What is the role of biopsy in the workup of neurosarcoidosis?

Updated: Nov 13, 2018
  • Author: Gabriel Bucurescu, MD, MS; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
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Biopsy of an enlarged lymph node or an active area on gallium scan may reveal noncaseating granulomas, which suggest sarcoidosis as the pathologic etiology. Biopsy of the sural nerve may reveal fiber loss with a combination of axonal injury and demyelination.

Biopsies show granulomas surrounded by normal muscle in 50-80% of asymptomatic patients. A case report of neurosarcoidosis (sarcoid brainstem encephalitis) demonstrated nemaline rods in every muscle examined. [31]

Because the granulomas can be scarce, a large sample should be taken. Granulomas are not specific for neurosarcoidosis and can be seen in patients with tuberculosis, fungal infections, collagen vascular disorders, or carcinoma.

In symptomatic patients, nodules are less frequent. In some cases, noncaseous granulomatous myositis or chronic myopathic changes can be seen. Peripheral nerve biopsies may show segmental demyelination, degenerating nerve roots with inflammatory cells, axonal degeneration, and mechanical destruction of nerves by granulomas.

Brain biopsy may be required in selected patients with isolated brain involvement. In other cases, the patient's history, MRI scans, and chest radiograph may be sufficient for arriving at the correct diagnosis. Blood vessel biopsies of both arteries and veins can show involvement of the vessel wall, most frequently in the perforating arteries.

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