Monday, 13 February 2017

Parkinson's Disease

Parkinson's is a relatively common disease, with one in every 500 people in the United Kingdom suffering from the condition. The symptoms are mainly motor-related unlike Alzheimer's which affects mostly cognitive functions. Patients with Parkinson's  tend to suffer from rigidity or stiffness, slowness in movement (bradykensia) and tremors. However symptoms such as depression, insomnia and some loss of cognitive abilities can also be found in sufferers of Parkinson's. In most sufferers the symptoms of the disease are evident when they are over the age of 50, but 1 in 20 develop symptoms when they are under 40. 

In the middle of the brain lies a small area called the substantia nigra. In Parkinson's the nerve cells here are lost which cause the motor-related symptoms associated with the disease. The cells in this region of the brain produce dopamine, a neurotransmitter essential for the transfer of electrical signals involved in coordinating movement. Since the end product of dopamine is melanin, the substantia nigra is significantly darker in healthy individuals than the rest of the brain and Parkinson's patients, who have damaged cells in these region, have lighter coloured substantia nigra as result.

The Substantia nigra in Parkinson's sufferers compared to healthy individuals
As both Parkinson's disease and Lewy Body disease involve the protein alpha-synuclein, it makes it difficult to differentiate between the two diseases. In both, lewy Bodies form as result of alpha-synuclein clumping and forming aggregate plaques in neurons. However a sufferer is considered to have Parkinson's if their motor-related symptoms appear at least a year before dementia, whereas in Lewy Body disease both symptoms appear at the same time.

Unlike most neurological conditions, Parkinson's can be diagnosed without a CT or MRI scan. Signs of tremor, stiffness and slowness of movement are in many cases a clear sign of Parkinson's Disease. However, a single-photon emission computerised tomography (SPECT) scan can also be used for diagnosis. It uses a radioactive trace that is injected inside the body to analyse the blood flow through regions of the brain, highlighting areas where blood flow is limited due to injury. This trace emits gamma rays that are detected by the scanner to form 2D cross sections that are pieced together to form a 3D image.There is some exposure to radiation from the tracer however there are no associated long-term health risks.
SPECT scan comparing the brain of a Parkinson's sufferer with a healthy individual
(Wikidotcom, 2017)
Parkinson's disease can be treated with a drug called levodopa. In fact, if a patient responds positively to the drug and there are signs of improvement then it further certifies that they are suffering from the disease. Like mentioned before, Parkinson's sufferers are unable to produce sufficient dopamine and the injected chemical cannot pass through the blood-brain barrier to be used in the brain. Levodopa is used instead. It is absorbed and converted by an enzyme called dopa-decarboxylase into dopamine in the brain, and consequently increasing dopamine levels to normal. This has proven to be the most effective form of medication for Parkinson's sufferers at the moment. Levodopa can be partnered with another drug called carbidopa that prevents Levodopa from being converted by the body too early before it has reached the brain. However, the use of levodopa is only a form of treatment for the Parkinson's disease as a cure is still yet to be found. 
How Levodopa is absorbed and used in the brain
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Monday, 5 December 2016

Systemic Lupus Erythematosus

Lupus is an autoimmune disease, which is where the body's antibodies attack healthy cells by mistaking them for pathogens. There are around 5 million sufferers of Lupus around the world, making it one of the most common autoimmune diseases.

In the autoimmune attack, the antibodies produced by the body are referred to as autoantibodies which are specific in targeting the body's own proteins. These antibodies may attach to the antigens of healthy body cells causing them to become targets for attack by white blood cells. As a result this leads to damage to the body's organs and tissues that are associated with the condition as the autoantibodies travel in the bloodstream and eventually enter through permeable plasma membranes of cells. The autoantibodies then attack the cells DNA by entering the nucleus which leads to inflammation. 

Lupus may cause a myriad of symptoms conning it the name 'The Great Imitator' of other conditions. The most common of these symptoms being fatigue, rashes and joint pain. The symptoms differ depending on what area of the body are affected by the condition, which ranges from the heart to the kidneys. The other less common symptom include: chest pain, abdominal pain, depression, recurring  mouth ulcers, memory loss, seizures and high blood pressure to name a few. Due to the nature of the disease, sufferers may experience fluctuating periods of seeming recovery and strong symptoms.
Symptoms of Lupus
For autoimmune diseases, the most common form of diagnosis is through an ANA (antinuclear antibody) panel test. This essentially identifies any antibodies in the blood that may have been released as part of an autoimmune response, and therefore the test cannot diagnose exactly which of the autoimmune diseases the sufferer may have but can only provide either a positive or negative result. The doctor would carry out further tests to achieve a final diagnosis. The accuracy rate is high, with 95% of Lupus sufferers receiving a positive result.
Image of immunofluorescence staining of antinuclear antibodies
There are more cases of women developing Lupus than men which has led some scientists to research a possible link between increased oestrogen levels and the condition. In fact, nine out of ten cases of Lupus are found in women, although so far no conclusive link has been made with the menstrual hormone.

