Thalamus, internal capsule and basal ganglia

Question 1

What are the divisions of the diencephalon?

Answer 1

Epithalamus (contains pineal gland)
Dorsal thalamus
Subthalamus (contains subthalamic nuclei)
Hypothalamus

Question 2

What are the major divisions of the dorsal thalamus?

Answer 2

Anterior, medial and lateral are divided by the internal medullary lamina. The thalamic reticular nuclei is a narrow band and appears draped over the lateral thalamus

Question 3

What are the 3 functional thalamic groups?

Answer 3

Specific/relay nuclei: well defined inputs/projections
Association nuclei
Nonspecific nuclei

Question 4

What are the specific/relay nuclei?

Answer 4

Anterior, ventral anterior, ventral lateral, ventral posterior, lateral dorsal, medial and lateral geniculate

Question 5

What is the purpose of the reticular nucleus of the thalamus?

Answer 5

Acts as a filter, modulates information to and from the thalamus

Question 6

What major tract makes up most of the internal capsule?

Answer 6

Corticospinal tract

Question 7

What thalamic nuclei are involved with motor actions?

Answer 7

The VA/VL nuclei relay informaiton from the basal ganglia and cerebellum to the motor cortex

Question 8

What thalamic nuclei are involved with somatosensory information?

Answer 8

VPL relays information from the spinothalamic tract to the somatosensory cortex.
VPM relays information from the trigeminal tract to the somatosensory cortex

Question 9

What thalamic nuclei are involved with auditory sensation?

Answer 9

Medial geniculate relays information from CN VII (through the inferior colliculus) to the auditory cortex

Question 10

What thalamic nuclei are involved with vision?

Answer 10

Lateral geniculate relays information from the optic tract to the visual cortex

Question 11

What artery supplies the thalamus?

Answer 11

The posterior cerebral artery gives off thalamic branches

Question 12

What is the primary function of the anterior thalamus?

Answer 12

Language and memory

Question 13

What is the primary function of the lateral thalamus?

Answer 13

Motor and sensory

Question 14

What is the primary function of the medial thalamus?

Answer 14

Vigilance, arousal, memory

Question 15

What is the primary function of the posterior thalamus?

Answer 15

Higher visual funciton

Question 16

What structures make up the striatum?

Answer 16

Caudate, putamen and nucleus accumbens

Question 17

What structures make up the lenticular nucleus?

Answer 17

Putamen and globus pallidus

Question 18

Describe the circuitry of the basal ganglia

Answer 18

A loop of excitatory and inhibitory signals:

The thalamus excites the cortex, which excites the striatum, which inhibits the GPi and SNr, which inhibit the thalamus.

Question 19

How do the basal ganglia affect LMN function?

Answer 19

No direct connection

LMNs are influenced by the BG through the cerebral cortex

Question 20

What neurotransmitter is involved with cortical input to the striatum?

Answer 20

Glutamate: excitatory neurotransmitter

Question 21

What neurotransmitter is involved with output from the BG via the GPi and SNr?

Answer 21

GABA: inhibitory neurotransmittor

Question 22

Describe the direct pathway of the basal ganglia

Answer 22

The striatum receives excitatory input from the association cortex and SNpc.
Striatum inhibits the GP from inhibiting the VA/VL of the thalamus, thus allowing VA/VL to excite the premotor cortex to initiate movement.

Question 23

What receptor is involved with the SNpc input to the striatum?

Answer 23

D1: dopamine receptor

Question 24

Describe the indirect pathway of the basal ganglia

Answer 24

The Striatum receives inhibitory input from the SNpc, which causes a transient inhibition of the GPe. Inhibited GPe leads to increased subthalamic nuclei activity, which strimulates the GPi. GPi can then decrease activity of the VA/VL leading to decreased movement.

Question 25

What changes are seen in the BG motor circuits in Parkinson's disease?

Answer 25

Dopaminergic signalling from the SN is lost which leads to decreased excitation of the direct pathway and increased activity of the indirect pathway. This leads to decreased excitation of the motor cortex, and thus less movement.

Question 26

What changes are seen in the BG motor circuits in Huntington's disease?

Answer 26

The inhibitory input of the striatum on the GPi is lost, which leads to decreased activity of the indirect pathway. This results in decreased inhibition of the VA/VL and thus increased excitation of the motor cortex presenting as chorea.

Question 27

What disease is associated with hypokinesia/akinesia?

Answer 27

Parkinsonism

Question 28

What disease is associated with hyperkinesia?

Answer 28

Huntington's disease | Choreoathetosis, hemiballismus

Question 29

What are the etiologies of basal ganglia disorders?

Answer 29

Infarct, hemorrhage, tumor Degenerative disorders Medication side effects

Question 30

What class of drugs can cause hyperkinesia?

Answer 30

Dopamine agonists can cause chorea, dystonia

Question 31

What class of drugs can cause hypokinesia?

Answer 31

Dopamine antagonists can cause parkinsonism

Question 32

What are the primary clinical signs of parkinsonism?

Answer 32

Resting "pill rolling" tremor Rigidity Bradykinesia Loss of postural reflexes (falls)

Question 33

Describe the parkinsonian gait

Answer 33

Stooped posture with shuffling and propulsive gait Lack of armswing Turns with multiple small steps

Question 34

What are the secondary (non-gait related) signs of parkinsonism?

Answer 34

``` Hypophonic speech Autonomic dysfunction Micrographia Masked facies (expressionless) Stooped posture ```

Question 35

What are rare disorders that may mimic Parkinson's disease?

Answer 35

Progressive supranuclear palsy Multiple system atrophy Dopamine antagonist side effects Manganese/CO poisoning

Question 36

Describe the pathology of Parkinson's disease

Answer 36

Gross pallor of the SN due to loss of pigmented (dopaminergic) neurons

Question 37

Describe the histologic findings of a patient with Parkinson's disease

Answer 37

Lewy bodies: eosinophilic intraneuronal cytoplasmic inclusions, which are accumulations of alpha synuclein

Question 38

What are the drug therapies for Parkinson's disease?

Answer 38

Anticholinergics have weak affect Amantidine (enhances release of dopamine) L-dopa (dopamine precursor) with Carbidopa

Question 39

What role does carbidopa play in Parkinson's disease treatment?

Answer 39

Prevents the peripheral catabolism of L-dopa before it enters the brain, thus increasing the effect of L-dopa

Question 40

What is the surgical treatment of Parkinson's disease?

Answer 40

Pallidotomy to stop excessive inhibitory output of the GPi | STN stimulator: implanted electrode that repeatedly fires to inhibit the STN

Question 41

Pathogenesis of Huntington's disease

Answer 41

``` Autosomal dominant (trinucleotide repeats of gene on c4) Symptoms onset between 35-40 yrs old Causes choreoathetosis, behavioral changes and dementia due to atrophied caudate ```