Chapter 26- Disorders of basal ganglia function

Questions

Define the following terms:

extrapyramidal, oxidative stress, parkinsonism, Parkinson disease, bradykinesia, delayed postural reflexes, resting tremor, cogwheel, festination, chorea, athetosis, hemiballismus, dystonia, "wearing off", "on-off", hypophonia.
The term "extrapyramidal" refers to those parts of the motor system that are not directly "pyramidal", that is not the corticospinal tracts (upper motor neurons). It always includes the basal ganglia and often is considered to include cerebellar systems.
Oxidative stress refers to the adverse effects on tissues of reactive oxygen species (free radicals).
Parkinsonism is the phenotypic description of a patient with bradykinesia, poor postural responses and rigidity from any cause (it is not always due to Parkinson's disease).
Parkinson disease is a dopamine deficiency syndrome characterized by bradykinesia, poor postural responses, rigidity and tremor (not all are present in any one patient).
Bradykinesia is pathological slowness of movement.
Delayed postural reflexes refers to a delay in the normal righting responses that permit stance and gait.
Resting tremor is a tremor that occurs with the hands resting in the lap or at the sides when walking or standing.
Cogwheel is a term referring to an irregular, ratchety resistance to passive movement which is the superimposition of tremor over rigidity.
Festination is shortening of stride such that the patient takes many short steps to cover a distance. They may become propulsive if they cannot catch up with their center of gravity.
Chorea is a random, purposeless, involuntary twitching movement.
Athetosis is a purposeless, involuntary writhing movement.
Hemiballism is a purposeless, involuntary flinging or flipping movement of a limb.
Dystonia is an abnormal sustained twisting posture of a part of the body. It may affect the entire body or only a small part.
"Wearing off" is a term that refers to a loss of effect of Parkinson's medication at a certain time-point after they are taken.
"On-off" refers to a sudden and unpredictable loss of effectiveness of Parkinson's medication.
Hypophonia is a pathological loss of power in the voice.


26-1. What are the functions of the extrapyramidal system?

Answer 26-1. The extrapyramidal system is responsible for sustained postures, resting tone and patterned movements.

26-2. What is the cause of Parkinson disease?

Answer 26-2. Parkinson disease is due to selective degeneration of substantial nigra and other pigmented CNS neurons. Ultimately, the specific cause is unknown although there may be hereditary influences and toxic effects that play a part.

26-3. What are the symptoms of Parkinson disease?

Answer 26-3. The symptoms of Parkinson disease include: rigidity, bradykinesia, delayed postural reflexes, difficulty initiating movements, resting tremor (none of these is present in all Parkinson patients). Other common symptoms include: mask face, stooped posture, increased flexor tone, drooling, shuffling, seborrhea, orthostasis, decreased blinking, soft voice (hypophonia). It is often asymmetrical (especially at the onset).

26-4. What is the pathology of Parkinson disease?

Answer 26-4. Dopamine is deficient in the brains of patients with Parkinson disease. Oxidative stress on cells is one theory of development of Parkinson disease.

26-5. What are the treatments for Parkinson disease?

Answer 26-5. Parkinson symptoms are due to deficient dopamine effects in the basal ganglia. Acetylcholine and dopamine have opposite effects in the basal ganglia. Therefore, agonists of dopamine and blockers of acetylcholine are use to treat it. The most common treatment is levodopa, which crosses the blood-brain barrier (while dopamine can not). Carbidopa is needed to block dopa decarboxylase, preventing generation of peripheral dopamine from levodopa, limiting side effects. Direct dopamine agonists are used as are some inhibitors of dopamine enzymatic degradation. Cholinergic blocking agents may help some patients.

26-6. What problems complicate treatment of Parkinson patients?

Answer 26-6. Parkinson patients may notice wearing off of drugs or unpredictable "on-off" phenomena (like turning off a switch). Overtreatment of Parkinson's disease, such as with excesses of dopamine receptor stimulating medication or oversensitivity of dopamine receptors, will result in abnormal movements at rest (such as chorea or athetosis) and hallucinations. Other potential side-effects include nightmares, orthostasis and nausea.

26-7. What surgical treatments are available for Parkinson disease?

Answer 26-7. The surgical treatments that are available for Parkinson disease include: thalamotomy (better for tremor); palidotomy (better for rigidity, bradykinesia); and stimulation (subthalamic nucleus).

26-8. What is essential tremor?

Answer 26-8. Essential tremor is a common condition that may be hereditary. It is more frequent with age, but may start early. The usual course is for gradual progression.

26-9. How do you recognize essential tremor?

Answer 26-9. The tremor appears with sustained postures and is often obvious with movements (an action tremor). It may start in hands (most often) but involve neck and jaw frequently. Alcohol often improves this tremor, although being nervous makes all tremors worse. It may be familial (usually autosomal dominant).

26-10. What are the available treatments for essential tremor?

Answer 26-10. The effective treatments are beta blockers and primadone/mysoline. Thalamotomy or stimulator implantation may be necessary.

26-11. What are potential causes of chorea and athetosis?

Answer 26-11. Chorea and athetosis are commonly due to long-term exposure to neuroleptics, excess of dopamine stimulating medicine, Huntington's disease or the choreoathetotic variety of cerebral palsy. Uncommonly, choreoathetosis may be due to various intoxications and poisonings, severe metabolic disturbances, encephalitis, autoimmune disease, Wilson's disease (of copper metabolism) or pregnancy.