The bucket test differentiates patients with MRI confirmed brainstem/cerebellar lesions from patients having migraine and dizziness alone

Abstract

Background: Amongst the most challenging diagnostic dilemmas managing patients with vestibular symptoms (i.e. vertigo, nausea, imbalance) is differentiating dangerous central vestibular disorders from benign causes. Migraine has long been recognized as one of the most common causes of vestibular symptoms, but the clinical hallmarks of vestibular migraine are notoriously inconsistent and thus the diagnosis is difficult to confirm. Here we conducted a prospective study investigating the sensitivity and specificity of combining standard vestibular and neurological examinations to determine how well central vestibular disorders (CVD) were distinguishable from vestibular migraine (VM).

Method: Twenty-seven symptomatic patients diagnosed with CVD and 36 symptomatic patients with VM underwent brain imaging and clinical assessments including; 1) SVV bucket test, 2) ABCD², 3) headache/vertigo history, 4) presence of focal neurological signs, 5) nystagmus, and 6) clinical head impulse testing.

Results: Mean absolute SVV deviations measured by bucket testing in CVD and VM were 4.8 ± 4.1° and 0.7 ± 1.0°, respectively. The abnormal rate of SVV deviations (> 2.3°) in CVD was significantly higher than VM (p < 0.001). Using the bucket test alone to differentiate CVD from VM, sensitivity was 74.1%, specificity 91.7%, positive likelihood ratio (LR+) 8.9, and negative likelihood ratio (LR-) 0.3. However, when we combined the SVV results with the clinical exam assessing gaze stability (nystagmus) with an abnormal focal neurological exam, the sensitivity (92.6%) and specificity (88.9%) were optimized (LR+ (8.3), LR- (0.08)).

Conclusion: The SVV bucket test is a useful clinical test to distinguish CVD from VM, particularly when interpreted along with the results of a focal neurological exam and clinical exam for nystagmus.

Keywords: Bucket test; Central vestibular disorder; Nystagmus; Subjective visual vertical (SVV); Vestibular migraine.

Fig. 1

ROC curve of SVV for differentiating CVD from VM. The area under the curve was 0.9, and the best threshold was 2.2. (solid line – ROC curve; dotted line - reference line)

Fig. 2

Two cases of unremarkable focal neurological or nystagmus findings but marked SVV deviations. a, b A young man (30–35 years) complaining of dizziness only had equivocal facial numbness and end-gaze nystagmus. However, the bucket test revealed an SVV deviation of 11 degrees to the left; MRI showed a tiny infarct in the left lateral medulla (arrow). c, d An older man (50–55 years) with 10 days of dizziness but no focal neurological signs or nystagmus: His bucket test showed an SVV deviation of 5 degrees to the left; MRI showed a cavernous hemangioma in the dorsal medulla