DEEP BRAIN SIMULATION FOR TREMOR SUPPRESSION IN PARKINSONS PATIENTS
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29-10-2010, 09:15 AM


DEEP BRAIN SIMULATION FOR TREMOR SUPPRESSION IN PARKINSONS PATIENTS
Presented by:
MOHAMMED SALMAAN
S7 , ROLL NO: 38
APPLIED ELECTRONICS AND INSTRUMENTATION
College Of Engineering, Trivandrum
2007-11 batch


.pptx   DEEP BRAIN SIMULATION FOR TREMOR SUPPRESSION IN PARKINSONS.pptx (Size: 770.56 KB / Downloads: 61)
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CONTENTS
DEFINITION
DEMOGRAPHICS
HOW IT WORKS
ELECTRODE IMPLANTATION
NEUROSTIMULATOR
FNS
OUTPUT STAGE
WORKING
DIAGNOSIS
AFTERCARE
RISK
COMPLICATIONS
ALTERNATIVES
RESULT
REFRENCES


DEFINiTION
Deep brain stimulation (DBS) is a neurosurgical treatment which stimulates the brain with mild electrical signals.
The signals reorganize the brain's electrical impulses, causing improvements in symptoms in a number of conditions affecting the brain.

PARKINSON'S DISEASE
Caused by the progressive impairment or deterioration of neurons in the substantia nigra.
Functioning normally, these neurons produce a vital brain chemical known as dopamine.
Dopamine serves as a chemical messenger allowing communication between the substantia nigra and another area of the brain called the corpus striatum.
A lack of dopamine results in abnormal nerve functioning, causing a loss in the ability to control body movements.

DEMOGRAPHICS
Parkinson's disease affects approximately ten million Indians.
The peak incidence is approximately age 62, but young-onset PD can occur as early as age 40.
Young-onset patients are more likely to become candidates for surgery than older-onset patients.
Younger patients tend to do better and have fewer adverse effects of surgery.
Approximately 5% of older PD patients receive one form or another of PD surgery


Video on Parkinson's disease
HOW IT WORKS
A thin, insulated wire lead with four electrodes at the tip is surgically implanted into the affected area of the brain.
A wire runs under the skin to a battery-operated pulse generator implanted near the collarbone.
The generator is programmed to send continuous electrical pulses to the brain.
It can be turned on or off when the patient swipes a special magnet over the generator.


Unilateral DBS, a single "burr hole" is made in the top of the skull.
Bilateral DBS requires two holes.
A strong topical anesthetic is used to numb the skin while this hole is drilled.
Since there are no pain receptors in the brain, there is no need for deeper anesthetic.
The electrode is placed very close to several important brain structures.
Sensory changes during electrode placement may indicate the electrode is too close to one or more of these regions.


VIDEO ON HOW IT WORKS
ELECTRODE IMPLANTATION
Neurosurgeon uses a stereotactic head frame
Magnetic resonance or computed tomography imaging is used to map the brain and pinpoint the problem area.
The patient's scalp is anesthetized before the procedure
The patient is awake to report side effects while the electrodes are placed .
This allows the lead to be placed for maximum effectiveness and minimum side effects.
The patient receive sedation or general anesthesia before the wire lead and the pulse generator are implanted.


NEUROSTIMUILATOR
FNS OUTPUT STAGE
DIAGRAM
WORKING
FUNCTIONAL NEUROMUSCULAR STIMULATION (FNS)
Functional neuromuscular stimulation (fns)is the electrical activation of paralyzed muscles and can be applied torestore partial functionality while providing a medical diagnosis of thenervous system.
FNS is embedded in many prosthetic devices aimingdifferent applications such as control activity of motor nerves and urinary bladder, pain relief, stroke victims, etc.

OUTPUT STAGE

Surface stimulators handing over voltage pulses do not guarantee a preset current intensity as the delivered current changes with the characteristicof the electrode/skin load.
Current-regulated bursts are thereforemost preferred since the charge transferred per stimulus is constant regardless the load impedance
No uncontrolled spikes occur at the current-step onset.

