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A 46-year-old man with a history of idiopathic hypoparathyroidism presented to the emergency department with “altered mental status.” His wife described the patient as having been restless and irritable for several days, and then he became quite confused—mumbling words and barely speaking to her. Neurologic examination revealed an alert but restless and inattentive, nonverbal man who was able to follow certain simple commands but required significant encouragement in order to do so. Cranial nerve examination was notable for fine nystagmus that was present nearly continuously, even in primary gaze. The motor examination was nonfocal other than the absence of deep tendon reflexes in the bilateral lower extremities. A computed tomography (CT) scan was performed and did not reveal any acute findings. His laboratory results were primarily notable for a serum calcium of 4.1 mg/dL and an albumin of 3.4 gm/dL. Intravenous (IV) calcium supplementation was initiated, and the patient was admitted; an endocrinologist was called for further recommendations. The patient’s astute admitting physician also ordered an electroencephalogram (EEG), given the patient’s hypocalcemia, severe encephalopathy, and the fine, continuous nystagmus noted on examination. The EEG was suggestive of nonconvulsive status epilepticus. The patient was given 2 mg of IV lorazepam that resulted in a cessation of epileptiform activity on the EEG. Within minutes, he began speaking again, and within hours he was nearly recovered in terms of his encephalopathy.

Definition and epidemiology of encephalopathy and delirium

The term encephalopathy derives from the Greek encephalos (brain) and pathos (suffering or experience). In general, encephalopathy is synonymous with an acute confusional state, eg, “altered mental status.” Patients may present with an alteration in level of consciousness (ranging from agitation to coma), fluctuating levels of attentiveness (delirium), disorientation or perceptual distortions (even hallucinations), and/or disorganized thought processes. These symptoms often wax and wane, both in terms of severity and temporally (“sundowning;” reversal of sleep-wake). Delirium is not infrequent in hospitalized patients and may occur in 5% to 40% of hospitalized patients in general and 11% to 80% of patients in the intensive care unit (ICU).1 Diagnostic tools have been developed to aid in the recognition of encephalopathy and delirium. One such tool—the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) scale2—was specifically developed to identify delirium in the ICU (Table 13-1).

Table 13-1.Confusion Assessment Method for the Intensive Care Unit (CAM-ICU)

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