Respiratory disorders in type-1 hereditary motor and sensory neuropathy

Type-1 hereditary motor and sensory neuropathy (HMSN I) is a slowly progressive disease resulting in distal muscle weakness with atrophy, and in sensory disturbance. Restrictive lung disease and respiratory muscle failure, common in many advanced neuromuscular disorders, is not a predominant feature of HMSN-I. Recently, there have been several reports of respiratory dysfunction in patients with HMSN I, complicated by diaphragmatic weakness. In five patients with HMSN I (3 men and 2 women, mean age 55.4 yrs), we measured spirometric variables, maximal inspiratory pressure, and maximal expiratory pressure, in both sitting and supine positions. We also studied phrenic nerve conduction by cutaneous stimulation at the posterior border of the sternocleidomastoid muscle. Four of five patients had low maximal inspiratory pressure and abnormally long phrenic nerve latency. Two patients showed evidence of a restrictive lung disorder and daytime alveolar hypoventilation. All-night polysomnography in those two patients revealed periodic decreases in arterial blood oxygen saturation, and episodes of central apnea. We conclude that diaphragmatic dysfunction is not rare in HMSN I, and that maximal inspiratory pressure and phrenic nerve conduction may be useful in the early detection of phrenic nerve involvement.