P2.C051: A pediatric case of Bickerstaff's Brainstem Encephalitis with relapse of symptoms following initial treatment with IVIG and steroids.

Introduction: Bickerstaff's brainstem encephalitis (BBE) is rare post infectious condition characterized by the triad of ophthalmoplegia, ataxia, and decreased consciousness attributed to its involvement of the CNS. Prognosis is generally favourable, with only rare instances of relapse reported. We present a case of BBE with relapse of symptoms after initial treatment with IVIG and steroids.

Case Description: A 7-year-old female presented to the ED with left-sided facial droop, noticed upon her return from school. Of note, patient had a history of upper respiratory and GI illness 2 weeks prior.
On arrival, the patient was vitally stable, alert and oriented. Neurological examination revealed mild ptosis, left lateral gaze palsy with right-sided nystagmus, complete weakness on the left side of her face including the forehead, 4/5 strength in upper and lower left extremities with brisk reflexes and mild gait ataxia.
MRI of the brain showed nonspecific left pontine/middle cerebellar peduncle restricted diffusion with T2/FLAIR hyperintensity and post-contrast enhancement, along with T2/FLAIR hyperintensities observed in the medulla. An extensive workup was initiated to rule out infectious, thrombophilic, metabolic and autoimmune etiologies all of which resulted negative.
Given CNS involvement and MRI findings a diagnosis of BBE was made. Treatment with IVIG and high-dose steroids led to clinical improvement except for ophthalmoplegia. Consequently, the patient was discharged home.
Patient returned 9 days later with 3 day history of worsening gaze palsy. Exam notable for bilateral horizontal gaze palsy and left sided dysmetria on finger to nose test. Repeat MRI revealed increased size of abnormal signal within the brainstem involving the left posteriolateral aspect of the pons, superior inferior and middle cerebellar peduncle and medulla. High dose steroids were repeated together with 4 doses of Rituximab. After a 16-day hospital stay, patient was discharged home with notable symptoms improvement.

Discussion: BBE poses a diagnostic challenge due to its rare occurrence and clinical resemblance to other syndromes. The presumed pathogenesis involves an immune mediated response triggered by prior infections. In our case, we ran an extensive panel of infectious diseases and, no potential trigger was identified.
MRI findings, observed in approximately 30% of cases, are important in diagnosis, typically showing brainstem involvement. While there is no specific biological marker for BBE, it is noteworthy that anti-GQ1b antibodies are detected in two-thirds of patients; however, they were not evaluated in our case. Antiganglioside antibodies, though nonspecific, were negative.

Conclusion: BBE is a rare neurological condition that requires prompt recognition and diagnosis, which is crucial for timely intervention and management. Our case underscores the importance of considering BBE in the differential diagnosis of pediatric patients, particularly if there is a history of recent viral illness.