Dementia is loss of cognitive ability in a person either due to global brain injury or some disease that results in memory loss. If it occurs before the age of 65 then it is known as early onset dementia. The word dementia comes from a Latin word meaning madness. It can be considered as a non-specific illness syndrome where the areas of brain concerned with memory, language, attention and problem solving are severely affected. About six months are required for the disease to be diagnosed and in later stages the affected persons may become disoriented in time. Dementia is treatable up to a certain degree but as the disease advance the symptoms become incurable. The symptoms of the disease may or may not be reversible and it depends upon the etiology of the disease.
The possibility of complete freedom from the symptoms of dementia is less than 10%. Dementia can be confused with the short-term syndrome delirium if careful assessment of the patient’s history is not done as the symptoms are somewhat similar. Depression and psychosis can be used for differentiating dementia and delirium. Many types of dementia are known that differing slightly in their symptoms. The symptoms of different types may overlap, so diagnosis is done by nuclear brain scanning techniques. Most common types of dementia include Alzheimer’s disease, vascular and frontotemporal dementia and dementia with Lewy bodies. A person may suffer from one or more types of dementia simultaneously at a time.
Dementia is of different types and the classification is mainly based on the intensity of symptoms whether they can be reversed or areas of brain affected.
1. Alzheimer’s disease
Alzheimer’s disease is the most common type of dementia frequently seen in the age group of 65 years or above. Reports suggest that about 4 million people in the United States are suffering from this disease. About 360,000 new cases of Alzheimer’s disease are reported every year and 50,000 Americans die annually. In majority of the individuals the symptoms appear after the age of 60 but the early onset of symptoms is linked to genes. The disease causes a gradual decline in the cognitive ability of an individual within 7-10 years and nearly all brain functions associated with memory, movement, language, judgment, behavior and abstract thinking are badly affected. Two chief abnormalities of brain are typically associated with Alzheimer’s disease namely, amyloid plaques and neurofibrillary tangles. Amyloid plaques are unusual clumps of protein (beta amyloid) containing degenerating bits of neurons and other cells that are present in the tissues between the nerve cells. Neurofibrillary tangles are bundles of twisted filaments present within the neurons and are chiefly made up of a protein known as tau. In healthy neurons tau protein helps in the functioning of microtubules but in this disease they twist to form helical filaments that join in the form of tangles resulting in disintegration of microtubules.
Early symptoms of the disease are identified by memory impairment, subtle changes in personality and judgment inabilities. As the disease progresses, symptoms associated with memory and language become worse and the individual finds difficulty in performing daily activities. Individuals may often suffer from visuo-spatial problems like difficulty in navigating an unfamiliar route, may become disoriented about time and places, even suffer from delusions may become short tempered and hostile. In late stages the person loses his control over motor functions and may feel difficulty in swallowing, lose bowel and bladder control. They also lose ability to recognize family members. Person’s emotions and behavior get affected in later stages and he may also develop symptoms of aggression, agitation, depression and delusions. A person survives for 8-10 years after the disease diagnosis but some may live for about 20 years or more. Individuals may often die due to aspiration pneumonia as they lose the ability to swallow food.
2. Vascular dementia
Vascular dementia is the second most common cause of dementia after Alzheimer’s disease. It is resultant of brain damage by cerebrovascular or cardiovascular problems and accounts for 20% of all types of dementias. Genetic diseases, endocarditis and amyloid angiopathy also play an important role. It is also known to co-exist with Alzheimer’s disease whose incidence increases with advancing age and affects both men and women equal in proportion. Symptoms usually appear suddenly after a stroke. Patients may have history of high blood pressure, vascular disease or heart attacks. In some cases the symptoms recover with time. Vascular dementia is known to affect mid-brain regions so brings changes in cognitive ability of a person. Individuals may often suffer from depression and incontinence.
