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Neuroradiology Case of the Week

Case 119

Clinical Presentation: A 43-year-old African American female presented with right-sided dystonia, left-eye ptosis, headache, and seizures, progressive over a 2 year period.

Radiological Findings:
  CT: There is diffuse hyperattenuation of left thalamus in comparison to the right (Fig.1). No other intracranial abnormalities are noted.
  MRI: Bilateral thalamic lesions are identified, left greater than right, which are hyperintense on T2 and FLAIR sequences (Figs. 2A&B) and hypointense on diffusion weighted and T1 imaging (Figs. 3A&B). These lesions enhance after administration of intravenous Gadolinium. Evaluation of the orbits was unremarkable.

Discussion: Sarcoidosis is a multi-system disorder of unknown etiology characterized by noncaseating granulomas. The incidence varies geographically. In the US, it is more common in rural areas and in the southeast. The prevalence in New York is 30 per 100,000. Females are more likely to be affected than males by a ratio of 2:1, with African American women being affected 10 to 17 times more frequently than Caucasian women. The incidence is greatest in the 3rd and 4th decades of life. Neurologic involvement occurs in approximately 5-10% of sarcoidosis patients usually as part of the systemic manifestation. Primary neurologic involvement alone is rare.
     The clinical presentation of neurosarcoidosis is widely variable, mimicking various disease processes ranging from malignancy to multiple sclerosis. Brain involvement can present as leptomeningitis with cranial nerve deficits, mass lesions in the hypothalamus, atrophy, cranial neuropathy, hypothalamic/pituitary dysfunction, or hydrocephalus. The disease has a predilection to spread from the leptomeninges to the Virchow-Robin spaces leading to invasion and thrombosis of associated blood vessels resulting in granulomatous angitis. Aseptic meningitis and seizures are other clinical manifestations.
     Neurosarcoidosis is usually a diagnosis of exclusion. However, the radiographic features are suggestive. There are classically two radiographic patterns described for neurosarcoidosis: (1) Chronic basilar leptomeningitis with involvement of the hypothalamus, pituitary stalk, optic nerve, and chiasm; and (2) Parenchymal sarcoid nodules, which occasionally calcify.
     Both CT and MRI are helpful in disease evaluation, however MRI is the modality of choice. The use of gadolinium improves sensitivity of detecting leptomeningeal lesions. FLAIR techniques are valuable in detecting ventricular abnormalities secondary to CSF suppression. Additional MR findings include: white matter and periventricular hyperintensity mimicking multiple sclerosis, hydrocephalus, atrophy, periventricular enhancement, chiasmal edema, extra-axial masses, and parenchymal or cord masses.
     Tissue biopsy from neural lesions is typically required for definitive diagnosis and to exclude other cerebral pathologies. Corticosteroids are the mainstay of CNS sarcoidosis treatment, alleviating symptoms and potentially slowing disease progression; however there is no known cure. Aggressive disease or frequent recurrence may require other immunosuppressive drugs such as methotrexate or cyclophosphamide. Approximately two thirds of patients with neurosarcoidosis have a self-limited illness, while the remainder have a chronic remitting relapsing course. The prognosis of chronic neurosarcoidosis is poor.

References:

1. Lexa FJ, Grossman RI. MR of sarcoidosis in the head and spine: spectrum of manifestations and radiographic response to steroid therapy. AJNR 1994; 15:973-982. [Medline]
2. Fels C, Riegel A, Javaheripour-Otto K, Obenauer S. Neurosarcoidosis findings in MRI. Journal of Clinical Imaging 2004; 28:166-169. [Medline]
3. Osborne AG, et al. Diagnostic Imaging: Brain. Amirsys Inc: Altona (2004), 1st ed., II 4:52-55.