EMG in Tomaculous Neuropathy

Source: Andersson PB, et al. Electrodiagnostic features of hereditary neuropathy with liability to pressure palsies. Neurology 2000;54:40-44.

Nine patients with hereditary neuropathy with liability to pressure palsies (HNPP, tomaculous neuropathy) were electrodiagnostically compared to 22 patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and 49 patients with diabetic polyneuropathy to determine which nerve conduction features should raise suspicion of HNPP and distinguish it from the latter, with which it is most likely to be confused. Sensory nerve conduction velocities (NCVs) were slowed in 93% of HNPP nerves (27 of 29 tested) with prolonged distal F wave and motor latencies in 90% (18 of 21) and 78% (25 of 32), respectively. Motor NCVs were slowed in only 31% of nerves studied (10 of 32), less frequently than either CIDP (69%) or diabetes (40%). By analysis of variance, mean distal latency prolongation and sensory NCV slowing in HNPP were significant compared to CIDP and diabetic polyneuropathy, and indicate that an underlying, distally predominant, demyelinating polyneuropathy is present in HNPP, quite apart from the focal entrapment neuropathies for which it is renowned. —mr


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