Several types of vascular dementia are known that differ from each other on account of their causes and symptoms for example, multi-infarct dementia (MID) are caused by presence of numerous small strokes in the brain. This type also includes multiple damaged brain areas and lesions in the white matter, nerves of brain. As multi-infarct dementia affects only isolated areas of brain only one or few specific functions of body are affected. Possibilities of dementia are increased if left side of brain or hippocampus is damaged. Another type of dementia is Binswanger’s disease, a rare disease where blood vessels of white matter are damaged so memory loss, brain lesions, disordered cognition and mood changes are noticed. Patients may often show symptoms of high blood pressure, stroke, blood abnormalities, and disease of large blood vessels of neck and heart valves. Other important symptoms include urinary incontinence, difficulty in walking, clumsiness, slowness, lack of facial expression and speech difficulty. The symptoms usually arise after the age of 60 and the treatment includes medications to control high or blood pressure and depression.
Other type of dementia can be coupled with a rare hereditary disorder known as CADASIL which stands for cerebral autosomal dominant ateriopathy with subcortical infarct and leukoencephalopathy. This disorder is linked to abnormalities of a specific gene, Notch3 located on chromosome 19. The first symptoms arise at the age of 20 or 35 or 40 and the individuals often die at the age of 65. Researchers are still working to find out the exact cause of CADASIL. Other causes of vascular dementia include vasculitis, hypertension and lesions caused due to brain hemorrhage. An autoimmune disease, lupus erythematosus and inflammatory disease temporal arteritis can also damage blood vessels resulting in dementia.
3. Lewy body dementia (LBD)
Lewy body dementia (LBD) is one of the most common types of progressive dementia sporadically occurring in individuals with no known familial history of the disease. The cells of brain’s cortex and substantia nigra die while the remaining cells of substantia nigra contain abnormal structures known as Lewy bodies that are the hallmark of this disease. Lewy bodies may also invade the cortex and are made up of a protein (alpha-synuclein) associated with Parkinson’s disease and other disorders. Researchers fail to give satisfactory answer about the accumulation of this protein in the nerve cells.
The symptoms of this form of dementia may overlap with symptoms of Alzheimer’s disease in many ways and include memory impairment, confusion and judgment inability. The typical symptoms include hallucinations, shuffling gait, flexed posture. The individuals may live for 7 years after disease diagnosis. In the present scenario this form of dementia lacks any cure and the treatments include controlling parkinsonian’s and psychiatric symptoms of the disease. Studies have shown that some neuroleptic drugs like clozapine and olanzapine give positive results against psychiatric symptoms but may cause side effects. The brains of persons suffering from Parkinson’s and Alzheimer’s disease frequently contain Lewy bodies.
4. Fronto-temporal dementia (FTD)
Fronto-temporal dementia is also known as frontal lobe dementia and is characterized by the degeneration of the nerve cells of the frontal and temporal lobes of brain. This disorder however lacks amyloid plaques but neurofibrillary tangles are present that disrupt normal activities of cells resulting in their death. Experts believe that fronto-temporal dementia accounts for about 2-10% of all cases of dementia. The symptoms usually appear between the ages of 40 and 65. In some cases, people have a familial history of the disease and in such case genetic factor strongly influences the disease. People with this disorder may live up to 5-10 years after the diagnosis of disease. The frontal and temporal lobes of brain are concerned with judgment and social behavior but in this disorder as the nerve cells are destroyed so the individual finds it difficult to make decisions as well as maintain social communication. Other possible symptoms include loss of speech and language, repetitive behavior, increased appetite and motor problems like stiffness and balance problems. Memory loss occurs in later stages of the disease.
Pick’s disease is one type of fronto-temporal dementia characterized by abnormal and swollen nerve cells that later die. The brains of individuals suffering from this disorder show presence of abnormal Pick bodies which contain tau protein. Exact cause of Pick’s disease is unknown but it is believed that some genes may be associated with it. The symptoms usually arise at the age of 50 and bring changes in personality and behavior that worsen with time. The symptoms are however similar with Alzheimer’s disease but may include inappropriate social behavior, loss of mental flexibility, language problems and difficulty in thinking and concentration. Although no possible cure of Pick’s disease is available but some drugs may be used to slow down aggression and depression. In cases with familial history of fronto-temporal dementia mutation of tau gene may be the possible cause of the disease. Primary progressive aphasia (PPA) is another form of fronto-temporal dementia occurring in the early forties and is characterized my language problems which in later stages bring changes in social behavior and personality of the individual.
