Bilateral Vestibulopathy Documented by Video Head Impulse Tests in Superficial Siderosis.

Abstract

Superficial siderosis (SS) of the CNS is associated with cerebellar ataxia, sensorineural hearing loss, and pyramidal symptoms, which result from iron depositions on CNS surfaces. SS can produce bilateral vestibulopathy as the vestibulo-cochlear nerve is particularly vulnerable. To our knowledge, however, vestibular dysfunction in SS has not been reported thoroughly in the literature. Here, we describe a case of bilateral vestibulopathy, documented quantitatively by the video head impulse test (vHIT), in a patient with SS. A 60-year-old man presented with slowly progressing bilateral hearing loss, oscillopsia, and a severe gait disturbance that worsened in the dark. After noticing deficits in the bedside head impulse test in all six semicircular canals, the patient underwent vHIT and brain MRI. MRI demonstrated a rim of hypointensities and signal losses in T2-weighted and gradient echo images around the cerebellum, brainstem, and vestibulo-cochlear nerve, which were compatible with an SS diagnosis. In addition, vHIT revealed reduced vestibule-ocular reflex (VOR) gains, and abnormal catch-up saccades (both covert and overt saccades) in all semicircular canals. The vHIT showed impaired VOR gains that were 0.55, 0.59, and 0.45 in the horizontal, anterior, and posterior canals, respectively. SS may result in chronic bilateral vestibulopathy with SNHL. Bilateral vestibulopathy originated peripherally in our participant, without cerebellar dysfunctions such as those reported in the literature. vHIT findings have not been previously reported in patients with SS, and our study suggests that vHIT is a useful tool to document vestibular dysfunction.