This chapter uses a case-based approach to discuss the electrographic patterns associated with focal cortical lesions in critically ill patients. Focal amplitude attenuation and/or slowing may suggest an underlying physiological dysfunction or a structural lesion. Additionally, epileptiform abnormalities such as sharp waves within the region may suggest increased seizure risk. A focal pattern of higher amplitudes, sharper morphologies, and faster activities is characteristic of breach effect from a craniotomy. Lateralized rhythmic delta activity (LRDA) is a pattern of rhythmic focal slowing that is associated with increased seizure risk. Epilepsia partialis continua (EPC) is an unusual form of focal motor status epilepticus that is often refractory to antiseizure medications. This pattern may be seen in a rare form of focal epilepsy called Rasmussen syndrome among other causes.