Paroxysmal ocular tilt reactions after mesodiencephalic lesions: Report of two cases and review of the literature

Background: To elucidate the mechanisms of paroxysmal ocular tilt reaction (OTR) from mesodiencephalic lesions by analyzing the associated ocular motor findings. Methods: Two patients with paroxysmal ipsiversive OTR due to mesodiencephalic lesions underwent evaluation of associated ocular motor abnormalities and one of them had three-dimensional recording of eye motion. We also reviewed previously reported six patients with paroxysmal OTR. Results: One patient showed contraversive torsional nystagmus during the paroxysms in association with vertical gaze limitation and vertical gaze-evoked nystagmus, which are consistent with baseline dysfunction and paroxysmal irritation of the interstitial nucleus of Cajal (INC) during the attacks. The other patient exhibited ipsiversive torsional nystagmus during the attacks, along with slowed vertical saccades and decreased amplitude of ipsitorsional nystagmus during the torsional vestibulo-ocular reflex between the attacks. These findings are best explained by underlying dysfunction and paroxysmal irritation of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). Conclusions: The associated ocular motor findings in our patients indicate that paroxysmal ipsiversive OTR in mesodiencephalic lesions is caused by intermittent hyperactivity of partially damaged ipsilesional riMLF or INC.