Clinical Presentation of Pseudo–Abducens Palsy

Abstract

Although considered to be a rare condition, it is important for the clinician to differentiate pseudo-abducens palsy from a classic abducens infranuclear palsy. Presented is a case displaying the typical features of a pseudo-abducens palsy, in conjunction with contralateral esotropia, which further supports the theory of a dysfunctional supranuclear vergence pathway.

Medial strabismus (esotropia) at rest associated with contralateral paramedian thalamic ischemic infarction in 2 dogs

“…13 These supranuclear pathways usually are independent of one another, and therefore when an eye movement is neurologically abnormal, neurologists focus on determining whether the deficit is caused by a supranuclear, nuclear or infranuclear lesion. 13 An infranuclear and nuclear origin of the lesion can be ruled out clinically when an eye movement remains intact with 1 supranuclear pathway stimulation despite impairment by another. 13 When evaluating patients with ocular abduction deficits, lesions anywhere along the pathway from the extraocular muscles to the supranuclear areas that control horizontal saccades are considered for the motility deficit.…”

“…13 An infranuclear and nuclear origin of the lesion can be ruled out clinically when an eye movement remains intact with 1 supranuclear pathway stimulation despite impairment by another. 13 When evaluating patients with ocular abduction deficits, lesions anywhere along the pathway from the extraocular muscles to the supranuclear areas that control horizontal saccades are considered for the motility deficit. 14 Specifically, esotropia can be a result of a muscular, neuromuscular junction (eg, myasthenia gravis), abducens nerve (eg, anywhere along its course from the dorsal pons to the orbit) or supranuclear (eg, convergence spasm or increased convergence tone, divergence insufficiency) cause.…”

“…In humans, neurologic deficits to the extraocular muscles can be classified as supranuclear (or upper motor neuron), nuclear, and infranuclear (or low motor neuron) lesions 13 . More specifically, any condition that disrupts signal transmission from the nucleus to the peripherally innervated region is considered infranuclear 13 .…”

“…In humans, neurologic deficits to the extraocular muscles can be classified as supranuclear (or upper motor neuron), nuclear, and infranuclear (or low motor neuron) lesions 13 . More specifically, any condition that disrupts signal transmission from the nucleus to the peripherally innervated region is considered infranuclear 13 . Multiple supranuclear pathways travel from the cerebrum to the brainstem for different types of eye movements (ie, smooth pursuit, saccadic, vergence, and vestibulo‐ocular eye movements) 13 .…”

“… 13 More specifically, any condition that disrupts signal transmission from the nucleus to the peripherally innervated region is considered infranuclear. 13 Multiple supranuclear pathways travel from the cerebrum to the brainstem for different types of eye movements (ie, smooth pursuit, saccadic, vergence, and vestibulo‐ocular eye movements). 13 These supranuclear pathways usually are independent of one another, and therefore when an eye movement is neurologically abnormal, neurologists focus on determining whether the deficit is caused by a supranuclear, nuclear or infranuclear lesion.…”