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Ocular Motor Cranial Neuropathies
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Zane Foster, Ashwini Kini, Bayan Al-Othman, Andrew G. Lee
The abducens nucleus is a part of the horizontal gaze center (discussed in detail below), when involved causes a gaze palsy as opposed to a unilateral motility deficit and allows for clinical localization distinct between the sixth nerve and its nucleus. When patients present with a conjugate lateral gaze palsy, this localizes it to the horizontal gaze center, indicating a nuclear lesion.17 However, if the patient simply has a unilateral abduction deficit in one eye, it is more likely an infranuclear lesion.
Physiology of Equilibrium
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
Floris L. Wuyts, Leen K. Maes, An Boudewyns
Upon head rotation to one side (Figure 49.14), denoted as the ipsilateral side, the ampulla of the ipsilateral horizontal canal is stimulated followed by an immediate increase in firing rate of the neurons, proportional to the velocity of the head turn. These signals project mainly on to the ipsilateral MVN, but other parts of the VN are also involved. From there, axons decussate onto the contralateral abducens nucleus which innervates the lateral rectus of the contralateral eye through the VIth nucleus. Additionally, the interneurons of the contralateral abducens nucleus project through the longitudinal medial fasciculus to the ipsilateral medial rectus subnucleus in the oculomotor nucleus (III) that activates the medial rectus muscle of the ipsilateral eye.
The Vestibular System: An Overview of Structure and Function
Published in Kenneth J Ottenbacher, Margaret A Short Degraft, Vestibular Processing Dysfunction in Children, 2013
to the oculomotor nuclear complex. Eye position commands, probably from the PPRF, are added at the MVN and at the abducens nucleus. The abducens nucleus send fibers to the lateral rectus muscle to abduct the eye on the same side. Internuclear neurons within the abducens nucleus give
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.
Eight-and-a-Half Syndrome Secondary to Neurotoxoplasmosis: A Rare Case Report
Published in Neuro-Ophthalmology, 2022
Joaquim Francisco Cavalcante-Neto, Gabriel Costa dos Reis, Mateus Aragão Esmeraldo, Bianca Ratts Freitas dos Santos, Paulo Roberto Lacerda Leal, Keven Ferreira da Ponte, Gerardo Cristino-Filho, Espártaco Moraes Lima Ribeiro
EHS is a combination of one-and-a-half-syndrome and an ipsilateral peripheral facial palsy (collicular/fascicular facial palsy) (1½ + 7). Its pathophysiology is explained by a lesion incorporating the facial nucleus/fasciculus, the medial longitudinal fasciculus, and the paramedian pontine reticular formation/abducens nucleus, which is the centre of horizontal gaze control, synchronising horizontal gaze during movements of the eyes and head.1,5,6 Therefore, the caudal paramedian tegmentum of the pons is the main lesion site which causes EHS. This spectrum may be classified into classic EHS (without accompanied symptoms), EHS variants (with vertical or bilateral gaze palsies), and eight-and-a-half plus syndrome (nine, thirteen-and-a-half, and fifteen-and-a-half syndromes).6
Horizontal gaze palsy and progressive scoliosis with two novel ROBO3 gene mutations in two Jordanian families
Published in Ophthalmic Genetics, 2019
Liqa A. Rousan, Abu Baker L. Qased, Ziad A Audat, Laila T. Ababneh, Saied A. Jaradat
All six patients in our study presented with the typical clinical manifestations, and the pathognomonic imaging findings of horizontal gaze palsy and progressive scoliosis reported in the literature: paralysis in the horizontal gaze with preservation of the vertical gaze and convergence with progressive scoliosis. Many theories proposed that the palsy in the horizontal gaze was attributed to abnormally decussated medial longitudinal fasciculus projections and abnormal innervation of the supranuclear abducens nerve (5). The abducens nuclei which are located in the lower part of the pontine tegmentum control the coordinated activity of the lateral and medial recti muscles responsible for the horizontal gaze (6). This was proved by neuroanatomical, electrophysiological, and clinical studies (7–10). Brain MRI shows the characteristic congenital anatomical abnormalities of the brainstem that explain the clinical manifestations in these patients: split pons sign, butterfly medulla, and absence of the facial colliculi. The split pons sign is a result of abnormally developed medial longitudinal fasciculus and abducens nuclei (11). The butterfly appearance of the medulla oblongata is a result of uncrossed corticospinal tracts (5). Thus, recognition of the characteristic imaging findings by the radiologist may be the first step for the clinical diagnosis of horizontal gaze palsy and progressive scoliosis.