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Horizontal gaze palsies can be caused by a lesion affecting any structure in these pathways. Lesions to abducens nucleus or PPRF typically create an ipsilateral gaze palsy, while lesions to MLF typically cause Internuclear ophthalmoplegia , a type of horizontal gaze palsy in which the affected eye cannot adduct in conjugation with the ...
Loss of horizontal saccades directed towards the side of the lesion, no matter the current position of gaze; Contralateral gaze deviation (acute lesions, such as early stroke, only) Gaze-evoked lateral nystagmus on looking away from the side of the lesion; Bilateral lesions produce horizontal gaze palsy and slowing of vertical saccades
As seen in horizontal saccadic palsy, the impairment of the contralateral side gaze is caused by the disrupted pathways coming from the PPRF, while the "half" impairment is from the signal passing through the medial longitudinal fascicles not being able to reach its target. One-and-a-Half syndrome is normally associated with horizontal gaze.
Conjugate gaze palsy: Conjugate gaze palsies typically affect horizontal gaze, although some affect upward gaze. Few affect downward gaze. Few affect downward gaze. These effects can range in severity from a complete lack of voluntary eye movement to mild impairments in speed, accuracy or range of eye movement.
More formally, it is characterized by "a conjugate horizontal gaze palsy in one direction and an internuclear ophthalmoplegia in the other". [1] [2] Nystagmus is also present when the eye on the opposite side of the lesion is abducted. Convergence is classically spared as cranial nerve III (oculomotor nerve) and its nucleus is spared bilaterally.
The conjugate gaze is the motion of both eyes in the same direction at the same time, and conjugate gaze palsy refers to an impairment of this function. The conjugate gaze is controlled by four different mechanisms: [4] the saccadic system that allows for voluntary direction of the gaze; the pursuit system that allows the subject to follow a ...
The diagnostic criteria for Athabaskan brainstem dysgenesis syndrome include: [1] Verification of sensorineural deafness by brainstem auditory evoked responses. [1]Upon conjugate lateral gazing, there is horizontal gaze palsy; however, the medial gaze remains intact with convergence.
The paramedian pontine reticular formation (PMPRF) is involved in coordinating horizontal conjugate eye movements and saccades. To do so, besides projecting to the ibsilateral abducens nucleus, the PMPRF projects fibers through the MLF to the contralateral oculomotor nucleus (specifically, those of its motor neurons that innervate the medial rectus muscle).