Parkinson’s disease is not fatal and does not shorten the average life expectancy of the patient, according to the National Institute of Neurological Disorders and Stroke. As the disease progresses, however, secondary complications may lead to death. Neurologists measure progression of the disease by using the Unified Parkinson’s Disease Rating Scale, which describes various symptoms, all of which may not be present to the same degree. A patient who receives the highest score on the scale will be someone who is completely disabled and helpless. Some patients live for 15 years following diagnosis and never reach this point, say Dr. William Weiner and colleagues in their book "Parkinson's Disease: A Complete Guide for Patients and Families. 2"

Movement and Balance Difficulties

The National Institute of Neurological Disorders and Stroke lists the four primary symptoms of Parkinson’s disease: tremor, rigidity, slowness of movement and impaired balance. These symptoms worsen until the person has a complete absence of facial expression, cannot speak and cannot stand or walk. According to Dr. Weiner and colleagues, movement problems include extreme loss of balance and freezing while walking, which result in the patient falling frequently.

Cognitive and Behavioral Problems

The patient may experience any of a variety of mental issues such as:

• confusion
  
• memory loss
  
• hallucinations
  
• delusions
  
• depression
  
• anxiety

According to Dr. Weiner and colleagues, confusion and memory problems, known as dementia, develop in one out of every four to five Parkinson’s patients at a level severe enough to interfere with daily activities.

Nervous System Impairments

The autonomic nervous system controls unconscious functions such as breathing, blood pressure, digestion and urination. In the end stage of Parkinson’s disease a patient becomes incontinent, constipated and subject to a drop in blood pressure when going from a seated position to standing, which may result in fainting, according to Dr. Weiner and colleagues.

Drooling and Difficulty Swallowing

In Parkinson’s disease the swallowing reflex deteriorates, which can lead to choking when eating or drinking. The patient will not swallow saliva frequently. As saliva pools in the mouth, the patient may drool and choke. Caregivers may need to feed some end stage Parkinson's patients through a tube inserted in the stomach through the abdomen.

Medication Problems and Drug-Induced Symptoms

According to the National Institute of Neurological Disorders and Stroke, as Parkinson’s disease progresses the response of the patient to medication becomes less predictable. The medication may wear off faster and no longer control symptoms adequately. The patient may need more frequent doses. As the drug dose increases so do the side effects, including dyskinesia, an uncontrollable, involuntary writhing movement, which may disable the patient as much as the original Parkinson’s symptoms do.