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Prion Disease

Prion diseases are Transmissible Spongiform Encephalopathies or TSE that affect humans and animals. In humans, they cause neurological disorders that are progressively degenerative. A prion is an abnormal pathogen that affects proteins found in the brain causing them to fold and clump unnaturally. This then leads to brain damage that is progressive. Prion diseases may occur spontaneously, may be inherited or may be acquired from contaminated material.


The most common form of prion disease is Creutzfeldt Jakob Disease or CJD. A variant of CJD is the 'mad cow disease'. The infection passes on to humans through contaminated meat. The most common pathologic feature of CJD is the formation of vacuoles (fluid filled spaces) in the brain giving rise to sponge-like appearance. CJD is one of several spongiform encephalopathies. Others include Kuru and Gerstmann Straussler Scheinker Syndrome.


Typical symptoms of prion disease include muscle stiffness, dementia, hallucinations, ataxia and fatigue. There is a change in the personality and behavior of the person. Diagnostic tests such as brain MRI, Spinal tap, EEG and blood tests are done to understand the condition. Brain tissue biopsy helps to confirm the disease. With rapid progression of the disease, the patient needs help in taking care of himself and might need to be moved to assisted care.


Kuru is another degenerative human spongiform encephalopathy disease that afflicted the Fore people from Papua, New Guinea due to ritual cannibalism.

GSS or Gerstmann Straussler Scheinker Syndrome is a rare neurological disorder due to brain degeneration. It is mostly inherited and sets in middle age. Initially the patient suffers cerebellar ataxia (lack of muscular coordination) and gradually deteriorates to dementia. There might be Nystagmus (rapid involuntary eye movements) and visual problems. There is a possibility of developing Parkinsons disease too. With rapid progression of the disease, the patient needs help in taking care of himself and might need to be moved to assisted care.


FFI or Fatal Familial Insomnia is a type of prion disease where the patient has difficulty in walking and falling asleep. There might be weight loss and excessive tears in the eye. It rapidly deteriorates to loss of consciousness and death. Initially the patient suffers insomnia that later worsens to include panic attacks, phobia and hallucinations. There might be weight loss and incontinence. After this, the patient might suffer dementia and sudden death.


Dementia

According to statistics, dementia affects about 36 million people globally and about 10% of people develop the disease at some point in their lives. It becomes more common with age. As more people are living longer, dementia is becoming more common in the population as a whole. Also known as Senility, dementia is a broad category of brain diseases that causes gradual decrease in the ability to think and remember. It is a collective term that is used to describe various underlying brain disorders or damage that can lead to memory loss, language and thinking.


While the likelihood of dementia increases with age, it is not to be misunderstood with normal part of aging. Light cognitive impairments and poorer short-term memory can happen as normal part of aging and this is known as age related cognitive decline and not dementia.
Alzheimer's disease is the best known and most common form of dementia, although there are others types including Vascular Dementia, Lewy Body Dementia and Frontotemporal dementia.


Causes

The loss or damage of nerve cells or neurons in the brain can cause dementia. Alzheimer's disease is the leading cause. Dementia can also be caused by head injury, a stroke or brain tumor. Brain cell death caused by conditions such as cerebrovascular disease like stroke can cause vascular dementia. This prevents adequate blood flow, depriving brain cells of oxygen.


Post traumatic dementia is directly related to brain cell death caused by injury. Some repetitive injuries suffered by sports players are linked to certain form of dementias appearing later in life. Dementia can also be caused by diseases such as Prion disease, from certain types of proteins, HIV infection, medication interactions, depression and vitamin deficiencies. A small proportion of dementia cases run in families.


Signs and symptoms

Other than the decrease in the ability to think and remember even daily functions, some common symptoms of dementia are:


  • Emotional problems
  • Problems with language, communication and forgetting simple words or using wrong ones
  • Reduced motivation
  • Recent memory loss – asking the same questions repeatedly
  • Difficulty in completing familiar tasks – like making a drink or cooking a meal
  • Disorientation with time and place, getting lost on a previously familiar street and not knowing to get home again
  • Poor judgment and total distraction
  • Problems with abstract thinking such as dealing with money
  • Misplacing things and forgetting about doing this
  • Mood swings and changes quickly through set of moods
  • Personality changes and becoming irritable, suspicious and fearful
  • Loss of initiative.

Diagnosis

The first thing is to assess memory performance and cognitive health. A healthcare professional would ask a set of questions to test knowledge of facts that should be known to any adult to get an indication whether there is dementia or not. The patient is asked to complete the standard tests, and answers are recorded to form a diagnostic indication. Tests to assess a person's mental ability are conducted and test scores are ascertained. Questions such as 'What is your age', 'What is the time', 'What is the year', Counting 20 backward etc are asked. One task for the patient is to write the hours of a clock face around a blank circle on a piece of paper and with accurate relative spacing. These cognitive tests measure dementia symptoms and other tests help to narrow down, if for example, it is Alzheimer's disease.


Mental examination measures include orientation to time and place, word recall, language abilities, attention and calculation, visuo-spatial skills. Ability to name objects, follow verbal and written commands, language and culture and if there are any sensory impairments are all assessed.
Doctors will evaluate the patient history and carry out a physical examination to uncover any signs of a stroke, heart condition or kidney disease and check neurological function, by testing balance, senses and reflexes.


Treatment

As brain cell death cannot be reversed, there is no known treatment to cure a degenerative cause of dementia symptoms or fully halt its progress. The aim is to provide care and treat symptoms rather than their underlying cause and manage the disorder. If dementia symptoms are due to reversible, non-degenerative cause, treatment is possible to prevent or halt further brain tissue damage.

