The diagnostic value of the palmo-mental reflex.

Abstract

The clinical value of the palmo-mental reflex was examined by neurophysiological investigation of 18 patients and clinical examination of 200 normal controls and 141 patients with suprasegmentary cerebral lesions. The importance of using a constant, slightly painful stimulus is stressed. Stimulated in this way, the reflex was found in 8 per cent of normals as a small, quick, and often capricious contraction in the homolateral mentalis muscle. The reflex habituated after 4 stimulations and was only elicitable from the thenar region. In patients with suprasegmentary lesions, the reflex was present in 74 per cent. In 11 per cent the reflex had the same qualities as in the normal controls. In 63 per cent the reflex was characterized by a strong contraction in the chin muscles without habituation and with a reflexogenic area extending beyond the thenar region and in some cases including nearly the total cutaneous surface. This pathological reflex was significantly correlated to the presence of pyramidal and extrapyramidal signs on the homolateral side. A pathological palmo-mental reflex may, however, be the only sign of a suprasegmentary lesion and thus have the same alerting significance for the clinical neurologist as an extensor plantar response.