Asymmetric Persistent Geotropic Horizontal Positional Nystagmus Due to Bilateral Horizontal Semicircular Canal Otoconial Pathology Following Mild Traumatic Brain Injury

A 20-year-old female sustained a mild traumatic brain injury (mTBI) on January 1, 2026, when a motorcyclist struck her while she was crossing the road. The injury resulted from cranial impact trauma because her head struck the road. She experienced no bleeding from the scalp, nose, ear, or throat. The period of unresponsiveness after the mTBI lasted less than 10 minutes. On day 1, she had multiple episodes of vomiting and vertigo, both spontaneous and positionally triggered. She reported no history of pain in the neck. She consulted our otoneurology facility on January 3, 2026. There was no spontaneous nystagmus. Smooth pursuits and saccades were normal. There was no limb dysmetria, and the patient could stand and walk in tandem. The bow and lean test (BLT) evoked right-beating horizontal leaning nystagmus and left-beating bowing nystagmus. The supine roll test (SRT) evoked horizontal right-beating lying-down nystagmus. Head yaw to the left and right evoked geotropic horizontal positional nystagmus, which was stronger with head yaw to the left than to the right. Based on these findings, we diagnosed the patient with left geotropic horizontal semicircular canal benign paroxysmal positional vertigo (BPPV) due to canalolithiasis in its long posterior non-ampullary arm. Yawing the head to the left a second time elicited persistent geotropic positional nystagmus lasting more than 1 minute. We performed the Gufoni maneuver for left-sided geotropic horizontal canal BPPV. After the Gufoni maneuver, the BLT and SRT elicited left-beating horizontal spontaneous nystagmus. We performed the head-shaking maneuver twice on day 1, but the patient became extremely dizzy with vomiting. We therefore decided to examine her on day 2. On day 2, there was left-beating spontaneous nystagmus that was unaffected by bowing, leaning, or supine head yaw to the left and right. At this stage, we performed a clinical head impulse test, which elicited a catch-up saccade with high-frequency head thrust to the right. We established a diagnosis of right horizontal semicircular canalith jam. Head shaking at high frequency (3 cycles per second) for 2 minutes abolished the spontaneous left-beating horizontal nystagmus, along with the disappearance of vertigo, both spontaneous and positionally triggered. The final diagnosis in this patient was left horizontal semicircular canalolithiasis of its long posterior non-ampullary arm and right horizontal semicircular canal canalith jam.