Masseter reflex latencies and amplitudes are not influenced by supratentorial and cerebellar lesions.

The aim of this study was to investigate possible influences of suprasegmental lesions on the masseter reflex. The masseter reflex was elicited in 54 patients with supratentorial (37 patients) or cerebellar (17 patients) lesions 3-11 days after the acute onset of clinical disease. Patients showing lesions within the pons and midbrain on thin-slice magnetic resonance imaging were excluded from evaluation. The testing procedure included an additional facilitating maneuver (opening and closing the jaw before tapping). Masseter reflex latencies, interside differences, and amplitudes were within the normal range in all patients. Latencies were not different with and without the facilitating maneuver. Amplitudes were significantly higher with the maneuver, but interside differences of amplitudes were unchanged. Masseter reflex abnormality can be taken as a reliable measure of direct involvement of the reflex arc.