[A case of the persistent vegetative state following symmetrical peduncular infarction]

A 64-year-old woman presented with sudden onset of disequilibrium and dysarthria. Two days later she became lethargic and tetraparetic. An emergency MRI disclosed multiple infarctions in the medulla oblongata and pons. An angiogram revealed severe stenosis of the rostral basilar artery. The patient underwent a rapidly progressive course with impaired consciousness and flaccid tetraplegia. MR images 7 days after the onset disclosed a symmetrical midbrain infarction that was localized mainly in the cerebral peduncles, suggesting a distal basilar artery occlusion as the cause of this pathology. Since 4 weeks after the onset the patient was in the persistent vegetative state, which was essentially unchanged during the 1-year follow-up period. Persistent vegetative state is known to be caused by diffuse supratentorial or bilateral thalamic lesions, but in our case the lesions were restricted to the infratentorial area. We speculate a mechanism to cause the persistent vegetative state by partial impairment of the connection to the thalamic ascending system or extrathalamic ascending system, which leads to the dissociation of arousal(preserved in this case) and awareness(impaired in this case) after the ventral midbrain infarction.