Symptoms of Alzheimer's can be reduced by drugs to improve the person's quality of life. Educating and providing emotional support is imperative. Exercise programs are beneficial. Treatment of behavioral problems of psychosis with antipsychotics is not usually recommended due to increased risk of death.


Prevention

Other than age which is the biggest predictor of dementia, certain risk factors are modifiable. These risk factors include:


  • Smoking and alcohol usage
  • Atherosclerosis
  • High levels of bad cholesterol
  • Above average blood levels of homocysteine, a type of amino acid
  • Diabetes
  • Mild cognitive impairment which can sometimes, if not always, lead to dementia.


CJD

This is a rare degenerative disease, a fatal brain disorder. One in every million worldwide is affected by Creutzfeldt Jakob disease which occurs about age 60, and about 90 percent of patients die within a year. Since first described in 1920, less than 1 percent of cases have acquired CJD.


Signs and symptoms

During the early stages of the disease failing memory, behavioral changes, lack of coordination and visual disturbances are exhibited. Impaired memory, judgment and thinking and insomnia, depression or unusual sensations are other symptoms. CJD may also cause fever or other flu-like symptoms. As the illness progresses, mental deterioration becomes severe. Involuntary movements, blindness and weakness of extremities are other symptoms.

Rapidly the disease progresses into dementia. Patients eventually lose the ability to move and speak and then enter a coma. Pneumonia and other infections may occur in these individuals and can lead to death. Some symptoms of CJD can be similar to Alzheimers or Huntington disease. CJD causes unique changes in brain tissue which can be seen at autopsy and the deterioration is more rapid than Alzheimer's disease or other types of dementia.


Major categories of CJD

Sporadic CJD: Here the disease appears even though the person may not exhibit any known risk factors. This is by far the most common type of CJD and 85 percent cases come under this category.

Variant CJD is caused by consuming meat from a cow that had Bovine Spongiform Encephalopathy (BSE) or mad cow disease, a prion disease similar to CJD. Strict controls have proved very effective since its discovery in 1996.

In hereditary CJD, the person has a family history of the disease and tests positive for a genetic mutation associated with CJD. About 5 to 10 percent of cases in the US are hereditary and the symptoms usually develop in early 50s.

In latrogenic CJD, the infection spreads from someone through medical or surgical treatment. A common instance of this is spread of CJD from someone with growth hormone treatment using human pituitary growth hormones extracted from deceased individuals who might have had CJD infection.
CJD is not contagious through casual contact with a CJD patient.


Causes

Researchers believe that an unusual slow virus or any other organism causes CJD. But they have never been able to isolate a virus or any organism in people with the disease. As the agent causing CJD has several characteristics other than known organisms such as bacteria and virus, it is difficult to destroy as it does not contain any genetic information in the form of nucleic acids. For example, prions are not destroyed by the extremes of heat and radiation used to kill bacteria and viruses, and antibiotics or antiviral medicines have no effect on them. It also incubates for a long period of time before the symptoms appear, as long as even 50 years. The leading scientific theory maintains that CJD is caused by a type of protein called as a prion. Also 5 to 10 percent of CJD cases are inherited. These cases arise from a mutation, or change in the gene that controls formation of the normal prion protein.


Diagnosis of CJD

There is no single diagnostic test for CJD. First, all treatable forms of dementia are ruled out. A neurological examination is performed and consultation with other physicians is sought. Spinal tap, electroencephalogram, CT and MRI and brain scans can reveal characteristic patterns of brain degeneration that can help diagnose CJD.


For a confirmed diagnosis of CJD, brain autopsy is the only way. A neurosurgeon removes a small piece of tissue from the patient's brain and it is examined by a neuropathologist. The procedure may be dangerous as it does not always obtain tissue from the affected part of the brain. Brain biopsy is discouraged unless it is needed to rule out a treatable disorder. In autopsy, the whole brain is examined after death. Special surgical and disinfection procedures can minimize the risk. Scientists are working to develop laboratory tests for CJD.


As such there is no treatment or cure to control CJD. Studies are on to try a variety of drugs but none of the treatments have shown consistent benefits in humans. Treatment aims at alleviating symptoms and making the patient as comfortable as possible. Opiate drugs can help relieve pain. During later stages of the disease, changing person's position frequently can keep them comfortable and help prevent bed sores. A catheter is used to drain urine if bladder control is lost. Intravenous fluids and artificial feeding are also used.


Avoid spreading CJD

To reduce the very low risk of CJD transmission from one person to another, it is better not to donate blood, tissues or organs if suspected or confirmed with CJD because of family history of the disease. As normal sterilization procedures such as cooking, washing and boiling do not destroy prions, the following precautions are suggested by the World Health Organization while dealing with patients contacted with CJD.


  • Cuts and abrasions should be covered with waterproof dressings.
  • Surgical gloves should be worn when handling a patient's tissues and fluids or dressing up patient's wounds.
  • Avoid cutting or sticking with instruments contaminated by patient's blood or tissues.
  • Use disposable bedclothes for contact with patient.
  • Use face protection if there is risk of splashing contaminated material such as blood or cerebrospinal fluid.
  • Soak instruments that have come in contact with patient in undiluted chlorine bleach for an hour or more and then autoclave to sterilize them in distilled water for at least one hour at 132-134 C.

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Collection of Pages - Last revised Date: November 12, 2019