Heterogeneous Presentation of Hereditary Neuropathy With Liability to Pressure Palsies: Clinical and Electrodiagnostic Findings in Three Patients.

Abstract

Hereditary neuropathy with liability to pressure palsies (HNPP) is characterized by the acute onset of focal sensory and/or motor deficits when the peripheral nerves are stressed by a mechanical force.Caused by a deletion in the PMP22 gene, this condition is often underdiagnosed or misdiagnosed due to the heterogeneity of clinical and electrophysiological presentation.This case series describes the clinical and electrodiagnostic (EDX) features of three patients presenting with clinically heterogenous phenotypes of HNPP.A retrospective analysis of patients referred to our facility for EDX studies identified three patients with genetically confirmed HNPP.The clinical presentations were unique in each patient, and the referring physicians did not consider HNPP in their differential diagnosis.The patients underwent comprehensive clinical and EDX evaluations, which led to the diagnosis of HNPP with subsequent confirmation by genetic studies.The reasons for referral for EDX studies were foot drop in one patient, carpal tunnel syndrome (CTS) in another, and wrist drop in the third patient.Patient #1 was initially diagnosed with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) at another facility and developed a foot drop while recovering from a cervical discectomy and fusion.A positive family history of neuropathy led to the suspicion of hereditary neuropathy, and further studies confirmed a PMP22 gene deletion.Patient #2 gave a typical history suggestive of CTS.EDX studies showed focal slowing of conduction at potential areas of entrapment/compression.A history of foot drop in the patient and many other family members led to the confirmation of HNPP by genetic testing.US studies aided in confirming CTS by documenting a significant drop in the diameter of the median nerve within the carpal tunnel.The third patient developed radial nerve palsy after using axillary crutches.The possibility of HNPP was considered due to the pattern of nerve conduction slowing and a family history of foot drop.Physicians should be cognizant of the varied presentation of HNPP and the potential for misdiagnosis and underdiagnosis of this condition.In each case, elicitation of a detailed family history led to the suspicion of HNPP.A high index of suspicion is necessary for patients with multiple episodes of compressive neuropathies, mono/multi mononeuropathies, unexplained polyneuropathy, and a family history of neuropathy.The EDX pattern in patients presenting with acute focal neuropathies, consisting of a global increase in distal motor latencies, moderately decreased motor nerve conduction velocities, and focal slowing of conduction in potential sites of entrapment, should trigger genetic testing for HNPP.