case_images: PMC8720997_01
case_images: Normal caloric asymmetry but abnormally high total for the slow component eye velocity. SCV, slow component velocity; d/s, degrees/second. The caloric asymmetry is 20% (Table 1). R, right; L, left.
case_images: fneur-12-814998-g0001.jpg
case_images: PMC8720997_01_fneur-12-814998-g0001.jpg
case_images: F1
case_images: The bi-thermal water caloric exam revealed a sum slow eye velocity of 180 d/s (Figure 1), exceeding the normal 45-157 d/s range of total slow eye velocities.
case_images: Downbeat nystagmus during positional testing and head rotated right. At 90 deg, the downbeat nystagmus has a peak velocity of 30 deg/sec, originally interpreted as evidence for otoconia dislodged within the lumen of the right anterior semicircular canal. LV, left vertical channel.
case_images: fneur-12-814998-g0002.jpg
case_images: PMC8720997_01_fneur-12-814998-g0002.jpg
case_images: F2
case_images: The supine roll test was normal at 45 degrees right or left, however, once he rotated his head beyond 75 degrees to the right he developed downbeat nystagmus with vertigo and an impending sense of syncope (Figure 2).
case_images: Radiograph evidence confirming severe stenosis of right and left vertebral arteries during rightward head rotation. Dark arrows reflect partial stenosis, white arrow reflects absent perfusion from complete stenosis.
case_images: fneur-12-814998-g0003.jpg
case_images: PMC8720997_01_fneur-12-814998-g0003.jpg
case_images: F3
case_images: Dynamic angiogram using digital subtraction angiography (DSA) revealed stenosis of the right vertebral artery at the C4-C5 level that increased with increasing amplitude of head rotation to the right (Figure 3).