Isolated Unilateral Oculomotor Neuropathy Following A Presumed Infection Treated With Corticosteroids in a Child

Introduction

Injury to the third cranial nerve (CN III) leads to oculomotor neuropathy [1]. Oculomotor nerve palsies are rare in children; the combined incidence of III, IV, and VI nerve palsies is approximately 8 per 100 000 children [2]. Oculomotor neuropathy has both congenital and acquired etiologies. Congenital causes include intrauterine infections and traumatic delivery [3]. Acquired oculomotor palsy may result from intracranial vascular pathology, trauma, systemic viral infections, central nervous system (CNS) infection, systemic lupus erythematosus, and idiopathic causes [4]. Congenital and structural etiologies (traumatic, neoplastic, and vascular) cause 92% to 94% of oculomotor neuropathy cases in children, whereas infectious and idiopathic etiologies cause only 6% to 8% [5]. Corticosteroids can be used to treat oculomotor neuropathy associated with viral infections, inflammation, or autoimmune conditions; however, evidence supporting their use is limited [6]. Post-infectious oculomotor neuropathy is often a diagnosis of exclusion; no standardized consensus exists regarding corticosteroid dosing or duration in pediatric cases. Given the rarity of the condition and lack of clear treatment guidelines, this report presents a case of isolated acute oculomotor neuropathy in a child after presumed infection.

Case Report

A 4-year-old boy presented to the emergency department with a 1-day history of left-sided eyelid drooping and diplopia. This was preceded by a 3-day history of subjective fever and decreased activity. He had previously been evaluated at a primary care center, where he was diagnosed with pharyngitis and prescribed azithromycin.

The eyelid drooping was associated with limited movement of the left eye. There was no history of gait disturbance, vomiting, headache, or altered level of consciousness. Family and developmental histories were unremarkable. Immunizations were up to date, and the perinatal history was unremarkable.

Physical examination was non-focal except for complete left-sided oculomotor neuropathy, characterized by impaired adduction and limitation of upward and downward gaze, ptosis, and anisocoria; the left pupil was larger than the right and sluggishly reactive to light (Figure 1). No other cranial nerve involvement, ataxia, or signs of meningeal irritation were observed. Motor and sensory examination findings were normal.

Computed tomography was performed in the emergency department to rule out a structural lesion in the posterior fossa; findings were normal. Ophthalmologic evaluation revealed no evidence of papilledema. The child was subsequently admitted under the care of the pediatric neurology team. Brain magnetic resonance imaging (MRI) (non-contrast and contrast-enhanced), along with magnetic resonance angiography and venography, was performed to exclude inflammatory or neoplastic pathology; no abnormalities were identified (Figure 2). Lumbar puncture demonstrated a normal opening pressure, unremarkable cerebrospinal fluid (CSF) analysis, negative bacterial culture findings, and negative findings in a multiplex meningitis polymerase chain reaction panel (including Haemophilus influenzae, herpes simplex viruses 1 and 2, cytomegalovirus, enterovirus, varicella zoster virus, and human herpesvirus-6); these results effectively ruled out intracranial hypertension and meningoencephalitis. CSF immunoglobulin G and both CSF and serum myelin oligodendrocyte glycoprotein antibody findings were negative; these markers may be present in immune-mediated CNS disorders.

The infectious disease team was involved early and recommended initiation of ceftriaxone for presumed partially treated CNS bacterial infection; this was discontinued after CSF results were obtained. Systemic Epstein-Barr virus and cytomegalovirus infections, as well as autoimmune thyroiditis, were excluded. Complete blood count and peripheral blood smear results were normal. Respiratory viral multiplex polymerase chain reaction findings were negative (including Mycoplasma pneumoniae, influenza A and B, parainfluenza, respiratory syncytial virus, adenovirus, enterovirus, and multiple coronavirus types).

