Role of primary motor cortex in gait: automatic-voluntary dissociation seen in paretic leg of a patient who had a stroke.

Objective: To examine the role of primary motor cortex in gait through exploring the dissociation of impaired voluntary leg muscle contraction and preserved rhythmic activities during gait in a patient who had a stroke. Subject and methods: A 49-year-old man with an infarct in the primary motor cortex exhibited automatic-voluntary dissociation in the paretic leg. Functional studies were conducted using surface electromyography (EMG) and near-infrared spectroscopy (NIRS). Results: The patient was incapable of voluntary contraction of individual leg muscles on the paretic right side but was able to walk automatically while contracting those muscles rhythmically. Surface EMG confirmed the earlier findings objectively. The preserved automatic activities helped recovery of gait capability, but NIRS showed no functional recovery in the corresponding motor cortex during treadmill gait. We considered that the loss of voluntary leg muscle contraction and the preserved gait capacity in this patient represented a form of automatic-voluntary dissociation. Conclusions: The preserved gait capability suggests that the leg representation of the primary motor cortex may not play a major functional role in gait, but other components of the nervous system, including the spinal central pattern generator, would serve important functions to maintain gait capability.

Repetitive Episodic Isolated Vertigo in a Patient with Cerebellar Infarction.

Isolated vertigo is an important symptom of posterior circulation stroke. It has been reported that 11.3% of patients with isolated vertigo have a stroke and that most lesions are located in the cerebellum, particularly in the posterior inferior cerebellar artery. We report the case of a 63-year-old man with multiple atherosclerotic risk factors and atrial fibrillation who showed repeated episodes of isolated vertigo. His repeated vertigo was short-lasting and was often triggered by body position, mimicking benign paroxysmal positional vertigo. Cranial computed tomography on the third hospital day showed left cerebellar infarction within the territory of the posterior inferior cerebellar artery. The vertigo was ameliorated on the fifth hospital day and warfarin was prescribed for secondary prevention. Clinicians should pay special attention to cases in which a patient presents isolated vertigo, even if it shows transient recurrence or is triggered by a positional change, especially in patients with multiple cerebrovascular risk factors.