The goal of the study is to assess the role of CT perfusion (CTP) in diagnosing patients with seizures or Rhythmic and Periodic Patterns (RPPs).

The utility of CTP for identifying seizures and ictal-interictal patterns is currently unclear. Few reports have evaluated the utility of hyper-perfusion in patients with non-convulsive status epilepticus. Some reports advocated for the inclusion of the results of CTP in the treatment algorithm when encountering patients with RPPs. However, large studies evaluating the utility of CTP in patients presenting with seizures or RPPs are lacking. 

We retrospectively reviewed patients who underwent a CTP and an EEG between 9/2019 - 3/2021 within our large academic medical institution. Patients who received both studies within 6 hours of each other were included. Medical records were reviewed for demographic information, indication for studies, exam, seizure type, and time from clinical onset to CTP/EEG. Two neuroradiologists and a single epileptologist blindly reviewed data independent of electronic medical record interpretation.

A total of 103 patients met the inclusion criteria. Hyper-perfusion on CTP had 40% sensitivity and 92% specificity (with an 86% negative predictive value) for electrographic seizure and/or lateralized periodic discharges / rhythmic delta activity (LPDs/LRDA), while having 34% sensitivity and 96% specificity for clinical seizures. Abnormal CTP, either hyper- or hypoperfusion, had an 85% sensitivity and 54% specificity for identifying electrographic seizures and/or LPD/LRDA with 94% negative predictive value. Patients with hyper-perfusion had higher risk of having electrographic seizures and/or LPD/LRDA compared to hypoperfusion/normal perfusion (54% vs 14%, p0.001). There were no patients with hyperperfusion on CTP with generalized rhythmic delta activity or generalized periodic discharges.

CTP may provide additional evidence to neurologist when evaluating patients presenting with clinical suspicion for seizures. CTP hyper-perfusion has high specificity while abnormal CTP (either hypo or hyper) has a high sensitivity for seizures and RPPs.