Parkinson’s disease

Overview

Parkinson’s disease (PD) is a progressive disorder of the central nervous system resulting in a lack of dopamine in the brain, among other changes. Dopamine, a chemical produced by cells in the brain, is necessary for smooth, controlled movement of muscles.

source: Parkinson's Institute

Symptoms

People with Parkinson’s disease can display a wide range of symptoms, and most manifest differently in different patients. There are two types of PD symptoms, motor and non-motor.

Motor Symptoms

The motor symptoms of Parkinson's disease are more typically known, as they are the most evident signs of the disease. The most common initial symptom is tremor. Symptoms of tremor or slowness usually begin on one side of the body, often involving either an arm or leg. Over time, the other limb on the same side and/or limbs on the opposite side are usually affected. Mobility may become limited as the disease progresses.

The Four Cardinal Signs and Symptoms for Diagnosing Parkinson’s disease:

  • Bradykinesia: Slowness & decreased dexterity
  • Rest Tremor: Involuntary shaking that goes away upon purposeful movement
  • Rigidity: Stiffness
  • Postural Instability: Imbalance

Non-Motor Symptoms

In addition to the well-known symptoms of tremor, slowness and imbalance, other problems such as excessive saliva, a soft voice, as well as hand and foot cramps may occur. Other non-motor symptoms associated with PD include:

  • Depression
  • Anxiety
  • Sleep disorders
  • Constipation
  • Anosmia (loss of smell)
  • Cognitive Decline
  • More frequent urination
  • Increased sweating
  • Low blood pressure
  • Skin changes
  • Difficulty swallowing

source: Parkinson's Institute

Causes

Normally, there are brain cells (neurons) in the human brain that produce dopamine. These neurons concentrate in a particular area of the brain, called the substantia nigra. Dopamine is a chemical that relays messages between the substantia nigra and other parts of the brain to control movements of the human body. Dopamine helps humans to have smooth coordinated muscle movements. When approximately 60 to 80% of the dopamine-producing cells are damaged, and do not produce enough dopamine, the motor symptoms of Parkinson’s disease appear. This process of impairment of brain cells is called neurodegeneration.

The current theory (so-called Braak’s hypothesis) is that the earliest signs of Parkinson’s are found in the enteric nervous system, the medulla and in particular, the olfactory bulb, which controls your sense of smell. Under this theory, Parkinson’s only progresses to the substantia nigra and cortex over the years. This theory is increasingly borne out by evidence that non-motor symptoms, such as a loss of sense of smell, hyposmia, sleep disorders and constipation may precede the motor features of the disease by several years. For this reason, researchers are increasingly focused on these “non-motor” symptoms to both detect PD as early as possible and to look for ways to stop its progression.

source: National Parkinson Disease

Diagnosis

Typically, the diagnosis is based on medical history and neurological examination.[1] The physician interviews and observes the patient in the search of the cardinal motor symptoms of the disease, while also attending to other symptoms that would exclude the diagnosis of PD.[1] Response to levodopa is another sign pointing towards PD.[1] However there is no definitive test for diagnosis although finding lewy bodies during autopsy has been traditionally considered the gold standard for diagnosis.[1] Common presentations of the disease are usually easily diagnosed, however the disease can be difficult to diagnose accurately, especially in its early stages, since parkinsonisms can occur due to a range of pathologies differing from PD.

source: wikipedia

Prognosis

PD is both chronic, meaning it persists over a long period of time, and progressive, meaning its symptoms grow worse over time. Although some people become severely disabled, others experience only minor motor disruptions. Tremor is the major symptom for some patients, while for others tremor is only a minor complaint and other symptoms are more troublesome. No one can predict which symptoms will affect an individual patient, and the intensity of the symptoms also varies from person to person.

source: NIH

Treatment

At present, there is no cure for PD, but a variety of medications provide dramatic relief from the symptoms. Usually, patients are given levodopa combined with carbidopa. Carbidopa delays the conversion of levodopa into dopamine until it reaches the brain. Nerve cells can use levodopa to make dopamine and replenish the brain's dwindling supply. Although levodopa helps at least three-quarters of parkinsonian cases, not all symptoms respond equally to the drug. Bradykinesia and rigidity respond best, while tremor may be only marginally reduced. Problems with balance and other symptoms may not be alleviated at all. Anticholinergics may help control tremor and rigidity. Other drugs, such as bromocriptine, pramipexole, and ropinirole, mimic the role of dopamine in the brain, causing the neurons to react as they would to dopamine. An antiviral drug, amantadine, also appears to reduce symptoms. In May 2006, the FDA approved rasagiline to be used along with levodopa for patients with advanced PD or as a single-drug treatment for early PD.

In some cases, surgery may be appropriate if the disease doesn't respond to drugs. A therapy called deep brain stimulation (DBS) has now been approved by the U.S. Food and Drug Administration. In DBS, electrodes are implanted into the brain and connected to a small electrical device called a pulse generator that can be externally programmed. DBS can reduce the need for levodopa and related drugs, which in turn decreases the involuntary movements called dyskinesias that are a common side effect of levodopa. It also helps to alleviate fluctuations of symptoms and to reduce tremors, slowness of movements, and gait problems. DBS requires careful programming of the stimulator device in order to work correctly.

source: NIH