04---滑车神经Trochlear-Nerve

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,CRANIAL NERVE ANATOMY,颅神经结构,The,Trochlear,Nerve or Cranial Nerve ,滑车神经,The,Trochlear,Nerve,The fourth cranial nerve provides motor,innervation,to only a single muscle, the superior oblique muscle,（上斜肌）,.,Real origin of,trochlear,nerve,Cerebral peduncle,（大脑脚）,Nucleus,（神经核）,Trochlear,nucleus,滑车神经核,The,trochlear,nucleus is situated at the level of the inferior,colliculus,（滑车神经核位于下丘水平）, just ventral to the aqueduct,（中脑导水管腹侧）, posterior to the MLF,（内侧纵束）,and just inferior to the,oculomotor,nerve complex. The localization of the nucleus very close to the MLF explains why lesions that involve the,trochlear,nucleus most often cause both a fourth nerve palsy and an,internuclear,ophthalmoplegia,(INO),（核间性眼肌麻痹）,.,Trochlear,nucleus,Axons leaving the nucleus course dorsally around the aqueduct and the left and right fascicular segments cross each other,（左右束交叉）,at the level of the superior,medullary,velum,（上髓帆）,before exiting the midbrain at its posterior surface,（中脑背侧出脑）, just caudal to the inferior,colliculus,. These are two unique features of the fourth cranial nerve: (1) it is the only cranial nerve crossing the midline, hence a superior oblique muscle is always innervated by the,contralateral,trochlear,nucleus,（上斜肌由对侧滑车神经核支配）,and (2) it is the only cranial nerve exiting the brainstem at its dorsal surface.,Apparent origin of,trochlear,nerve,Inferior,colliculus,Cistern of great cerebral vein,Cisternal,segment,The trick is to look for the superior,medullary,velum, a small flat band at the back of the superior part of the fourth ventricle. At that level, the nerves exit the brainstem in a nearly horizontal,mediolateral,direction,（水平沿中间外侧方向）,until they reach the free edge of the,tentorium,（天幕游离缘）,.,Cisternal,segment,They then course,anteriorly,around the brainstem and pass through the gap between the superior cerebral artery and superior,cerebellar,artery, lateral to the,oculomotor,nerve. Because the nerves have to turn around the complete brainstem, they are the,crainal,nerves with the longest intracranial segment.,Intracavernous,and orbital course,Cavernous sinus,Cavernous Segment,The,trochlear,nerve then enters the lateral wall of the cavernous sinus below the,oculomotor,nerve. As already mentioned, the cavernous segment of the,trochlear,nerve initially is situated below the third nerve but then gradually ascends along the lateral border of the third nerve as the nerves approach the SOF,（眶上裂）,and once in the SOF the,trochlear,nerve can be found at the,superolateral,border of the third nerve.,Superior orbital fissure,Trochlear,(pulley) of superior oblique muscle,Extracranial,Segment,The,trochlear,nerve then crosses over the superior border of the third nerve to run medially toward the superior oblique muscle. This nerve courses above the annulus of,Zinn,and does not pass through the annulus like the,oculomotor,and,abducens,nerve.,Arteries for,Trochlear,Nerve,The,trochlear,nerve is supplied by arterioles from three different sources,the posterior part of the arterial cerebral circle (Willis polygon), or its branches in its posterior course,the internal carotid artery,（颈内动脉）,in its intermediate course,the ophthalmic artery,（眼动脉）,in the orbit,Thank you!,