Bilateral horizontal gaze palsy with preserved convergence is an uncommon neuro-ophthalmic presentation, particularly in the pediatric population. It suggests involvement of the abducens nerve fascicles along with the medial longitudinal fasciculi (MLF).1,2 Brainstem demyelination presenting with isolated ocular motor abnormalities is rare in children and requires careful clinical and radiological evaluation.3,4 Clinical Description A 13-year-old previously healthy girl presented with acute-onset binocular horizontal diplopia of 2 days’ duration, preceded by 1 month of generalized weakness and bilateral lower-limb paresthesia. There was no history of headache, fever, trauma, visual loss, or facial weakness. Ophthalmic examination revealed an unaided visual acuity of 6/6 in both eyes with normal color vision and pupillary reactions. In primary gaze, a mild left esotropia was noted. Ocular motility evaluation showed bilateral limitation of abduction with impaired adduction, while vertical eye movements and convergence were preserved Fig. 1a and b. Horizontal vestibulo-ocular reflex failed to overcome the limitation, indicating a nuclear or fascicular lesion. No nystagmus or facial nerve involvement was noted. Anterior and posterior segment examinations were unremarkable.Figure 1: Serial ocular motility photographs. (a) Bilateral limitation of adduction and abduction with preserved vertical movements at presentation. (b) Preserved convergence at presentation. (c) One-week follow-up showing complete recovery of adduction with partial recovery of abduction. (d) Preserved convergence at follow-up. (e) One-month follow-up showing full ocular motility with minimal residual esotropiaFigure 2: Schematic illustration of lesion localization. (a) Initial involvement of bilateral medial longitudinal fasciculi and abducens fascicular regions. (b) Follow-up schematic showing recovery of MLF lesions with residual lateral involvement explaining sequential recovery patternInvestigations MRI of the brain with contrast demonstrated symmetrical FLAIR hyperintensities involving the dorsal pons and ventral medulla, with mild diffusion restriction and patchy enhancement, consistent with a demyelinating process (Fig. 3, arrows). Visual evoked potentials showed delayed P100 latencies bilaterally, suggestive of subclinical optic nerve demyelination. Labs showed raised ESR (44 mm/h) with normal blood work and negative viral/treponemal tests.Figure 3: MRI brain (FLAIR images) showing symmetrical hyperintensities in the dorsal pons and ventral medulla with patchy enhancement suggestive of demyelinationFurther evaluation for the cause of demyelination was performed. Serum aquaporin-4 IgG and myelin oligodendrocyte glycoprotein IgG antibodies were negative. There was no evidence of optic nerve or spinal cord involvement on neuroimaging. Cerebrospinal fluid examination could not be performed due to parental refusal. Based on clinical, radiological, and serological findings, a diagnosis of monophasic idiopathic brainstem demyelination was considered. Management and Outcome Intravenous methylprednisolone was advised; however, due to parental refusal for hospital admission, the patient was treated with oral prednisolone at a dose of 60 mg/day (approximately 1 mg/kg/day), tapered over 4 weeks. Alternate eye patching was advised for symptomatic relief of diplopia. At 1-week follow-up, she reported improvement.Ocular examination showed partial recovery of right abduction, persistent left abduction deficit, and residual esotropia with preserved convergence Fig. 1c and d. Secondary deviation exceeded primary, suggesting partial resolution of MLF involvement with residual abducens fascicular dysfunction consistent with the schematic representation shown in Fig. 2a and the follow-up changes illustrated in Fig. 2b. After 1 month, complete resolution of diplopia with full horizontal ocular movements and minimal residual esotropia was observed Fig. 1e. At 3-month follow-up, she remained asymptomatic with normal ocular motility, a visual acuity of 6/6 in both eyes, and no recurrence of neurological symptoms. Teaching Point This photo essay demonstrates a rare pediatric presentation of bilateral abducens nerve palsy with bilateral internuclear ophthalmoplegia due to brainstem demyelination. Systematic evaluation to identify the etiology of demyelination and careful ocular motility assessment aid in accurate localization. Even when intravenous steroid therapy is not feasible, appropriately dosed oral corticosteroids may result in complete recovery, with close follow-up to monitor for recurrence. Authors’ contributions Concept: Dr. Payal Patel; Design: Dr. Payal Patel; Definition of Intellectual Content: Dr. Payal Patel, Dr. Devdatta J. Gohel; Literature Search: Dr. Payal Patel; Clinical Studies: Dr. Payal Patel, Dr. Neel Vala; Experimental Studies: Not applicable; Data Acquisition: Dr. Payal Patel, Dr. Neel Vala; Data Analysis: Dr. Payal Patel, Dr. Devdatta J. Gohel; Statistical Analysis: Not applicable; Manuscript Preparation: Dr. Payal Patel; Manuscript Editing: Dr. Payal Patel, Dr. Neel Vala; Manuscript Review: Dr. Devdatta J. Gohel; Guarantor: Dr. Payal Patel. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.
Patel et al. (Wed,) studied this question.