[Hypogeusia in a 9-year-old girl with multiple sclerosis]

We reported a case of hypogeusia in a 9-year-old girl with multiple sclerosis (MS). She had two episodes of neurological disturbances resembling those associated with MS, and diagnosed by McDonald's criteria. She complained of gustatory disturbance on the first attack. A quantitative test with four fundamental tastes (measurements with a filter paper disc) suggested decreased gustatory sensitivity in the right anterior part of the tongue. Magnetic resonance imaging (MRI) revealed a right thalamic lesion involving the ventral posteromedial nucleus parvocellular part (VPMpc). The patient was successfully treated with steroid pulse therapy, and improvement of neurological abnormalities involving gustatory disturbances was seen. Some studies of monkeys have demonstrated that the secondary neurons in the gustatory part of the solitary nucleus project ipsilaterally to VPMpc in the brainstem. The gustatory pathway in humans has not yet been demonstrated, but is speculated to be present based on that of monkeys. In the present case, we considered that the thalamic lesion involving VPMpc caused a decreased sense of taste in the ipsilateral part of the tongue. Several neurological abnormalities caused by multifocal demyelinating lesions can be observed in MS, but gustatory disturbance is rare. We quantitatively investigated unilateral gustatory disturbance in our patient, and concluded that the ipsilateral thalamic lesion detected by MRI could be causative.