Abstract
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A 38-year-old man had a 3-month history of bitemporal headaches, horizontal diplopia, and right-sided hearing loss at presentation. Physical examination revealed a right sixth nerve palsy but was otherwise normal. Audiometric evaluation revealed a mild-to-moderate sloping sensorineural hearing loss in the right ear. Findings on the chest x-ray film were negative. MRI of the head revealed an enhancing 3- × 2- × 1-cm mass within the right cerebellopontine angle (CPA) (Fig 1). With a retrolabyrinthine approach, the lesion was found to be based on the posterior fossa dura and adherent to the arachnoid membranes, the surface of the brain stem, and the seventh and eighth cranial nerves at the level of the CPA. The lesion was solid, grayish white, and minimally vascular, and it had a cobblestone texture. Intraoperative frozen sections were interpreted as revealing a granulomatous lesion with no evidence of neoplasm. Therefore only subtotal decompression of the mass was carried out, and additional specimens were sent for panculture. The patient's postoperative course was unremarkable.
Permanent sections revealed nonnecrotizing and necrotizing granulomas with varying degrees of surrounding fibrosis (Fig 2). Special stains for bacteria, including acid-fast bacilli and fungi, were negative. The patient's serum angiotensin-converting enzyme level was elevated at 89 units/L (normal range 8 to 52 units/L).
In view of all the above data, the diagnosis of neurosarcoidosis was made.
DISCUSSION
Sarcoidosis is a chronic, multisystemic granulomatous disease whose cause is multifactorial. The prevalence of sarcoidosis is 10 to 40 per 100,000 persons in the United States, with the black/white ratio ranging from 10:1 to 17:1. 1 Isolated neurologic manifestations occur at an estimated frequency of 5% to 6% of all cases and may involve any component of the nervous system. Cranial nerve palsies and meningitis are the most common manifestations, with seventh nerve palsy occurring in 20% to 50% of patients with neurosarcoidosis. 1 The diagnosis of isolated neurosarcoidosis is challenging and requires tissue biopsy. Histopathology traditionally has been reported as multiple noncaseating granulomas surrounded by a mixed inflammatory infiltrate. However, necrotizing granulomas are being reported as features of sarcoid lesions with increasing frequency, further complicating the diagnosis. 2 Angiotensin-converting enzyme, which is variably reported as useful in the diagnosis of sarcoidosis, despite its less-than-optimal specificity and sensitivity, is elevated in approximately two thirds of patients. 3 Neither CT nor MRI is specific for neurosarcoidosis, but they may be helpful for initial evaluation and localization of the disease and for follow-up. 4 The clinical course of neurosarcoidosis is difficult to assess; in some patients it may be chronic, relapsing, or progressive, eventually leading to death despite the treatment 5 Although most authors recommend early diagnosis and early treatment with steroids, the role of therapy is not yet entirely clear and even less so for neurosarcoidosis.
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T1-weighted MRI scan of the head with gadolinium contrast. An enhancing 3- × 2- × 1-cm mass is revealed within the right CPA.
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Photomicrograph of hematoxylin and eosin-stained section of specimen demonstrating 2 granulomas with necrotizing centers (right and left). One nonnecrotizing granuloma is present (upper middle). (Bar = 100 μm.)
In conclusion, in rare cases, sarcoidosis may present as a lesion of the CPA and should be considered with an atypical presentation at surgery and based on results of intraoperative biopsy. Treatment is medical, and aggressive surgery should be avoided.