Paralysis agitans is a chronic, slowly progressive, worsening central nervous system (CNS) disorder, characterized by muscular rigidity, a tremor of resting muscles, slow and decreased voluntary movements, and position instability. The condition is also referred to as Parkinson's disease.

The cause of the condition is unknown. A deficiency of the neurotransmitter dopamine has been identified as preventing affected brain cells from performing their normal inhibitory functions within the CNS. The condition may also result from loss of or interference with the action of the dopamine in the basal ganglia within the brain due to other idiopathtic diseases; drugs or external toxins; and ingestion of antipsychotic drugs or tranquilizers. Onset usually occurs in persons over the age of 50, and affects more men than women.

Early signs and symptoms of the condition may include: infrequent blinking; lack of facial expression; decreased movement; and impaired postural reflexes. The condition is characterized by muscle tremors at rest which diminish during movement and are absent during sleep. The tremors are enhanced by emotional tension or fatigue and the hands are most affected. Muscle rigidity may be present without tremors. As the muscle rigidity progresses, movement becomes slow (bradykinesia), decreased or diminished (hypokinesia), and difficult to initiate (akinesia). Other signs and symptoms may include: muscular aches and fatigue; mask-like expression with open mouth; drooling; stooped posture; gait characterized by involuntary, short, accelerating steps; difficulty in walking; loss of postural reflexes (tendency to fall forward or backward with respective shift in center of gravity); and low speech volume with stuttering or slurred speech. The voice may have uniformity of tone and be high-pitched. Other manifestations may include dysphagia.

A diagnosis is made based on the person's age, history, and clinical presentation. There are no specific tests for paralysis agitans (Parkinson's disease), although computed tomography (CT) scan or magnetic resonance imaging (MRI) are often performed to rule out alternative causes of similar findings.

The goal of treatment is to relieve symptoms, and keep the person functional as long as possible. Drug therapy may include: dopaminergic agents; Monoamine oxidase (MAO) inhibitors; anticholinergics; or antiviral agents. Measures are taken to protect the individual with motor impairments from injury, and to help promote performance of the activities of daily living (ADL). Physical therapy is a part of the treatment. Neurosurgery may possibly be instituted to relieve some cases that include disabling tremor.

Residuals may involve varying degrees of any or all of the signs and symptoms of the condition. There are gradual restrictions in performing ADLs and the disease is slowly progressive over time. In addition, there may be an increased risk to urinary infections and constipation due to inactivity and drugs.

• In those cases where there is severe neurologic deficit, consider entitlement under 38 CFR 3.350 [Special monthly compensation ratings] and ancillary benefits under 38 CFR 3.807.

• This disease shall be granted service connection although not otherwise established as incurred in or aggravated by service if manifested to a compensable degree within the applicable time limits under 38 CFR 3.307 following service in a period of war or following peacetime service on or after January 1, 1947, provided the rebuttable presumption provisions of 38 CFR 3.307 are also satisfied [38 CFR 3.309 [Disease subject to presumptive service connection], 38 CFR 3.309(a) [chronic disease].

• Minimum rating of 30%.

• It is required for the minimum ratings for residuals under diagnostic codes 8000-8025, that there be ascertainable residuals. Determinations as to the presence of residuals not capable of objective verification, i.e., headaches, dizziness, fatigability, must be approached on the basis of the diagnosis recorded; subjective residuals will be accepted when consistent with the disease and not more likely attributable to other disease or no disease. It is of exceptional importance that when ratings in excess of the prescribed minimum ratings are assigned, the diagnostic codes utilized as bases of evaluation be cited, in addition to the codes identifying the diagnoses.

• Disability in this field is ordinarily to be rated in proportion to the impairment of motor, sensory or mental function. Consider especially psychotic manifestations, complete or partial loss of use of one or more extremities, speech disturbances, impairment of vision, disturbances of gait, tremors, visceral manifestations, injury to the skull, etc. In rating disability from the conditions in the preceding sentence refer to the appropriate schedule. In rating peripheral nerve injuries and their residuals, attention should be given to the site and character of the injury, the relative impairment in motor function, trophic changes, or sensory disturbances.  38 CFR 4.120

• With the exceptions noted, disability from the following diseases and their residuals may be rated from 10 percent to 100 percent in proportion to the impairment of motor, sensory, or mental function. Consider especially psychotic manifestations, complete or partial loss of use of one or more extremities, speech disturbances, impairment of vision, disturbances of gait, tremors, visceral manifestations, etc., referring to the appropriate bodily system of the schedule. With partial loss of use of one or more extremities from neurological lesions, rate by comparison with the mild, moderate, severe, or complete paralysis of peripheral nerves” 38 CFR 4.124a