Optokinetic Analysis in Patients With Spontaneous Horizontal Gaze-Evoked Nystagmus Without Radiological Neuropathology

Abstract

Gaze-evoked nystagmus is not rare among those who have acute balance problem and may indicate a cerebellar dysfunction that is associated with a broad spectrum of disorders. The aim of this study is to analyze optokinetic response in those patients. Eleven males and 7 females (age range: 25-60, 42.5 [9.75]) with gaze-evoked nystagmus were analyzed with optokinetic test (Micromed Inc). Nystagmus was elicited by a stimulator light spot moving across the patient’s visual field at a target speed of 30 degree/second. Ten age-matched healthy participants served as controls. The gain and slow-phase velocity difference in oculomotor response from left and right stimulus was compared in patients and the control participants. One-way analysis of variance test was used for multiple variance analysis of the groups. Statistical significance was set at P < .05. Slow-phase velocity of gaze-evoked nystagmus was ranging between 6 and 19 degree/second. The mean slow-phase velocity of gaze-evoked nystagmus to the right and left was 8.1 (3.81) and 6.8 (4.67) degree/second, respectively. Optokinetic gain was out of normal limits in 10 (55.5%) patients. Comparison of mean gain difference between the patients and the normal participants was statistically significant ( P = .025). No statistical difference was found in mean slow-phase velocity difference in optokinetic nystagmus between control participants and patients ( P > .05 [.099]). An acute-onset balance problem may be associated with dysfunction of separate populations of neurons in the brainstem and cerebellum even if there is no radiological neuropathy since gaze-evoked nystagmus is a sign of neural integrator dysfunction. Patients with gaze-evoked nystagmus and optokinetic abnormalities may have disruption of cerebellar pathways and should be followed closely.

Prevalence and Characteristics of Physiological Gaze-Evoked and Rebound Nystagmus: Implications for Testing Their Pathological Counterparts

“…In comparison to studies performed in patients with cerebellar disease, GEN eye drift velocities found in our study were at the low end of reported velocities (1-24 • /s) (9,11,23,26,27). Eye drift velocities of RN in patients with cerebellar disease were rarely reported.…”

“…We demonstrate that even persistence of GEN over time is not a solid sign for being pathological. While prior reports described GEN to be pathological if persistent over 20 s (27,29), we observed that (although the velocity of drift decreased during prolonged eccentric gaze) GEN commonly persisted for the duration of 30 s (in 64-100% of subjects depending on gaze eccentricity). Furthermore, while the velocities found in our study were generally at the low end of ranges presented in prior studies in patients, these results still indicate that certain cases might have been wrongly identified as pathological.…”

Nystagmus Based Screening System for Vestibular Schwannoma in Patients With Asymmetric Hearing Loss

“…Furthermore, to not miss a certain central sign, we included vertical nystagmus and direction changing GEN in our screening system which are known to be the nystagmus occurring by disorganization of neural integrator or impairment of cerebellar gaze-holding mechanism. 21,22) In our study, sensitivity and specificity of presence of nystagmus after head shaking test (positive HSN) were 84.8% and 51.3%, respectively. They were significantly different from previous studies of HSN, 14,15) which proposed lower sensitivity of HSN for detecting VS. Humphriss, et al 14) have reported a sensitivity of 22% as a result of 22 positive HSN among 102 subjects.…”

“…[14][15][16][17][18][19][20] Herein, the authors devised a nystagmus based screening system (NBSS) for VS in ASNHL patients. The NBSS is composed of four different types of nystagmus: vertical spontaneous nystagmus (SN) and direction changing gaze evoked nystagmus (GEN), which are previously studied central sign nystagmus, [21][22][23][24] and two types of HSN which firstly show ipsilesional nystagmus after head shaking. We also compared the sensitivity and specificity of NBSS with ABR and confirmed the usefulness of the new screening system.…”

Vertigo Associated With Cochlear Implant Surgery: Correlation With Vertigo Diagnostic Result, Electrode Carrier, and Insertion Angle

“…According to Yetiser et al, optokinetic testing can detect evidence of central disorders, particularly cerebellar damage and brainstem damage. Because none of the patients in this study had postoperative abnormalities, it can be concluded that cochlear implantation did not result in central lesions (51). These could be excluded preoperatively as a cause of vertigo among all patients in vertigo classes 2 and 3.…”