Using CT Perfusion in the Interictal State

Periodic discharges seen in patients undergoing continuous EEG pose a challenge to physicians in falling into the interictal-ictal continuum and need for appropriate diagnostic and management approach. The authors herein present an 83-year-old male patient with an acute subdural hematoma who developed intermittent right upper and lower extremity weakness with change in mental status post craniotomy and hematoma evacuation. The patient was intubated and sedated with midazolam and propofol and placed on anti-seizure medications to control seizures. He was placed on continuous EEG monitoring and later developed lateralized periodic discharges. To guide treatment, a computed tomography perfusion study of the brain was performed. The results were consistent with an ictal phenomenon because of the presence of left hemispheric hyperemia. This increased cerebral blood volume and blood flow was used as a diagnostic tool to warrant more aggressive antiepileptic regimen. The patient was then started on an additional anti-seizure medication and dosages were further optimized. This led to an improvement in the patient's EEG and clinical state. There are numerous studies that show lateralized periodic discharges are seen as examples of subclinical status epilepticus and demonstrate hypermetabolism and hyperemia on positron emission tomography and single-photon emission computed tomography scans. When such imaging modalities are unavailable, cortical hyperperfusion on a computed tomography perfusion study might be a valid predictor of ongoing, subclinical, ictal activity and may be used as a complementary diagnostic tool to EEG to guide treatment.