Altered mental status, despite its frequency, the term is vague and has several synonyms such as confusion, not acting right, confusional state, altered behavior, generalized weakness, lethargy, agitation, psychosis, disorientation, inappropriate behavior, inattention, and hallucination. Such lack of standardized terminology makes the assessment and appropriate management of patients with altered mental status difficult. It is important to ditinguish red flags, since acute altered mental status is a medical emergency. The first step in the evaluation of a patient with altered mental status is to establish the time course. Altered mental status may be classified as dementia, delirium, psychosis, and other neurological causes according to its origin.

• Altered mental status may be classified according to its origin into 4 major groups: dementia, delirium, psychosis, and neurologic causes.

• Dementia is a slow and progressive disorder characterized by cognitive decline beyond what might be expected from normal aging. Dementia involves memory and at least 1 of the other domains, including personality, praxis, abstract thinking, language, executive functioning, complex attention, social and visuospatial skills.^[1] Individuals usually present normal vital signs, normal level of conscioussness. Several diseases may cause dementia, being Alzheimer’s disease the most common.^[2]

• Delirium is an acute and relatively sudden (developing over hours to days) decline in attention, focus, perception, and cognition that usually appears in the elderly.^[3][4] The clinical presentation may vary from hyperactive or hypoactive psychomotor behavioral disturbances. Hypoactive delirium is oftenly missdiagnosed with other disorders such as depression; the rapidly fluctuating time course of delirium is used to help in the latter distinction.^[5]

• Psychosis is a generic psychiatric term for a mental state that results in a loss of contact with reality.^[6] Psychosis is a common characteristic to many psychiatric, neuropsychiatric, neurologic, neurodevelopmental, and other medical conditions.^[7] It caused most of the times by fluctuations of neurotransmitters such as dopamine, acetylcholine, gamma-amino-butyric acid (GABA), and glutamate, which ultimately results in in high levels of distress and deterioration of normal social functioning.^[8]

• Some focal neurological deficits can produce changes in perception, psychomotor skills or behavior. This group’s presentation vary widely depending on the localization and cause of impairment. Within this group there may be found subclassifications such as the levels of consciousness (confusional state, lethargy, obtundation, stupor, coma), vegetative state, locked-in syndrome, and brain death.^[9]