Dementia is a syndrome of impairment of cognition and memory accompanied by interference of daily life activities, without a disturbance in consciousness or level of alertness. Dementia should always be differentiated from normal memory loss that occurs with ageing. This change enhanced by old age does not meet the criteria and severity for dementia that limits a person’s physical activity.
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Dementia is a syndrome of impairment of cognition and memory accompanied by interference of daily life activities, without a disturbance in consciousness or level of alertness.
Impairment of cognition may involve:

  • Language disturbances (Aphasia)
  • Loss of memory (Amnesia)
  • Inability to carry out motor activities (Apraxia)
  • Inability to recognize objects in the setting of intact sensory function (Agnosia)
  • Emotion and personality defects

Epidemiology of Dementia

Above 65 years of age, old people are more susceptible to develop dementia in approximately  17 to 20 %, 70% of these cases develop dementia have Alzheimer disease dementia, 17% develop a vascular disease and 13 % develop dementia with Lewy bodies, Parkinson related dementia, alcoholic dementia, and frontal lobe dementia. In 2011, it was estimated that 36 million people worldwide were diagnosed with dementia.

The disease is more common among the elderly, its prevalence increasing with age to a rate of ≥ 20% for patients over the age of 85 years. There is 10 to 15 % chance of developing Alzheimer disease from mild dementia. The average survival period of dementia patients is 4.5 years.

Due to the alterations in the ability to perform daily functions the syndrome has serious economic and social impact as these patients require a helper; medications for rest of their life.

Classification of Dementia

Dementia arises from neurodegeneration of basal ganglia, thalamus, and cerebral cortex, It may have several causes categorizing them in different types. Although the causes are different their clinical presentation may overlap with distinctive features.

The various types of dementia include:

  • Alzheimer’s disease (AD)
  • Vascular dementia
  • Dementia with Lewy bodies (DLB)
  • Parkinson’s disease dementia (PDD)
  • Frontotemporal dementia (FTD)
  • Other rare forms of dementia
  • Creutzfeldt Jacob disease
  • Mixed dementia
  • Wernicke-Korsakoff syndrome
  • Huntington disease

Alzheimer’s disease is the commonest cause of dementia accounting for 70–80 % of the dementia cases.

Vascular Dementia


It is defined as a decline in mental function caused by brain damage after insufficient or impaired blood supply to the brain.


It is the second most common cause of dementia after Alzheimer’s disease accounting for about 10 % of the cases.


Vascular dementia is classified into

  1. Uncomplicated type
  2. Vascular dementia with delirium
  3. Vascular dementia with delusions
  4. Vascular dementia with depressed mood


It is caused by a stroke that blocks an artery to a specific region of the brain or by narrowing of blood vessels.


The risk factors for stroke such as alcohol use, smoking and presence of a vascular disease also increase the risk of developing vascular d, mentia. Vascular blockage results from a stroke or a pathogenic narrowing of the vessel compromising distal flow of blood. This leads to ischemia induced demyelination or axonal loss in the areas that are responsible for memory and behavior control.

Clinical features

The diagnostic criteria entail:

  • Patient must fulfill general criteria for dementia
  • Multiple large infarcts in the cerebrum
  • More than three microscopic infarcts identified in a systematic screening of the cortex and deep cerebral structures

The patients’ clinical presentation involves confusion, trouble paying attention, restlessness, reduced ability to organize thoughts, unsteady gait, depression, and neurological deficits,such as inability tounderstand speech or formulate speech, loss of vision associated with the stroke.


There is no specific diagnostic test but tests are done to correlate clinical findings and help in confirming the diagnosis.

  • Blood pressure, sugar and cholesterol level are estimated to check for any risk factors
  • Brain CT scan shows areas of shrinkage and hemorrhage
  • MRI of the brain is more specific about soft tissue damage and smaller infarcts identification

Neuropsychological tests asses one’s ability to speak, work with numbers, memory and making of solutions.


Control of risk factors

  • Lower blood pressure, cholesterol, and blood sugar

Alzheimer’s medications

  • They are used to alleviate symptoms and improve the quality of life in these patients


Studies show that patients with vascular dementia survive for an average of 3 years. However some dementias have improved with the improvement of stroke symptoms a feature traced to the development of new vessels that neovascularizes the ischemic part of the brain.

Dementia with Lewy Bodies (DLB)


Dementia with Lewy bodies is defined as a type of dementia that develops progressively with abnormal deposition of Lewy bodies responsible for mental impaired functions related to thinking, movement, behavior, and mood.


It is the third cause of dementia after Alzheimer’s disease and vascular dementia accounting for 10 % of the cases. It has a slight male predilection. The disease is more common among the elderly population with its peak age being 50–85 years.

