Ocular Neuromyotonia in Thyroid Eye Disease

Ocular neuromyotonia (ONM) in thyroid eye disease (TED) seems to be a rare finding. We present the case of a 61-year-old male TED patient who developed spontaneous transient neuromyotonic infradeviation of the right eye every   ~1 minute in the setting of prominent enlargement of the right inferior rectus muscle and restriction of supraduction. Neither carbamazepine or lacosamide were able to abate ONM. Following subsequent TED worsening with almost complete restriction of the right eye, ONM was no longer observed. ONM has been described in 7 TED cases, either in conjunction with underlying restrictive strabismus or in isolation. Chronic compression and inflammation seem to lead to nerve hyperirritability, demyelination, and/or axonal damage and predispose to ONM in TED. Importantly, ONM might develop during active or inactive TED. Voltage gated sodium channel blockers should be used in TED-related ONM, albeit clinical response might be incomplete, suggesting the presence of other mechanism(s), besides ephaptic transmission. Newer neuronal membrane stabilizers acting on sodium and calcium channels (e.g. lamotrigine, oxcarbazepine) as well as newer monoclonal antibodies (e.g. teprotumumab, tocilizumab, infliximab) might play a role in TED-related ONM and their potential therapeutic effect should be investigated in future studies.

甲状腺眼病（Thyroid Eye Disease, TED）相关的眼神经肌强直（Ocular Neuromyotonia, ONM）实为罕见临床表现。本研究报告1例61岁男性甲状腺眼病患者，该患者因右侧下直肌显著肿大伴上转受限，每间隔约1分钟即出现自发性短暂性右眼下转肌强直发作。卡马西平（carbamazepine）与拉科酰胺（lacosamide）均无法缓解该ONM症状。后续患者甲状腺眼病病情恶化，右眼几乎完全活动受限，此后未再观察到ONM发作。

目前已有7例甲状腺眼病相关ONM的病例报道，此类病例可合并限制性斜视（restrictive strabismus），亦可单独出现。慢性压迫与炎症反应可导致神经兴奋性增高、脱髓鞘改变及/或轴索损伤，进而使甲状腺眼病患者易发生ONM。值得注意的是，ONM既可发生于活动性甲状腺眼病阶段，亦可出现于非活动性甲状腺眼病时期。

电压门控钠通道阻滞剂（voltage gated sodium channel blockers）可用于甲状腺眼病相关ONM的治疗，但临床应答往往不完全，提示除电突触传递（ephaptic transmission）外，尚存在其他致病机制。新型作用于钠、钙通道的神经元膜稳定剂（neuronal membrane stabilizers，如拉莫三嗪（lamotrigine）、奥卡西平（oxcarbazepine））以及新型单克隆抗体（monoclonal antibodies，如替妥木单抗（teprotumumab）、托珠单抗（tocilizumab）、英夫利昔单抗（infliximab））或可在甲状腺眼病相关ONM的治疗中发挥作用，其潜在治疗价值有待未来研究进一步探索。