University of Illinois College of Medicine at Peoria, Room 4646, 530 N. Glen Oak Avenue, Peoria, IL, 61637, USA.
OSF Saint Francis Medical Center, Peoria, IL, USA.
Neurol Sci. 2022 Jul;43(7):4519-4529. doi: 10.1007/s10072-022-05970-8. Epub 2022 Mar 4.
Vestibular compensatory eye movements provide visual fixation stabilization during head movement. The anatomic pathways mediating a normal horizontal vestibulo-ocular reflex (h-VOR), when lesioned, cause spontaneous nystagmus. While previous reports address the effect of convergence on different spontaneous nystagmus types, to our knowledge, a study of acute vestibular nystagmus suppression viewing near targets comparing patients with peripheral or central vestibular lesions has not been previously reported.
We attempt to clarify potential vestibular and near-reflex interaction by comparing near and far h-VOR gain in 19 healthy controls, six patients with acute/subacute peripheral vestibular lesion (PVL), and one patient with unilateral vestibular nuclear lesion (VNL) in the pontine tegmentum.
The horizontal (h)-VOR in normal subjects increased with convergence in both eyes (P = 0.027, P < 0.001). In unilateral PVL patients, gain failed to increase in either direction (P = 0.25, P = 0.47). In contrast, when fixating at 15 cm, the h-aVOR in the VNL lesion, gain did not increase, and a right h-nystagmus developed. Even though we found inability to increase gain in PVL with near target fixation, this did not interfere with h-nystagmus suppression upon converging. Our VNL patient had normal h-nystagmus suppression viewing far distance targets and lacked near target h-nystagmus suppression.
We hypothesize that normal IO/flocculus pathway suppressed spontaneous nystagmus in PVL. Impaired h-VOR near adaptation in the medial vestibular nucleus was responsible for h-nystagmus direction with fixation block. Additionally, impaired viewing distance estimate contributed to near h-nystagmus suppression failure.
前庭代偿性眼动为头部运动时的视觉固定提供稳定性。正常水平前庭眼反射(h-VOR)的解剖途径,当受损时,会导致自发性眼球震颤。虽然以前的报告涉及会聚对不同自发性眼球震颤类型的影响,但据我们所知,以前没有报道过比较外周或中枢前庭病变患者的急性前庭眼球震颤抑制观看近目标的研究。
我们试图通过比较 19 名健康对照者、6 名急性/亚急性外周前庭病变(PVL)患者和 1 名桥脑被盖部单侧前庭核病变(VNL)患者的近和远水平(h)-VOR 增益,来阐明潜在的前庭和近反射相互作用。
正常受试者的水平(h)-VOR 在双眼会聚时增加(P = 0.027,P < 0.001)。在单侧 PVL 患者中,无论哪个方向增益都没有增加(P = 0.25,P = 0.47)。相比之下,当在 15 厘米处注视时,VNL 病变的 h-aVOR 增益没有增加,并且出现了右眼球震颤。尽管我们发现 PVL 患者在近目标注视时无法增加增益,但这并没有干扰会聚时的 h-眼球震颤抑制。我们的 VNL 患者在观察远距离目标时具有正常的 h-眼球震颤抑制,并且缺乏近目标 h-眼球震颤抑制。
我们假设正常的 IO/绒球叶途径抑制了 PVL 中的自发性眼球震颤。内侧前庭核的 h-VOR 近适应受损是固定阻断时眼球震颤方向的原因。此外,视距估计受损导致近 h-眼球震颤抑制失败。