A 32-year-old woman is admitted to the hospital after losing consciousness and collapsing in the middle of the street. A neurologic examination reveals absence of the accommodation reflex of her right eye. Which of the following is most likely involved in the pathology in this patient?
Correct Answer: Edinger-Westphal nucleus
Description: The accommodation reflex is performed by constriction of the pupil when trying to focus on a near object. This function is controlled by the parasympathetic nerve fibers carried in the oculomotor nerve from the Edinger-Westphal nucleus of the midbrain that synapse in the ciliary ganglion. Postganglionic axons act on the sphincter pupillae muscle to cause reduction in pupil diameter and on the ciliary muscle to cause relaxation of the suspensory ligament, allowing the lens to adopt a more spherical shape for near focusing. If there is a lack of accommodation, it means the action of the ciliary muscle is compromised. The ciliary muscle also gets parasympathetic innervation by postganglionic neurons evoked from the ciliary ganglion by GVE fibers of oculomotor nerve whose cell bodies are located in the Edinger-Westphal nucleus. The superior salivatory nucleus is involved with lacrimation and salivation, not the ciliary muscle and accommodation. The superior cervical ganglion is a sympathetic ganglion; its postganglionic axons innervate the dilator pupillae muscle, which causes mydriasis, but not the miosis of accommodation. The trigeminal ganglion does not have parasympathetic fibers and does not innervate the ciliary muscle for accommodation.
Category:
Anatomy
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