Paralysis Research Today is a free monthly online journal that collates and summarizes the latest research about Paralysis, including details on treatment, diagnosis, facial paralysis, sleep paralysis.

Lack of modulation of Ib inhibition during antagonist contraction in spasticity.

Morita H, Shindo M, Momoi H, Yanagawa S, Ikeda S, Yanagisawa N

Department of Medicine, Shinshu University School of Medicine, Japan. hmorita@hsp.md.shinshu-u.ac.jp

OBJECTIVE: To examine the modulation of non-reciprocal group I (Ib) inhibition during tonic contraction of antagonist muscles in patients with spasticity vs normal subjects. METHODS: The authors studied 10 patients with spastic paraplegia due to cervical compression myelopathy and 16 age-matched normal subjects. Ib inhibition to soleus motoneurons was recorded as the change in size of the H-reflex of the soleus, evoked by conditioning stimulus to the nerve innervating the medial gastrocnemius muscle. The extent of inhibition was studied at rest and during tonic contraction of the pretibial muscles of variable strength. RESULTS: In the resting state, the extent of inhibition in the patients did not differ from normal controls. During antagonist contraction, the extent of inhibition increased both in the normal subjects and patients. The increment was smaller in the patients, especially in those with severe spastic gait. The smaller increment in the inhibition was correlated with the time required to walk 10 m in the patients. CONCLUSION: The authors observed a lack of modulation of Ib inhibition during tonic antagonist contraction in patients with spasticity, especially those with gait disturbance. Disturbed central modulation of non-reciprocal (Ib) interneurons may be responsible for spasticity.

Published 11 July 2006 in Neurology, 67(1): 52-6.
Full-text of this article is available online (may require subscription).

© 2004-2008 Paralysis Research Today. All Rights Reserved.