5. HIV-associated dementia (HAD)
Human immunodeficiency virus (HIV) is responsible for causing AIDS and this form of dementia. HIV-associated dementia is responsible for destroying white matter of brain. The typical symptoms include memory impairment, apathy, social withdrawal and difficulty in concentrating. In later stages individuals may often develop movement problems. No promising drugs are yet available to cure the symptoms but the drugs used for treating AIDS may help to reduce some symptoms.
6. Huntington’s disease (HD)
Huntington’s disease is a hereditary disorder caused by a wrong gene forming a protein known as huntingtin and the children of individuals suffering from this disease have 50% chances of acquiring the gene. Many regions of brain and spinal cord are destroyed. The symptoms usually arise in the thirties and forties and a person may live for 15 years after the disease diagnosis. The typical symptoms include mild personality changes like anxiety, irritability, depression, and muscle weakness, arrhythmic movements of body, clumsiness and gait disturbances.
7. Dementia pugilistica
This disorder is also known as chronic traumatic encephalopathy or Boxer’s syndrome caused by severe brain injury. Most common symptoms include dementia and Parkinsonism and affected individuals show slurred speech and poor co-ordination. A single brain injury may also cause post-traumatic dementia (PTD) characterized by long term memory problems.
8. Corticobasal degeneration (CBD)
It is a progressive disorder characterized by atrophy of multiple areas of brain and loss of nerve cells. Brain cells show abnormal accumulation of tau protein and the disease takes 6-8 years for the development of symptoms that include poor co-ordination and rigidity similar to those found in Parkinson’s disease. Other symptoms include memory loss, dementia, visuo-spatial problems, apraxia, halting speech and difficulty in swallowing. Death may occur due to pneumonia or other pulmonary infections. There is no effective treatment available for corticobasal degeneration disease but drugs like clonazepam can be used to cure some primary symptoms.
9. Creutzfeldt-Jakob disease (CJD)
It is a rare, degenerative but fatal brain disorder affecting very a small fraction of persons. The symptoms usually arise at the age of 60 and the person dies within a year. Many researchers believe that this disorder is the result of an abnormal protein known as prion. About 5-10% cases reported in the United States share a genetic basis where this form of dementia is caused by a mutation in the gene for the prion protein. Patients with Creutzfeldt-Jakob disease suffer from the problems associated with muscle coordination, personality changes, impaired memory, judgment making, thinking disability and impaired vision. Other possible symptoms include insomnia and depression. In later stages the persons may also develop myoclonus and may become blind. They finally lose the power to speak and enter coma. Pneumonia and other infections may also be responsible for the death of the individual. This disorder belongs to the transmissible spongioform encephalopathies (TSEs) family of human and animal diseases.
10. Other rare hereditary dementias
They include Gerstmann-Straussler-Scheinker (GSS) disease, fatal familial insomnia, familial British dementia and familial Danish dementia. Symptoms of Gerstmann-Straussler-Scheinker (GSS) disease include ataxia and progressive dementia occurring at the age of 50-60 and may persist till the death of the individual. Fatal familial insomnia is characterized by damaged thalamus that upsets sleep of an individual. Other symptoms include dementia, poor reflexes, hallucinations and coma. The disease becomes fatal within 7-13 months after the appearance of symptoms. Familial British and familial Danish dementias are linked with defects on the gene located on chromosome 13. The symptoms of both the diseases include progressive dementia, paralysis and loss of balance.
Dementia can also occur in individuals suffering from movement problems. The relationship between primary dementia and these problems is not clear. Although dementia frequently affects adults but it can also occur in children for example infections and poisoning may lead to dementia in individuals of any age. Some disorders unique to children may also cause dementia. Niemann-Pick disease is a type of inherited disorder where specific gene mutations affect metabolism of cholesterol and lipids so excessive amount of cholesterol accumulates in liver and spleen while excessive lipids accumulate in brain. The symptoms include dementia, confusions and problems of learning and memory. The disease is known to affect the young school going children but may also affect teen agers.
Batten disease is also a fatal hereditary disorder of the central nervous system occurring in childhood. The symptoms include formation of lipopigments in body tissues and early symptoms include personality and behavior changes, clumsiness or stumbling. As the disease advances children may experience mental impairment, loss of sight and motor skills, become blind and bedridden. Lafora body disease is a rare genetic disorder responsible for causing progressive dementia and movement problems. The symptoms arise in the early childhood or late teens and are characterized by the presence of Lafora bodies in brain, skin, muscles and liver and death of child within 2-10 years.
