抄録
We report herein on a case of unique head position-induced dizziness and nystagmus. A 64-year-old man complained of recurrent dizziness during head shaking following hair washing for over 20 years. Because a medullary lesion was suspected at another clinic, he was referred to our university hospital. He showed no cochlear or abnormal neurological symptoms. Routine equilibrium function and neurological tests showed unremarkable findings. A T2-weighted image on brain MRI revealed a high-intensity signal area on the ventral medullary surface. No abnormalities of the vertebral artery were found on MRA imaging and transcranial ultrasonography, namely disappearance, meandering, malformation, or stoppage. On examination, the patient showed down beating nystagmus and dizziness when he bent forward swiftly and shook his head in a sitting position. His nystagmus had a small amplitude and lasted for a few seconds during dizziness. From the MRI findings and a history of Fallot's tetralogy, he was diagnosed as having a congenital neuroenteric cyst. He was followed without any conservative management and surgery because his symptoms disappeared by avoidance of the dizziness-inducing head position. Downbeat nystagmus typically occurs in patients with lesions involving the caudal midline of the cerebellum and the lower brain stem. A distinct vertical head-shaking nystagmus suggests the existence of a central lesion. It is speculated in our case that the unique head position and head shaking caused temporary circulatory disturbance of the cerebellum and the lower brain stem systems.
