Subcortical Dementias (Parkinson's and Huntington's)

Question 1

What is Huntington’s Disease?

Answer 1

A subcortical dementia

Destruction of the striatum and the globus pallidus (to a degree) causes jerky, rapid, uncontrollable movements.

Question 2

What causes Huntington’s?

Answer 2

A genetic mutation
Abnormal protien folding destroys GABAergic and cholinergic neurons
— Neurons in the striatum (caudate nucleus + putamen), + globus pallidus to a degree

Question 3

Cognitive Symptoms of Huntington’s

Answer 3

Difficulties with:
> Initiating behaviour
> Selecting a response
> selecting a stimulus (on the basis of particular attributes)
> Switching mental sets

Reduced:
> Verbal fluency
> Perservative techniques

Loss of cognitive flexibility

Deficits in memory recall
> Difficulty making self-guided search through memory that is required for recall

Question 4

HD and Emotional function

Answer 4

~50% of patients have major depressive episodes (often before motor symptoms)

Often irritable, apathetic, impulsive, aggressive, emotionally reactive

MIGHT exhibit psychotic symptoms (like delusions)

Often act in socially inappropriate ways, have difficulty recognizing emotion in others

Question 5

Huntington’s diagnosis

Answer 5

Identifying those who carry the Huntington’s gene, but are asymptomatic
> with regard to motor signs, exhibit poorer performance than noncarriers on tasks of memory and executive functioning

Question 6

Treatment for HD

Answer 6

Currently, there is no cure

Treatment aims to address motor and psychiatric symptoms

Question 7

What is Parkinson’s Disease?

Answer 7

A subcortical dementia

Affects dopamine reception

Has motor symptoms, dementia (~30% of patients), and cognitive impairments (mild but may develop into dementia)

Question 8

What causes Parkinson’s?

Answer 8

Specific cell loss in the substantia nigra of the basal ganglia.
> Primary source of dopanergic neurons.

Question 9

Cognitive Symptoms of Parkinson’s

Answer 9

> Difficulties with Executive Function
Difficulties in memory encoding and retrieval processing
Bradyphrenia
Emotional changes (including depression)
Parkinsonian Mask

Question 10

Bradyphrenia

Answer 10

Common symptoms of Parkinson’s disease

The general slowing of motor and thought processes

Question 11

Parkinsonian Mask

Answer 11

Expression/ Face in PD patients that appears to lack emotion

Question 12

Parkinson’s and dopamine

Answer 12

Patients have deficient dopamine in the dopaminergic path from the midbrain to the subcortical and cortical regions of the frontal lobe
> Dopamine in the profrontal cortext faciliates executive function
> Deficient dopamine may not explain all cognitive symptoms

Question 13

Cognitive decline in Parkinson’s

Answer 13

> Some researchers argue that dementia occurs when the typical dopamine deficits of Parkinson’s are combined with pathology typical of Alzheimer’s disease, i.e. amyloid plaques and neurofibrillary tangles.

> Others argue that the presence in the cortex of “Lewy bodies” – clumps of abnormal proteins inside cells – can account for cognitive decline.

** Could be a combo of both. **

Question 14

Dopamine Treatment (PD)

Answer 14

L-dopa is a precursor to dopamine that can pass the blood-brain barrier
> Associated with dykinesia in ~35% of patients and hallucinations in others
> Loses efficacy over time

Levodopa can improve aspects of executive function but impair other functions (i.e. inhibitory control)

Question 15

PD and Deep Brain Stimulation

Answer 15

When L-dopa resistance builds, this invasive treatment is considered:
> *Deep brain stimulation or ablation of the thalamus or the internal portion of the globus pallidus (GPi)