Other conditions causing dementia
Doctors have found many conditions that can cause dementia and some symptoms can be reversed with proper treatment. For example, medications can sometimes cause symptoms of dementia. They can be caused either by a single drug or by the activity of multiple drug interactions. Thyroid problems can also cause depression and dementia. Hypoglycemia also causes confusion and personality changes. Too high or too low sodium and calcium levels can also result in mental problems. Some individuals are unable to absorb vitamin B12 so they suffer from pernicious anemia resulting in personality changes, irritability or depression. Thiamine deficiency resulting from chronic alcoholism can also cause mental impairment. Severe deficiency of vitamin B6 causes pellagra resulting in dementia. Dehydration can also cause mental illness. Many infections cause neurological illness that develop symptoms of dementia for example, meningitis and encephalitis cause severe mental impairment, judgment problems or memory loss. Untreated syphilis also causes dementia.
A rare disease known as Lyme disease also causes dementia. Individuals suffering from leukemia and AIDS develop an infection known as progressive multifocal leukoencephalopathy (PML) that causes mental illness. Subdural hematomas also cause symptoms of dementia and other mental problems. Exposure to lead, other heavy metals or other toxic elements also cause dementia. The symptoms may or may not be reversed as they depend upon the total area of brain damaged. Individuals who consume alcohol or other recreational drugs also show symptoms of dementia and the responses are short lasting and the condition is known as substance-induced persisting dementia. Even individuals with brain tumors may also suffer from dementia as their brains are damaged. The symptoms include personality changes, speech and language problems and memory loss. Anoxia is caused by heart attacks, heart surgery, asthma, high altitude exposure or smoke also develops symptoms of dementia.
Conditions that are not dementia
With advancing age individuals experience difficulty in learning and mild memory impairment. Some neurons are also lost with advancing age that causes the brain volume to decline a little. Some individuals often develop cognitive and memory problems that are not severe enough to be categorized as dementia. Patients suffering from depression seem confused, forgetful and other symptoms may also sometimes mimic dementia. Delirium is a condition characterized by confusion and rapidly altering mental states and the individual may show personality changes.
Dementia is the result of death of nerve cells or loss of communication between neurons. Human brain is a very complex machine and a number of factors can alter its proper functioning. Although researchers have found the factors responsible for causing dementia but more precise study is still required. Different types of dementias for example, Alzheimer’s disease, Parkinson’s dementia, Pick’s disease are identified by the presence of abnormal inclusions in the brain developing symptoms of dementia. Genes also play very important role in the development of some types of dementias where lifestyle factors and environmental influences are important. Researchers have identified many genes that increase the susceptibility of an individual to Alzheimer’s disease but among them mutation in three genes that control the production of proteins like amyloid precursor protein (APP), presenilin 1 and presenilin 2 is important. Variation in a gene known as apolipoprotein E is responsible for causing late symptoms of Alzheimer’s disease.
Studies have also indicated that mutations in another gene CYP46 increase the risk of late onset of Alzheimer’s disease. The gene is responsible for the production of a protein responsible for the brain cholesterol metabolism. Scientists are working to find out how beta amyloid influences the development of Alzheimer’s disease. Vascular dementia may arise due to cerebrovascular disease or any condition that prevents normal blood supply to brain. When the blood supply to brain cells is insufficient they suffer from oxygen deficiency and finally die.
Doctors employ a number of strategies while dealing with the individuals suffering from dementia and it is always beneficial to rule out all the conditions that can be easily treated by medications. Disease diagnosis can be done by the following methods:
1. Patient’ history
While starting the diagnosis a doctor may ask about the family background of the patient by asking questions like how and when the symptoms developed as well as what is the overall medical condition of the patient. The doctor may also try to evaluate the mental state of the patient. Questions from the family members can be asked to know the family history in order to ensure whether the disease was present in the family earlier or not.
2. Physical examination
Physical examination of the patient may help to identify the signs or other disorders that can contribute to dementia. It can also identify the presence of heart or kidney disease that may overlap with dementia.
