NQ-077: (C) Hereditary motor sensory neuropathy (HMSN I), also known as Charcot-Marie-Tooth (CMT 1) neuropathy

Diagnosis: Hereditary motor sensory neuropathy (HMSN I), also known as Charcot-Marie-Tooth (CMT 1) neuropathy

Pathology of the case: This is a cross section of the sural nerve at medium magnification. The salient pathologic feature is all fibers are cuffed by multilayered whorls of Schwann cell. The formation of these "onion bulbs" or hypertrophic changes is a result of repeated episodes of demyelination and remyelination. The onion bulbs and their associated collagen fiber greatly increase the volume of the nerve on macroscopic examination and would also make the peripheral nerve palpable. Onion bulbs are seen in chronic demyelinating diseases that affect primarily the Schwann cell or myelin sheath. They are typically seen but not pathognomonic in Hereditary motor sensory neuropathy (HMSN I), also known as Charcot-Marie-Tooth (CMT 1) neuropathy and other conditions such as Refsum's disease, and neuropathy associated with paraproteinaemia.

 

Perinerioma: are characterized by concentric whorls. However, those being shown here are too regular to be neoplastic.

 

Meningioma: The same is true for meningioma. In addition, meningiomas that has a strong tendency to form meningothelial whorls tend to have psammoma body at the center of the whorls and there is no psammoma body here.

 

Amyotrophic lateral sclerosis (ALS): This is characterized by axonal degeneration in motor nerve second to the loss of motor neurons in the spinal cord. Nerve biopsies are very rarely taken from a motor nerve but usually from the sural nerve for obvious reasons. In the case of motor nerve from a case of ALS, there will be extreme axonal degeneration.