Sunday, February 14, 2010

What is Parkinson's Disease?

PD Basics
Parkinson's disease is a chronic, progressive neurodegenerative disease - meaning, according to the CDC, that it will last longer than 3 months or in this case until death do us part.

It has the 2nd highest number of neurodegenerative disease patients; only Alzheimer's is higher. It is estimated that there are almost 1.5 million people who have PD in the US alone and more than 5.5 million globally. The numbers point to more men than women developing PD and to more whites with PD than Black Americans of African ancestry, Africans or Asians.

Parkinson's is classified as a motion disorder and is treated by specialists in movement disorders. The original diagnosis should be made by a neurology specialist.  There is also a significant number of non-movement symptoms as well; and some of the precursor symptoms are not motion related.

A rose by any other name 
Parkinson's disease has been called many things. Paralysis Agitans has been called a disease of old age.  While younger people can develop it and do, it more commonly develops in late middle age with the odds increasing every 10 years of age up to 89.

It has been called a disease of sleep disorder and of depression.  Of course everyone knows its modern history when it was called "the shaking palsy" by James Parkinson in 1817 and subsequently named after him a few decades later by Jean Martin Charcot who also studied the condition.

Parkinson's has also been called a prion disorder by Dr Stanley Prusiner because of the alpha synuclein pathology.

The disease has been known for centuries.  PD has a documented history dating back about 5,000 years in India where it was known in Ayruvedic medicine as Kampvata (severe body shivers). 2,500 years later its symptoms and treatment were described in China. A specific genetic line has been followed from China to the US. The disease appears to have been identified in Greece in around 800 BC and certainly by 310 BC it was known and studied. It was described in Rome about 2,000 years ago. It was later described by the Greek physician, Galen, about 1,800 years ago.

How will I know?
The disease begins to manifest early in many people with seemingly unrelated symptoms such as diminished sense of smell (partial usually), depression, sleep disorders, foot or leg drag and lack of arm swing when walking.  In some people it can manifest as smaller handwriting (microphagia) and in women as pain in the neck or shoulders. About 75% of people with PD begin to have tingling or tremors in the extremities on one side of the body as a symptom which eventually sends them to the doctor for a diagnosis.

The tremors and actually most of the above precursor symptoms manifest because of chemical imbalances in the brain. Parkinson's is usually diagnosed after the death of about 60-80% of the dopamine neurons in the substantia nigra pars compacta of the basal ganglia.  But before PD can actually develop a significant number of norepinephrine neurons must die also.  As a precursor of norepinephrine, dopamine is the target area for PD treatment.

The predominant motor symptoms are defined by the acronym TRAP.  Tremors, Rigidity, Akinesia (Bradykinesia) and Postural Instability all movement related. 

What's Going On?
Essentially it is the lack of balance or homeostasis between acetylcholine (which is in its normal abundant state) acting as an excitatory neurotransmitter and the diminishing supplies of the primary monoamine transporters dopamine, norepinephrine and serotonin, which serve as a message inhibitor. In other words the acetylcholine instructs the muscle to act or tense up while the dopamine sends the message to relax.
When the relax message cannot be sent as often, the rigidity and stiffness, the tremors and dyskinesias which typify PD, are seen. The stiffness can result in cramping and a little discussed symptom of Parkinson's known as pain. Usually treating the symptoms will relieve some of the physical pain.

Although the norepinephrine tries to take up some of the slack, there are fewer norepinephrine neurons in the brain to begin with and so with fewer precursor cells to make it, it too has been degenerating.

The why of dopamine cell death is being researched now and although there are some differences of opinion, it is thought that the cells die possibly when excess calcium in the cell causes the dopamine to leave the vesicle too early to be used and by hanging around in the cytosol it combines with alpha synuclein to become a gummy mess and ultimately die.  Dopamine continues to die throughout the course of Parkinson's disease.
It's not all in the family 
The disease is not contagious and at this point has only been identified as being about 15% or at most 20% genetic. Because there are several genes which have proteins mutations (doubled or triples) associated with PD and because they are each more common to specific geographic areas for specific gene lines although there are almost certainly trade route connections and migration or emigration patterns.