Etiology and Pathophysiology

The cause of the disorder is largely unknown but several factors have been associated with increased incidence. The genetic mutation in CYP2D6B gene confers susceptibility to interruption of the metabolic pathway of environmental toxins in the brain. α-synuclein proteins are the chief components of Lewy bodies. They are found abundantly in brain cells of people suffering from DLB, Parkinson’s disease dementia and Alzheimer’s disease.

The presence of Lewy bodies alters the level of neurotransmitters and neuromodulators in the brain, principally dopamine. This depletion compromises the flow of information from the striatum to the neocortex. It begins in the brainstem and later spreads to the outer layers of the brain that are involved in perception and behavior.

Clinical features

Dementia with Lewy bodies commonly presents features seen in other diseases. They include motor features of Parkinson’s disease such as

  • Altered balance
  • Hunched posture
  • Visual hallucinations
  • Rigidity
  • Features of Alzheimer’s disease
  • Anterograde memory loss
  • Extrapyramidal symptoms
  • Delusions
  • Problems in understanding things and making judgements

Other features of the disease include:

  • Fluctuating periods of alertness and loss of attention
  • REM sleep disorder where the patient is violent and restless as he/she acts out his/her nightmares
Note: It is always necessary to differentiate the three conditions based on specific clinical findings in one condition but not in the other.

Important findings on physical examination include:

  • Impaired cognitive function as seen in the mini mental state examination (MMSE)
  • Alternate periods of alert and oriented patient vs confused and unresponsive
  • Motor signs that do not meet the criteria for Parkinson’s disease


The diagnosis is made from clinical findings. Investigations are done to support your diagnosis or to rule out other likely differential diagnoses.

  1. Brain imaging by MRI/CT/PET scans may identify infarcts that suggest vascular dementia or brain atrophy that suggests Alzheimer’s disease.
  2. CSF analysis, DLB can be diagnosed by identification of an increased level of Tauproteins.

Vitamin B12 levels as deficiency could explain behavioral problems.

Differential diagnosis

Alzheimer’s disease dementia
  • Lacks hallucinations, motor features and fluctuations in alertness and lapse in concentration
  • Memory loss is more prominent
Parkinson’s disease dementia
  • Memory loss is a feature that is prominent and always seen
  • Motor symptoms are more pronounced
Vascular dementia
  • Associated with a recent stroke


There are no medications to halt the progress or completely cure the disease. Available medications focus on improvement of the quality of life by symptomatic relief.

  • Cholinesterase inhibitors (donepezil) increase the amount of available neurotransmitters and thus transmission of signals
  • Antipsychotics (clozapine and quetiapine) alleviate behavioral symptoms and may lead to altered consciousness, confusion, and hallucinations
  • Clonazepam is administered to treat REM sleep disorder

Parkinsonism medications (carbidopa-levodopa) treat motor symptoms

Parkinson’s Disease Dementia (PDD)


Parkinson’s disease  is the second most common neurodegenerative disorder and the most common movement disorder. It is characterized by progressive loss of muscle control, which leads to trembling of the limbs and head while at rest, stiffness, slowness, and impaired balance.The disease affects approximately 1 percent of persons older than 60 years, and up to 4 percent of those older than 80 years.


Parkinson’s disease dementia results from presence of α-synuclein deposits like those seen in dementia with Lewy bodies. There is the loss of pigmented dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the presence of Lewy bodies.This leads to destruction of brain cells and depletion of dopamine in basal ganglia. (the hormone that controls muscle coordination).

The electrophysiologic changes such as altered dischared rates, increased incidence of burst firing, interneural compatibility , oscillatory activity and altered sensorimotor processing is hindered in basal ganglia , thalamus and cerebral cortex adversely affect voluntary movements of extremities and sensory functions. The disease thus represents itself as a movement disorder and upon involvement of other brain areas that control memory and concentration, resulting in dementia.

Clinical features

In addition to diagnostic features of Parkinson’s disease (tremors, stiffness, slow movement and loss of balance and coordination), Parkinson’s disease dementia has additional features of:

  • Changes in memory, concentration, and judgement
  • Visual hallucination
  • Depression
  • Delusions
  • Irritability
  • Anxiety
  • REM sleep disorder


Like other causes of dementia, available tests are used to support your diagnosis or rule out differential diagnosis. The clinical representation of Parkinson’ disease is guideline for the diagnosis and imaging of the brain should be done to rule out tumors or vascular diseases that may give motor symptoms and dementia.


