AssessmentsDementia and delirium: Clinical practice
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 68-year-old man is brought to the clinic by his partner due to an inability to focus. For the past 2 months, the patient has been unable to complete his daily sudoku puzzle. His partner recalls that the patient has been increasingly withdrawn and no longer attends social gatherings. The patient has also been sleeping more due to worsening fatigue and has experienced a 5 kg (11 lb) weight gain over this same time period. Past medical history is significant for hypertension, which is well-controlled with medications, and constipation for the past 8 weeks, which he has been self-treating with fiber supplements. In the office, temperature is 36.0°C (96.8°F), pulse is 48/min, respirations are 12/min, and blood pressure is 125/84 mmHg. Physical examination reveals cold, dry skin. The abdomen is mildly distended with hypoactive bowel sounds. Fecal occult blood test is negative. Sensation in the extremities is intact. Which of the following tests is most likely to identify the cause of this patient’s condition?
Content Reviewers:Rishi Desai, MD, MPH
The brain is responsible for various mental functions, including memory, language, visuospatial function, concentration, executive function, praxis, which is the ability to carry out complex motor activities, and personality. A subtle decline in cognitive function like a slowed reaction time, is a common part of normal aging, and usually doesn’t impair daily functioning and independence - this is called mild cognitive impairment. On the other hand, if there’s a decline in cognitive skill that does impair daily functioning and independence, then it’s called dementia. The major risk factor for most forms of dementia is advancing age, but dementia is not considered an inevitable consequence of normal aging.
Most of the time, in dementia, a close family member or friend notices the individual’s change in cognition. This includes impaired memory, which leads to repeating conversations or misplacing belongings. Language impairment can make it hard to think of common words. Additionally, concentration and executive function are impaired, so individuals have a hard time with complex tasks, like managing their finances. Impairment in praxis leads to an inability to perform complex motor tasks, such as buttoning one’s shirt. Visuospatial impairment can lead to an inability with recognizing familiar faces or using simple instruments like utensils. Sometimes, family members will notice a change in the individual’s personality. To do a neurological examination, the Montreal cognitive assessment or MOCA or the mini-mental status examination, or MMSE, can be done to assess orientation, registration, recall, attention, and language. For example, orientation is assessed by asking individual what time it is, where they are, or who the president is. Registration is assessed telling the individual three words - like dog, table, and cake, and then asking them to repeat it immediately. Then, they’re asked to repeat those three names five minutes later, which assesses recall. Attention can be assessed by asking the individual to spell a word backwards. Language is tested by asking the individual to name presented objects, repeating a phrase, and following a 3-step command such as: “take this paper, fold it in half, and place it on the table”. Additionally, individuals are asked to obey a command written on a paper, such as “pick up the pen on the table”. Finally, individuals are asked to write a sentence and copy an illustration, such as a pentagon. The MMSE totals to 30 points, and a score of less than 24 implies cognitive impairment, which may suggest dementia or delirium, which can be differentiated by the time course and the clinical context. Now it’s important to differentiate delirium from dementia. Delirium is usually acute in onset, lasts only a couple of hours to days, and the cognitive symptoms fluctuate - meaning they come and go. On the other hand, dementia is usually gradual in onset, lasts months to years, and the cognitive symptoms are usually progress over time. Also consciousness and awareness are almost always impaired in delirium. However, they are only impaired in the later stages of dementia. Additionally, delirium usually occurs in the event of an acute insult, such as an infection, electrolyte imbalance, change in medication or intoxication. It can also be due to a psychiatric condition, like schizophrenia or major depression. In fact, cognitive impairment associated with depression is called “pseudodementia”.
Okay, now dementia can result from reversible and irreversible causes. Some reversible causes include alcohol dependence and various medical conditions which can be identified with laboratory investigations. It’s helpful to send off TSH levels for hypothyroidism, vitamin B12 levels to assess for a deficiency, and an rapid plasma reagin test, or RPR for syphilis. Another reversible cause is normal pressure hydrocephalus or NPH which is caused by abnormal venous drainage of the cerebrospinal fluid, resulting in a backup of fluid and hydrocephalus. Individuals with NPH usually present with a triad of symptoms - dementia, urinary incontinence, and gait disturbance that’s described as a “magnetic gait”, because it seems like the person’s feet are glued to the ground. A brain MRI shows ventriculomegaly of all the ventricles, a patent cerebral aqueduct, and no signs of cortical atrophy. As suggested from the name, a lumbar puncture will show a normal opening pressure.
