NB9-5 - Movement Disorders: Basal Ganglia and DLAs

Question 1

What is athetosis and what usually causes them?

Answer 1

It is the inability of a hand to maintain a posture. The affected hand is often involuntarily placed behind the back during walking. They are almost always caused by strokes to the contralateral basal ganglia.

Question 2

List and describe the basic types of tremors we should know.

Answer 2

Resting Tremor - tremors that occur when the muscles are relaxed (common with Parkinson’s)

Action Tremor - tremors that occur with voluntary movement of muscle (includes postural and intention tremor)

Postural Tremor - occurs when a posture is maintained against gravity

Intention Tremor - occurs with purposeful movement toward a target and is worst when close to target

Question 3

What is an essential tremor?

Answer 3

A movement disorder distinct from Parkinson’s disease and no known cause. These tremors only occur during voluntary movement and are therefore commonly described as action or postural tremors

Question 4

What is a dystonia?

Answer 4

A neurological movement disorder syndrome in which sustained or repetitive muscle contractions result in twisting and repetitive movements or abnormal fixed postures

Question 5

What is chorea?

Answer 5

Sporadic, brief, sudden, and purposeless jerk (commonly seen with Huntington’s).

Question 6

What is tardive dyskinesia?

Answer 6

An involuntary movement disorder associated with chronic exposure to neuroleptics (antipsychotics).

Question 7

What is Dopa-Induced Dyskensia?

Answer 7

Parkinsonian patients who are being treated with dopaminergic agents commonly develop hyperkinetic abnormal involuntary movements. This is called dopa-induced dyskensia

Question 8

What is spasmodic torticollis?

Answer 8

A partial or segmental dystonia with turning of the neck as the major manifestation. Often patients will maintain a strange posture that helps to control these movements.

Question 9

What is hemiballismus?

Answer 9

An abnormal involuntary movement disorder characterized by affecting only the arm and leg on one side. The movements are usually of a rotatory nature. Usually caused by a lesion to the subthalamic nucleus, corpus luysi, and globus pallidus.

Question 10

What is Parkinsonism?

Answer 10

A symptom complex composed of four different kinds of symptoms:

1. Resting Tremors
2. Akinesia - difficulty initiating and carrying out purposeful movements (often presents with small shuffling steps while walking with no arm movement, many steps used to turn, resumption of normal gait when asked to step over lines, and bland facial expression)
3. Rigidity - increased resistance to passive movement
4. Loss of Postural Reflexes - unable to maintain a posture upon application of force

Question 11

Describe the stages of Parkinson’s Disease

Answer 11

1. Unilateral symptoms
2. Bilateral symptoms (normal postural reflexes)
3. Bilateral symptoms, impaired postural reflexes, resting tremor, and some disabilities
4. All of the above and severe disability but still able to get out of a chair (albeit with difficulty)
5. Effectively chair or bed bound. When standing the feet appear to be glued to the floor. Somehow they may still be able to walk over lines on the floor

Question 12

What are the components of the basal ganglia?

Answer 12

Striatum

Globus Pallidus

Subthalamic nucleus

Substantia Nigra

Question 13

Answer 13

F

Question 14

What does the striatum consist of? Which parts of the striatum is responsible for motor processing and reward processing?

Answer 14

The striatum consists of the caudate and putamen

Dorsal striatum is for motor processing while the ventral striatum is for reward processing

Question 15

What does the globus pallidus consist of and which component is the chief output nucleus?

Answer 15

The lateral part is the globus pallidus external (GPe) and the medial part is the globus pallidus internal (GPi). The GPi is the chief output nucleus

Question 16

List the components of the substantia nigra.

Answer 16

Pars reticulata (SNr)

Pars compacta (SNc)

Question 17

Answer 17

Question 18

Why is the substantia nigra considered to be part of the basal ganglia? What happens if the SN is underactive?

Answer 18

It projects axons to the rest of the basal ganglia that release dopamine which facilitates their functions, thus indirectly regulating cortical control of movement.

An underactive SN will result in hypokinetic disorder

Question 19

Describe how the GPi influences the thalamus and how the GPi is regulated in this regard.

Answer 19

The GPi exerts inhibitory control over the thalamus. There are two pathways that regulate the GPi:

Direct Pathway - inhibits the GPi therefore disinhibiting the thalamus and resulting in facilitation of movement

Indirect Pathway - stimulates the GPi thereofre inhibiting the thalamus and diminishing movement

Question 20

Answer 20

C

Question 21

Describe the direct pathway of the basal ganglia

Answer 21

1. Cortex stimulates a section of the striatum
2. Striatum releases GABA on the GPi, inhibiting it
3. This disinhibitis the thalamus which, in turn, stimulates the cortex
4. Cortex activates corticospinal tract to elicit movement

Question 22

Describe the indirect pathway of the basal ganglia

Answer 22

1. Cortex stimulates a portion of the striatum
2. Striatum inhibits GPe which stimulates the subthalamic nucleus (GPe inhibits the subthalamic nucleus)
3. Subthalamic nucleus stimulates the GPi which inhibitis the thalamus, diminishing movement.