Checkpoint inhibitor-related immune-mediated encephalitis

Background

Onset variable, days to weeks to months
Symptoms are most frequently cognitive (confusion, agitation, altered mental status, memory impairment) and neuropsychiatric (behaviour changes, hallucinations, emotional lability)
Can have headache, nausea/vomiting, fevers, confusion, gait impairment, dysautonomia, and seizures
May be concurrent with other organ involvement, such as dermatitis, hepatitis, hypophysitis, and thyroiditis

MRI findings can include:
- Within normal limits
- Bilateral temporal or multiple T2/FLAIR lesions
- Leptomeningitial or dural enhancement, particularly in patients with CSF pleocytosis
- Can have an appearance typical for limbic encephalitis or autoimmune encephalitis
CSF findings:
- Within normal limits about a quarter
- CSF pleocytosis is common, most commonly with lymphocyte predominance (occasionally neutrophilic)
- Elevated protein
- Negative flow cytometry and cytopathology
- May have one or more detectable autoantibodies, including anti-Hu, anti-Ma2, anti-GAD65, anti-GFAP, and anti-NMDAR

Discontinue the causative medication
Methylprednisolone 500-1000 mg IV daily for 3 to 5 days followed by tapering corticosteroid
Sometimes adjunctive IVIg is tried
Recovery can take several weeks