mesencéfalo neuroanato aula

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III nervo - Músculos oculares extrínsecos
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III nervo – músculos oculares intrínsecos
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Keane: Arch Neurol, Volume 61(2).February 2004.280 
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53 anos, fem., súbita instabilidade da marcha, diplopia vertical ao olhar p/baixo, ataxia moderada.
E.F.: inclinação espontânea da cabeça p/esq., piora da diplopia ao inclinar a cabeça p/dir. (paralisia do IV nervo direito).
RNM: infarto cerebelar bilateral e teto do mesencéfalo esq. (Art. Cerebelar. Superior).
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Trochlear nerve schwannoma
Neurology vol. 62(9) 11 May 2004 p 1643 
Thömke, Frank MD; Gawehn, Joachim MD
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Oftalmoplegia internuclear
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Bilateral internuclear ophthalmoplegia with exotropia in primary position. Jung: Arch Neurol, Volume 61(3).March 2004.429 
53 anos, masc.,
Traumatismo craniano
Diplopia e vertigem, instabilidade da marcha
Oftalmoplegia Internuclear com exotropia
RNM: hemorragia pontina focal superior
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Overview of the visceral motor component Provides parasympathetic innervation of the constrictor pupillae and ciliary muscles of the eye. The visceral motor component of CN III is involved in the pupillary light and accommodation reflexes. 
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Somatic motor component, final innervation Within the orbit CN III fibers pass through the tendinous ring of the extraocular muscles and divide into superior and inferior divisions. The superior division ascends lateral to the optic nerve to innervate the superior rectus and and levator palpebrae superioris muscles on their deep surfaces. The inferior division of CN III splits into three branches to innervate the medial rectus and inferior rectus muscles on their ocular surfaces and the inferior oblique muscle on its posterior surface 
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The trochlear nerve has only a somatic motor component: Somatic motor (general somatic efferent)Somatic motor innervates the superior oblique muscle of the contralateral orbit. The superior oblique muscle is one of the six extraocular muscles responsible for the precise movement of the eye for visual tracking or fixation on an object. See the occulomotor nerve (CN III) chapter for a discussion of eye movements and the interaction between the three nuclei and nerves that innervate the extraocular muscles The trochlear nerve innervates the superior oblique muscle of the contralateral orbit. Contraction of the superior oblique muscle depresses, intorts (rotates inward), and abducts the eye 
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Limitation of the right superior oblique muscle on gaze down and left. B, Magnetic resonance image (FLAIR [fluid-attenuated inversion recovery]) shows infarcts in the territory of the superior cerebellar arteries of both cerebellar hemispheres and the left pontomesencephalic tectum, interrupting right fourth nerve fascicles just before their decussation. 
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Precontrasted axial T1-weighted MRI showing an isointense enlargement of the cisternal segment of the left trochlear nerve (left) with enhancement after gadolinium (right) in a 66-year-old man with diplopia on downgaze. Neurologic examination was normal except for an ipsilesional superior oblique palsy (limited depression in adduction to about 75% of normal). Trochlear nerve schwannomas (figure) are usually associated with additional signs of brainstem compression, 1 but may also cause isolated 4th nerve palsies in the absence of neurofibramato-sis. 1,2 This is a rare, but probably under-recognized and underdiagnosed entity, as MRI-documented 4th nerve schwannomas were reported in 6 of 68 patients with isolated superior oblique palsies. 2 (We also observed two patients within 1 year.) Observation with serial MRI was recommended as an appropriate management to ensure that the lesion is stable, which was seen in five of six patients over a follow-up period of 11 to 26 months 
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T1-weighted (A) and gradient-echo (B) magnetic resonance images showing a
Bilateral internuclear ophthalmoplegia with exotropia in primary position discrete subacute hemorrhage extending ventrally from the floor to fourth ventricle at the upper pontine level. 
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Cranial Nerve IV - Trochlear Nerve Page 3 of 7 Origin and central course The fibers of the trochlear nerve originate from the trochlear nucleus located in the tegmentum of the midbrain at the level of the inferior colliculus. The nucleus is located just ventral to the cerebral aqueduct. It is readily identifiable by its close association with the myelinated medial longitudinal fasciculus that allows communication between various brainstem nuclei. Fibers leaving the trochlear nucleus travel dorsally to wrap around the cerebral aqueduct. All fibers of the two trochlear nerves decussate (i.e. cross) in the superior medullary velum and exit the dorsal surface of the brainstem just below the contralateral inferior colliculus. 
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Visceral motor component, origin and course The visceral motor component originates from the Edinger-Westphal nucleus located in the rostral midbrain at the level of the superior colliculus. In a coronal cross-section of the brainstem the Edinger-Westphal nucleus sit within the "V-shaped" oculomotor nuclei just ventral to the cerebral aqueduct. Preganglionic parasympathetic fibers course ventrally through the midbrain, interpeduncular fossa, cavernous sinus, and superior orbital fissure along with the somatic motor fibers of CN III.