Anterior canal benign paroxysmal positional vertigo: An underappreciated entity

Objective: Evaluate the frequency and characteristics of benign paroxysmal positional vertigo (BPPV) arising from involvement of the anterior semicircular canal (AC) as compared with the posterior canal (PC) and horizontal canal (HC). Study Design: Prospective review of patients with BPPV. Setting: Tertiary referral center. Patients: A total of 260 patients who were evaluated for vertigo were identified as experiencing BPPV. Interventions: Standard vestibular assessment including the use of electrooculography (EOG) or video-oculography (VOG) was completed on all patients. Based on EOG/VOG findings, the BPPV origin was attributed to AC, PC, or HC involvement secondary to canalithiasis versus cupulolithiasis. Treatment was performed with canalith repositioning maneuvers (CRMs) appropriate for type of canal involvement. Results: For the 260 patients, the positionally induced nystagmus patterns suggested the canal of origin to be AC in 21.2%, PC in 66.9%, and HC in 11.9%. Cupulolithiasis was observed in 27.3% of the AC, 6.3% of the PC, and 41.9% of the HC patients. Head trauma was confirmed in the history preceding the onset of vertigo in 36.4% of the AC, versus 9.2% of the PC and 9.7% of the HC patients (p < 0.001). The number of CRMs completed to treat the BPPV did not differ between canals involved (1.32 for AC, 1.49 for PC, and 1.34 for HC). Conclusion: The direction of subtle vertical-beating nystagmus underlying the torsional component is critical in differentiating AC versus PC origin; EOG/VOG aids in accurate assessment of the vertical component for the diagnosis of canal involvement. AC involvement may be more prevalent than previously appreciated, particularly if the examiner does not appreciate the vertical component of the nystagmus or the diagnosis is made without the assistance of EOG/VOG. Head trauma history is significantly more frequent in AC versus other forms of BPPV, and patients with a history of head trauma should be examined closely for AC involvement. CRM is as successful for treatment of AC BPPV as for other types of BPPV.