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Neuro-Ophthalmology - part 8

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SM của hệ thống ròng rọc có innervation tự trị, trong đó có ba con đường có khả năng: (1) có cảm tình với một dự norepinephrine từ hạch cổ tử cung cao cấp; (2) cholinergic phó giao cảm, có lẽ từ hạch lông mi, | the lower eyelid Muller s inferior tarsal muscle and connective tissues extending to the inferior tarsal plate are also coupled to the conjoint IR-IO pulley coordinating lower eyelid position with vertical eye position during vertical gaze shift. The SM of the pulley system has autonomic innervation mcludmg three likely pathways 1 sympathetic with a norepinephrine projection from the superior cervical ganglion 2 cholinergic parasympathetic probably from the ciliary ganglion and 3 nitroxidergic probably from the pterygopalatine ganglion 15 . Although the rigid SO pulley - the trochlea - has been known since antiquity 17 18 its immobility is exceptional and also unique that the SO s OL inserts via the SO sheath on the SR pulley s medial aspect 5 . Net SO pulling direction probably changes half as much as duction despite an immobile pulley because of the uniquely thin broad SO tendon wrapping over the globe 19 . Most of these anatomical relationships are evident in gross dissections and surgical exposures. After surgical transposition of a rectus tendon for the treatment of e.g. strabismus due to LR palsy the path of the transposed EOM continues to be obliquely toward the original pulley location. The effect of rectus EOM transposition can be improved by suture fixation from a posterior point on the transposed EOM belly to the sclera adjacent to the palsied EOM 20 a maneuver shown by MRI to displace the pulley further in the transposed direction 21 . Functional Anatomy of Pulleys The insertion of each rectus EOM s OL on its pulley appears to be the main driving force translating linearly moving that pulley posteriorly during EOM contraction. There is consensus that in both humans and monkeys fibers on the orbital surface of each rectus EOM insert into the dense encircling tissue 4 6 in a distributed manner over an anteroposterior region in which successive bundles of fibers extend up to 1 mm into the surrounding cttnnective tissue1 7 . 1While they may properly be said