Currently, Lupus is a chronic disease and therefore cannot be cured but only treated with medication. The inflammation that characterises the condition can be with Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibruprofen, naproxen and diclofenac. Furthermore, immunosuppressants are also effective in reducing the symptoms caused by Lupus, however as the drugs are cause many side effects it is often only prescribed only for severe cases.


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Thursday, 17 November 2016

Lewy Body Dementia

Lewy Body Dementia is a disease that causes the loss of cognitive abilities. Although unheard of to many, it is in fact the second largest cause of dementia in the UK, with more than 100,000 sufferers in the UK alone.

The symptoms of the disease include hallucinations, cognitive difficulties, depression, difficulty with movement and many more that are associated with dementia. What symptoms expressed is dependent on the locations of the Lewy Bodies in the brain. A build up of Lewy Bodies in the outer parts of the brain affect the cognitive abilities, thus producing symptoms similar to that of Alzheimer's. Similarly, if found in the base of the brain, movement is affected producing symptom's of Parkinson's Disease.
Image showing Lewy Body proteins in brain cells
(University of Nottingham, 2017)
The disease is not genetically linked therefore cases may arise spontaneously even though the patient has no known family history of the condition. The core cause of the disease is the build up of proteins called alpha-synuclein. In healthy individuals alpha-synuclein is involved in regulating the release of some neurotransmitters between neurones. When deposited in the brain they form aggregates named Lewy Bodies inside neurons, causing reduced levels of neurotransmitters such as dopamine and acetylcholine. As a result the brain's cognitive processes are affected, leading to symptoms associated with dementia.

The disease is often misdiagnosed even though 10-15% of dementia cases are due to Lewy Bodies. This is largely because few doctors are familiar with the disease and its overlap of symptoms with other forms of dementia. Like Alzheimer's, the process of diagnosis may involve examining the patient's motor and cognitive abilities. However, the only definitive indicator of Lewy Body dementia is to certify the presence of the Lewy bodies, and this at present can only be done in a post mortem brain autopsy. 

At the moment, there is no cure for the disease, however some forms of treatment have shown to be effective such as the use of acetylcholinesterase inhibitors in treating the hallucinations associated with Lewy Body dementia. Since the Lewy Body proteins essentially reduces acetylcholine (a common neurotransmitter in the brain), by inhibiting the enzyme that breaks it down, it allows levels of the neurotransmitter to increase thus improve signalling within the brain. Other forms of treatment are physiotherapy to improve motor abilities, occupational therapy and cognitive stimulation to name a few. 


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Tuesday, 30 August 2016

Hyperthyroidism and Graves Disease

The thyroid is simply a gland positioned on the windpipe, just below the Adam's apple. It resembles a butterfly as it consist of two lobes connected by a bridge known as the isthmus. The gland is very important in the  excretion of thyroid hormones, in particular thyroxine (T4) which makes up the majority of the hormones secreted into the bloodstream. Thyroid hormones play a vital role in regulating the metabolism of the body and are salient for healthy brain development in children.
Anatomy of the Thyroid
Like the name suggests, Hyperthyroidism is the over-production of the hormones produced and secreted by the thyroid. Therefore, an excess in these hormones causes the metabolic processes in the body to undergo at a fast rate than normal, which leads to a myriad of symptoms such as anxiety and hyperactivity. The thyroid gland can also be seen as visibly swollen around the neck, portraying a lump that is also known as a goitre.
Diagram of a goitre and hyperthyroidism
One of the most common causes of hyperthyroidism is Grave's Disease. This is an autoimmune response where antibodies of the immune system target the Thyroid gland rather than pathogens in the body. Consequently, the thyroid produces an excess of thyroxine. Not only is the thyroid targeted, but the antibodies can also attack the tissue behind the eyes. Sufferers with Grave's Disease can often have protruding and swollen eyes as a result which is known as exophthalmos
Grave's Disease and Hyperthyroidism
Both conditions are difficult to treat and have no original cause, although both are thought to be due to a combination of both environmental and genetic factors. The disease is more common in women than men and most often occurs between the ages of 20 to 40 years old. It is often treated with Thionamides which helps limit the amount of thyroxine produced by the thyroid. Other options include radioiodine treatment to shrink the thyroid or surgery to remove parts of the gland. However, both treatments may lead to the thyrroid gland becoming under-reactive also known as hypothyroidism.


