Dementia is a broad term used to describe a decline in mental ability that is severe enough to interfere with daily life. It is not a specific disease, but rather a group of symptoms caused by various diseases or conditions. Many different conditions can cause dementia or mimic dementia-like symptoms. Identifying the underlying cause is important because some causes may be reversible if caught early. This article explores the various conditions that should be ruled out when evaluating a patient with suspected dementia.
Normal aging
Mild memory loss and cognitive decline are normal parts of the aging process. As we get older, most people experience some slowing of thinking and recall. Difficulty finding the right word, losing one’s train of thought mid-conversation, or misplacing items from time to time are common experiences.
These normal age-related changes are distinct from dementia in that they are often subtle, tend to come and go, and do not severely disrupt daily activities. True dementia worsens over time and significantly impacts function.
Mild cognitive impairment (MCI)
Mild cognitive impairment (MCI) involves more extensive cognitive deficits beyond normal aging, but the impairments are not severe enough to meet the criteria for dementia. People with MCI have observable lapses in memory and thinking that are greater than expected for their age and education level. However, they are still able to independently carry out their normal daily activities.
MCI may represent an early stage of Alzheimer’s disease or other dementia for some individuals. However, MCI itself is not dementia. Around 50% of people diagnosed with MCI develop dementia within 5 years, while the other 50% remain stable or even improve.
Depression
Depression can mimic dementia in several ways. The cognitive symptoms of depression such as slowed thinking, trouble concentrating, and memory problems may be mistaken for dementia. People with severe depression may also become less engaged in their usual activities, resulting in functional declines that could appear similar to dementia.
Features that point more towards depression than dementia include:
- Symptoms like sadness, guilt, hopelessness, social withdrawal
- Cognitive problems are patchy – memory is fine one moment, but poor the next
- Cognitive ability rebounds when depression lifts
- History of depression and/or family history of mood disorders
Identifying and properly treating depression in older adults is crucial. Cognitive symptoms often improve significantly once the depression is addressed.
Delirium
Delirium is an abrupt change in mental state marked by inattention and either lethargy or hyperactivity. It develops over a short period of time, such as hours or days. Delirium is most often caused by an underlying medical issue or medication side effect.
Some features of delirium that differentiate it from dementia include:
- Fluctuating course – mental status can swing wildly
- Inattention is a core symptom
- Disorganized thinking and speech
- Altered level of consciousness or awareness
- Develops rapidly over hours or days
Delirium often occurs with infections, dehydration, malnutrition, medications, surgery, or other medical conditions. Finding and treating the underlying cause can resolve delirium, unlike dementia which is ongoing.
Vitamin deficiencies
Deficiencies in certain vitamins, particularly B vitamins and vitamin D, can lead to dementia-like symptoms. Vitamin B12 deficiency is a known cause of cognitive problems and dementia if left untreated.
Risk factors for B vitamin deficiencies include:
- Malabsorption disorders
- Surgeries affecting the stomach or intestines
- Vegetarian or vegan diet
- Excessive alcohol intake
Vitamin D deficiency has also been linked to cognitive impairment. Older adults are at particular risk due to reduced skin synthesis of vitamin D.
Testing vitamin levels through bloodwork is recommended if dementia is suspected. Vitamin deficiencies can often be corrected through supplementation, diet changes, and/or sun exposure.
Infections
Infections, particularly urinary tract infections (UTIs) and upper respiratory infections, can trigger abrupt changes in mental status in older adults. Dehydration often accompanies infections as well.
Signs an infection may be the culprit include:
- Fever, chills, cough, or other symptoms of infection
- Delirium-like symptoms (fluctuating course)
- Lab tests positive for infection
As the infection is treated, the dementia-like symptoms often improve. Recurrent UTIs in an older adult with cognitive decline should be addressed, as repeated or chronic infections can cause ongoing damage.
Thyroid problems
Both hypothyroidism and hyperthyroidism can prompt cognitive changes resembling dementia. Hypothyroidism, an underactive thyroid, causes fatigue and sluggish thinking. Hyperthyroidism speeds up metabolism leading to agitation, anxiety, and confusion.
