Module 7.3Movement Disorders

Parkinson’s Disease• A neurological disorder

characterized by muscle tremors, rigidity, slow movements and difficulty initiating physical and mental activity

• Associated with an impairment in initiating spontaneous movement in the absence of stimuli to guide the action

• Symptoms also include: – depression– memory and reasoning deficits– loss of olfaction

Parkinson’s Disease• Caused by gradual and progressive death of neurons,

especially in the substantia nigra.• Substantia nigra sends dopamine-releasing axons to the

caudate nucleus and putamen (of the basal ganglia)• Loss of dopamine leads to less stimulation of the motor

cortex and slower onset of movements.

Parkinson’s Disease• The basal ganglia is a group of large subcortical structures

in the forebrain important for initiation of behaviors.• Comprised of the following structures:

– caudate nucleus– putamen– globus pallidus

Parkinson’s Disease: Genetics• Studies suggest early-onset Parkinson’s has a genetic link.• Genetic factors are only a small factor to late on-set

Parkinson’s disease (after 50).

Parkinson’s Disease: Risk Factors

• Exposure to certain drugs (MPTP) • Environmental exposure to toxins, including

herbicides, insecticides, and fungicides• Head trauma

Parkinson’s Disease

• Cigarette smoking and coffee drinking are related to a decreased chance of developing Parkinson’s disease.

Parkinson’s Disease: L-Dopa Treatment

• The drug L-dopa is the primary treatment for Parkinson’s and is a precursor to dopamine that easily crosses the blood-brain barrier.– Often ineffective and especially

for those in the late stages of the disease.

• Does not prevent the continued loss of neurons.

• Enters other brain cells producing unpleasant side effects.

Parkinson’s Disease: Other Therapies

• Other possible treatments for Parkinson’s include:– Drugs that stimulate dopamine receptors or block the

breakdown of dopamine– Neurotrophins (chemicals that support cell growth)– Drugs that decrease apoptosis (cell death)– High frequency electrical stimulation of the globus pallidus– Transplant of neurons from a fetus– Stem cells: immature cells grown in tissue culture that are

capable of differentiating

Huntington’s Disease• A neurological disorder

characterized by various motor, cognitive, and mood symptoms.– affects 1 in 10,000 in the

United States– usually appears between

the ages of 30 and 50.• Associated with gradual and

extensive brain damage especially in the caudate nucleus, putamen, globus pallidus and the cerebral cortex.

Huntington’s Disease• Initial motor symptoms include

arm jerks and facial twitches.• Motors symptoms progress to

tremors and writhing that affect the persons walking, speech and other voluntary movements.

• Also associated with various psychological disorders:– Depression, memory

impairment, anxiety, hallucinations and delusions, poor judgment, alcoholism, drug abuse, and sexual disorders.

Huntington’s Disease

• Presymptomatic tests can identify with high accuracy who will develop the disease.– Controlled by an autosomal

dominant gene on chromosome #4.

– The higher the number of consecutive repeats of the combination C-A-G, the more certain and earlier the person is to develop the disease.

• No treatment is effective in controlling the symptoms or slowing the course of the disease.

Huntington’s Disease

• A variety of neurological diseases are related to C-A-G repeats in genes.

• For a variety of disorders, the earlier the onset, the greater the probability of a strong genetic influence.