A presumed post-infectious immune-mediated process was considered; oral prednisolone was initiated at a dose of 2 mg/kg/day for 5 days, followed by a 5-day taper. Follow-up at 3 weeks demonstrated partial improvement, and complete resolution of oculomotor neuropathy was observed at 3 months (Figures 3, 4). Patching of the right eye was recommended to prevent amblyopia.

Discussion

Oculomotor neuropathy in pediatric patients is rare and has diverse etiologies. One study detected oculomotor neuropathy in only 28 patients younger than 20 years after reviewing more than 3 million inpatient records [1]; another study identified 49 patients younger than 18 years through a review of over 65 000 records, and 4 of those patients had bilateral oculomotor palsy [7]. Male predominance has been observed [1,7].

The pathophysiology of oculomotor neuropathy involves multiple mechanisms, including direct neurotropism, in which viruses infect neurons and disrupt their function, and infection-induced neuroinflammation characterized by cytokine release and subsequent neuronal injury. Additionally, viral antigens can trigger autoimmune responses that further exacerbate neural damage [8]. The pathogenesis of immune-mediated neurological disorders in children may differ from that in adults. Mechanisms such as molecular mimicry and post-viral inflammatory demyelination are well documented in pediatric conditions, including Guillain-Barré syndrome and acute disseminated encephalomyelitis [9,10].

Clinical manifestations of oculomotor neuropathy may be complete or partial, depending on the affected pathway. Patients with complete oculomotor neuropathy display an inability to adduct, supraduct, or infraduct the eye; a dilated pupil with a sluggish light response; complete ptosis; anisocoria; and diplopia [7]. In the present case, the patient exhibited complete left-sided oculomotor neuropathy, characterized by impaired adduction, limited upward and downward gaze, ptosis, and anisocoria; the left pupil was larger than the right.

Although radiological findings are often nonspecific in cranial nerve pathologies, MRI with heavily T2-weighted three-dimensional steady-state free precession sequences – providing high spatial resolution and excellent contrast between CSF and the cisternal segments of cranial nerves – along with contrast-enhanced T1-weighted sequences, can facilitate detection of abnormalities [11]. Computed tomography angiography should be performed when there is clinical suspicion of an aneurysm [12]. In the present case, computed tomography, MRI, and CSF findings were normal.

Most adult patients with ischemic oculomotor neuropathy demonstrate improvement within 1 to 3 months [13]. Injection of botulinum toxin into the lateral rectus muscle may be effective in acute partial oculomotor neuropathy [13]. In adults with pupil-sparing acquired palsy, surgery is recommended after 6 months if no improvement occurs [13].

The best-established model for corticosteroid use in cranial nerve injury is likely Bell’s palsy [14]. A few studies have explored the effectiveness of corticosteroids in treating oculomotor neuropathy associated with viral infections, inflammation, and autoimmune conditions [6,15–18]. In children, the literature describes post-viral oculomotor neuropathy after coronavirus disease 2019 (COVID-19), norovirus infection, measles, and other viral mononeuritides. Some cases resolved spontaneously, whereas steroid pulse therapy was effective in others [19–21]. Because the patient in this case was clinically stable and had no systemic manifestations other than a resolved fever, oral corticosteroids were administered rather than intravenous pulse therapy. Complete recovery of oculomotor neuropathy was achieved within 3 months. Although a definitive causal relationship between corticosteroid therapy and clinical improvement cannot be established, recovery followed treatment in this case.

Conclusions

Acquired oculomotor neuropathy is rare in children. Nevertheless, the present case suggests that corticosteroids can serve as a therapeutic option when an immune-mediated pathogenesis is suspected. This approach should be considered only after a comprehensive negative workup – including MRI, CSF analysis, and infection screening – to avoid masking or exacerbating an underlying pathology. Oral corticosteroids may be used as an alternative to intravenous pulse therapy in hemodynamically stable children without systemic involvement. Further studies and multicenter case series are needed to establish standardized timing and tapering protocols for corticosteroid use in post-infectious neuropathies.