Nystagmus in Enlarged Vestibular Aqueduct: A Case Series

Abstract

Enlarged vestibular aqueduct (EVA) is one of the commonly identified congenital temporal bone abnormalities associated with sensorineural hearing loss. Hearing loss may be unilateral or bilateral, and typically presents at birth or in early childhood. Vestibular symptoms have been reported in up to 50% of affected individuals, and may be delayed in onset until adulthood. The details of nystagmus in patients with EVA have not been previously reported.The objectives were to describe the clinical history, vestibular test findings and nystagmus seen in a case series of patients with enlarged vestibular aqueduct anomaly.Chart review, included computed tomography temporal bones, infrared nystagmography with positional and positioning testing, caloric testing, rotary chair and vibration testing.Clinical history and nystagmus varied among the five patients in this series. All patients were initially presumed to have benign paroxysmal positional vertigo, but repositioning treatments were not effective, prompting referral, further testing and evaluation. In three patients with longstanding vestibular complaints, positional nystagmus was consistently present. One patient had distinct recurrent severe episodes of positional nystagmus. Nystagmus was unidirectional and horizontal. In one case horizontal nystagmus was consistently reproducible with seated head turn to the affected side, and reached 48 d/s. Nystagmus associated with enlarged vestibular aqueduct is often positional, and can be confused with benign paroxysmal positional vertigo. Unexplained vestibular symptoms in patients with unilateral or bilateral sensorineural hearing loss should prompt diagnostic consideration of EVA.

Seltene Erkrankungen des vestibulären Labyrinths: von Zebras, Chamäleons und Wölfen im Schafspelz

“…Furthermore, an association with mild head trauma / pressure changes has also been reported for vestibular symptoms in EVA [205,210,211]. Third window A positive Tullio phenomenon and a vibrationinduced nystagmus beating towards the affected ear are characteristic signs of a third window commonly observed in EVA [205,207]. Furthermore, reduced o-and cVEMP thresholds and increased oVEMP amplitudes have been reported for the affected ear [204,205,[212][213][214].…”

“…Rapid head movements and changes in body position may trigger nystagmus and vertigo, which may be due to an undamped transmission of intracranial pressure oscillations to the inner ear endolymph space through the enlarged vestibular aqueduct. In contrast to BPPV, this type of nystagmus appears without latency, cannot be attributed to a certain semicircular canal and does not respond to repositioning maneuvers [207] (▶table 4). Benign paroxysmal positional vertigo On the other hand, around 20 % of patients with EVA experience "true" BPPV that might be caused by a disturbed calcium homeostasis in the inner ear (▶ table 6).…”

“…Ähnlich wie bei beim Hörverlust wird auch für die vestibulären Symptome in Fallberichten eine Assoziation mit Bagatelltraumata/ Druckänderungen berichtet [205,210,211]. Drittes Fenster Als charakteristische Zeichen eines dritten Fensters wurden bei Patienten mit EVA ein positives Tullio-Phänomen und ein Vibrationsnystagmus in Richtung des betroffenen Ohres beschrieben [205,207]. Zudem wurden erniedrigte c-und oVEMP-Schwellen sowie erhöhte oVEMP-Amplituden für das entsprechende Labyrinth gemessen [204,205,[212][213][214] [217] und danach in mehreren klinischen Studien beschrieben [218,219].…”

“…Pure tone audiometry (PTA) in EVA patients covers the whole spectrum from low-frequency inner-ear conductive hearing loss (indicative of a third window) up to high-grade sensorineural hearing loss for all frequencies (representing the chronic degeneration of the cochlear sensory epithelium) 204 205 206 207 . Beside slowly-progressive sensorineural hearing loss, there are also cases where a rapid deterioration of hearing thresholds is observed immediately after a mild head trauma or pressure changes in the intracranial space / the middle ear (e. g., Valsalva maneuver, rapid changes in ambient pressure).…”

Temporal bone congenital anomalies and variatons

“…The vestibule and semicircular canals may be normal or malformed. This malformation was first described by Mondini [2,[12][13][14][15][16][17] . We didn't determine Mondini dysplasia among our patients.…”