Symptoms that may indicate a thyroid condition:
- Weight changes
- Heat or cold intolerance
- Hair loss
- Palpitations or rapid heart rate
- Goiter (enlarged thyroid gland)
Testing the levels of thyroid hormones (T3 and T4) can readily identify thyroid dysfunction. Hypothyroidism is treated with synthetic thyroid hormone replacement. Hyperthyroidism is managed with antithyroid medications, radioactive iodine, or surgery.
Sleep apnea
Sleep apnea, where breathing stops and starts repeatedly during sleep, has been connected to cognitive impairment. This makes sense since sleep apnea diminishes oxygen supply to the brain and interrupts deep restorative sleep.
Characteristics of sleep apnea include:
- Loud snoring
- Daytime sleepiness and fatigue
- Observed episodes of breath stopping during sleep
- Frequent nighttime awakenings or restless sleep
A sleep study can objectively measure the presence and severity of sleep apnea. Treatment with CPAP machine prevents airway closure during sleep and improves symptoms.
Medications
Many common medications can impact cognition, especially in older adults who may be more sensitive to drug effects. Medications with anticholinergic effects are known to cause cognitive impairment. Other drugs linked to brain fog or confusion include:
- Benzodiazepines
- Narcotics
- Muscle relaxants
- Antihistamines
- Sleep aids
- Some blood pressure medications
Reviewing all medications and supplements is recommended when evaluating dementia. Stopping or reducing any unnecessary or problematic medications may improve mental clarity.
Stroke
Cognitive changes can occur after strokes, especially a series of small strokes which cause cumulative damage. Multi-infarct dementia or vascular dementia are terms for dementia caused by impaired blood flow to the brain.
Features of vascular dementia:
- Stepwise progression – plateaus between symptom worsening
- Patchy deficits – some cognitive domains affected more than others
- MRI reveals evidence of small strokes
- Risk factors for stroke present: high blood pressure, diabetes, smoking, etc.
Good control of vascular risk factors can help prevent further damage. Physical and speech therapy may improve specific cognitive deficits post-stroke.
Normal pressure hydrocephalus
Normal pressure hydrocephalus occurs when excess cerebrospinal fluid (CSF) accumulates in the brain’s ventricles. This causes pressure on surrounding brain tissue leading to problems with walking, bladder control, and cognition.
Hallmark symptoms of normal pressure hydrocephalus:
- Cognitive impairment
- Urinary incontinence
- Gait disturbance
Brain imaging like CT or MRI reveals enlarged ventricles. If caught early, some patients improve with the surgical placement of a shunt to drain excess CSF.
Brain tumors
Both malignant brain tumors and benign tumors can disrupt cognitive function when they grow large enough to compress brain matter. Brain tumors may also block the flow of cerebrospinal fluid, leading to fluid build up.
Symptoms possibly signaling a brain tumor include:
- Headaches
- Seizures
- Nausea and vomiting
- Vision loss or double vision
- Gradual mental decline
MRI or CT scans can detect brain tumors. Treatment depends on the type of tumor and may involve surgery, radiation, chemotherapy, or targeted medications.
Traumatic brain injury
Moderate to severe traumatic brain injury (TBI), such as from an accident or sports injury, inflames brain tissue which can result in long-term cognitive effects resembling dementia. Symptoms tend to appear shortly after the TBI occurred.
Memory, attention, speed of thinking and emotional regulation are common problem areas. With milder TBI, cognitive symptoms often resolve after weeks or months.
Lewy body dementia
Lewy body dementia shares overlap with both Alzheimer’s and Parkinson’s diseases. Clumps of abnormal protein deposits called Lewy bodies develop in the brain, damaging cognition and movement control.
Early signs of Lewy body dementia:
- Fluctuating alertness, attention, hallucinations
- REM sleep behavior disorder
- Well-formed visual hallucinations
- Parkinson’s type movement symptoms
Lewy body dementia tends to progress faster than Alzheimer’s. Cholinesterase inhibitors may help symptoms temporarily.
