Abstract
Arnold-Chiari malformation (ACM) is categorized into 4 types on the basis of the severity of hindbrain herniation and cerebellar dysplasia. Type I malformation, also known as adult ACM, there is caudal descent of the cerebellar tonsils only and can be a cause of unexplained headaches, dizziness, blurred vision, vomiting, vertigo, and drop attacks. In this unique case report, a 52-year-old man who suffered a fresh sudden hearing loss (SHL) of the left ear, accompanied with dizziness, tinnitus and difficulty to fall asleep. His history also included a first attack of SHL and tinnitus in the right side 15 months ago. A pure-tone hearing test showed sensorineural hearing loss on the bilateral sides (slight loss on left and moderate loss on right). On vestibular evaluation, a spontaneous down beating nystagmus was seen. Then a head MRI demonstrated the existing of ACM type I. Two months after the neurosurgical decompression, the patient's nystagmus diminished thoroughly, whilst mild improvement of hearing. It is suggested that the finding of abnormal central vestibular nystagmus or abnormal vestibular-visual interaction is a useful sign to help determine whether a ACM is underlying some otolaryngological symptoms such as hearing loss, dizziness or tinnitus. MRI is the first choice to diagnose the ACM type I.