The good news is that reversible causes can be treated, and when that happens, the dementia symptoms go away. Alcohol dependence can be treated with medications like acamprosate, disulfiram, and naltrexone. Hypothyroidism can be treated with thyroid hormone replacement, vitamin B12 deficiency is treated with vitamin B12 supplementation, and syphilis is treated with penicillin. The treatment for NPH is placing a ventriculoperitoneal shunt, which drains the excess cerebrospinal fluid. However, although placement of a ventriculoperitoneal shunt helps improve walking, it does not help improve cognition.
Now, let’s explore the irreversible causes. Alzheimer's disease is by far the most common cause of dementia, accounting for the vast majority of cases. Individuals with Alzheimer's disease usually go through 3 phases. First is the asymptomatic phase - during which there are changes happening at the tissue level but no clinical symptoms. Second is a predementia phase called mild cognitive impairment, during which there’s gradual onset of memory impairment without much impairment in the other cognitive domains, and no impairment in daily functioning. This differs from normal aging, because the memory impairment is greater than expected for the individual’s age, and eventually progresses to dementia. The third phase is the dementia phase, and that’s where individuals develop more significant memory loss, followed by slow, gradual loss of the other cognitive functions, such as language, visuospatial, and executive functions. Now, there are two main types of memory: episodic memory, which is memory of events, and semantic memory, which memory of words and vocabulary. Early on, episodic memory is impaired and semantic memory remains intact. Later on both episodic and semantic memory get impaired. Episodic memory can be subclassified into be immediate, recent, or long term. Immediate memory is sometimes called procedural memory, and it’s the memory that you use to repeat back a phone number right away. Recent memory is the the memory you use to remember a list three words five minutes later - like those 3 words from earlier. This is the type of memory that’s impaired early on in Alzheimer's disease because the disease affects the hippocampus first, which is responsible for recent memory. Long-term memory is the memory of events that have occured years ago, and these are not impaired until late in the course of this disease. For example, an individual with Alzheimer's may remember the details of their wedding 50 years ago, but they won’t be able to remember where they were yesterday. The presumptive diagnosis of Alzheimer's disease is made clinically and investigations are done to exclude reversible causes of dementia. Also, in Alzheimer's disease a brain CT or MRI can show hippocampal atrophy that can progress to diffuse cortical atrophy. A brain biopsy is the only investigation that would definitively diagnose Alzheimer's disease, but that’s invasive and isn’t usually done until there’s an autopsy after death.
It’s thought that lower acetylcholine levels may contribute to the cognitive symptoms seen in Alzheimer's disease. So, cholinesterase inhibitors like donepezil, rivastigmine and galantamine can be used for treatment. Side effects from cholinesterase inhibitors include diarrhea, vomiting, syncope, bradycardia, and heart block. In individuals that can’t tolerate cholinesterase inhibitors, NMDA-receptor antagonists, like memantine can be used. Now, combining these two types of medications has not been shown to be more effective than cholinesterase inhibitors alone. These medications don’t slow the progression of the disease, but they do help mitigate some of the cognitive and behavioral symptoms, making day-to-day life relatively easier for affected individuals. For example, the medication may help the individual recognize family members, which helps strengthen family ties. Finally, depression is common in Alzheimer's disease, and selective-serotonin reuptake inhibitors, or SSRIs, are an effective treatment option.
Next up is vascular dementia, which the second most common type of dementia, and it’s associated with cerebrovascular disease. Individuals typically have manifestations of atherosclerosis like hypertension, diabetes, and coronary artery disease. One type of vascular dementia is multi-infarct dementia, which results from multiple strokes and causes a stepwise decline in cognitive function. For example, the individual develops a stroke, and as a consequence demonstrates a sudden decline in their memory. Then, in between stroke events, there is no progression of their cognitive dysfunction, until another stroke occurs, and they suddenly lose another cognitive domain such as language, and so on. This pattern is what differentiates it from Alzheimer's disease, in which the decline in cognitive function is steady and gradual. To be clear, simply having a history of strokes and having dementia doesn’t mean that it’s due to multi-infarct vascular dementia. The key is that the cognitive decline has to be temporally related to the stroke. Another type of vascular dementia that diffusely affects the white matter of the brain is called Binswanger disease, and this is usually characterized by a slowly progressive dementia. In vascular dementia, there are often associated symptoms like urinary incontinence, cranial nerve palsy, and focal neurological deficits. Also, unlike in Alzheimer's disease where recent memory is usually lost first, the pattern of cognitive decline in vascular dementia varies depending on which area was infarcted. Unfortunately, there is no available treatment that can help reverse vascular dementia. Instead, treatment mainly focuses on preventing another stroke from happening. This includes blood pressure, diabetes and cholesterol control, lifestyle modification; such as exercise, dietary changes, and smoking cessation, as well as starting antiplatelet agents like aspirin.