ICL 4.1: Basal Ganglia & Movement Disorders Flashcards

Question

What is the hyperdirect pathway?

Answer 1

Cortex —> STN —> GPi —> thalamus —> cortex So the cortex will excite the STN STN is excitatory so it will go and excite the GPi GPi is inhibitory so it will go and inhibit the thalamus — normally the thalamus excites the cortex but since it’s inhibited, the cortex can’t be excited and there will be no movement So if you chose the wrong program on accident and need to stop it really fast, you use the hyperdirect pathway —> so when this pathway is activated, it’s the stop signal for motor programs that are already in progress

Answer 2

D1 receptors are excitatory D2 receptors are inhibitory Medium spiny neurons are normally not active = off state If you increase dopamine, it maintains the off state which prevents activation; it prevents background static noise randomly coming into the basal ganglia and activating a pathway However, when you really want to move, you send a strong signal from the motor cortex to the basal ganglia, you turn on the striatal cells and in this situation, the dopamine will actually modulate the on state! So it prevents involuntary movements and also facilitates voluntary movements too! It helps you initiate the correct motor activity

Answer 3

Motor activity —> positive outcome —> increased dopamine which then goes to basal ganglia and increases that motor activity Motor activity —> negative outcome —> decreased dopamine which means that motor activity won’t be facilitated as much So with a baby or kid, they want the reward so they’ll do an activity but eventually they’ll start moving towards a goal after repeated reward Eventually they’ll figure out what the goal is like walking will get you places without the help of an adult so goal directed activity will eventually become habit! It’s no longer about what will walking bring me, you just walk because you want to

Answer 4

Aka Parkinson’s! Due to low dopamine in the striatum due to degeneration of the dopaminergic neurons of SNc which normally make dopamine! You’ll see Levy body’s due to deposition of alpha-synuclein in the cells! Because this disease is due to low dopamine, the treatment is dopamine replacement

Answer 5

Cerebral cortex —> striatum —> GPi which is the direct pathway Dopamine in the direct pathway produces an excitatory effect and facilitates movement Dopamine will inhibit the indirect pathway which will allow for movement since the indirect pathway normally inhibits movement If you get rid of dopamine like in Parkinson’s, the direct pathway doesn’t work as well so the patient won’t be able to start motor programs and they’re can’t easily start a movement! Think about a Parkinson’s patients trying to walk and how much they stutter or get stuck For the same reason of low dopamine, the inhibiting activity of the indirect pathway has increased which leads to more inhibition of movement! This is because dopamine normally inhibits the indirect pathway

Answer 6

1. Tremor (low frequency resting tremor) 2. Gait disturbance 3. Stiffness 4. Slowness 5. Handwriting disturbance 6. Forward bent posture 7. Pisa syndrome = leaning posture

Answer 7

Clinical criteria, there isn’t really a test that will do it UK Parkinson’s Disease Society Brain Bank’s clinical criteria for the diagnosis of probable Parkinson’s disease So you have to have bradykinesia = slowness and inability to start movement then you need one of the following: rigidity, resting tremor, or postural instability not caused by primary visual, vestibular cerebellum or proprioception dysfunction Then you also have to exclude other causes of Parkinsonism The only way to confirm a diagnose is through biopsy and finding Lewy bodies

Answer 8

Dopamine replacement 1. Levadopa 2. Amantadine = helps release dopamine better 3. Dopamine agonists 4. anti-cholinergics Slide 34; go look at where all these drugs act on the basal ganglia and receptors

Answer 9

1. Dopamine replacement 2. Physical therapy 3. Electricity therapy which inhibits GPi and subthalamic nucleus

Answer 10

This happens when the patient is actively doing something so that’s different from Parkinson’s which is a resting tremor

Answer 11

Related to essential tremor The frequency is related to something wrong with a specific nuclei of the basal ganglia These tremors have a specific axis and at a certain axis, the tremor is the worst and you can see this by telling the patient to draw a spiral If a spiral doesn’t have an axis, then it is NOT an essential tremor

Answer 12

1. Propranolol 2. Primidone 3. Topiramate 4. Gabapentine 5. Alprazolam 6. Clonzepam

Answer 13

1. Meds 2. Chemodenervation is using toxins to block the nerves that are causing the tremors 3. DBS 4. MRI focused ultrasound to burn the cells that are messed up

Answer 14

Abnormal muscle spasm that causes abnormal posture of the neck Sometimes people will describe it as a sensory trick and if they touch a certain part of their neck or head, it will straighten out! This is the hallmark for this disease So you’d want to turn off the direct pathway in the basal ganglia and activate the indirect pathway to turn off the tick that’s causing the neck spasms It’s so weird though because if the doctor touches them in the same spot it won’t work but if the patient does it, the tremor or the neck twitch will stop/improve

Answer 15

1. Oral medications 2. Botulinum toxin injections 3. Deep brain stimulation 4. Rehabilitation

Answer 16

A non-respective, random, combination of fast and slow movements The patient will try to make it a voluntary movement to mask the involuntary movements; initially when this disease is mild they can be successful with hiding it

Answer 17

Huntington’s This is an AD, CAG trinucleotide repeat disorder on chromosome 4 On MRI scans, you will see caudate nucleus atrophy of the basal ganglia You can see this happen after a strep infection due to an autoimmune reaction = Sydenham’s chorea You can also see this happen after pregnancy! = chorea graviderum

Answer 18

A lesion of the subthalamic nucleus that causes really big and fast involuntary movements —> the contralateral STN is what’s effected; so if there’s a right STN lesion, then there will be spasms on the left side of the body STN usually excites GPi which inhibits the thalamus to inhibit involuntary movements So without STN, GPi isn’t as active so it doesn’t inhibit the thalamus to inhibit involuntary movements The classic presentation is STN hemorrhage due to hypertension but it can also happen with a stroke (infarct) Intermittent hemiballismus can also be seen in patients with hyperglycemia or TIA (transient ischemic attack aka a mini stroke)