Gupta Vinod Kumar
Dubai Police Medical Services, P.O. Box 12005, Dubai, United Arab Emirates.
Med Hypotheses. 2005;64(6):1177-81. doi: 10.1016/j.mehy.2004.11.031.
Motion sickness is a common and distressing but poorly understood syndrome associated with nausea/vomiting and autonomic nervous system accompaniments that develops in the air or space as well as on sea or land. A bidirectional aetiologic link prevails between migraine and motion-sickness. Motion sickness provokes jerk nystagmus induced by both optokinetic and vestibular stimulation. Fixation of gaze or closure of eyes generally prevents motion sickness while vestibular otolithic function is eliminated in microgravity of space, indicating a predominant pathogenetic role for visuo-sensory input. Scopolamine, dimenhydrinate, and promethazine reduce motion-related nystagmus. Contraction of extraocular muscles generates proprioceptive neural traffic and can provoke an ocular hypertensive response. It is proposed that repetitive contractions of the extraocular muscles during motion-related jerk nystagmus rapidly augment brain stem afferent input by increasing proprioceptive neural traffic through connections of the oculomotor nerves with the ophthalmic nerve in the lateral wall of the cavernous sinus as well as by raising the intraocular pressure thereby stimulating anterior segment ocular trigeminal nerve fibers. This verifiable hypothesis defines the pathophysiological basis of individual susceptibility to motion sickness, elucidates the preventive mechanism of gaze fixation or ocular closure, advances the aetiologic link between MS and migraine, rationalizes the mechanism of known preventive drugs, and explores new therapeutic possibilities.
晕动病是一种常见且令人苦恼但了解甚少的综合征，与恶心/呕吐及自主神经系统伴随症状相关，在航空、航天以及海上或陆地环境中均可发生。偏头痛与晕动病之间存在双向病因联系。晕动病会引发由视动刺激和前庭刺激诱发的急跳性眼球震颤。注视固定或闭眼通常可预防晕动病，而在太空微重力环境中前庭耳石功能会消失，这表明视觉感觉输入起主要致病作用。东莨菪碱、茶苯海明和异丙嗪可减少与运动相关的眼球震颤。眼外肌收缩会产生本体感觉神经冲动，并可引发眼内压升高反应。有人提出，在与运动相关的急跳性眼球震颤期间，眼外肌的反复收缩通过增加动眼神经与海绵窦外侧壁的眼神经之间的连接所产生的本体感觉神经冲动，以及通过升高眼内压从而刺激眼前段三叉神经纤维，迅速增强脑干传入输入。这一可验证的假设定义了个体对晕动病易感性的病理生理基础，阐明了注视固定或闭眼的预防机制，推进了晕动病与偏头痛之间的病因联系，使已知预防药物的机制合理化，并探索了新的治疗可能性。
