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Role of fluorodeoxyglucose positron emission tomography in the diagnosis of neurosarcoidosis

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Abstract

A 45-year-old man developed seizures and myelopathy. MRI showed bitemporal and cervical spinal cord hyperintense lesions on T2-weighted and FLAIR images that contrast-enhanced. Initial evaluation for sarcoidosis was negative, including serum angiotensin converting enzyme (ACE) and chest X-ray. Whole body fluorodeoxyglucose positron emission tomography (FDG-PET) revealed multiple hypermetabolic hilar and mediastinal foci and spinal cord hypermetabolism at the site of MRI abnormality. Temporal lobe MRI lesions were hypometabolic. Mediastinal lymph node biopsy was consistent with sarcoidosis. The brain, spinal cord, and chest metabolic abnormalities together with the clinical presentation were interpreted as being most consistent with sarcoidosis. FDG-PET helped target the site of biopsy that subsequently confirmed the diagnosis histologically. In patients with perplexing neurologic presentations, whole body FDG-PET can help secure a timely and minimally invasive diagnosis of neurosarcoidosis.

Introduction

Sarcoidosis is an idiopathic systemic granulomatous disease. Central nervous system involvement is reported in approximately 5% cases and usually occurs early in the disease [1]. Neurosarcoidosis includes a wide variety of clinical presentations such as cranial neuropathy, aseptic meningitis, neuroendocrine dysfunction and hydrocephalus [1], [2]. Hilar adenopathy on chest X-ray, abnormal gallium scan, and elevated serum and cerebrospinal fluid (CSF) angiotensin converting enzyme (ACE) levels in the presence of neurologic involvement are suggestive of neurosarcoidosis. However, neurosarcoidosis may occur with a normal chest X-ray and normal ACE levels, posing a diagnostic challenge. Fluorodeoxyglucose positron emission tomography (FDG-PET) may be useful in the diagnosis of systemic sarcoidosis [3], [4], [5], [6], [7], [8], [9]. We report a young man with bilateral temporal and cervical cord lesions with a normal chest X-ray and normal serum ACE. Whole body FDG-PET was useful in making the diagnosis of sarcoidosis leading to biopsy confirmation. To our knowledge, this is the first reported case of neurosarcoidosis demonstrating the diagnostic utility of FDG-PET.

Section snippets

Case report

A 45-year-old man noted a strange chemical smell several times a day and numbness and tightness around his chest during the previous 4 weeks. General physical examination was unremarkable. Neurologic examination showed a T-1 sensory level. Interictal EEG revealed left temporal spike and wave discharges. Carbamazepine was prescribed for probable olfactory seizures. Erythrocyte sedimentation rate, complete blood count, chemistry profile and serum ACE were normal. Cerebrospinal fluid analysis

Discussion

Neurosarcoidosis may be difficult to diagnose because of its wide spectrum of clinical manifestations. A range of abnormalities in neurosarcoidosis may be detected on craniospinal MRI. Reported presentations include leptomeningitis, meningoencephalitis, periventricular white matter disease, hydrocephalus, diffuse atrophy, cranial neuritis, optic chiasm lesions, periaqeductal lesions, arteritis, myelopathy, and craniospinal mass lesions [1], [2], [10], [11], [12]. Involvement of bilateral

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