Eccentric topic of the Week
Question 2.
Regarding the oculomotor nerve:
A. False: It originates from the superior pons
B. True: It has many subnuclei
C. False: Pupillary-sparing palsy usually indicates a compressive lesion
D. True: It can be a false localizing sign in herniation syndromes
E. False: It is responsible for innervating the dilator pupillae
The oculomotor nerve originates from the midbrain at the level of the superior colliculus. It has two components: the somatic motor and the parasympathetic Edinger Westphal nucleus. The somatic motor component has three subnuclei: the lateral, medial, and central subnuclei (these nuclei lie at the level of the superior colliculus). The oculomotor nerve elevates the upper eyelid, turns the eyeball upward, downward, and medially; it also constricts the pupil and accommodates the eye. A compressive lesion of the oculomotor nerve produces pupillary dilation as the first sign (so-called surgical oculomotor nerve palsy); the medical oculomotor nerve palsy is pupillary-sparing (like the classical diabetic acute 3rd nerve palsy). It supplies the constrictor pupillae and ciliary muscles with parasympathetic fibers.*
*Snell RS. The cranial nerve nuclei and their central connections and distribution. In: Clinical Neuroanatomy for Medical Students, 4th edition. Philadelphia: Lippincott-Raven, 1997: 406.
Visit:
http://www.colenpublishing.com/
for more information.
C. False: Pupillary-sparing palsy usually indicates a compressive lesion
D. True: It can be a false localizing sign in herniation syndromes
E. False: It is responsible for innervating the dilator pupillae
The oculomotor nerve originates from the midbrain at the level of the superior colliculus. It has two components: the somatic motor and the parasympathetic Edinger Westphal nucleus. The somatic motor component has three subnuclei: the lateral, medial, and central subnuclei (these nuclei lie at the level of the superior colliculus). The oculomotor nerve elevates the upper eyelid, turns the eyeball upward, downward, and medially; it also constricts the pupil and accommodates the eye. A compressive lesion of the oculomotor nerve produces pupillary dilation as the first sign (so-called surgical oculomotor nerve palsy); the medical oculomotor nerve palsy is pupillary-sparing (like the classical diabetic acute 3rd nerve palsy). It supplies the constrictor pupillae and ciliary muscles with parasympathetic fibers.*
*Snell RS. The cranial nerve nuclei and their central connections and distribution. In: Clinical Neuroanatomy for Medical Students, 4th edition. Philadelphia: Lippincott-Raven, 1997: 406.
Visit:
http://www.colenpublishing.com/
for more information.
No comments:
Post a Comment