Bow and Lean Test
What it measures:Used to identify the involved side of the horizontal semicircular canal (SCC) in benign paroxysmal positional vertigo (BPPV) (1)
Target Population:People with benign paroxysmal positional vertigo (BPPV)
Lee et al (2) reported that using the Bow and Lean test to identify the affected side in horizontal SCC canalithiasis significantly increased treatment efficacy compared with use of the roll test only. The additional information provided by the Bow and Lean test to determine side of involvement improved the treatment efficacy rate of those with horizontal canal BPPV canalithiasis from 67.4% to 83.1% after 2 sessions of canalith repositioning treatment, and, of those with cupulolithiasis, from 61.1% to 74.7%.
Use in Patient Classification
BPPV is classified according to:
1. The SCC involved (posterior, anterior, horizontal)
2. Location of the displaced otoconia-inside the canal (canalithiasis), or adhering to the cupula (cupuloithiasis)
These classifications guide intervention.
The involved SCC is determined based on the observation that nystagmus occurs when the patient is in the provoking position. The nystagmus elicited in BPPV takes the form of a jerk nystagmus-a slow drift toward one direction and then a fast corrective saccade back the other way. The nystagmus is named for the direction of the fast component. All eye movement directions are named with respect to the patient, not the observer.
In patients with horizontal SCC BPPV, the Dix-Hallpike Test and side-lying test might not provoke vertigo and nystagmus because the horizontal SCC is not placed in the plane of the pull of gravity. The patient is supine and the head is rolled 90 degrees to the right and left in the plane of the horizontal SCC. (3-5)
The direction of the nystagmus elicited (geotropic versus apogeotropic)-as well as duration of nystagmus-are used to identify the canalithiasis versus cupulolithiasis form of horizontal SCC BPPV.
The Bow and Lean test is used to determine the affected side in horizontal SCC BPPV. (1) First, the roll test is used to determine whether the BPPV is the canalithiasis or cupulolithiasis form, based on the duration of the nystagmus. Then, the Bow and Lean test is used to determine which side is affected by observing the direction of the nystagmus.
The determination of whether a person has the canalithiasis or the cupulolithiasis form of horizontal SCC BPPV is based on the direction of nystagmus; however, clinicians need to be aware that horizontal SCC canalithiasis typically presents as geotropic nystagmus that is brief, and cupulolithiasis as apogeotropic nystagmus that is prolonged. Nystagmus that is geotropic and prolonged is not typical of BPPV and more likely is from a migraine equivalent event. It is recommended, therefore, that clinicians note both the direction of the nystagmus and the duration of the nystagmus as criteria for distinguishing between horizontal SCC canalithiasis and cupulolithiasis.
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