To describe cerebral computed tomography (CT) perfusion patterns and electroencephalogram (EEG) abnormalities in a patient presenting with focal neurological deficits.

New-onset focal neurologic deficits are typically ascribed to ischemic causes, however, seizures and other interictal states may have similar presentations. Cerebral CT perfusion is a valuable tool that allows differentiation between these etiologies.

A 61-year-old woman with aplastic anemia on chronic cyclosporine therapy developed Klebsiella bacteremia. On day 8th of antibiotic treatment, she complained of a severe right-sided headache with photophobia. Subsequently, she became unresponsive and had a brief tonic-clonic seizure. Initial brain CT and CT angiogram were unremarkable. EEG showed abundant intermediate in duration ~1 and up to 2Hz lateralized rhythmic delta activity (LRDA) in the right frontotemporal region. The 2HELPS2B score was 3. Brain magnetic resonance imaging (MRI) with contrast exhibited thin diffuse pachymeningeal enhancement without diffusion restriction. Cerebrospinal fluid showed protein levels of 146mg/dl, white blood cell counts of 15/ul, and normal glucose levels. She was started on Levetiracetam and received escalated antibiotic therapy due to suspected bacterial meningoencephalitis. The patient remained encephalopathic and developed new left-sided neglect two days later. Cerebral CT perfusion showed right frontal cortical hyperperfusion, suggestive of an ictal process. Subsequent continuous EEG monitoring demonstrated ongoing fluctuating 1-2Hz right frontotemporal LRDA and later two right frontal onset seizures. Her mental status improved, and the hemineglect was resolved following intensified antiseizure treatment.

These findings suggest that patients with LRDA or lateralized ictal-interictal continuum (IIC) accompanied by focal neurological deficits may benefit from perfusion imaging evaluation. The relative increase in cerebral perfusion in the concordant EEG areas with IIC or LRDA facilitates treatment decision-making. Additionally, the 2HELPS2B scoring system may provide valuable support for advancing diagnostic assessments.