Blink reflex in primary lateral sclerosis.

OBJECTIVE To investigate the underlying pathophysiology of primary lateral sclerosis (PLS) regarding possible changes in blink reflex (BR) circuit. METHODS BR was studied in 10 patients in whom diagnosis of PLS was established by comparing them to two control groups: ten patients with amyotrophic lateral sclerosis (ALS) and 30 healthy volunteers. All patients were followed up annually for a 5 year period. A typical evoked potential study of the BR was employed. RESULTS Significantly lower values of R(2) and R(2)' amplitude were found both in the PLS and ALS groups compared with the healthy control group. All these differences were highly significant (p<0.001). R(1) amplitude and latency, as well as R(2) and R(2)' latencies, were normal in all patients. Annually recorded follow up data revealed no significant changes in BR values for PLS patients. In contrast, for ALS patients, BR progressively disappeared following clinical impairment. CONCLUSIONS The study suggests that BR is abnormal in PLS. It also adds some clues regarding PLS pathophysiology and can be helpful as a marker of ALS progression.