Daniel R. Gold, DO, Departments of Neurology, Ophthalmology, Neurosurgery, Otolaryngology - Head & Neck Surgery, The Johns Hopkins School of Medicine; Daniele Nuti, University of Siena; Marco Mandalà, MD, PhD, Otology and Skull Base Unit Azienda Ospedaliera Universitaria Senese
Although the anterior canal (AC) variant of benign paroxysmal positional vertigo (BPPV) is rare, mainly owing to its orientation relative to gravity (which makes otoconial debris much less likely to enter it), it can occur. Because of the relatively para-sagittal orientation of the AC (more so than the posterior canal), in a patient with AC BPPV, nystagmus may be provoked by the right or left Dix-Hallpike maneuvers, as well as with straight head hanging, as it was in this particular patient. A right Dix-Hallpike maneuver will stimulate the right posterior canal (PC) as well as the left AC. This patient was diagnosed with left AC BPPV - left AC excitation causes stimulation of left superior rectus and right inferior oblique muscles, initiating an upward and torsional (towards right ear) slow phase. This generates downward-torsional (towards left ear) fast phases, as seen here. She was treated with repositioning maneuvers, but there was no response in the office. Her neurologic and ocular motor/vestibular examinations were otherwise unremarkable, and when she returned 1 week later, the positional nystagmus had spontaneously resolved. ; Alternatively, there are some patients who may have otoconia in the distal, non-ampullary arm of the PC. If this is the case, it may be possible to produce an inhibitory pattern of nystagmus, so that some cases labelled as AC BPPV may actual be an atypical variant of PC BPPV. This possibility could not be ruled out in her case.
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