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C3 CLINICAL > Surgery in Movement Disorders > Flashcards

Surgery in Movement Disorders Flashcards

1
Q

Traditional Neurosurgery restores abnormal anatomy

A
  1. Aims to modify pathological anatomy
  2. Usually deals with acute disease
  3. Often lifesaving surgery
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2
Q

Why should we perform functional neurosurgery?

A
  1. Surgical intervention - change in function
    - patient with chronic neurological disorders
    - Rarely life threatening
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3
Q

What is the ultimate aim for functional neurosurgery?

A

To improve symptoms and quality of life

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4
Q

What are the indications for functional neurosurgery?

A
  1. symptoms of movement disorders: PD, dystonia, tremor
  2. Chronic pain syndromes: phantom pain, cluster headache
  3. Neuropsychiatric conditions: Tourette, OCD, depression
  4. Epilepsy
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5
Q

What does functional neurosurgery demand?

A

Minimal risk of inflicting morbidity and mortality

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6
Q

In 1930, what did the american neurosurgeon suggest?

A

Basal Ganglia were involved in the control of movement

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7
Q

What is the history of surgery for movement disorders: desperate measures?

A

Lesions can modulate the brain circuits that control the movement

  1. Victor Horsley-1890
    - Corticospinal tract
    - Stereotaxis
  2. Meyers 1930
    - Basal Ganglia
    - Open procedures
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8
Q

What is the stereotactic technique?

A
  1. Accurate navigation within the brain in a minmally invasive fashion
  2. Horsely and Clarke frame (1905)
    - Hindered by lack of imaging
  3. Spiegel & Wycis (1947)
    - Ventriculography
    - Internal landmarkers
    - Need for stereotactic atlases
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9
Q

What did Irving Cooper do?

A
  • He made a small temporal craniotomy – lifted the brain up and he went underneath the brain to cut the cerebropeduncle – he was cutting the corticospinal tract rather than taking all of the cortex out disconnecting the cortex by dividing the corticospinal tract
  • He nicked the anterior choroidal artery on his way in – he couldn’t stop the bleeding
  • Place a small silver clip across the small blood vessel to occlude it
  • Anterior choroidal artery goes to the basal ganglia
  • Ligation of the left anterior choroidal artery
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10
Q

What can lesions positively alter?

A

Neural function

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11
Q

History: lesions can positively alter neural function

A
  1. Surgery for Parkinson’s disease, chronic pain, psychiatric disorders
  2. Tens of thousands of pallidotomy/thalamotomy procedure was performed - there was no other treatment
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12
Q

What happens if you ligate the anterior choroidal artery in 40 patients?

A

About 2-3 patients will die because the anterior choroidal artery has variability it is very big

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13
Q

Why did surgery fall out of favour?

A
  1. The age of drugs
    - L-dopa 1967 (Cotzias)
    - Chlorpromazine
  2. Indiscriminate use of lobotomy by psychiatrists
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14
Q

Why has surgical neuromodulation made a come back?

A
  1. Intolerable side effects
  2. Lack of efficacy
  3. Motor fluctuations
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15
Q

Parallel circuits … with significant crosstalk!

A
  • This shows you some of the major connections between different areas of the brain – doesn’t show you all of the connections
  • The model is clear that the cortex sends information via the corpus stratium through the Basal Ganglia and back to the cortex via the thalamus
  • There are circuits that are running in parallel between motor parts of the cortex, limbic part of the cortex and cognitive/associative part of the cortex – these go through the basal ganglia in parallel but there is a lot of crosstalk between them
  • There is a lot off cross talk between these circuits
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16
Q

Parkinson’s disease

A

you lose a lot of neurons in particular neurons of the substantia Nigra in pars compacta
• Parkinson’s disease has various stages – start losing nigral neurons quite late – start losing gut cells and medullary cells far before we start losing substantia nigra cells – you have to lose 50-70% of your nigra cells before you get symptoms

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17
Q

What is substantia nigra pars compacta?

A

Susceptible pathophysiology of alpha-synuclein accumulating in parkinsonian nerve cells - they have a very high metabolic requirement

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18
Q

What does alpha-synuclein affect?

A

Mitochondrial functions

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19
Q

What do each substantia nigra pars compacta cells thought to make?

A

100,000 synapses with different neurons throughout the brain

20
Q

What happens when you lose substantia nigra?

A

You get a mismatch and cardinal symptoms of Parkinson’s diseaseget mismatch of activity in various parts of the basal ganglia

21
Q

What happens when the thalamus doesn’t excite the cortex?

