Somatosensory pathway dysfunction in patients with amyotrophic lateral sclerosis in a completely locked-in state

To investigate somatosensory pathway function in patients with amyotrophic lateral sclerosis (ALS) dependent on invasive ventilation and in a completely locked-in state (CLIS).

We examined median nerve somatosensory evoked potentials (SEPs) in 17 ALS patients in a CLIS, including 11 patients with sporadic ALS, one with familial ALS with genes not examined, four with a Cu/Zn superoxide-dismutase-1 (SOD1) gene variant (Val118Leu, Gly93Ser, Cys146Arg), and one with a fused-in-sarcoma gene variant (P525L). We evaluated N9, N13, N20 and P25, and central conduction time (CCT); the data were compared with those of 73 healthy controls.

N20 and N13 were abolished in 12 and 10 patients, and their latencies was prolonged in four and three patients, respectively. The CCT was prolonged in five patients with measurable N13 and N20. Two patients with SOD1 gene mutations had absent or slightly visible N9. Compared to the CCT and latencies and amplitudes of N13 and N20 in the controls, those in the patient cohort were significantly abnormal.

The central somatosensory pathway is severely involved in patients with ALS in a CLIS.

Our findings suggest that median nerve SEP cannot be utilized for communication in patients with ALS in a CLIS.