Cognitive-motor dysfunction after severe traumatic brain injury: A cerebral interhemispheric disconnection syndrome.

BACKGROUND/OBJECTIVES: In most right-handed people, the left hemisphere is dominant for programming the temporal and spatial "how" (praxis) aspects of purposeful skilled movements, and the right hemisphere is dominant for control of the intentional "when" aspects of actions that mediate initiation, persistence, termination, and inhibition. Since the interhemispheric axons of the corpus callosum are especially susceptible to shearing from torsional forces during traumatic brain injury (TBI), the goal of this study was to learn whether participants with a history of severe traumatic brain injury demonstrate three types of cognitive-motor impairments that may result from callosal injury: ideomotor apraxia of the left hand, limb kinetic apraxia of the left hand, and hypokinesia of the right hand in response to left hemispatial stimuli.

METHOD: Nine participants with severe TBI and nine healthy control participants were studied for the presence of ideomotor apraxia, limb kinetic apraxia, and hypokinesia.

RESULTS: When compared to the control participants, the participants with TBI revealed ideomotor apraxia and limb kinetic apraxia of the left hand and hypokinesia in response to left-sided visual stimuli when tested with the right hand.

CONCLUSIONS: TBI appears to cause unilateral disorders of cognitive-motor functions. Future research is needed to understand how these cognitive-motor disorders are related to interhemispheric disconnection most likely induced by injury to the corpus callosum.