Ipsilateral gustatory disturbance by thalamic hemorrhage

Animal studies have recently demonstrated that the gustatory pathway ascends in the brainstem ipsilaterally without crossing, and terminates in the ipsilateral lower caudal limit of the thalamus, i.e., the nucleus ventralis posteromedialis parvocellularis (VPMpc). However, little is yet known about the corresponding anatomical arrangement in man. Some clinical reports on cases of ipsilateral gustatory disturbance caused by tegmental pontine hemorrhage have suggested that the human gustatory pathway may also ascend ipsilaterally in the brainstem. Our case is a 35-year-old man, who was admitted to the hospital because of double vision. Computed tomography revealed a small high density area in the right paramedian tegmentum of the upper midbrain. On the 7th hospital day, the patient suddenly complained of dysesthesia on the right side of the oral cavity. Neurological examination demonstrated remarkable total hypogeusia on the right side of the tongue. MR imaging revealed upward extension of the hematoma toward the lower caudal portion of right thalamus. This is first report to demonstrate unilateral gustatory disturbance due to lesion in the ipsilateral thalamus. It is also worth of note that unilateral gustatory disturbance caused by thalamic lesion can be accompanied by sensory impairment in the ipsilateral oral cavity.