Delirium is one of the most perplexing psychiatric findings in older adults. It is defined as a disturbance of attention and a change in cognition. Delirium can be a cause of altered mental status (AMS), which is a general term defined as a change in mental functioning affecting cognition, consciousness (from slight confusion to coma), or both. Delirium affects both cognition and consciousness, whereas dementia affects cognition but preserves consciousness. This article will shed some light on assessing and working up delirium in older adults.

Time frame

Start by establishing the period over which the symptoms developed. Family and friends are often helpful here. Knowing the episode’s duration can help you narrow down its cause and choose your next course of action.

Delirium occurs over minutes to days. The more acute and rapid the change, the more often it’s life threatening. Subacute AMS happens over weeks to months, while chronic AMS takes place over months to years (Smith AT and Han JH, Semin Neurol 2019;39:5–19). See “Selected Causes of Altered Mental Status” table for potential causes of AMS as well as other important considerations.

Table: Selected Causes of Altered Mental Status
(Click here to view full-sized PDF.)

Predisposing and precipitating risk factors for delirium

Delirium is a relatively common cause of AMS. It is always caused by underlying medical conditions or medications/substances. Typically, there’s more than one cause. It’s important to identify the cause(s) of delirium because correcting the underlying disturbance is the primary treatment. While mental health clinicians may not be responsible for treating core medical illnesses, we often must be the ones to ensure that a complete workup has been done. It’s also within our role to review the medication list and work with other clinicians to taper off problematic drugs.

It’s important to pay attention to risk factors, because reducing them can help prevent or shorten the course of delirium. Predisposing risk factors increase the risk of delirium, while precipitating risk factors trigger delirium. Precipitating risk factors are further separated into acute insults, environmental exposures, and delirium-inducing medications. See “Contributing Causes of Delirium” table.

Table: Contributing Causes of Delirium
(Click to view full-sized PDF.)

Physical/neurological examination—high-yield pearls

A focused physical exam can provide valuable information about the origin of a patient’s AMS.

Head

Look for signs of trauma, which could suggest an intracranial hemorrhage. Battle’s sign (bruising behind the ear) indicates a possible skull base fracture.

Eyes

1. Pinpoint pupils (1–2 mm) are a hallmark of opioid toxicity. Dilated pupils are seen with anticholinergic toxicity.
2. Bulging eyes can be a sign of hyperthyroidism, infection, or trauma.
3. Paralysis of the outward eye movements is an indicator of either Wernicke’s encephalopathy, caused by thiamine deficiency, or increased intracranial pressure.
4. Yellowed eyes occur in liver failure and are due to increased bilirubin.

Neck

Neck stiffness, headache, and photophobia point toward meningitis.

Neurological

1. Disorientation is seen in delirium.
2. Impaired attention is the hallmark feature of delirium. You can rapidly assess attention by asking the following two questions:
   • “Please tell me the day of the week.”
   • “Please tell me the months of the year backwards starting with December.”

In a study of 201 participants (mean age 84 years, 62% female), if both answers were incorrect, this screen had 93% sensitivity and 64% specificity in picking up AMS (Fick DM et al, J Hosp Med 2015; 10(10):645–650).

1. New-onset gait disturbances could indicate Wernicke’s encephalopathy, normal pressure hydrocephalus (NPH), drug toxicity, or a stroke.

Skin

1. Jaundice suggests liver disease.
2. Dry or rough skin is seen in hypothyroidism.
3. Darkened or bronzed skin could mean Addison’s disease.
4. Small, reddish-purple spots beneath the skin’s surface can signify a number of medical problems, including life-threatening infections.
5. Keep an eye out for drug patches. Some, like fentanyl or scopolamine (anticholinergic), can contribute to AMS (Smith and Han, 2019).

Differential diagnosis

Delirium in an older adult is often due to a combination of factors. It’s helpful to tailor your workup by thinking systematically through medical and psychiatric contributors. Assess for medication and substance use by reviewing medication lists (including over-the-counter products), consulting data from prescription drug monitoring programs, checking drug levels, and obtaining alcohol/urine toxicology screens. Other diagnoses to consider include infections, metabolic/electrolyte abnormalities, nutritional deficiencies, non-convulsive status epilepticus, or structural causes.

Several psychiatric disorders can also cause AMS. See “Differential Diagnosis for Confusion” table for three of the most common psychiatric disorders to cause AMS. In addition to these, consider depression, apathy, and catatonia.

Table: Differential Diagnosis for Confusion
(Click to view full-sized PDF.)

Labs and imaging

While it may be tempting to “throw the kitchen sink” at the patient, it’s often better to order a standard workup and add studies as needed. Customary labs include:

1. Complete blood count. Look for anemia and thrombocytopenia. Elevated white blood cells (WBC) could indicate an infection, though keep in mind that older adults don’t always have a WBC response when sick.
2. Basic metabolic panel (BMP). Pay attention to sodium levels and ionized calcium. Kidney dysfunction can arise from dehydration.
3. Fingerstick glucose. While glucose is part of the BMP, the results won’t be available right away. A fingerstick will help you immediately check for hypoglycemia, which if present can be quickly reversed with orange juice or crackers.
4. Liver function tests. Consider adding an ammonia level if other signs of liver impairment are present.
5. Urinalysis and culture. UTIs are a common cause of delirium in older adults. However, this population also frequently has asymptomatic bacteria in the urine, which aren’t thought to cause delirium.
6. Urine toxicology and alcohol levels. Toxicology tests, though, are prone to both false negatives and false positives.
7. Vitamin B12, folate, and vitamin D levels.
8. Thyroid-stimulating hormone. Both hyper- and hypothyroidism can cause AMS in older adults (Smith and Han, 2019).

In select cases, I might also consider:

• Syphilis and HIV
• EKG, cardiac enzymes
• Chest x-ray
• Antinuclear antibody test
• Lumbar puncture
• Electroencephalogram (EEG)
• Head CT/brain MRI