Bilateral Deafness and Skin Lesions in a 23-Year-Old Man

Sumaira Nabi, MBBS; Shahzad Ahmed, MBBS; Mazhar Badshah, MBBS

Disclosures

October 12, 2016

Discussion

NF2 was diagnosed on the basis of bilateral vestibular schwannomas. The typical subcutaneous lesions along with a positive family history further supported the diagnosis. The patient was given intravenous steroids and mannitol and was referred to the neurosurgery department for tumor resection.

Neurofibromatosis is a set of three distinct genetic syndromes: NF1, also known as von Recklinghausen disease; NF2; and schwannomatosis.[1] These are characterized by a variable number of cutaneous lesions coupled with various tumors of the central and peripheral nervous system.

NF2 has an autosomal dominant mode of inheritance, with variable expressivity and incomplete penetrance.[2] The disease was first described by Wishart[3] in 1822 and was further elaborated by von Recklinghausen and Cushing.[4] Affected individuals have multiple tumors of the nervous system. NF2 is associated with a paucity of skin lesions, unlike NF1. Bilateral vestibular schwannomas, intracranial and spinal meningiomas, and spine tumors are the most frequent neoplasms seen in these patients.[5,6]

The underlying genetic defect is mutation of the NF2 gene, which is located on chromosome 22; the NF2 gene normally produces merlin, a tumor suppressor protein.[7,8] The mutation is present in over 93% families affected by the syndrome. The estimated incidence ranges from 1 in 25,000 to 1 in 37,000.[9,10]

The age of onset varies; however, affected individuals usually present around age 20 years.[11] NF2 is a multisystem disorder, and the clinical features involve the central and peripheral nervous system and eyes, with a relative lack of involvement of skin.

Neurologic manifestations are secondary to various types of tumors. Vestibular schwannomas are benign but lead to progressive sensorineural deafness, vertigo, tinnitus, and balance dysfunction in different combinations and cause significant morbidity.[12,13] In untreated cases, these can extend and cause brainstem compression and hydrocephalus. Bilateral vestibular schwannomas that arise from the vestibular branch of the eighth cranial nerve are the diagnostic hallmark of NF2. Other cranial nerves are also involved, commonly cranial nerves V and VII.

Intracranial meningiomas, ependymomas, and gliomas lead to focal neurologic signs, headache, visual impairment, and seizures.[14] Meningiomas may be single or multiple and arise much earlier than sporadic ones.[15] These tend to be more aggressive, with higher chances of anaplasia. Cranial and peripheral nerve schwannomas are also seen.[16] Those ramifying from the dorsal root tend to assume a characteristic "dumbbell" shape. Extra- and intramedullary spinal tumors present with paresthesias, limb weakness, and sphincter dysfunction. Neuropathy can present as mononeuropathy that involves a single nerve, or peripheral polyneuropathy with loss of reflexes and muscle wasting.[17]

Ophthalmologic involvement is seen in the form of cataracts, posterior subcapsular lenticular opacities, optic nerve meningioma, and retinal hamartomas.[10] Cataracts are the most frequently encountered ocular manifestation. All of these can lead to visual dysfunction.

Cutaneous manifestations are less frequent and subtle in NF2 compared with NF1.[13,18,19] Subcutaneous neurofibromas are usually seen in 50%-70% of patients. Intracutaneous schwannomas are occasionally seen. Some patients may also have pigmented plaques often with excess hair. Café au lait spots are rarely seen. Axillary or inguinal freckling, Lisch nodules, and malignant transformation of tumors very rarely occur in NF2, unlike in NF1, which is associated with florid skin lesions.

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