Altered mental status is a broad category applied to geriatric patients with a change in cognition or level of consciousness (LOC) – delirium, agitation, coma, stupor.

Common causes of altered mental status in the elderly

Delirium occurs in 7%-10% of geriatric patients in the emergency department (ED). It presents as an acute change in consciousness and loss of cognition that waxes and wanes. Patients' conditions can range from sleepy to agitated and combative. Inattention is the hallmark sign/symptom. Delirium is easier to recognize in patients who become hyperactive; "quiet" delirium may be more difficult to identify. It is often mistaken for dementia.
Clinicians should use validated screening tools to evaluate patients, which may help investigate delirium in a systematic way.

Most strokes do not impact a patient's LOC or mental state; however, some strokes can alter both. They must be included on the differential diagnosis of any geriatric patient presenting to the ED for confusion; many strokes are amenable to reperfusion therapy and endovascular intervention if identified quickly.

Older adults who have a history of a recent fall, or who use anticoagulants and present to the ED with confusion, should be evaluated for the possibility of a subdural hematoma. Families may report a minor fall and a slow cognitive decline over several days. Although these events can present in the acute stage (< 3 days), many geriatric patients present to the ED with subacute subdural hematomas (4-20 days). Patients on anticoagulant or antiplatelet agents can have spontaneous bleeding events and may not report a history of trauma.
A neurosurgeon should be consulted if a subdural bleed is identified in the ED.

Normal pressure hydrocephalus has an average age of onset of 70 years, and its incidence increases after age 80. Patients usually present with impaired cognition, gait disturbance, and urinary incontinence that progressively worsen over three or more months.
Computed tomography scanning will show ventriculomegaly, but the diagnosis should be pursued in patients with suspicious clinical findings, such as impaired executive thinking and memory.

Digoxin toxicity. Many elderly patients may report nausea, vomiting, or diarrhea in early cases of toxicity but, over time, confusion and yellow vision may develop. Clinicians should look for the presence of ST depression, bradycardia, heart block, atrial fibrillation with slow ventricular response, or slow supraventricular tachycardias.

Drugs with anticholinergic properties (diphenhydramine, meclizine, promethazine) are common causes of LOC. Elderly patients taking these medications at the time of admission to hospital are significantly more likely to develop delirium. In addition, they may also develop urinary retention, dilated pupils, dry skin, and flushing.

Wernicke encephalopathy is caused by thiamine deficiency and can present as changes in gait, altered mental status, and ophthalmoplegia. It is characteristically associated with alcoholic patients, but can be overlooked in other patients at risk for thiamine deficiency, such as those with cancer or malnutrition.

Nonconvulsive status epilepticus is a potentially reversible cause of altered mental status in the elderly. This condition is more common in patients with a history of seizure disorder and therefore should be considered in those who have a seizure before arriving in the ED. Patients may present with a decreased LOC, echolalia, nystagmus, automatisms, or emotional lability. An abrupt onset of signs/symptoms or recurrent episodes of confusion lasting hours to days can be characteristic.

Hypertension can cause altered mental status in the form of hypertensive encephalopathy. If not rapidly diagnosed and treated, it can result in coma and death. Patients may present with signs/symptoms including loss of vision, headache, seizures, or altered mental status alone.

The incidence of bacterial meningitis has declined since the introduction of the Hemophilus influenza type B and pneumococcal conjugate vaccines, but mortality from this disease remains around 20% for seniors. Neisseria meningitidis is the most common cause in young adults, whereas Streptococcus pneumoniae is the most frequent etiology in older adults.
Some geriatric patients may present to the ED with the classic meningitis triad of fever, headache, and neck stiffness; however, others may have fewer specific symptoms (altered mental status, seizure, decreased LOC). One-third of all elders with meningitis will also have sepsis; subtle examination findings may include aphasia, focal motor deficits, and cranial nerve palsies.

Elderly persons have increased susceptibility to severe infection, due to waning immunity and decreased physiologic reserve, and are at increased risk for delayed diagnosis, due to atypical presentations. Some seniors with infectious disease will present to the ED with a change in mentation as their only symptom. Cognitive dysfunction occurs frequently in geriatric patients with pneumonia, urinary tract infections, or sepsis.

Hypoxia and uremia account for some changes in mental status, whereas hypotension and dehydration can exacerbate delirium. Cardiovascular collapse can result in tissue hypoperfusion and ischemic or hemorrhagic strokes.

The proinflammatory state seen in sepsis can cause brain dysfunction and subsequent alterations in consciousness.
Careful screening for infection is an important part of the workup of all geriatric patients with LOC, as early diagnosis and treatment are critical to improving survival. Mortality remains over 20% in those with sepsis and altered mental status.

See reference for more information.

Adapted from Drug & Diseases. 9 causes of altered mental status in the elderly. Internet. Available at https://reference.medscape.com/slideshow/altered-mental-status-elderly-6010546?src=wnl_critimg_190920_mscpref&uac=6705FY&impID=2101009&faf=1#. Accessed on January 28, 2020. To view the entire article and all other content on the Medscape News a