Phenotypes and Electrophysiological Features of Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) According to Physical Activities: A Single Military Hospital Experience

Background: HNPP typically presents as focal nerve palsy with complete or near-complete recovery, often involving upper extremity weakness due to brachial plexus involvement during military service. This study aimed to analyze the clinical features and neurophysiological examination results of HNPP occurring in the Korean military to determine whether the clinical presentations and electrodiagnostic patterns differ according to the trigger activity and to obtain useful information for the early diagnosis of HNPP. Methods: Sixty-four patients with HNPP were included over an 11-year period, and medical records and electrophysiological tests were analyzed. Results: Thirty-five patients presented with isolated compressive neuropathy and 18 patients presented with brachial plexopathy. Analysis of phenotypes according to triggering activity revealed that 13 of 16 patients with symptom onset after military training showed a type of isolated compressive neuropathy and that 11 of 20 patients with symptom onset after push-ups or after backpack carriages showed a type of brachial plexopathy. Six patients experienced symptoms following sleep, while four reported symptoms after trauma. Atypical features were observed in 11 cases (17.2%), including 3 lower lumbosacral radiculopathy-like presentation. Abnormal findings were observed in 91.2% of distal latency of the peroneal motor nerve. Conclusions: The phenotype varied according to the physical activity that triggered HNPP onset in soldiers. These results are expected to help in the early diagnosis of HNPP in soldiers or those who develop it after physical activity.