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Saturday, 14 May 2016

Alzheimer's Disease

Before tackling this notorious disease, the difference between dementia and Alzheimer's must be clarified. Dementia is a symptom caused by Alzheimer's disease, and is characterised by memory loss as well as many other cognitive processes.  

Alzheimer's itself is a progressive disease that affects 520,000 people in the UK. Its causes are unknown, although there are a number of factors that increase the risks of developing this disease. These include: if it is in the family history, experiencing a severe head injury and increasing age. As a result, the condition  is most common  in sufferers aged 65, with women also at greater risk. Research has also shown that the lifestyle factors associated with cardiovascular disease, such as smoking and obesity, also correlate with Alzheimer's disease.

Mainly the cognitive abilities are affected gradually with Alzheimer's. The first signs are usually minor memory loss, but this can then progress to problems with communication, hallucinations, confusion and personality changes.

All of Alzheimer's symptoms characterise the symptoms of dementia, which can be explained by understanding the changes the disease causes in the brain. In essence, the condition stimulates nerve cell death, which can deteriorate large portions of brain tissue.

Diagram showing the middle part of a healthy and diseased brain
As a result, many areas of the brain are lost. The cerebral cortex shrivels, removing with it the billions of cells, called grey matter, which control thinking and processing.  In addition, the hippocampus also experiences shrinkage, which thus affects the storage of long term memory and the ability to recall specific events. Also, the ventricles, which are cerebrospinal fluid-filled sacs, increases in size. This creates a build up of pressure as the brain is forced to press against the skull. 
Areas of loss in AD brain compared to healthy brain
Under a microscope, scientists are able to identify the extent that the disease affects the brain. At high magnification, the brains of sufferers show fewer nerve cells and synapses, which are fundamental for the travel of neurones and thus the travel of information in the brain. Nerve cells are also affected. Abnormal pieces of the amyloid precursor protein (APP) form aggregated plaques by clumping together, blocking these synapses and again preventing the transport of information. 
In healthy brain tissue, proteins named tau provide orderly tracks, allowing the transport of nutrients and other essential materials to cells. However, the disease causes these tau proteins to twist and from tangles. The once orderly tracks therefore disintegrate, stopping the delivery of materials, causing the cells to die.

Acetylcholinesterase inhibitors are most commonly used to treat Alzheimer's. Like in their name, these drugs are used to inhibit the enzyme that breaks down the neurotransmitter acetylcholine, therefore allowing the acetylcholine to remain for longer and increase the activity of cholinergic neurones. The inhibitors prescribed for the early to middle stages of Alzheimer's include donepezil, galantamine and rivastigmine.

Alzheimer's - A progressive disease

Notoriously, sufferers with Alzheimer's deteriorate over time as the disease develops and conquers more of the brain. The time this takes differs from person to person, but it is largely affected by how early the sufferer was diagnosed and any other diseases they may have. Therefore, although on average, sufferers survive for 8 years, some may live for 20 years.

The early stages of the disease is also referred to as early dementia or mild cognitive impairment. Often at this stage, memory loss is not drastic, with short term memory mostly affected and adversely, long term largely retained. The ability to think or plan, known as executive functioning, may also be difficult. This is all due to the tangles beginning to form in areas of the brain that control these cognitive abilities.

These symptoms develop and worsen over time, leading to middle stages of Alzheimer's disease, also known as the moderate stage. Some sufferers here will show more aggressive behaviour, such as refusing to take orders. Again this frustration is as a result of the more drastic damage to synapses and nerve cells, making performing tasks and making decisions difficult. Unable to remember certain events, confusion and mood changes are also other characteristics of this stage of dementia.

At the final stages of the disease, sufferers become almost completely dependent on their carers. Physically, sufferers at this stage may lose many essential functions of movement, including swallowing and walking. Not only do they become mentally vulnerable, but their immunity weakens causing sufferers to become prone to infections such as pneumonia. As their cognitive abilities deteriorate, holding a conversation becomes near to impossible and all the severity of all symptoms before heighten. 

