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.
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.
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.
Memories of persons vary depending on the individual's state of mind and the content of the information. There are 2 basic types of memory - Implicit which refers to the unconscious level occurring in basal ganglia and the Explicit that refers to the conscious level (occurring in medial temporal structures). Episodic memory refers to the record of events (episodes) and the relationship with the person. Short term memory is synonymous with working memory. This is a specialized term referring to information about the current task. Commonly also referred to as amnesia, memory loss can be described as a degree of forgetfulness or failure to recall past events which is above the normal level. At times, memory loss is limited to an inability to recall events that are recent, but sometimes it could also be for events from the past or both.
Types of memory loss
Depending upon its cause, memory loss could be sudden or gradual, and permanent or temporary. A transient global amnesia is rare and is a complete but temporary memory loss. In anterograde amnesia on the other hand, the individual cannot recall recent events occurring after a trauma but can recall events of distant past. Retrograde amnesia is when the individual cannot recollect events preceding or leading up to the trauma. But he/she can recall all subsequent events. A transient global amnesia is rare and is a complete but temporary memory loss.
Causes for short term memory loss
Short term memory loss is a symptom of many possible causes including disease, dyslexia, depression, injury or chronic drug and alcohol abuse. Other possible causes for amnesia can be Alzheimer's disease, brain tumor, Creutzfeldt-Jakob disease, meningitis, Parkinson's disease, Pick disease, epilepsy, stroke and West Nile virus. A stroke is construed as one of the most serious reasons for a short term memory loss.
Research findings have established that the structural differences in cortical neurons depend on gonadal hormones in laboratory animals. Other studies on women show that their cognitive tasks changed throughout the menstrual cycle based on the fluctuating estrogen levels.
A head trauma can sometimes result in short term memory loss and this can happen even when concussion is not sustained. Psychiatric disorders such as dissociative fugue, dissociative identity disorder and other types of amnesia can cause short term memory loss. Severe psychological stress can push a person beyond his/her coping abilities can cause memory loss among other mental disturbances. Research reveals that stress hormones kill or inhibit the growth of brain cells adversely affecting memory. The more prolonged the depression, the more extensive the damage. Hormonal imbalance can play havoc and lead to short term memory loss. During menopause, memory loss symptoms are often seen in women.
Treating memory issues
Mental exercises, herbal supplements, certain drugs as well as a healthier lifestyle can all help in treating short term memory loss. If the memory loss is chronic and it interferes with everyday life then it is essential to consult the doctor to identify the cause and eliminate the serious condition.
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Bibliography / Reference
Collection of Pages - Last revised Date: December 4, 2023