China
Africa
Explore chapters and articles related to this topic
Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The main projections of the vestibular nuclei are to: (i) the cerebellum, mainly to the flocculonodular node from the medial and inferior vestibular nuclei, (ii) the thalamus, mainly the ventral posterior complex of the thalamus, and thence to the cerebral cortex, including areas in the parietal and temporal regions, motor and premotor regions, and frontal eye fields; (iii) the nuclei controlling extraocular muscles that mediate eye movements, namely, the oculomotor nucleus, the abducens nucleus, and the trochlear nucleus; these projections are mainly from the superior and medial vestibular nuclei; (iv) the spinal cord via the vestibulospinal tract, and (v) other vestibular nuclei on the same side or the opposite side.
Neuro-ophthalmology
Published in Mostafa Khalil, Omar Kouli, The Duke Elder Exam of Ophthalmology, 2019
The trochlear nuclei are located in the midbrain at the level of the inferior colliculus. Each trochlear nucleus innervates the contralateral SO muscle. CNIV passes through the lateral wall of the cavernous sinus inferior to CNIII and enters the SOF above the common tendinous ring. CNIV characteristics include: Only cranial nerve to exit dorsally from the brainstem.Smallest cranial nerve in number of axons.Longest unprotected intracranial course.
Discussions (D)
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
There is some suggestion that other authors may also consider the two nuclei to be identical. For example, authors of seven texts mention only one of the nuclei, not both (dorsal nucleus of the raphe: Brod, p. 411; W&G, p. 250 [Fig. 6–7B]; N&F, p. 209; MarMar, p. 198, 210 [Fig. 30–6]; dorsal tegmental nucleus: B&K, p. 146 [Fig. 9–2], 148 [Fig. 9–5]; A&B, p. 175 [Fig. 7–7], 176; Rom-S, p. 106 [Fig. 6–4]); and, of those who mention only the dorsal tegmental nucleus, several describe it as being a raphe nucleus (e.g., B&K, p. 146 [Fig. 9–1]; Rom-S, p. 106 [Fig. 6–4]). Also, some of these authors show their “dorsal tegmental nucleus” as lying just dorsal to the trochlear nucleus (B&K, p. 148 [Fig. 9–5]; A&B, p. 175 [Fig. 7–7]), while another shows his “dorsal raphe nucleus” as lying in exactly the same place (MarMar, p. 210 [Fig. 30–6]).
Superior oblique palsy: A case report
Published in Cogent Medicine, 2020
Ngozika Esther Ezinne, Kingsley Kenechukwu Ekemiri, Aliyah Khan
The trochlear nerve arises from the trochlear nucleus of the brain, emerging from the posterior aspect of the midbrain (it is the only cranial nerve to exit from the posterior midbrain) (Brazis, 1993). It runs anteriorly and inferiorly within the subarachnoid space before piercing the dura mater adjacent to the posterior clinoid process of the sphenoid bone. The nerve then moves along the lateral wall of the cavernous sinus (along with the oculomotor nerve, the abducens nerve, the ophthalmic and maxillary branches of the trigeminal nerve and the internal carotid artery) before entering the orbit of the eye via the superior orbital fissure. The trochlear nerve innervates the superior oblique, which is a muscle of oculomotion (Kim et al., 2020). The tendon of the superior oblique is tethered by a fibrous structure known as the trochlea, giving the nerve its name. Although the mechanism of action of the superior oblique is complex, in clinical practice it is sufficient to understand that the overall action of the superior oblique is to depress and intort the eyeball (Morillon & Bremner, 2017).
Vertical One-and-a-Half Syndrome with Pseudoabducens Palsy and Midbrain Horizontal Gaze Paresis
Published in Journal of Binocular Vision and Ocular Motility, 2022
Yasser Aladdin, Bader Shirah, Khurshid Khan
A 75-year-old woman with treated hypertension presented with sudden left-sided hemiplegia and vertical diplopia. The examination showed equally reactive pupils to light with an equal pupil size of 4 mm bilaterally. Right-sided ptosis of 4 mm was noted. Conjugate horizontal gaze palsy to the left, including saccade and pursuit, was noted. On rightward gaze, the right eye abduction was limited and the left eye adduction was intact with intermittent adduction nystagmus. Horizontal saccade was bilaterally impaired except for adduction saccade in the left eye. The horizontal vestibulo-ocular reflex (VOR) was bilaterally intact except for a diminished adduction slow phase in the right eye. Convergence was also impaired in the right eye. Upgaze was conjugately limited with monocular loss of infraduction in the right eye and intact infraduction in the left eye consistent with the vertical one-and-a-half syndrome. The upward vertical saccades and smooth pursuit were bilaterally impaired. The downward saccades and smooth pursuit were unilaterally impaired on the right and intact on the left. The vertical upward VOR was bilaterally impaired, but the downward slow phase was bilaterally intact (Table 1, Figure 1). Left lid retraction was noted in the primary position along with globe retraction and convergence retraction nystagmus on attempted upgaze (Video). Bell’s phenomenon was absent in the right eye. On tilting the head in roll to the right, the rightward torsional saccadic quick phase was conjugately absent. Conjugate torsional deviation to the left with left beating torsional nystagmus was also observed during the first week. Intact deorsumduction of the left eye suggested the integrity of the right trochlear nucleus.
Trochlear nerve palsy and contralateral internuclear ophthalmoplegia: an unusual crossed syndrome
Published in Clinical and Experimental Optometry, 2020
Trochlear nerve palsies can be identified by a vertical deviation that worsens in contralateral gaze and ipsilateral head tilt.2014 Each trochlear nucleus is located in the dorsal tegmentum of the midbrain at the level of the inferior colliculus.2015 As the trochlear nerve is the only cranial nerve that decussates after leaving the brainstem, a left trochlear nucleus lesion would result in a right trochlear nerve palsy, as in this case.2015