title: Positional and positioning down-beating nystagmus without central nervous system findings.
abstract: We report the clinical features of 4 cases with positional or positioning down-beating nystagmus in a head-hanging or supine position without any obvious central nervous system disorder. The 4 cases had some findings in common. There were no abnormal findings on neurological tests or brain MRI. They did not have gaze nystagmus. Their nystagmus was observed only in a supine or head-hanging position and it was never observed upon returning to a sitting position and never reversed. The nystagmus had no or little torsional component, had latency and tended to decrease with time. The positional DBN (p-DBN) is known to be indicative of a central nervous system disorder. Recently there were some reports that canalithiasis of the anterior semicircular canal (ASC) causes p-DBN and that patients who have p-DBN without obvious CNS dysfunction are dealt with anterior semicircular canal (ASC) benign paroxysmal positional vertigo (BPPV). There are some doubts as to the validity of making a diagnosis of ASC-BPPV in a case of p-DBN without CNS findings. It is hard to determine the cause of p-DBN in these cases.
authors.affiliation: Department of Otorhinolaryngology, Tokyo Medical University, Japan. y-ogawa8@tokyo-med.ac.jp
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Mamoru
authors.initials: M
authors.lastname: Suzuki
authors.forename: Koji
authors.initials: K
authors.lastname: Otsuka
authors.forename: Shigetaka
authors.initials: S
authors.lastname: Shimizu
authors.forename: Taro
authors.initials: T
authors.lastname: Inagaki
authors.forename: Mami
authors.initials: M
authors.lastname: Hayashi
authors.forename: Akira
authors.initials: A
authors.lastname: Hagiwara
authors.forename: Naoharu
authors.initials: N
authors.lastname: Kitajima
mesh_terms: D000328:Adult; D001927:Brain Diseases / Q000175:diagnosis* / Q000503:physiopathology; D003937:Diagnosis, Differential; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D007759:Labyrinth Diseases / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D009759:Nystagmus, Pathologic / Q000175:diagnosis* / Q000503:physiopathology; D009760:Nystagmus, Physiologic / Q000502:physiology*; D010037:Otolithic Membrane / Q000503:physiopathology; D012665:Semicircular Canals / Q000503:physiopathology*; D016683:Supine Position / Q000502:physiology*; D014717:Vertigo / Q000175:diagnosis / Q000503:physiopathology; D055815:Young Adult