Neurology: Parkinson Disease

Question 0

What 5 chromosomes and which 3 genes are involved in hereditary forms of Parkinson Disease?

Answer 0

Chromo: 1,2,4,6,12
Genes:
alpha-synuclein & parkin - both involved in a proteosome pathway

DJ-1 gene is involved in antioxidant pathways

Question 1

How many neurons in the Substantia nigra die before Parkinsonian symptoms start to arise?

Answer 1

80-90%

Question 2

What are two environmental toxins associated with PD?

Answer 2

1. MPTP

2. Fertilizers/Pesticides

Question 3

Describe the INTRINSIC mechanism leading to PD.

Answer 3

1. DA metabolism by MAO-B forms free radicals
2. Free radicals cause lipid peroxidation of cell membranes
3. Membrane dysfunction leads to nigral damage and PD

Question 4

Describe the EXTRINSIC mechanism leading to PD.

Answer 4

1. Some toxin (ex. MPTP) is metabolized by MAO-B (forms MPP+)
2. The toxin (MPP+) causes mitochondrial dysfunction
3. Dysfunctional mitochondria causes nigral damage and PD.

Question 5

What are 5 risk factors associated with oxidative damage that are especially damaging to brain tissue?

Answer 5

1. Brain is mostly lipids which are affected by radicals easily
2. Brain uses 20% of body’s O2 demand so oxygen is abundant
3. Brain doesn’t have much oxidative protection
4. Brain is postmitotic (non-dividing)
5. Brain has lots of iron which acts as a catalyst in free radical generation

Question 6

How is the PD tremor and rigidity described?

Answer 6

Resting and pill rolling tremor

Cogwheel rigidity

Question 7

What is the Myerson Sign?

Answer 7

Glabellar Sign

• physician taps between the eyes of a patient and the patient keeps blinking
• indicates PD

Question 8

Which classes of drugs are most common to induce Parkinsonian like symptoms?

Answer 8

Antipsychotics and antiemetic drugs

Question 9

What is the best way to diagnose PD?

Answer 9

H&P

-there are no definitive tests for it, the only confirmatory diagnosis is brain biopsy during autopsy.

Question 10

How does selegiline treat PD?

Answer 10

MAO-B inhibitor: prevents DA metabolism

Question 11

What types of drugs should be avoided if a patient is taking selegiline and why?

Answer 11

Any drugs that increase the amount of 5HT in the synapse
-TCAs, meperidine, SSRI’s

Can lead to serotonin syndrome

Question 12

How does rasagiline treat PD?

Answer 12

MAO-B inhibitor taken 1x/day

Has anti-apoptotic effects to preserve mitochondria in substantia nigra cells

Question 13

How do benztropine, trihexyphenidyl and biperiden treat PD?

Answer 13

Anti-cholinergics

• treat rigidity and tremors
• does not treat the Bradykinesia
• not used in elderly

Question 14

Which drug should be given to elderly patients that cannot tolerate the Anti-cholinergic medications and how does it work?

Answer 14

Amantadine: weak dopaminergic effects

Question 15

How do bromocriptine, ropinirole, pramipexole, rotigotine, and cabergoline function?

Answer 15

DA agonists used in early stages of PD.

May be more effective in parkinsonian-like diseases.
Do NOT require intact substantia nigra to function.

Question 16

How do tolcapone and entacapone treat PD?

Answer 16

They are catechol-o-methyl transferase (COMT) inhibitors that prevent the metabolism of DA.
Often used in conjuction with L-dopa and carbidopa.
(entacapone has less liver toxicity)

Question 17

How does Sinemet Treat PD?

Answer 17

Combo of L-dopa (dopamine analog) and carbidopa (inhibits dopa decarboxylase). The combination allow L-dopa to make it to the CNS without metabolism so that it can be used by the brain.

Question 18

How much carbidopa is required in order to inhibit dopa decarboxylase?

Answer 18

70mg

Question 19

What can happen in a PD patient when too much L-dopa is given?

Answer 19

The main effect is dyskinesia. This refers to the dance-like movements or chorea seen in PD patients after a new dose. Usually resolves as the L-dopa is metabolized and cleared by the system.

Question 20

What type of meal can inhibit the uptake of L-dopa from the GI tract?

Answer 20

High protein meals, the L-dopa competes for the same transporters as Amino Acids from the diet.

Question 21

How do surgical procedures generally treat PD?

Answer 21

They treat the movment symptoms.

• pallidotomy, thalamotomy
• pacemaker in subthalamic nucleus

Question 22

What is Progressive Supranuclear Palsy (PSP)?

Answer 22

Neurodegenerative disease with Parkinsonian symptoms: bradykinesia, rigidity, pseudobulbar signs, dementia, and Babinski. Very hyperreflexive.

Much more aggressive, death occurs in 10 years.

Question 23

What is one general characteristic that differentiates PD from PSP on physical exam?

Answer 23

Due to posturing:
PD patients tend to fall forwards late in the disease
PSP patients tend to fall backwards late in the disease