To study the neurophysiological features of Kennedy disease (KD) and to figure out the function of the nervous system.

Subjects were recruited from the outpatient and the ward of Peking University Third Hospital from November 2010 to November 2022. Sixty patients with KD (29 patients with KD alone, 31 KD cases with the complication of diabetes mellitus) and 60 patients with diabetic polyneuropathy (DPN) were included in this study. Electrophysiological tests were performed in all subjects, including electromyogram, nerve conduction study, somaosensory evoked potential (SEP), contact heat evoked potential (CHEP) and triple stimulation technique (TST). Student′s t-tests were conducted to compare differences intra or inter groups of nerve conduction velocity and action potential of nerve conduction study, latency and interphase of SEP, initial peak latency of CHEP and other parameters.

Compared with the normative value, the amplitude of the sensory nerve action potential (SNAP) declined by 30%-80% in KD patients [median nerve (0.7±0.4) μV, ulnar nerve (0.8±0.3) μV, sural nerve (1.8±0.1) μV], the amplitude of the median and ulnar nerves was lower than the sural nerves (t=2.43, P=0.010; t=2.40, P=0.010). The conduction time of peripheral segments of SEP and CHEP was prolonged by 115%-130%, while that of the central segments was prolonged by 104%-115% in SEP. TST_test/TST_control declined by 40%-60% in 17 patients with KD. The amplitude of SNAP declined by 30%-50% in patients with DPN [median nerve (2.9±0.5) μV, ulnar nerve (2.6±0.6) μV, sural nerve (1.6±0.2) μV], the amplitude of the sural nerves was lower than the median and ulnar nerves (t=2.52, P=0.006; t=2.47, P=0.007). The conduction time of peripheral segments of SEP and CHEP was prolonged by 75%-112%, while that of the central segments was normal in both SEP and CHEP in DPN patients. Compared with DPN patients, the upper limb SNAP amplitude was lower in KD patients with the complication of diabetes mellitus [median nerve (0.7±0.3) μV, t=3.18, P=0.001; ulnar nerve (0.8±0.4) μV, t=3.20, P=0.001].

Sensory nerve is involved in patients with KD, including the large fiber and the small one. The central segments was abnormal in the deep sensory pathway, and the pyramid tract may be involved besides the anterior horn cell.

Bulbo-spinal atrophy, X-linked; Electromyography; Neural conduction; Evoked potentials, somatosensory