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An Approach to Oculomotor Anomalies in a Child
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
The oculomotor nucleus resides in the midbrain and is divided into individual subnuclei for each extraocular muscle. Interestingly, the SR subnucleus innervates the contralateral SR muscle, while the remainder of the subnuclei innervates the ipsilateral corresponding muscles. The Edinger-Westphal nucleus, which supplies innervation to the pupillary constrictors, is shared by both sides. The oculomotor nerve fascicle exits the brainstem through the ventral midbrain in the interpeduncular fossa.
Spinal Cord Disease
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Macroscopically, brain and spinal cord often appear normal; the precentral gyrus and corticospinal tracts may show atrophy (Figures 23.28–23.32). Microscopic findings (Figures 23.33, 23.34) are: Loss of Betz’ cells of the motor cortex.Degeneration and gliosis of the corticospinal tracts.Degeneration of lower brainstem motor nuclei (not oculomotor nuclei) in most cases.Cytoplasmic eosinophilic inclusions (Bunina's bodies) and ubiquitin immunoreactive inclusion bodies (containing TAR DNA binding protein 43 [TDP-43]) in degenerating cranial motor nuclei, anterior horn cells, and Betz’ cells.Muscle shows features of denervation.Nonmotor pathways also demonstrate pathologic changes, including sensory pathways and peripheral sensory nerves.
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.
Complete Horizontal Gaze Paresis Due to Medial Pontine Haemorrhage
Published in Neuro-Ophthalmology, 2023
Joan Pei Yun Sim, Jackie Jia Lin Sim, Sameer Saleem, Dennis Cordato
Horizontal gaze is controlled by specific pathways and nuclei in the pontine tegmentum. The abducens nucleus receives projections from the ipsilateral paramedian pontine reticular formation (PPRF) to mediate abduction of the ipsilateral eye. It also projects efferent fibres that innervate the contralateral oculomotor nuclei through the medial longitudinal fascicle (MLF) to coordinate simultaneous adduction of the contralateral eye in the same direction.2,6 Pathological lesions arising in the PPRF or abducens nucleus can result in a gaze palsy.7 Given the role of the PPRF in the initiation of conjugate horizontal eye movements, damage to this structure will result in impairment of horizontal gaze towards the side of the lesion (including horizontal pursuit, vestibulo-ocular reflex, and saccades), and very occasionally bilateral conjugate horizontal gaze palsies should both PPRFs be affected.1,8 Additionally, complete horizontal gaze palsy may also be attributed to damage to bilateral abducens nuclei and MLFs.9,10 Our patient demonstrated impaired vertical gaze consistent with involvement of vertical gaze pathways as well as a skew deviation, which is a well-documented finding in lesions involving the MLF. Our patient’s gaze palsy was at the nuclear level, which can be distinguished from a supranuclear gaze palsy by the demonstration of a negative doll’s head manoeuvre.
Horizontal Gaze Palsy and Progressive Scoliosis in Dizygotic Twins
Published in Journal of Binocular Vision and Ocular Motility, 2022
Catarina Xavier, Miguel Vieira, Ana Filipa Duarte, Ana Xavier, Eduardo D. Silva
As it has been hypothesized in literature, the maldevelopment of the tegmentum plays a crucial role in the pathogenesis of HGPPS. Pathways that cross the midline such as the medial longitudinal fasciculus are affected and so communication from the abducens to the contralateral oculomotor nucleus is deficient, preventing a normal horizontal gaze.2,12 Contrary to what is described in the literature,14 we believe that the synergistic divergence in our patients is not due to miswiring of nerve fibers between the IIIrd and VIth nerves. Instead, we speculate that our patients’ ocular movements are due to supranuclear and internuclear abnormalities. Such as happens in internuclear ophthalmoplegia, our patients have a normal convergence of the eyes due to intact medial rectus innervation.
Disorders of vision in multiple sclerosis
Published in Clinical and Experimental Optometry, 2022
Roshan Dhanapalaratnam, Maria Markoulli, Arun V Krishnan
Hering’s law dictates that conjugate movements of the eyes require yoked coordination of the extraocular muscles, via the supranuclear communication of ipsilateral and contralateral signalling pathways.81 For example on looking to the left, the left lateral rectus muscle works in tandem with the right medial rectus muscle, and this communication all occurs via pathways involving the brainstem nuclei. The midbrain comprises vertical gaze centres, the rostral interstitial nucleus of the medial longitudinal fasiculus (MLF), trochlear and oculomotor nucleus. Lesions in these areas can result in vertical gaze palsy, superior oblique palsy, third nerve palsy and convergence-retraction nystagmus. The pons contains the abducens nucleus, paramedian pontine reticular formation and the MLF, and lesions can result in an internuclear opthalmoplegia, horizontal gaze palsies, sixth nerve palsies and skew deviation.