3. Neurological evaluation
Neurological examinations can be performed by the doctors by checking balance, sensory function, reflexes or other symptoms in order to make sure whether they can be recovered by drugs or not.
4. Cognitive and neuropsychological tests
Doctors perform tests to check the memory, language skills, maths skills and other tests in order to find out the mental alertness of the patient. They can often use a test known as Mini-Mental State Examination (MMSE) which analyses the orientation, memory and attention as well as language commands. Doctors also use other tests with variable scales in order to judge the mental state of the patient.
5. Brain scans
Doctors may use brain scans in order to find out strokes or tumors that can cause symptoms of dementia. Degeneration of brain’s cortex is very common in many types of dementias and brain scans can easily detect it. Most commonly used brain scans are the computerized tomography (CT) and magnetic resonance imaging (MRI). Doctors frequently use the CT brain scans which use X-rays and can detect changes in brain structures. MRI scans use magnetic fields and radio waves to detect hydrogen atoms present in body tissues. Medical experts can also use electroencephalogram (EEGs) in case of suspicious individuals. EEGs record the electrical activity as well abnormalities in brain structures. Several types of brain scans are available that help the medical experts to keep a check over the brain activity. The functional brain scans include MRI (fMRI), single photon-emission computed tomography (SPECT), positron emission tomography (PET) and magnetoencephalography (MEG). fMRI uses radio waves and a strong magnetic field that keeps a regular check on the activities going inside the active parts of the brain. SPECT increases brain activity by showing distribution of blood in the brain. PET detects changes in glucose and oxygen metabolism and blood flow revealing abnormalities in brain function. MEG shows electromagnetic fields caused by neurons of brain.
6. Laboratory tests
Doctors may use a variety of laboratory tests in order to find out whether the individual is suffering from dementia or not. The list of tests includes total blood count, blood glucose test, urinalysis, drug and alcohol tests, cerebrospinal fluid test, and thyroid gland analysis.
7. Psychiatric evaluation
A psychiatric evaluation is done to check whether the symptoms are due to dementia or some other factors are coupled with it.
8. Presymptomatic testing
Testing the individuals before the symptoms appear and develop into dementia is not possible in many cases.
A study carried out at the University of Bari, Italy concluded that consumption of alcoholic beverages had a slower progression to dementia. Although there is no cure for dementia but cholinesterase inhibitors can be used while dealing with this disorder. Educating as well as giving emotional support to the patient can be of help. Patients with dementia always complain of persistent pain which difficult to explain, diagnose and treat and this pain badly affects the quality of life and psychosocial functions of life of the patient. Although none of the medications used for treating dementia have given perfect results acetylcholinesterase inhibitors and N-methyl-D-aspartate (NMDA) receptor blockers have given some better results. These medications must be taken only after consulting a medical expert.
Risk factors for dementia
Researchers have identified many factors that can be held responsible for developing one or other types of dementia. Some of these factors are modifiable while others are not. These factors include:
The symptoms of Alzheimer’s disease, vascular dementia and other types of dementia generally appear with advancing age.
2. Genetics or family history
Scientists have found a number of genes responsible for causing Alzheimer’s disease but persons with a family history of the disease are at an elevated risk of developing the disease.
3. Smoking and Alcohol consumption
Smoking and use of alcohol also increases the risk of mental declination and dementia. Individuals who smoke regularly are at an elevated risk of suffering from atherosclerosis and other vascular diseases that can be coupled with dementia.
High levels of low-density lipoproteins (LDL) also known as the bad cholesterol increase the risk of vascular diseases that can be linked with increased risk of Alzheimer’s disease.
5. Plasma homocysteine
Researchers have indicated that higher levels of blood homocysteine increase the risk of vascular dementia.
Diabetes is a very common factor associated with many types of dementias as well as it also increases the risk of atherosclerosis and stroke that ultimately cause vascular dementia.
7. Mild cognitive impairment
People with mild cognitive impairment are at an increased risk of developing dementia especially if they are above the age of 65 or more.
8. Down syndrome
Studies have shown that the individuals suffering from Down syndrome develop amyloid plaques and neurofibrillary tangles in their middle ages but all the individuals do not develop symptoms of dementia.