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.

Blink reflex in migraine and tension-type headache.

The blink reflex was studied in 19 patients with migraine, 10 patients with tension-type headache, and 30 healthy controls. Significantly lower values of R2 and R2' amplitude and size were found in the migraine group, compared with the healthy control group. The differences were independent of the stimulation side (headache or nonheadache) and highly significant (P<0.001). The abnormalities of R2 and R2' amplitude and size were found only during the headache phase of migraine, being normal between migraine attacks. R1 latency and amplitude were normal in all patients. The blink reflex was normal in all the patients with tension-type headache. Subcutaneous injection of sumatriptan in 10 of the 19 migraineurs, during the headache phase, restored R2 and R2' amplitude and size values to normal. Our findings indicate that the brain stem interneuron part of the blink reflex arc may be diffusely suppressed in migraine, only during the headache phase. Furthermore, blink reflex may be an objective laboratory method to monitor the effectiveness of specific drugs proposed for the treatment of migraine.