Different Types of Dementia
Wessam Bou-Assaly, MD
AD is a chronic neurodegenerative disease that usually has a progressive worsening course. It is characterized by loss of neurons and synapses in the cerebral cortex, resulting in gross atrophy of the affected regions, mainly the temporal and parietal lobes and parts of the frontal cortex and cingulate gyrus.
It is the cause of 60% to 70% of cases of dementia.
The most common early symptom is difficulty in remembering recent events ( short-memory loss). As the disease advances, symptoms can include problems in language, disorientation (including easily getting lost), mood swings, loss of motivation, not managing self care, and behavioral issues. The patients often withdraw from family and society.
Gradually, bodily functions are lost, ultimately leading to death.
Although the speed of progression can vary, the average life expectancy following diagnosis is three to nine years.
The cause of Alzheimer’s disease is poorly understood.. About 70% of the risk is believed to be genetic with many genes usually involved. Other risk factors include a history of head injury, depression or hypertension.
Frontotemporal dementia ( Pick’s Disease)
Frontotemporal dementia ( also known as Pick’s disease or frontotemporal lobar degeneration) primarily affect the frontal and/or temporal lobes of the brain and are generally associated with personality and behavior.
In frontotemporal dementia, portions of these lobes atrophy. Clinical features are early personality and behavioral changes ( Disinhibition, euphoria, apathy), Compulsive behaviors (peculiar eating, habits), executive disfunction and later appearance of memory deficits. The dramatic changes in the personality is associated with socially inappropriate, impulsive or emotionally blunted behaviors.
Frontotemporal dementia is often misdiagnosed as a psychiatric problem or as Alzheimer’s disease, but it tends to occur at a younger age than does Alzheimer’s disease, typically between the ages of 40 and 70, with a more delayed occurrence of memory problems.
Dementia with Lewy Bodies
Dementia with Lewy bodies (DLB) is one of the most common types of progressive dementia.
The central feature of DLB is progressive cognitive decline, combined with three additional defining features:
1- Visual hallucinations.
2- Fluctuations in alertness and attention, often leading to misdiagnose as delirium. ( frequent drowsiness, lethargy, lengthy periods of time spent staring into space, or disorganized speech;
3-Parkinsonian motor symptoms, such as rigidity and the loss of spontaneous movement.
People may also suffer from depression. The symptoms of DLB are caused by the build-up of Lewy bodies (alpha-synuclein protein) inside the nuclei of neurons in areas of the brain that control particular aspects of memory and motor control.
The similarity of symptoms between DLB and Parkinson’s disease, and between DLB and Alzheimer’s disease, can often make it difficult for a doctor to make a definitive diagnosis. In addition, Lewy bodies are often also found in the brains of people with Parkinson’s and Alzheimer’s diseases. These findings suggest that either DLB is related to these other causes of dementia or that an individual can have both diseases at the same time. DLB usually occurs sporadically, in people with no known family history of the disease. However, rare familial cases have occasionally been reported.
Normal Pressure Hydrocephalus
Normal pressure hydrocephalus (NPH) is a form of hydrocephalus( Dilated ventricles).
It can occur without a known cause, or it may be caused by any condition that blocks the flow of cerebrospinal fluid (CSF), resulting in increased volume of CSF in the ventricles.
Ataxia ( lack of voluntary coordination) and urinary incontinence appear early in the disease. The dementia symptoms of NPH can be similar to those of Alzheimer’s disease.
NPH can be reversed in many people with appropriate treatment. But first it must be correctly diagnosed. NPH is thought to account for about 5% of all dementias.
Vascular dementia is an umbrella term that describes impairments in cognitive function caused by problems in the brain blood vessels. It accounts for 15-20 % of dementia cases and the risk increases dramatically with age.
Risk factors for cerebrovascular disease include hypertension, hyperlipidemia, smoking diabetes.
Usually there is stepwise decline in memory, with early executive dysfunction. Cerebral infarcts or white matter changes are seen on MRI.
Creutzfeldt-Jakob Disease or Prion disease
Creutzfeldt-Jakob disease (CJD) is a rare, degenerative, fatal brain disorder. It affects about one person in every one million people per year worldwide.
CJD usually appears in later life and runs a rapid course. Typically, onset of symptoms occurs about age 60, and about 90 percent of patients die within 1 year.
The disease is characterized by behavioral changes, rapidly progressive memory problems with myoclonus and seizures.
As the illness progresses, mental deterioration becomes pronounced and involuntary movements, blindness, weakness of extremities, and coma may occur.
Wernicke-Korsakoff syndrome is caused by a thiamine ( Vitamin B1) deficiency.
It involves damage to multiple nerves in both the central nervous system (brain and spinal cord) and the peripheral nervous system.
The cause is generally attributed to malnutrition, especially lack of vitamin B1 (thiamin), which is common in those with alcoholism. Heavy alcohol use interferes with the breakdown of thiamin in the body, so even if someone with alcoholism follows a well-balanced diet, most of the thiamin is not absorbed.
Wessam Bou-Assaly, MD is a Radiologist specialized in Neuroradiology and Head and Neck Imaging.