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Deep brain stimulation (DBS)
DBS suits a Parkinson patient who still responds to levodopa but suffers ON-OFF fluctuations and dyskinesias — levodopa response predicts surgical response, except for tremor, which improves even when levodopa does not help.
Why it matters in the exam
DBS questions return to four axes: who is a candidate (idiopathic Parkinson disease with at least 30% improvement in the UPDRS-III motor score on a levodopa challenge, no dementia and no uncontrolled psychiatric disease), who is not (atypical parkinsonism such as MSA and PSP, dementia, marked atrophy), which target for which disease (STN or GPi in Parkinson disease, thalamic VIM in essential tremor, GPi in dystonia, the anterior nucleus of the thalamus in epilepsy), and what happens when the lead is off target. High-frequency stimulation, usually 130 to 185 Hz, disrupts pathological synchronous beta activity and mimics a functional lesion — it does not destroy tissue.
Stereotactic planning uses a Cartesian coordinate system centred on the midpoint between the anterior and posterior commissures (AC-PC); the frame fixes the head and translates imaging coordinates into a point in the brain. Microelectrode recording identifies the STN by fast, irregular firing. Stimulation side effects reveal lead position: too lateral — internal capsule with muscle contraction and dysarthria; too medial — third nerve fibres with diplopia; too posterior — medial lemniscus with persistent paraesthesia. After STN DBS levodopa can usually be reduced by about half; GPi directly reduces dyskinesia. Complications: intracerebral haemorrhage in about 1 to 2% and hardware infection in about 3 to 5%.
Key points
- Candidate: idiopathic Parkinson disease, levodopa response of at least 30%, no dementia.
- STN or GPi in Parkinson disease; VIM in tremor; GPi in dystonia.
- High frequency disrupts pathological beta synchrony.
- Planning on AC-PC coordinates in a stereotactic frame.
- Lateral — capsule; medial — third nerve; posterior — paraesthesia.
Summary table
| Disease | Target | What improves | Note |
|---|---|---|---|
| Parkinson disease | STN or GPi | Fluctuations, tremor, rigidity, dyskinesia | Needs at least 30% levodopa improvement |
| Essential tremor | Thalamic VIM | Hand tremor | Alternative: focused ultrasound |
| Primary dystonia | GPi | Dystonic movements | Improvement builds over months |
| Drug-resistant epilepsy | Anterior nucleus of the thalamus | Seizure frequency | For patients who are not resection candidates |
| Atypical parkinsonism | — | No benefit | MSA and PSP are contraindications |
Free exam questions
אילו מחולי הפרקינסון הבאים הוא קונטראינדיקציה לניתוח DBS ? (the question as examined, in Hebrew)
- א. מטופל עם הפרעה בשיווי משקל( PULL TEST חיובי)
- ב. מטופל עם הפרעות זכרון ברמה של MCI
- ג. מטופל עם דכאון וחרדה
- ד. מטופל שמשתפר משמעותית על טיפול תרופתי במבחן UPDRS III ON-OFF
בן 60 סובל מרעד דו- .צדדי סימטרי בפעולה, הגורם להפרעה תפקודית משמעותית טופל בשלושה קווי טיפול ללא הטבה מספקת. כעת מועמד להשתלת קוצב DBS (. Deep brain stimulation ) לאיזה מבנה אנטומי יוכנסו האלקטרודו ת על מנת לקבל את התוצאה המיטבית? (the question as examined, in Hebrew)
- א. Ventro medial Thalamic Nucleus
- ב. Anterior Thalamic Nucleus
- ג. Subthalamic Nucleus
- ד. Head of Caudate
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Sources
- Movement Disorder Society evidence-based review of treatments for Parkinson disease, 2018 — Surgical therapies
- CAPSIT-PD core assessment program for surgical interventional therapies in Parkinson disease, 1999 — Patient selection
- Youmans and Winn Neurological Surgery, 8th edition (2022) — Deep brain stimulation for movement disorders; Stereotactic principles
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.