Despite the genetic research for PD, it is still called an idiopathic disease because the primary cause is unknown. There is YOPD, young onset PD and Juvenile Parkinson's both of which are felt to be predominantly genetic in origin.There are also other categories such as LBD or Lewy Body disorder which can occur before Parkinson's with parkinsonian symptoms developing later as well as PDD, Parkinson's disease with dementia in which the PD occurs first.

Even the genetic cases in older adults appear to have an environmental trigger. Parkinson's symptoms can also be drug induced. Other triggers include severe head trauma, certain heavy metal exposure, certain chemical exposure. It is difficult to establish if stress is an early contributor or a body reaction to the subtle loss of homeostasis.

When the cause is genetic, Parkinson's can be autosomal dominant or autosomal recessive. There is no reason to cast blame as the genes can be hiding in the woodwork just waiting as the disease can skip generations.

We Are the World 
There are other areas of the world which appear to have a lower incidence of Parkinson's disease. That may be due to a few different reasons, however, there are places where there is a high prevalence due to oddities of diet which cause parkinsonism if not PD.

PwPs around the world are generous in sharing their experiences with others.  Support groups abound and fund raising never stops because so much funding is needed to support research for better treatments and cures.

There are signs everywhere
Parkinson's is also known as primary parkinsonism because it appears to be a collection of symptoms which manifest in different ways and combinations in different people. Parkinson's is a disease which can cause any combination of the symptoms.

Tremors, slowness of movement (bradykinesia), stiffness and rigidity, swallowing and choking issues, change of voice, lack of facial expression, dyskinesia and dystonia (especially as a medication side effect) leg drag, lack of arm swing, urinary issues (such as incontinence, urinary frequency and urinary hesitancy) constipation, erectile dysfunction, dental problems, vision issues, loss of sense of smell, depression and apathy, hallucinations (usually a side effect of medications) dementia, cognition issues, drooling, breathing problems, postural instability, parkinsonian gait, freezing of motion, microphagia, change of skin condition (dry, oily) and the list goes on.

Symptoms and disease progression of the disease result in the inability of the patient to perform tasks of daily living and eventually unable to feed themselves or eat.  The end stage symptoms can require feeding tubes and nursing homes.

One unusual feature of the disease is that many of the physical symptoms begin on one side of the body only, unilaterally.  Tremors are usually resting tremors, meaning that the person is not initiating an action.  As the disease progresses, the symptoms begin to appear bilaterally.

Can we make a difference?
Certain treatments can delay the progression of the disease.  Slowing the progression of all PD cases is crucial.  Some people have a slower progression of the disease than others but until there is a cure, the slower the progression, the better the quality of life. Other medications target specific symptom relief via dopaminergic action.

What Parkinson's becomes is an insidious disease which can steal normal body function from people and replace it with huge expenses, create additional family stress and adjustment, subject people to public ignorance and ridicule.  It is also amazing to know that it is a disease with a surprisingly low suicide rate, surprising when you consider that at least 40% of PwPs have PD depression. But it is also a disease of hope.

Although current medications and therapies help to relieve symptoms or slow progression, different people respond in different ways and much attention to detail is required by both patients and physicians. Patients and their caregivers learn to be their own best advocates, with special thanks to the printers attached to their computers.

Is there light at the end of this long tunnel? 
There is much ongoing research by some of the best scientific minds in the world. At least one medication in the pipeline shows serious promise.  More is being learned everyday as scientists worldwide are exploring and sharing small and large aspects of the causes, treatment targets, improvement of existing treatments. While the cure may be years or a couple of decades away, the body of knowledge is increasing and with it the hope that when the cure(s) are found that the regulatory bodies will fast track them for the people who have lived with hope for so long.

2014 Addendum:
It is now known that there appear to be two types of Parkinson's disease. The first type is the one which we commonly identify with the disease and that is motor symptom predominant.  The other type, the one in which medication should be initiated as soon as a diagnosis is made is non-motor symptom predominant PD. The latter can be a real fooler because the symptoms are subtle, easily attributable to other conditions.
We've all read the warnings about beginning L-dopa treatment early because the wearing-off times can begin often with even worse motor side effects, but in non-motor symptom predominant PD, there isn't a minute to spare.
At the time of the original posting of this article, this information simply was not available.

1 comment:

  1. Thanks so much for this overview - very helpful to me as my friend has just been diagnosed with PD.


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