Premium
Clinicophysiologic concepts of spasticity and motor dysfunction in adults with an upper motoneuron lesion
Author(s) -
Mayer Nathaniel H.
Publication year - 1997
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(1997)6+<1::aid-mus2>3.0.co;2-d
Subject(s) - spasticity , muscle tone , medicine , reciprocal inhibition , neuroscience , stretch reflex , physical medicine and rehabilitation , reflex , weakness , clonus , electromyography , amyotrophic lateral sclerosis , psychology , anatomy , inhibitory postsynaptic potential , pathology , epilepsy , disease
Spasticity is a disorder of the sensorimotor systme characterized by a velocity‐dependent increase in muscle tone with exagerated tendon jerks, resulting from hyperexcitability of the stretch reflex. It is one component of the upper motoneruon syndrome, along with released flexor reflexes, weakness, and loss of dexterity. Spasticity is an important “positive” diagnostic sign of the upper motoneuron syndrome, and when it restricts motion, disability may result. The “negative” signs‐‐weakness and loss of dexterity‐‐invariably alter patient function when they occur. In an upper motoneuron syndrome, the alpha motoneuron pool becomes hyperexcitable at the segmental level. This hyperexcitability is hypothesized to occur through a variety of mechanisms, not all of which have yet been demonstrated in humans. Spasticity caused by spinal cord lesions is often marked by a slow increase in excitation and overactivity of both flexors and extensors with reactions possibly occurring many segments away from the stimulus. Cerebral lesions often cause rapid build‐up of excitation with a bias toward involvement of antigravity muscles. Chronic spasticity can lead to changes in the rheologic properties of the involved and neighboring muscles. Stiffness, contracture, atrophy, and fibrosis may interact with pathologic regulatory mechanisms to prevent normal control of limb position and movement. In the clinical exam, it is important to distinguish between the resistance due to spasticity and that due to rheologic changes, because the distinction has therapeutic implications. Diagnostic nerve or motor point blocks and dynamic or multichannel EMG are useful to distinguish the contributions of spasticity and stiffness to the clinical problem. 1997 John Wiley & Sons, Inc. Spasticity: Etiology, Evaluation, Management, and the Role of Botulinum Toxin Type A MF Brin, editor. Muscle Nerve 1997; 20 (suppl 6):S1‐S13.