Perineuritis

Clinical History:

This 60-year-old patient presented with clinical and electrophysiologic features of mononeuritis multiplex. Their past medical history was significant for rheumatoid arthritis. Laboratory studies showed elevated ESR, negative/normal cANCA, pANCA, MPO and PR3.

What term would you use to describe the changes in this patient’s nerve biopsy?

A. Demyelinating

B. Perineuritis

C. Perineurioma

D. Traumatic neuroma

Answer:

Perineuritis (perineurium – inflammation)

The nerve biopsy shows patchy thickening of the perineurium with associated inflammatory cells (best demonstrated with CD3 immunostain) and neovascularization. Associated significant loss of myelinated axons is present (i.e. axonopathic changes). There is also some inflammation around epineurial small blood vessels, but no infiltration of blood vessel walls or fibrinoid necrosis to enable a definitive pathologic diagnosis of vasculitis.

Perineuritis can present as a mononeuritis multiplex and may be seen in a variety of settings, including partially sampled vasculitis, connective tissue disorders and infection. As the vascular supply of nerves must traverse the perineurium, axonal injury is felt to be due to “vascular strangulation” of the endoneurial compartment. Please see references below.

Reference(s) / Additional Reading:

• Sorenson EJ, Sima AA, Blaivas M, Sawchuk K, Wald JJ. Clinical features of perineuritis. Muscle Nerve. 1997;20(9):1153-1157. doi:10.1002/(sici)1097-4598(199709)20:9<1153::aid-mus10>3.0.co;2-u
• Collins MP, Hadden RDM, Shahnoor N. Primary perineuritis, a rare but treatable neuropathy: Review of perineurial anatomy, clinicopathological features, and differential diagnosis. Muscle Nerve. 2023;68(5):696-713. doi:10.1002/mus.27949