Huntington disease: early indentification by H reflex testing

This investigation was undertaken to determine the potential use of the H reflex of Hoffmann as a means of early detection of Huntington disease. Three groups of subjects were tested: 9 having Huntington disease, 8 first-generation offspring "at risk" of Huntington disease, and 30 normal persons as controls. The deep peroneal nerve was stimulated by a monopolar needle electrode, and the muscle potentials of the anterior tibialis and the extensor digitorum brevis were recorded with surface elctrodes. The action potentials were examined for the direct M response and the presence or absence of an H reflex response. The H reflex response was found in the anterior tibialis muscle, at least unilaterally if not bilaterally, in eight of nine subjects with Huntington disease and in five of eight persons at risk. The H reflex was present in 1 of 30 controls unilaterally. This significant difference between the patients with Huntington disease and at risk subjects compared to the control group, indicates that H reflex testing may be useful for the early identification of at risk individuals who will ultimately develop Huntington disease. This would be most helpful in family counseling terms, and also may aid in further understanding of this complex diseases.