Bilateral Vestibular Weakness

Abstract

Bilateral vestibular weakness (BVW) is a rare cause of imbalance. Patients with BVW complain of oscillopsia. In approximately half of the patients with BVW, the cause remains undetermined; in the remainder, the most common etiology by far is gentamicin ototoxicity, followed by much rarer entities such as autoimmune inner ear disease, meningitis, bilateral Ménière's disease, bilateral vestibular neuritis, and bilateral vestibular schwannomas. While a number of bedside tests may raise the suspicion of BVW, the diagnosis should be confirmed by rotatory chair testing. Treatment of BVW is largely supportive. Medications with the unintended effect of vestibular suppression should be avoided.

Keywords: bilateral vestibular weakness; oscillopsia; ototoxicity; rotatory chair testing; vestibular testing; vestibulo-ocular reflex.

Figure 1

Distribution of etiologies of bilateral vestibular weakness at Chicago Dizziness and Hearing, n = 213.

Figure 2

MRI of a patient with meningitis. The upper left panel is a post-contrast T1 axial image; the upper right panel is a post-contrast coronal image; the arrows indicate enhancement of the vestibulo-cochlear nerves. The lower panel displays a coronal CISS sequence image; the structures indicated by the arrows demonstrate that the vestibulocochlear nerves are of relatively normal caliber, with no evidence of vestibular schwannoma. Images courtesy of Dr. Manuel Perez Akly.

Figure 3

MRI of a patient with siderosis showing hemosiderin deposition along the vestibulocochlear nerves. The image on the left is an axial gradient-echo (GRE) T2*-weighted sequence. The image on the right is an axial T2-weighted image. Both figures are through the internal auditory canals. The study was performed on a 1.5-Tesla strength MR.

Figure 4

High resolution three-dimensional reconstruction MRI of the internal auditory canals and inner ear structures of a patient with bilateral vestibular weakness from bilateral labyrinthine dysplasia. The top image is in the coronal aspect. The bottom image is in the axial aspect. In these images it is evident that the horizontal canals are dysplastic, with the horizontal canal and vestibule appearing as a single abnormal structure on each side (indicated by the arrows). The superior and inferior canals are present as true canals, but are somewhat hypoplastic.

Figure 5

Slow harmonic acceleration from rotatory chair testing. The panel on the left is a plot of the gain, which is low at all frequencies. The panel on the right is a plot of the phase, which could not be calculated at 0.01–0.16 Hz, and showed phase lead at 0.32–0.64 Hz.

Figure 6

Video head impulse testing of the horizontal canals in bilateral vestibular weakness, showing bilaterally low gain and overt saccades.

Figure 7

Video head impulse testing of all six semicircular canals in bilateral vestibular weakness, showing diffusely low gain and overt saccades.