Basal Ganglia

Question 1

What are the parts of the Basal Ganglia?

Answer 1

- striatum
  v putamen
  v caudate nucleus
- globus pallidus (external and internal)
- substancia nigra
- subthalamic nucleus

Question 2

What are the parts of the Striatum?

Answer 2

• putamen

- caudate nucleus

Question 3

What are the parts of the Lentiform nucleus?

Answer 3

• putamen

- globus pallidus

Question 4

What is the main principle of basal ganglia pathway?

Answer 4

Disinhibition (double inhibition):

1 neuron inhibits 2 neuron which inhibits 3 neuron => 3 neuron is activated

Question 5

How is a direct pathway of the basal ganglia performed?

Answer 5

Cortex activates striatum -> striatum inhibits globus pallidus (internal part) -> globus pallidus inhibits thalamus (disinhibition => thalamus is activated) -> thalamus activates cortex

=> direct pathwy promores movement

Question 6

How is an indirect pathway of the basal ganglia performed?

Answer 6

Cortex activates striatum -> striatum inhibits globus pallidus (external part) -> globus pallidus inhibits subthalamic nucleus (disinhibition => subthalamic nucleus is activated) -> subthalamic nucleus activates globus pallidus (internal part) -> globus pallidus inhibits thalamus -> thalamus inhibits cortex

=> indirect pathway suppresses movement

Question 7

What does substantia nigra do?

Answer 7

Enhance direct pathway (by dopamine) => promotes movement

Question 8

What does the striatum do?

Answer 8

Enhance indirect pathway (by acetylcholine) => suppresses a movement

Question 9

What is affected in Parkinson disease? What are the features?

Answer 9

Substancia nigra (=> direct pathway)

• bradykinesia
• cogwheel rigidity
• pillrolling (resting) tremor
• shuffling gate
• stooped posture
• masked face
• depression
• dementia

+Lewy bodies: intracytoplasmic eosinophilic inclusions,
contain α-synuclein

Known causes of parkinsonism: infections, vascular,
and toxic insults (e.g., MPTP)

Question 10

What is affected in Huntington disease? What are the features?

Answer 10

Caudate nucleus of Striatum (=> indirect pathway)

• chorea (multiple, rapid, random movements)
• athetosis (slow, writhing movements)
• personality changes
• dementia

+ Onset: 20−40 years

+Autosomal dominant
+ Unstable nucleotide repeat on gene in chromosome 4,
which codes for huntingtin protein

+Disease shows anticipation and genomic imprinting

+Treatment: antipsychotic agents, benzodiazepines,
anticonvulsants

CAG - caudate atropy of GABA

Question 11

What is affected in Wilson disease? What are the features?

Answer 11

Putamen (by copper)

• tremor
• asterixis (“wing beating” tremor)
• parkinsonian symptoms
• chorea
• neuropsychiatric symptoms
• fatty change, hepatitis, or cirrhosis of liver

+ Autosomal recessive defect in copper transport

+Accumulation of copper in liver, brain, and eye (Descemet membrane, producing Kayser-Fleischer ring)

+ Treatment: penicillamine (a chelator), zinc acetate
(blocks absorption)

Question 12

What is affected in Hemiballism? What are the features?

Answer 12

Hemorrhagic destruction of contralateral subthalamic
nucleus

• Wild, flinging movements of limbs
• Hypertensive patient

Question 13

What is the target of high-frequency brain stimulation (Parkinson disease)?

Answer 13

Subthalamic nuclei (destruction of the part of the indirect pathway)

Question 14

How to distinguish basal ganglia tremor from cerebellar tremor?

Answer 14

Basal ganglia - tremor in calm

Cerebellar - intention tremor