Clinical and electrophysiological studies in vincristine induced neuropathy

Eighteen patients of lymphoma, treated with vincristine (VCR) were assessed clinically and electrophysiologically before and for 3 months after therapy. The earliest evidence of neuropathy was impaired ankle jerk (around 2 weeks) and the earliest symptom was paraesthesia (by 4-5 weeks). At the end of the study, all the patients had absent ankle jerks and 75% had sensory symptoms and/or signs, the most frequent being impaired vibration sensation (62.5%). Motor abnormalities were much less common (18.7%) and constipation (62.5%) was the only autonomic manifestation. Concentric needle electromyography showed evidence of denervation (46.7%), especially in the small muscles of hand. Conduction studies showed prolonged mean distal latencies, decreased mean amplitudes of compound muscle action potentials, with almost unchanged conduction velocities. However, no conduction block was noted and F-wave studies were normal. During early weeks, in spite of impaired absent ankle jerks, H reflex was elicitable in the majority. However, later 56.2% had absent H reflex. The present study concludes that vincristine produces a distal symmetrical sensorimotor neuropathy, predominantly involving the large diameter fibers in the early stages. Electrophysiological studies characterize it as a distal axonopathy. However it is dependent on the dose of VCR and the duration of therapy: though in the usual doses it does produce neuropathy, it is rarely disabling in the early months.