Parkinson's Disease

Parkinson's Disease

Introduction:

It is a nervous system disease which falls into the category of motor system diseases or movement disorders because it primarily affects motor control and its primary manifestations affect movement.

The disease leads to a loss of neurons, the nerve cells in the brain, in specific locations, particularly a large group of cells called the substantia nigra. This nucleus is part of the basal ganglia which is important principally for coordinating and controlling the initiation of movement. Therefore, as these cells are lost, the symptoms that become apparent are generally disorders of movement and its initiation. Common symptoms that are classic for Parkinson's disease include tremor (shakiness at rest), rigidity and slowed movements (bradykinesia) and others.

Parkinson's primarily affects older individuals and its incidence increases with age. Although its initial symptoms primarily affect movement, as it progresses it can involve other functions of the brain including cognition and lead to a form of dementia.

Causes of Parkinson's Disease:

The underlying etiology (causative factors) that lead to Parkinson's disease are poorly understood. It is probably multifactorial, meaning that there are several factors which contribute to its development. Clues to the causes of Parkinson's disease can be found in the risk factors which are associated with the disease. Although most cases are sporadic, there does seem to be some genetic predisposition. People with a close relative with the disease are slightly more likely to develop the disease themselves, although the risk is still rather small. Likewise, it is known that older age and male gender are risk factors as the risk increases with age and is higher in men than women. There may also be some toxins or viruses, exposure to which may increase one's risk for Parkinson's.

Although the actual initial causes of Parkinson's Disease are poorly understood, the actual pathophysiology that occurs in the brains of patients is well described. For unknown reasons, abnormal clumps of protein build up in certain neurons (nerve cells) in the brain. These clumps are called Lewy Bodies. As the disease progresses, neurons in certain parts of the brain die. One of the most pronounced areas of damage in this disease is in a group of cells (nucleus) in the brain called the substantia nigra. These cells normally use dopamine as their neurotransmitter and are part of the basal ganglia, a collection of nuclei important for control and coordination of initiation of motor functions.

The death of these dopamine-secreting cells in the brain lead to imbalance and dysfunction of the basal ganglia, affecting motor system control. This imbalance is progressive, getting worse over time, and explains the motor symptoms (tremor, rigidity, etc.) that are common in patients with Parkinson's disease.

Although the cells of the substantia nigra is the most profoundly affected early, other areas of the brain can become affected with time, leading to imbalance in other systems and with other neurotransmitters (such as norepinephrine), leading to other late symptoms such as dementia and dysfunction of the autonomic nervous system.

Just as what causes Parkinson's Disease is not clear, why the dopamine containing cells of the substantia nigra are most affected by this disease is poorly understood. There is ongoing current research that aims to more clearly elucidate the underlying risk factors, pathophysiology and causes of Parkinson's Disease.

Symptoms of Parkinson's Disease:

There are several symptoms of Parkinson's Disease, most of the affecting motor functions of the nervous system. Parkinsons disease is a progressive degenerative disease, meaning that the cell death and resulting dysfunction in the brain begin slowly and continue in a progressive way. They slowly get more pronounced over time. Therefore, Parkinson's disease symptoms generally present slowly and subtly. As time progresses the symptoms will become more pronounced and severe. Additionally, further symptoms that were not first evident can become apparent.

The classic "triad" of symptoms of Parkinson's disease include tremor, rigidity and bradykinesia because they are common in patients with the disease and are some of the first symptoms to present.

Tremor is an involuntary shaking of the body, usually most pronounced at rest (called a "resting tremor"). Other forms of tremor sometimes seen include a "pill-rolling" tremor.

Rigidity is an increased tone of muscles, meaning the passive movement of the extremities (arms or legs) is more difficult than normal.

Bradykinesia means "slow movement". Most movements are slowed. This can particularly affect fine motor control, making fine motor skills quite difficult. This can also be evident in the general lack of excessive movements, such as decreased expressive gestures (waving hands when talking, etc.) and decreased facial movement and facial expressions (sometimes described as "masked" face).

Other symptoms include freezing (sudden cessation of movement), akinesia (difficulty initiating movements), inbalance, impaired posture, speech changes, abnormal gait (a "shuffling" gate), and others.

As the disease progresses and becomes more severe, these initial symptoms will become more pronounced, but other symptoms may become evident as well. For example, a form of dementia can develop with slowed thinking (bradyphrenia) and problems with memory.

While some of these symptoms are classic symptoms of Parkinson's Disease, many can be caused by other nervous system diseases as well. Therefore, the diagnosis of Parkinson's disease requires a careful assessment by a neurologist to distinguish Parkinsons disease from other similar movement disorders which may cause tremor, rigidity or other such symptoms.

