Comprehensive Neuropathy Characterization Protocol

Nerve conduction and sympathetic skin response (SSR) studies were performed only at baseline to characterise the neuropathy, on a Medtronic Keypoint electromyogram system (Medtronic, Minneapolis, MN, USA) (3 (link)). Antidromic sensory action potentials for the sural and superficial peroneal nerves and orthodromic sensory action potentials for the medial and lateral plantar, median, and ulnar nerves on both sides were recorded. For the sural, superficial peroneal, medial plantar, and ulnar nerves, action potentials of <5 μV amplitude were considered abnormal, while for the lateral plantar and median nerves, amplitudes of <2.5 and <10 μV were considered abnormal, respectively. Sensory conduction velocities of <50 and 40 m/s were considered abnormal for upper and lower limb nerves, respectively. The nerve compound action potentials were recorded using standard described techniques, and the issue of skin resistance was mitigated by: i) carrying out pre-recording skin preparation identically in all subjects, and ii) by using the identical type of recording electrodes in all subjects. These were also the methods employed while collecting normative data from our control subjects. SSRs were recorded from both palms and both soles in response to a sudden unexpected tactile stimulus and a sudden inspiratory gasp. An absent SSR was considered abnormal.