Unilateral pallidotomy produces motor deficits and excesses in rats

To better understand the behavioral effects of pallidotomy as a treatment for a range of movement disorders, including Parkinson's disease, chorea, and ballismus. In some cases, pallidotomy increases movement whereas in others it decreases unwanted motor behavior.

The present study investigated the effects of unilateral pallidotomy in rats with an otherwise healthy nervous system. Pallidotomized and sham lesion rats were evaluated on a battery of tests that measure sensorimotor behavior.

Compared to sham lesion controls, pallidotomized rats showed motor deficits (forelimb placing; bracing) and excesses (locomotor behavior) as well as sensorimotor asymmetries (ipsilateral adhesive patch bias; increased contralateral foot faults).

Motor deficits observed after pallidotomy were similar to those reported in previous research from this and other laboratories following damage to the nigrostriatal pathway or sensorimotor cortex. Motor excesses after pallidotomy are consistent with current theories of globus pallidus function. Taken together, these data suggest hypokinetic effects of pallidotomy may be related to fibers of passage (i.e. internal capsule), while hyperkinetic effects may be related to damage of pallidal cell bodies. These data may have important clinical implications because they suggest that regardless of the state of existing pathology, pallidotomy may create unwanted behavioral side effects.