Parkinson's Disease Diagnosis:

Parkinson's Disease diagnosis can be tricky. Without looking at the cells of the brain itself, there are no definitive tests, exams or studies which can be performed that make the diagnosis. Because there are other diseases which can share some of the common symptoms of Parkinson's disease, it can be difficult to distinguish this disease from others and make a confident diagnosis.

However, an accurate diagnosis is required to initiate the most appropriate management and treatment plan for Parkinson's disease. The treatment and prognosis of other similar diseases may be quite different.

Therefore, patients with symptoms suggestive of Parkinsons disease generally undergo a thorough work-up by a competent neurologist with experience in diagnosing Parkinsons. This generally consists of a thorough history and physical examination, focusing on the patient's symptoms, their personal and family history and an examination of the nervous system, focusing on motor function which is most affected by Parkinson's.

A Parkinson's disease diagnosis is considered a "diagnosis of exclusion". Because there is no gold-standard test that can be performed to confirm the diagnosis, all other similar or related diseases must be ruled out before the confident diagnosis of Parkinsons Disease can be made. This may include tests and imaging studies (such as brain MRI or CT scan) to help rule out other potential causes of the patient's symptoms.

Even though there are other diseases which can present with similar symptoms, most do not overlap 100% in the details of their presentation. Therefore, careful care is taken to document all the signs and symptoms in each patient to make sure Parkinsons Disease is the best fit diagnosis, rather than some other diagnosis.

Other movement disorders which may have some similar symptoms include Huntington's Disease, multisystem atrophy, Lewy body dementia, progressive supranuclear palsy, corticobasal degeneration and others. Likewise, Alzheimer's disease, the most common cause of dementia, should be distinguished from Parkinsons, in which dementia can occur but is generally a later finding in more advanced disease. Other causes of tremor (such as essential tremor or "limb-shaking TIAs) and abnormal gait (normal pressure hydrocephalus, etc.) should be ruled out as well. As you can see, because the differential diagnosis is quite large, an experience physician is needed to help make a Parkinson's disease diagnosis.

Once the diagnosis is confident, then management options can be discussed.

Parkinson's Disease Treatment:

Parkinson's Disease treatment aims to reduce the symptoms of this progressive disease and improve each patient's quality of life. There is no cure for Parkinson's, all the treatments simply aim to lessen symptoms of the disease.

When a diagnosis is first made, the initial treatment is generally medical, focusing on prescription of medications which are known to reduce symptoms in most patients.

Of all the drug options for treatment of Parkinson's Disease, levodopa (or L-dopa) is the most commonly used and the most effective. Levodopa is a compound which is a naturally-occurring precursor to dopamine which is lacking in parts of the brain in Parkinsons disease. The idea is that brain cells can pick up the levodopa and make dopamine and at least partially replace the lack of the neurotransmitter in the brain. While this does often improve symptoms, it is not a perfect treatment. Its benefits are often modest. Also, the drug must be given frequently and its effect may deteriorate over time. Another drug, carbidopa is often given along with levodopa to help prolong its effect. As Parkinson's disease symptoms progress, the use of levodopa, and/or carbidopa, will often change dramatically with frequent adjustments in doses, timing of dosing and going on and off the medication.

There are several other medications which may also be used in Parkinson's disease treatment. Dopamine agonists are drugs that act like dopamine to stimulate cells in the brain. MAO B inhibitors and COMT inhibitors may be used to help increase the availability of dopamine and levodopa. Anticholinergic medications and NMDA blocking drugs may also be used in some patients. All these alternative medications may be used alone or in addition to levodopa therapy to help maximize symptom control. They may be frequently swapped or adjusted as the patient learns what works best in their own particular case.

In addition to medications, initial medical treatment of Parkinson's Disease may often include physical therapy to help maintain mobility, improve general health and to maintain flexibility and muscle strength. While these treatments do not stop the progression of the disease, they may help patients to maintain function for longer and to improve their quality of life and ability to care for themselves.

Surgical Treatments: In patients with more advanced disease, when medications alone are no longer controlling symptoms, surgical options may be considered as part of Parkinson's disease treatment. The most common surgical option offered to patients is called a deep brain stimulator which uses an implanted electrode to stimulate parts of the brain. The goal is to restore some balance to the activity in the parts of the brain most affected in Parkinson's disease and therefore reduce symptoms. It is particularly good at controlling tremor. However, the effects of surgical procedures such as this are quite variable, and, like other treatments, are not a cure for the disease.

Deep Brain Stimulator for Parkinson's Disease:

A deep brain stimulator is an implanted device which is used to treat some patients with Parkinson's Disease, as well as a few other diseases. It is currently the most commonly employed surgical treatment for Parkinsons disease.

Most patients with Parkinsons disease are first treated with medication and physical therapy. However, in patients with more advanced disease which is no longer adequately and reliably controlled with medication, these procedures may help to stabilize symptoms and resolve abnormal movements such as tremor.