Movement Disorders and Neurosurgery (Week 4--Pouratian and Bordelon)

Question 1

Reasons chemical neuromodulation (pharmacology) can fail

Answer 1

1) Disease progression
2) Excessive side effects of medical therapies
3) Lack of efficacy of available therapeutics

Question 2

Why would we do deep brain stimulation?

Answer 2

For patients with complications or ineffective relief from pharmacotherapy

Effective dose of L-DOPA window narrows over time

Question 3

How does DBS work?

Answer 3

1) Restores more normal pattern of electrical rhythms in the brain
2) Disrupts or interferes with abnormal electrical patterns induced by neurodegenerative process

Question 4

Advantages of DBS over lesioning (old method)

Answer 4

1) Reversible (just stop the stimulation)
2) Modulatable (make adjustments by programming)

Question 5

Which PD patients do we give DBS to?

Answer 5

1) Patients with advanced disease that have developed motor fluctuations
2) Patients who are intolerant of side effects of standard medications

Question 6

Surgical (DBS) candidates

Answer 6

1) Diagnosis of PD
2) Responsive to carbidopa/levodopa
3) Cognitive“intact” without significant dementia

Question 7

Where do we stimulate to treat PD?

Answer 7

Stimulate structures that are hyperactive in PD

1) Subthalamic nucleus: may allow for greater medication reduction
2) Globus pallidus internus (GPi): considered if psychiatric or cognitive issues present but nor exclusionary

Studies have shown equivalent motor response though

Question 8

Does DBS treat all symptoms of PD?

Answer 8

No, only treats motor symptoms

Can adversely affect psychological and cognitive function

GPi is generally more well-tolerated target for therapy than STN

Question 9

DBS treatment for essential tremor

Answer 9

DBS used when Essential Tremor interferes with patient’s life

Stimulation target is Ventral intermediate nucleus (Vim) of thalamus, which receives major inputs from dentato-rubro-thalamic tract

Remember, dentate nucleus is in cerebellum; lateral cerebellar hemispheres have pathology that results in abnormal activity in cerebellar projections to thalamus

Question 10

DBS to treat dystonia

Answer 10

FDA approved to treat genetic dystonias but is used off-label for cervical dystonia and other focal and segmental dystonias

Stimulation target is GPi, usually bilaterally

Question 11

What is the best predictor of DBS effectiveness?

Answer 11

Levodopa responsiveness

L-DOPA response approximates DBS efficacy; non-L-DOPA responsive symptoms generally not improved with DBS

Question 12

Programming after DBS implantation

Answer 12

Need to program the device to give constant stimulation, but must adjust parameters (takes 3-6 months):

Amplitude (0-10 volts)

Pulse width (msec)

Frequency (130-185 Hz)

Electrode configuration (pseudomonopolar, bipolar, guarded cathode)

Question 13

Essential tremor

Answer 13

Most prevalent movement disorder

Bilateral postural tremor with or without kinetic tremor, involving hands and forearms, that is visible and persistent

>5 years

Etiology not clearly defined but maybe association with LINGO1, cerebellar changes, Lewy bodies in locus coeruleus

Question 14

Dystonia

Answer 14

Uncontrolled co-contraction of agonist and antagonist muscles resulting in abnormal posture or movement

DYT-1 (Oppenheim Dystonia) is a generalized primary dystonia and kids are given DBS to treat DYT-1

Treat dystonia with BoTox, trihexyphenidyl, baclofen, benzodiazepines

Question 15

Side effects of DBS

Answer 15

Dysarthria

Others too…