Physiological effects of selective tibial neurotomy on lower limb spasticity

OBJECTIVES To assess by electrophysiology the effect of tibial selective neurotomy on muscle imbalance of the spastic ankle. METHOD The amplitudes of the H reflexes, M responses (muscle contractions recorded after stimulation of the tibial nerve), and Hmax:Mmax ratio were recorded in 12 patients with chronic lower limb spasticity, before and one month after tibial selective neurotomy. Recordings were done on medial and lateral gastrocnemius and soleus muscles. Clinical evaluation was done with both global (Held’s score) and analytical tests (step measurements, gait velocity, and ankle angulation during active and passive movements). RESULTS After neurotomy, gait improved in all patients. Held ’s score of spasticity was better in all patients. Active dorsiflexion of the ankle was unchanged in three patients, but the others improved by 5° to 12°. Hmax, Mmax, and Hmax:Mmax ratios were lower. The Hmax on the gastrocnemius muscle, clinical strength, Mmax of all the muscles, and Hmax:Mmax ratio for the soleus and lateral gastrocnemius muscle were significantly lower after surgery. CONCLUSION There was an improvement of clinical and electrophysiological spastic indices after selective tibial neurotomy. Neurotomy acted not only on motor neurons by decreasing strength, but also the reflex enlargement by decreasing sensory afferents.