second, somatic mutation occurs later in specific cells, leading to tumor growth.

Inherited vs. De Novo: In about 50% of cases, the mutated gene is inherited from an affected parent. The other 50% of cases are caused by a new, de novo mutation (spontaneous), meaning there is no family history.

Mosaicism: Some individuals have mosaic NF2, meaning the genetic change occurred early in development, causing the mutation to be present only in certain cells

Diagnosis

Bilateral Vestibular Schwannomas: Tumors on both eighth cranial nerves, which is often considered diagnostic for NF2.

Family History: A first-degree relative with NF2 combined with a one-sided (unilateral) vestibular schwannoma or two of the following: meningioma, glioma, schwannoma, or juvenile cataracts.

Additional Tumors: Meningiomas (brain/spine lining), ependymomas (spinal cord), or other schwannomas.

Ocular Findings: Juvenile cataracts (subcapsular lenticular opacities) or other vision-related findings, often the first symptom in children. 

MRI Scan (Brain/Spine): The preferred method for imaging; it can identify tumors before symptoms occur.

Genetic Testing: A blood test analyzing the NF2 gene can confirm the diagnosis, especially if clinical signs are inconclusive or to confirm sporadic cases.

Comprehensive Clinical Exams: Annual hearing tests (audiology), ophthalmology exams, and neurology assessments.

Treatment

Surgery: The main treatment for removing symptomatic, large tumors (vestibular schwannomas and meningiomas).

Stereotactic Radiosurgery (SRS): Used to stop or slow the growth of smaller tumors and in patients who cannot undergo surgery.

Medications (Targeted Therapy): Bevacizumab (Avastin) is a common chemotherapy agent used to shrink tumors and improve hearing, as it targets vascular endothelial growth factor (VEGF). Other drugs like everolimus are also being studied.

Hearing Rehabilitation: Auditory brainstem implants (ABI) or cochlear implants are used to assist with hearing loss caused by tumors.

Observation: Regular annual MRIs are recommended to monitor for changes in tumor size.

Supportive Care: Physical therapy, vestibular rehab, and counseling are used to manage symptoms.

Type of Doctor Department : A neurologist and neurosurgeon specializing in tumors


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