Utility of CT perfusion in seizures and rhythmic and periodic patterns

CT hyper-perfusion has been reported in non-convulsive status epilepticus (NCSE), while its occurrence and relevance after single seizures or with rhythmic and periodic patterns (RPPs) that lie along the ictal-interictal continuum (IIC), remain unclear. The goal of the study is to assess the role of CT perfusion (CTP) in diagnosing patients with clinical seizures, subclinical seizures, or RPPs that lie along the IIC, to help in the clinical assessment of these entities.

We retrospectively reviewed inpatients who underwent a CTP and an EEG within 6 h of each other. CTP and EEGs were blindly reviewed independent of electronic medical records.

Out of 103 patients, 15 patients (15 %) demonstrated hyper-perfusion, 40 patients (39 %) had hypo-perfusion, while 48 patients (47 %) had normal CTP. Patients with focal CTP hyperperfusion were more likely to have clinical seizures, electrographic seizures, and/or lateralized rhythmic periodic patterns (RPPs) compared to those without CTP hyperperfusion. Focal CTP hyper-perfusion had 34 % sensitivity and 96 % specificity for identifying patients with clinical seizures, and a 40 % sensitivity and 92 % specificity for identifying patients with electrographic seizures or lateralized RPP. Although the numbers were small, none of the patients with generalized periodic discharges or generalized rhythmic delta activity had CTP hyper-perfusion.

Focal CTP hyper-perfusion has low sensitivity but high specificity for identifying patients with seizures and lateralized RPPs, and may be considered in the clinical assessment of patients where the clinical information are unclear or insufficient.

The presence of CTP hyper-perfusion should alert the physician to the possibility of an ictal related etiology accounting for the patient's symptoms.