Nonconvulsive status epilepticus (NCSE) is an under recognized cause of mental status decline. Given the wide spectrum of clinical presentations, a high index of suspicion must be maintained for prompt diagnosis and treatment. This chapter presents a case study of a 55-year-old male with a history of shunted hydrocephalus, seizure disorder, and hypothyroidism presented to the emergency department with complaints of nausea, vomiting, headache, and confusion persisting for several days. An electroencephalogram (EEG) was performed showing diffuse slowing of activity suggestive of encephalopathy with intermittent rhythmic activity representing possible seizures. The patient was placed on continuous EEG monitoring and lorazepam was administered. Fosphenytoin was also added to his antiseizure regimen. The seizure activity subsequently stopped after the addition of fosphenytoin and the patient's neurologic status stabilized. The patient's neurologic status improved and EEG evidence of seizure activity resolved possibly sparing the patient further prolonged cognitive deficits.