Contractures and involuntary muscle overactivity in severe brain injury

The aim of the present study was to evaluate the association of contractures with an increase or reduction of non-spastic muscle overactivity due to severe cerebral damage.

Forty-five patients with tetraparesis after severe cerebral damage were investigated. Three groups were defined based on the presence of spasticity (revealed as resistance to passive stretch (= hypertonia)), and the presence of contracture of the relevant knee joint: Group(s) (17 patients with hypertonia without contracture), Group(s+c) (20 patients with hypertonia and contracture), and Group(c) (eight patients without hypertonia and with contracture). In all groups spontaneous involuntary muscle activity was assessed continuously over a 12-hour period through isometric measurement of knee joint flexion torque. A mathematical algorithm differentiated an hourly muscle activity spectrum (PI(h)). The frequency of peaks (peaks(h)) from the activity spectrum was determined.

We revealed that Group(s) had higher PI(h) and more frequent peaks(h) compared with Group(s+c) and Group(c) (p<0.05). Group(c) had comparable PI(h) and peaks(h) compared with Group(s+c) (p>0.05).

The presence of contractures was associated with lower involuntary muscle overactivity in terms of lower PI(h) and less frequent peaks(h), indicating that contractures may be associated with reduced non-spastic positive features of the upper motor neurone syndrome in patients with severe brain damage.