Using CT Perfusion in the Interictal State

Abstract

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.

“It's not mine!” First description of somatoparaphrenia possibly reflecting an undergoing ictal epileptic activity

“…4 According to the literature, LPDs can reflect NCSE if they are associated with focal hyperemia on CT perfusion or with hypermetabolism on positron emission tomography. [4][5][6] However, in our patient the EEG recording showed a periodic pattern of focal LPDs in right centro-temporal regions at a rate of 1-1.5 Hz, which-taken alone-is not indicative of continuous ictal activity, and does not necessarily reflect NCSE, but could represent postictal dysfunction of right hemispheric structures. Despite these limitations, the clinical, neurophysiological, and neuroimaging data pointed to symptoms arising from a right (non-dominant hemisphere) frontoparietal zone.…”

Significance of thalamic hyperperfusion patterns in computed tomography perfusion in patients with nonconvulsive status epilepticus: possible utility in predicting antiseizure medication resistance

“…11 While there have been reports of an association between changes in CTP patterns and EEG ictal-interictal continuum patterns or electrographic seizure (ESz), no consensus has been established regarding the use of CTP in NCSE patients. 12,13 Furthermore, to the best of our knowledge, no previous study has investigated the relationship between a hyperperfusion pattern (HPP) in CTP and antiseizure medication (ASM) responses in patients with NCSE. Therefore, this study investigated the characteristics of CTP patterns in NCSE patients and their association with ASM responses with the aim of achieving better prognostication.…”