Behaviour-Induced Neural Events after Brain Injury

Gitendra Uswatte
guswatte@uab.edu

Dear Dr. Hawrylak,

Thank you for you question.

The learned nonuse formulation predicts that stroke patients with a paresis of a lower extremity are also liable to develop deficits in use.  These deficits, however, are probably better characterized as learned misuse than learned nonuse.  Whereas patients with an upper extremity paresis can function in the life situation using one arm, patients with a lower extremity paresis can not walk using just their less-affected leg.  Patients with a lower extremity paresis must use both legs to ambulate, but will develop degraded gait patterns in the acute and subacute phases to adjust to their unilateral deficit in motor ability.  Since most patients are able to carry out some progression in their environment, as opposed to being entirely nonambulatory, these abnormal patterns of coordination are reinforced and, consequently, persist in the chronic phase, even when some of the motor deficits that made them necessary have resolved.  The gait patterns that are unnecessarily exaggerated include (a) hip flexion, knee extension, ankle plantar flexion and lower limb circumduction during swing; (b) hip flexion, limited knee flexion, and ankle plantar flexion during loading; (c) knee hyperextension during midstance; and (d) lack of roll-off at toe-off (Perry, 1969).  They produce inefficient ambulation and cause damage to bone, ligament, and muscle tissue (Giuliani, 1990).  The use of the maladaptive lower extremity coordination can be overcome by repeated practice of improved gait patterns in the laboratory and attention in the home to the use of new gait patterns practiced in the laboratory.  Learned nonuse per se may occur in stroke patients with a lower extremity paresis who are nonambulatory in the acute and subacute phases; this condition of greatly reduced walking may persist into the chronic phase even though the underlying neurological recovery makes substantial walking possible.  However, only a relatively small percentage of chronic stroke patients do not walk at all.  Learned misuse is thus a much more common condition.
     Our laboratory, to date, has treated the lower extremity of 12 patients with chronic stroke (3 received combined lower and upper extremity therapy) with substantial success (Spear, King, Yakley, Willcutt, & Taub, 1998).  These patients have had a wide range of disability extending from close to nonambulatory to moderately impaired coordination.  The treatment has involved shaping and practice of improved coordination for 7 hours per day for 2 or 3 weeks.  Initially, we thought that it might be more difficult to overcome learned misuse than learned nonuse because in the former case bad habits of coordination would need to be overcome before more appropriate patterns of coordination could be substituted, while in the latter case there is simply an absence of use in the life situation.  Surprisingly, this expectation proved to be incorrect.  We have obtained improvements in the quality of movement of the lower extremity on laboratory motor tests in some patients that are approximately equivalent to those we have obtained for the upper extremity.  We still have insufficient lower extremity Motor Activity Log data to draw conclusions about the permanence of the transfer of these gains in motor ability to use in the real world.  We have recently treated a wheelchair-bound, incomplete spinal cord injury patient and have obtained substantial improvement in endurance in walking and specific gait parameters and in ability to ambulate, climb stairs, and step over low obstacles.

We hope that this answer is helpful.

Sincerely,

Gitendra Uswatte, M.A.       Edward Taub, Ph.D.