What is the pathophysiology of neuropathy in 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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Answer

Neuropathy occurs via 2 mechanisms. The tissue can be involved directly: in muscle, a slow and indolent myositis results, and in the nerve, a neuropathy results. Granulomas in the nerve are seen most often in the perineurium and the epineurium, with local effects leading to axonal damage.

Some studies reveal sparing of the endoneurium, while others show prominent infiltration of the endoneurium, suggesting that all 3 nerve layers may be involved. Occasionally, myelin loss is prominent, with appearance of myelin ovoids. Whether the latter are caused by compression from the granulomas, by regional toxic effects, or by specific targeting of the myelin sheath is unclear.

Tajima suggested a predominance of helper T cells in the sarcoid granulomas. Inflammation of the vasa nervorum or the arterioles to the muscles can result in ischemic injury or severe vasculitic neuropathy. A significantly higher prevalence of the HLA allele DQB1*0602 has been reported in sarcoidosis patients with small fiber neuropathy, and this allele has been associated with a severe course of disease. [2]

Peripheral nerve injury from these mechanisms may result in a diffuse polyneuropathy, mononeuritis multiplex, focal mononeuropathies, or polyradiculopathy from involvement of spinal root sheaths. The spinal root sheaths are an extension of the pachymeninges, a tissue for which sarcoid granulomas have a particular predilection.


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