Purpose: We looked for electrodiagnostic features that raise suspicion of hereditary neuropathy with liability to pressure palsies (HNPP).
Method: A retrospective review of eight cases with confirmed histologic (one case) or chromosome 17 deletion (seven cases) analysis was performed.
Results: Autosomal dominant disease was present in 63% of the patients, 75% being men. Mean age at examination and at first symptom was 27 and 22 years respectively. Five patients have one or more acute nerve palsies, without residual deficit, but one presented sensory symptoms in internal saphena territory. Three patients had others phenotypes: a man presented with four episodes of facial palsy and one woman was asymptomatic; another patient with diabetes mellitus presented an associated chronic sensorimotor polyneuropathy. In agreement with other studies of HNPP we found in most patients a diffuse increase in distal motor latence, contrasting with normal or moderately decreased motor nerve conduction velocity, multiple electrophysiologic entrapment and diffuse reduction in sensory nerve action potential and/or velocity. However, this electrophysiological pattern was incomplete or masked in HNPP with cranial nerves palsies, in asymptomatic form of HNPP or in HNPP associated with polyneuropathy.
Conclusion: These data confirm the clinical phenotypic heterogeneity of the 17p11.2 deletion and highlight the limits of the classic electrophysiological pattern in asymptomatic HNPP or associated with uncommon clinical features.