Jacquin-Piques A, Thauvin-Robinet C, Latour P, Beauvais K, Lemesle-Martin M, Soichot P and Giroud M
Introduction: The diagnosis of Hereditary Neuropathy with Liability to Pressure Palsy (HNPP) is frequently
missed or delayed because of its clinical and electrophysiological heterogeneity. Nonetheless, electrophysiological
criteria were published 15 years ago. Our aim was to highlight the Terminal Latency Index (TLI) disorders by
describing the electrophysiological characteristics in patients with HNPP.
Methods: All the consecutive patients with the clinical and genetic diagnosis of HNPP due to the 1.5Mb deletion
of PMP22 or to others mutation or deletion were included. Motor and sensory conductions were studied using
surface electrodes placed near the median, ulnar, fibular, tibial, superficial fibular and sural nerves in accordance
with standard techniques. The results were compared with our own laboratory standards.
Results: All of the 22 included patients had low TLI in the median, ulnar and peroneal nerves, whereas 6% of the
patients had low tibial TLI. The other frequent electrophysiological characteristics were increased distal motor
latency and low sensory conduction velocity, especially of the median nerve.
Conclusions: TLI abnormalities are almost constant in HNPP, which is a great argument to define HNPP as a
distally accentuated myelinopathy. TLI disorders should be added to HNPP electrophysiological criteria to improve
their diagnosis accuracy.