Frontotemporal dementia
In frontotemporal dementia, progressive cell loss occurs in the brain’s frontal lobes or temporal lobes. This damages personality, behavior regulation, language, and movement abilities.
Common symptoms:
- Changes in personality and social etiquette
- Loss of language or aphasia
- Repetitive compulsions and behaviors
- Hyperorality and appetite changes
Genetic testing may reveal a known frontotemporal dementia mutation. Supportive therapies can sometimes slow progression.
Creutzfeldt-Jakob disease
Creutzfeldt-Jakob disease (CJD) is a rare, fatal brain disorder caused by misfolded prion proteins. It appears similar to dementia, causing progressive loss of memory, coordination, and visual acuity.
Characteristics of CJD:
- Rapid progression – dementia symptoms within months
- Muscle jerks and twitching
- Blindness or changes in vision
There is no cure for CJD which is eventually fatal. However, it only affects about 1 in 1 million people per year.
Huntington’s disease
Huntington’s disease is an inherited disorder causing the breakdown of nerve cells in the brain. It causes movement, cognitive and psychiatric symptoms typically beginning between ages 30-50.
Common signs of Huntington’s disease:
- Jerky, uncontrollable movements
- Clumsiness and lack of coordination
- Forgetfulness and inability to focus
- Irritability, depression, or other psychiatric problems
There is currently no cure for Huntington’s disease. Cognitive decline and motor dysfunction worsen steadily over a 10-15 year period.
Parkinson’s disease dementia
In Parkinson’s disease, Lewy body deposits form in dopamine producing areas leading to movement symptoms. As more areas become affected, dementia frequently develops in the later stages.
Indicators Parkinson’s dementia may be developing:
- Existing diagnosis of Parkinson’s disease
- Mental slowness, apathy, depression
- Impaired judgment, confusion, hallucinations
- Problems recalling information
- Difficulty following conversations
Parkinson’s dementia worsens as the overall disease progresses. Cholinesterase inhibitors may provide mild benefit.
Progressive supranuclear palsy
Progressive supranuclear palsy (PSP) involves tau protein accumulation deep in the brain tissue which controls balance, walking, eye movements, and cognition. This leads to prominent motor disabilities along with dementia.
Typical features of PSP:
- Unsteady walking and frequent falls
- Stiff movements
- Difficulty moving the eyes
- Slurred speech
- Behavior and personality changes
There are no treatments to slow or stop the progression of PSP. Palliative therapies help manage symptoms. Life expectancy after diagnosis averages 5-7 years.
Posterior cortical atrophy
Posterior cortical atrophy (PCA) is a neurodegenerative syndrome where the brain’s occipital and parietal lobes begin to atrophy. These posterior brain regions control visual-spatial orientation and identification.
Common features of PCA:
- Difficulty interpreting images
- Problems locating objects in space
- Disorganized visual environment
- Misreaching for objects
- spelling and number errors
PCA is most often an atypical, early onset presentation of Alzheimer’s disease. Visual aids and routines may help compensate for deficits.
Corticobasal degeneration
Corticobasal degeneration (CBD) involves shrinkage and dysfunction of multiple areas in the cerebral cortex. It manifests with movement abnormalities, cognitive changes, and speech/language deficits.
Clues pointing to CBD include:
- Asymmetric rigidity or limb stiffness
- Apraxia – inability to perform learned movements
- Alien limb phenomena
- Myoclonus – sudden involuntary jerks
- Non-fluent aphasia
CBD is progressive over a course of 5-8 years. Physical and occupational therapy promote safety and function.
Conclusion
In summary, dementia has a broad differential diagnosis. Many conditions beyond primary neurodegenerative diseases can mimic dementia or cause cognitive impairment. A thorough evaluation checking for reversible causes is crucial when dementia is suspected. Testing for vitamin deficiencies, infections, thyroid dysfunction, depression and other medical issues can discover treatable conditions.
Neurodegenerative dementia is a diagnosis of exclusion after other potential causes are ruled out. Even among primary brain diseases, accurate diagnosis guides prognosis and symptom management. Considering the wide range of diagnostic possibilities is key to properly evaluating an individual’s cognitive symptoms and changes.