2024 American Academy of Neurology Abstract Website

Objective:

To highlight a rare but clinically relevant complication of immune checkpoint inhibitor (ICI) use in a breast cancer patient with new-onset refractory status epilepticus (NORSE).

Background:

Use of ICIs such as pembrolizumab, a monoclonal antibody to the programmed death-1 receptor (PD-1), is growing increasingly common in cancer treatment. Although rare, these agents can affect the central nervous system (CNS), where both encephalitis and aseptic meningitis have been described. We report a difficult case of a breast cancer patient presenting with encephalopathy, fevers, and seizures, initially treated for presumed meningitis without symptom alleviation, found ultimately to be suffering from NORSE and CNS encephalitis secondary to ICI use. This case highlights the importance of early recognition and management of ICI-induced CNS encephalitis.

Design/Methods:

Case report and literature review

Results:

A 51-year-old woman with stage 3 ductal carcinoma (on taxol/cisplastin/pembrolizumab) presented with one month of fever and encephalopathy requiring ICU admission for airway protection from worsening mentation. CSF studies revealed protein of 109 mg/dL and 41 nucleated cells with initially negative meningoencephalitis panel. She was placed on broad spectrum antibiotics without relief of symptoms, eventually developing NORSE. Repeat LP revealed possible Parechovirus which was later felt to be an aberrant result. MRI brain was unrevealing. Her course was complicated by hepatomegaly, splenomegaly, ferritin to >16,500 ng/mL, DIC and concern for possible systemic hemophagocytic lymphohistiocytosis (HLH). The patient remained in NORSE despite three anti-epileptics, ultimately put into 50% burst suppression with high levels of intravenous midazolam. She subsequently improved with use of high dose steroids and IVIG for presumed pembroluzimab-induced toxic encephalitis.

Conclusions:

Early recognition of ICI-induced CNS toxicity is imperative to initiate prompt treatment and thus mitigate patient morbidity and mortality. Clinicians are encouraged to recognize this rare but clinically significant complication of ICI use.