So-called posterior internuclear ophthalmoplegia due to a pontine glioma: a clinicopathological study

Abstract

Sirs: So-called posterior internuclear ophthalmoplegia (pINO) is referred to as a putative supranuclear disorder of horizontal gaze, characterized by unilateral abduction paresis and dissociated adduction nystagmus in the contralateral eye. In contrast to internuclear ophthalmoplegia (INO), the pathophysiological concept of pINO has been debated since it was first proposed by Lutz [1] as a lesion of a supranuclear pathway of abduction. Except for a clinicopathological study by Rothstein and Alvord [2], in which a lesion of "aberrant pyramidal tract" fibers to the abducens nucleus was postulated, there has been no pathological material to support the concept of pINO as a supranuclear entity. We report a clinicopathological study of unilateral so-called pINO secondary to a pontine glioma. The clinical findings, electro-oculography, and pathological study suggested a unilateral lesion of the abducens fasciculus, mimicking features of a supranuclear oculomotor disturbance.A 59-year-old man was admitted to our hospital with complaints of dysarthria and ataxia for 2 weeks. Three months previously he had developed intermittent horizontal diplopia on right gaze. Ophthalmological and neurological results at that time were normal. In the following weeks he noticed progressive bilateral trigeminal sensory loss and dysphagia. His medical history was unremarkable except for chronic polyarthritis. On admission the patient had broad-based gait, dysphagia, and dysarthria. Pupils were equal and reactive, and the corneal reflex was decreased on the left. Convergence was full with a normal near response of the pupils. The gag reflex was absent, and there was paresis of the soft palate on the left. An incomplete peripheral facial palsy was evident on the right, and sensory functions below the face were normal. Limb strength was normal, and slight dysdiadochokinesia was present in the right arm. Reflexes were brisk, and Babinski signs were present bilaterally.

Abduction paresis with rostral pontine and/or mesencephalic lesions: Pseudoabducens palsy and its relation to the so-called posterior internuclear ophthalmoplegia of Lutz

“…An impaired inhibition of the antagonistic medial rectus muscle was discussed by Collard et al [4] suggesting a medial longitudinal fasciculus (MLF) lesion contralateral to the paretic eye. Finally, some authors attributed such cases to a lesion of the intrapontine segment of the 6th nerve thereby rejecting a pre- or supranuclear origin of the abduction paresis [11-14]. …”