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The Odd Syndrome of Bilateral 8th Nerve Tumors

Bilateral 8th cranial nerve tumors, also known as vestibular schwannomas or acoustic neuromas (see figure), are pathognomonic of a fascinating syndrome called central neurofibromatosis or neurofibromatosis type 2 (NF-2). NF-2 is a rare, autosomal-dominant disease with an incidence of 1 in 30,000 live births. The mechanism by which the genetic changes underlying NF-2 produce these tumors of a cranial nerve remains a mystery. Interestingly, two other associations are also sufficient to make a diagnosis of NF-2. These are unilateral VS at early age (< 30 years) plus two other specific lesions (meningioma, schwannoma other than VS, glioma or pre-senile cataract), and unilateral VS at early age with an affected first-degree parent, sibling or child. Patients with NF-2 usually present between the ages of 18 and 24 years with tinnitus, hearing loss and balance difficulties. Symptoms of unilateral tinnitus, asymmetric hearing loss or unresolving vertigo or imbalance warrant a gadolinium-enhanced MRI with a neurotological consultation to rule out brainstem pathology.

NF-2 is caused by inactivation of the NF-2 tumor suppressor gene on chromosome 22 (22q12.2) which encodes the "Merlin" protein. Like a double negative, inactivation of a tumor suppressor gene produces an autosomal-dominant inheritance pattern identical to classical activating mutations.

When a diagnosis of NF-2 is entertained, evaluation should include a complete family history; a detailed head and neck and neurological examination with attention to cranial nerve deficits, and an MRI of the brain with dedicated images to detect bilateral VS, meningiomas and optic gliomas. Spinal MRI with gadolinium should be performed to look for spinal meningiomas or schwannomas, and ophthalmologic evaluation should be obtained in cases with visual loss or with suspicion of juvenile cataracts.

Unilateral VS and NF-2

Defining Tertiary Care for Neurological Diseases

Health care for patients with neurological diseases in the United States occurs across mul­tiple levels, ranging from primary to tertiary care and, less common­ly, quaternary care.

The World Health Organization has defined primary care as the point where first medical contact occurs, and where coordination and continu­ity of medical services is managed. Primary care focuses on a broad range of ser­vices, rather than the diagnosis and treatment of diseases of a specific organ system, and thus primary-care providers (PCPs) have varying levels of comfort in the treatment of neurologi­cal disorders.

Secondary care is provided by specialists, such as general neurologists, who focus on dis­eases affecting a specific organ system, usually upon referral by a PCP. Both primary care and secondary care are provided in an outpatient setting or a general hospital setting.

Tertiary neurological care is provid­ed by subspecialists who treat a subset of conditions that affect the nervous system. Examples include:

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