Can the bending forward test be used to detect a diseased anterior semi-circular canal in patients with chronic vestibular multi-canalicular canalithiasis (BPPV)?

Patients with chronic vestibular multi-canalicular canalithiasis (CVMCC) can have serious morbidities, for example, musculoskeletal pain, dizziness, fatigue, and cognitive difficulties. Involvement of the anterior semi-circular canal (SCC) is common in CVMCC. A mono-canalicular diseased anterior SCC is rare. To examine if the Bending forward test can be used to detect a diseased anterior semi-circular canal in patients with CVMCC. Prospective consecutive observational cohort study in patients with relapse of an earlier successfully treated chronic CVMCC, where 16 patients have a diseased anterior SCC, 11 without any involvement of the anterior SCC, and 15 healthy controls. Patients are tested in sitting and in bending forward position. The difference in downwards directed nystagmus count and slow phase velocity in the two test positions reported movement illusion are the main outcome. The sensitivity of the Bending forward-test is 81%; the specificity 91%. Five of the healthy controls have positional nystagmus without movement illusion. This is interpreted as cupulolithiasis. Positional nystagmus with movement illusion is interpreted as canalithiasis. Bending forward-test is a valuable test. Only positional nystagmus accompanied by a movement illusion, that is canalithiasis, is of clinical relevance. These findings may assist in diagnosing compound musculoskeletal disorders.