Test	Best triggers	Clinical role	Evidence qualification
EEG	Fluctuating examination, reduced responsiveness, suspected nonconvulsive seizure, myoclonus, grade ≥2 encephalopathy	Distinguish seizure from diffuse encephalopathy and support severity assessment	Observational EEG series; selective early use supported, routine universal testing unproven
Selected preinfusion EEG	Seizure history, CNS disease, baseline cognitive abnormality, anticipated diagnostic ambiguity	Risk context and baseline comparison	Single observational adult study; association does not prove clinical benefit
MRI/CT	Focal deficit, prolonged or refractory course, concern for stroke, hemorrhage, infection, or edema	Exclude structural alternatives	Adjunctive diagnostic role; routine imaging in mild ICANS unsupported
CSF	Atypical or refractory course with concern for infection, malignant CNS involvement, or competing inflammation	Narrow differential diagnosis	Selective use based mainly on guidance and clinical reasoning