A

The cortex gives the bradykinesia

22
Q

When do we get an improvement?

A

• If we put a lesion in the subthalamic nucleus in the Globus pallidus interna or stick an electrode and pass an electrical current through the area blocking the information that is going through that pathway

23
Q

What is the function of the parallel circuits?

A
  • Function of the brain is information processing
  • Brainstem is the vegetative part of the brain – breathing and cardiac function, acid-base balance, homeostasis
  • Reactive system – saw tooth
  • Subconsciously you are making a prediction of what is going to happen – if the prediction is wrong, the movement will be pathological
  • Emotion is an internal prediction of what is happening on outside
24
Q

What will help with movement?

A

If we lesion STN

25
Q

What can different circuits control?

A

Different symptoms of different movement

26
Q

What can treat different symptoms?

A

Different targets of the brain

27
Q

Where is subthalamic nucleus situated between?

A

Midbrain and diencephalon - target that and improve all cardinal symptoms in Parkinson’s disease - improve motor fluctuations

28
Q

What do symptoms dictate?

A

Brain target: tailored surgery

29
Q

Subthalamic nucleus (STN)

A
  1. Can help with dopamine responsive symptoms
  2. Improves motor fluctuations, braykinesia/akinesia, rigidity, gait, tremor
  3. Reduction in medication
    - psychological side effects
  4. Speech articulation
30
Q

Pallidum

A
  1. Effective for dyskinesia/dystonia
  2. Less likely to interfere with psychology
  3. Does not improve bradykinesia much
31
Q

Motor thalamus (Vim)/Zona incerta (ZI)

A

Useful in tremor

32
Q

What are the advantages and disadvantage of lesion?

A
  1. Advantages:
    - Cheap
    - No implanted hardware
  2. Disadvantage:
    - Irreversible
33
Q

What are the advantages and disadvantages of high frequency stimulation

A
  1. Advantages:
    - socially more acceptable
    - Relative reversible
  2. Disadvantages
    - Expensive
    - Labour intensive
    - Hardware problems
34
Q

Deep Brain Stimulation: Mechanism of action:

A
  • It has an effect on voltage gated channels by blocking action potentials
  • It activates inhibitory axons and most neurons in your brain are inhibitory
  • You can deplete transmitters at synapses
  • Disrupting network activity
35
Q

DBS: mechanism of actions?

A
  1. High frequency stimulation has a similar clinical effect to lesioning
  2. Effect increases with rate and reaches a plateau
36
Q

What are the physiological effect of DBS?

A
  1. Effect on V-gated channels block action potentials (depolarisation blockade
  2. DBS activates inhibitory axons (synaptic inhibition)
  3. Transmitter depletion (synaptic depression)
  4. Disruption of network activity (desynchronisation)
37
Q

What are the many initial concern for MRI in functional neurosurgery?

A
  1. Geometric distortion
  2. Targeting accuracy
  3. Efficacy

Methods of compensating for geometric distortion

38
Q

What does MRI raise the possibility of?

A

Acquiring the target on the first pass through the brain in the majority of cases
- important safety implications

39
Q

What is the reference point

A

mid-commissural point– that is between the anterior commissure and the posterior commissure – you can see these points in ventriculograms, also seen on CT and MRI

40
Q

The subthalamic nucleus

A

roughly 12mm from the midline and 2mm behind the mid-commissural plane, 5mm below the AC-PC line

41
Q

What is found lateral to the lentiform nucleus?

A

the putamen, medially there is Globus pallidus – divided into both externa and interna and there is a lamina between them

42
Q

If your motor is post-lateral

A

your limbic is inferior-medial (temporal lobe) and you associative is in the front – those circuits are the same

43
Q

What does recognising the firing of patterns of neurons tell us?

A

that we are in the subthalamic nucleus

44
Q

What is the brain?

A

Very vascular organ– it receives 20% of your blood flow

45
Q

Adjust target to visualised image

A
  1. Direct Targeting
  2. Corrects for anatomical variation
  3. Requires the recognition of the imaging correlates of anatomical structures
  4. Multiple imaging planes (redundancy)
46
Q

Thalamic Targets

A
  1. Thalamic nuclei not reliably visualised at 1.5T
  2. More reliance on atlas based coordinates
    - more forigiving target
    - stronger role for LA
  3. Anatomical clues from pallidothalamic border/ relationship to ZI

C3 CLINICAL (27 decks)

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