Symptomatic relief is achieved by:

  • Cholinesterase inhibitors (donepezil) increase the available neurotransmitters and thus increase transmission of signals through neurons.
  • Antipsychotics (clozapine and quetiapine) alleviate behavioral symptoms and may lead to altered consciousness, confusion, and hallucinations
  • Clonazepam is administered to treat REM sleep disorder
  • Antidepressant medications such as SSRIs may be effective in many cases.
  • Parkinsonism medications (carbidopalevodopa) treat motor symptoms (may aggravate hallucinations and confusion)

Frontotemporal Dementia (FTD)


It is a clinical syndrome associated with shrinkage of the frontal and temporal lobes of the brain. It is also known as Pick’s disease or frontal lobe dementia or frontotemporal disorders. These disorders occur as a result of the damage of neurons in the frontal and temporal lobes of brain.with the death of the neurons , these lobes get atrophied  leading to behavioral change and diminished thought processes.


Frontotemporal dementia is a rare cause of dementia that is more common in the younger population. The peak age of  incidence of  the disease is 45–65 years.
It has no sex predilection as seen with other dementia causes.


Genetic mutation in MAPY, GPN and C90RF72 genes.


The brain parts responsible for behavioral reactions, speech and emotional reactions get shrinked due to progressive damage to the neurons involved in these areas, Death of these brain cells(neurons)  is thought to arise from presence of abnormal proteins in these cells. The  progress of the disease damages the connecting neurons in these regions leading to changes in behavior, speech, and personality with an intact memory.

Clinical features

Presentation takes any of the three main variants that gives its classification:

  1. Behavioral variant frontotemporal dementia (BvFTD) is the commonest variant of FTD. It is characterized by changes in social behavior and conduct, with loss of social tact, neglect of personal hygiene and poor impulse control. They lack empathy and insight into one’s behavior but have an increased interest in sex and blunt emotions.
  2. Semantic dementia (SD) is characterized by the difficulty in understanding and making speech. They suffer from impaired word comprehension, intact grammar, and memory.
  3. Progressive non-fluent aphasia (PNFA) is characterized by progressive difficulties in speech production. The patient’s speech is punctuated with omission of words that leads to grammatical errors. They also have a sluggish speech.


The diagnosis is made from clinical findings and investigations are done to support your diagnosis or to rule out other likely differential diagnoses.

  • Brain MRI is superior for assessment for suspected brain atrophy
  • CT scans can help to rule out vascular dementia
  • PET scans may identify infarcts that suggest vascular dementia or brain atrophy that suggests Alzheimer’s disease

Differential diagnosis

Atypical Alzheimer’s disease
  • Lacks memory loss
  • Has prominent behavioral symptoms


Care of these patients involves:

  • Physiotherapy and occupational therapy to allow for some function of basic chores
  • Supportive care of the patient since he/she cannot express herself/himself
  • Speech therapy such as encouraging the use of small sentences
  • Antipsychotic medications are considered in the control of extreme alterations in behavior


Just like dementia, delirium is not a disease but a syndrome of disturbance in consciousness, abrupt change in cognition. The syndrome is characterized by clouding of consciousness, restlessness, confusion, psychomotor retardation or agitation, and affective lability.
Delirium is caused by

  • General Medical Condition
  • Drug/substance abuse
  • Multifactorial delirium (multiple causes)
  • Delirium not otherwise specified (cause not known)

It has been classified into

  • Hyperactive delirium (restlessness, agitation, and rapid mood changes are the hallmarks)
  • Hypoactive delirium (sluggishness or loss of motor function)
  • Mixed delirium (includes both hyperactive and hypoactive symptoms and switches between the two)

Delirium and dementia are commonly confused due to the superficial similarities in the two diseases such as

  • Both diseases are more common among the elderly population (> 65 years)
  • Both diseases may occur concurrently and presence of dementia leads to brain damage that predisposes one to delirium
  • REM sleep disorder may be evident in both syndromes
  • Both diseases lack tests that can confirm the diagnosis

The differences are clear and should be sought for during diagnosis. While delirium is always of acute onset, dementia progresses gradually with worsening of the symptoms. The dementia patients are consciously alert and give attention to the current happenings whereas patients of delirium have altered conscious levels.the dementia symptoms are worse at the day time whereas delirium symptoms may fluctuate at the day time with some improvement becoming worse at night.

Difference between delirium and dementia

Delirium Dementia
Clouding of consciousness Loss of memory/intellectual ability
Acute onset Insidious onset
Lasts 3 days to 2 weeks Lasts months to years
Orientation impaired Orientation often impaired
Immediate/recent memory impaired Recent and remote memory impaired
Visual hallucinations common Hallucinations less common
Symptoms fluctuate, often worse at night Symptoms stable throughout day
Usually reversible 15% reversible
Awareness reduced Awareness clear
EEG changes (fast waves or generalized slowing) No EEG changes
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