Stages of Alzheimer's disease and its effects on the brain
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Friday, 11 March 2016

Parry Romberg Syndrome

Parry Romberg syndrome is a very rare disorder, more common in women than men. It is characterised by progressive deterioration of the facial tissue (hemi-facial atrophy), particularly the left-side, and in severe cases bones. If limbs are affected, it is commonly on the same side as the facial atrophy.

The deterioration begins between the nose and upper lip. This then slowly progresses across the face, and may even affect the roof of the mouth, tongue and gums. Tissue beneath the skin (subcutaneous) and fat shrink, which characterises the atrophy. As a result, sufferers show a sunken appearance in these areas. Due to the extensiveness of the areas affected, a number of conditions can occur. This includes: alopecia, facial pain and seizures due to neurological abnormalities. Of course, the severity of the symptoms vary, with the majority of sufferers experiencing mild deterioration.
Child with facial atrophy on his right side
Atrophy lasts from 2 to 10 years, after which it enters a stable phase. Parry Romberg syndrome can arise both in adulthood and late childhood, although the majority of sufferers have symptoms before the age of 20. Often, the earlier the deterioration begins, the quicker it progresses. 

At the moment, Parry Romberg Syndrome is incurable and untreatable. This is largely because the cause of this disorder is unknown, as the syndrome appears to happen sporadically. However, reconstruction surgery is available, to repair facial tissue.

There are a few theories for the causes of this syndrome. It must be considered that Parry Romberg syndrome may be due to a somatic mutation. This is where a mutation occurs in one of the cells in a zygote, at the very early stage of fertilisation. Thus, cells that had divided from this one cell, will carry the mutation. Furthermore, this 'somatic mutation' hypothesis agrees with the idea that Parry Romberg is not inheritable, which may increase the theory's credibility.

However, a more popular theory for its cause suggests that it is due to an autoimmune reaction, where the body perceives healthy tissue as foreign, thus attacks it with antibodies. In this case, since the antibodies are attacking healthy tissue, they have coined the term autoantibodies. This unusual response may be triggered by an inflammation of the nerves that produce skin and fat.


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Friday, 4 March 2016

Acromegaly (Gigantism)

Acromegaly, also known as gigantism, has the literal definition of enlargement of the body. It is most commonly caused by a gland tumour (adenoma) in the pituitary gland. This gland is located in the brain with the purpose of secreting growth hormones. Although, the tumour heightens the production of these growth hormones, the tumour itself is benign and therefore has little risk of developing into cancer.
Pituitary gland labelled

The adenoma can grow to 1cm in size which can exert pressure on cranial nerves in the brain and those leading to the eyes. Sufferers can therefore experience blurred vision and headaches.

The condition can be easily identified through physical diagnosis. It is characterised by very large hands, feet, toes and fingers with a prominent jawline and forehead also being common features caused by acromegaly.
Acromegaly common features
However, in order to certify the condition is present, a blood test can be carried out by testing the levels of growth hormone, which would normally decrease when the patient is given a sugary drink. Insulin-like growth factor 1 (IGF-1) is also tested. By it being produced by the liver, it provides an alternative cause for abnormal growth, therefore being liver damage.

The graph below shows that in non-sufferers, growth hormones are secreted predominantly during sleep. However, it is clear in the acromegaly sufferer's graph that GH levels keep at a constant level showing that the pituitary is secreting continuously. 
Graphs comparing Growth Hormone levels between sufferers and non-sufferers
A positive result for the growth hormone leads to MRI scans of the head to see whether there is a tumour present in the pituitary gland.
MRI scan of a Pituitary gland with a tumour
Acromegaly is rarely inherited but can be in the form of familial isolated pituitary adenoma or as part of multiple endocrine neoplasia (MEN). In familial isolate pituitary adenoma, the tumour growth occurs in adolescence, when the bones are still malleable enough for the excess growth hormones to make a significant effect.

The most effective treatment involves the surgical removal of the main cause of the condition, the tumour growth in the pituitary gland. Preferably, the adenoma should not be near any key structures of the brain, in order to limit possible complications during surgery.

An incision is first made under the nose or upper lip to allow an endoscope, and other surgical instruments, to access the sphenoid sinus, hence why it is defined as transsphenoidal surgery. The sinus space leads directly to the pituitary gland and therefore the adenoma. As a result, the tumour can be removed.
Transsphenoidal surgery


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