It consistsof a pair of transformers with full-bridge rectifiers, a voltage-regulator,an astable multivibrator, a photocoupler, and a driving stage,which is composed by a switching circuit and a V=I converter.
WORKING
Line transformer T1 and rectifierfeed a voltage-regulator, whose output VR sets the astable supply-voltage.
Since the astable is loaded by the primary of step-up transformer T2, a self-excited HV oscillation across the secondary windings is attained.
After rectification and filtering, a high dc voltage, which is therefore proportional to VR, is supplied to a switched V=I converter built upon a cascode current-mirror that delivers to the load a pulsed current with constant amplitude.
Pulse duration is externally determined by a monostable, which is triggered by a transistor–transistor logic level signal.
The resulting one-shot pulse is input to a photocoupler that drives a switching circuit made up of discrete transistors.
WORKING

Transformer T1 (6:1,15 VA) lowers the power-line voltage from 127 Vac rms to 30 Vpeak.
The full-bridge rectifier comprises diodesD1–D4 (1N4007) and filter capacitor C1.
The resulting dc voltage supplies the voltage-regulator(LM317T).
Ultimately, the stimulus magnitude is proportional to VR,which is manually adjusted by potentiometer R2 in the present design.
Diodes D6–D9 (1N4007) produce the voltage drop that ensures 0 V as the lowest VR supplied to the astable,which comprises BJT devices Q1–Q2 (TIP41C), base resistors R3–R4 and collector-coupling capacitors C4–C5.


Since oscillation takes place across the center-taped primary of step-up transformer T2, a HV oscillation is developed at its secondary.
Supply voltages V +DDO and V DDOare available after ac/dc conversion by the bridge D10–D13 (1N4007)and C7.
Fig. 3 displays the driving-stage schematic, based on a self-biased current mirror formed by MOS transistors M1–M4 (MPT2N60).
REand CE are the components of the electrode/skin interface and RS isthe tissue resistance.
Fixing R5 and denoting VDDO = V +DDO-V-DDO,it comes out Iskin = (VDDO-VGS1-VGS3)=R5.
Both VDDO and R5 set the stimulus current, which is load-independent at good extension.
DIAGNOSIS/PREPARATION
The patient will undergo a variety of medical tests, and one or more types of neuroimaging procedures, including MRI, CT scanning, angiography (imaging the brain's blood vessels) and ventriculography (imaging the brain's ventricles).
On the day of the surgery, the stereotactic frame is fixed to the patient's head.
A local anesthetic is used at the four sites where the frame's pins contact the head; there may nonetheless be some initial discomfort.
A final MRI is done with the frame in place, to set the coordinates of the targeted area of the brain in relation to the frame.

Aftercare

The procedure is lengthy, and the patient will require a short hospital stay afterward to recover from the surgery.
Following the procedure itself, the patient meets several times with the neurologist to adjust the stimulation.
The pulse generator is programmable, and can be fine-tuned to the patient's particular needs.
Pulse generator batteries must be replaced every three to five years. This is done with a small incision as an outpatient procedure.
Since the generator is in the chest area, no additional brain surgery is required.

Risks
There are acute surgical risks, including hemorrhage and infection
The risks of general anesthesia.
The electrodes can be placed too close to other brain regions, which can lead to visual defects, speech problems, and other complications.
Because a device is left implanted under the skin, there is the risk of breakage or malfunction, which requires surgical removal.
A patient with implanted electrodes must not receive diathermy therapy.
Diathermy poses a risk of death in a patient with DBS electrodes.

POST-OPERATIVE COMPLICATIONS
Asymptomatic intracranial bleed (10% of procedures)
Symptomatic intracranial bleed (2%)
Seizures (3%)
Headache (25%)
Infection (6%)

DEVICE RELATED COMPLICATIONS
Lead replacements (9%)
Lead repositionings (8%)
Extension wire replacements (6%)
Implantable pulse generator replacements (17%), approximately half of which were due to malfunction
The risk of death is less than 1%.


ALTERNATIVES
Pallidotomy
Thalamotomy
Both destroy brain tissue to achieve the same effect as the stimulation.
Pallidotomy is performed for Parkinson's diseaseonly when tremor is the only debilitating symptom.
DBS for dystonia is the only really promising neurosurgical treatment for this condition.
RESULTS
Deep brain stimulation improves the movement disorder symptoms of Parkinson's disease by about 75%, depending on the care of the placement and the ability to find the optimum settings.
These improvements are seen most while off levodopa; DBS does little to improve the best response to levodopa treatment.

REFRENCES
[1] S. G. Patel and B. J. Roth, IEEE Trans. Biomed. Eng., vol. 47, pp.1284–1287, Sept. 2000.
[2] W. Mokwa, "Medical Implants Based on Microsystems", Measurement Science and Technology, vol. 18, pp. 47-57, 2007.
[3] A Beuter, R Edwards, and MS. Titcombe. Nonlinear Dynamics inPhysiology and Medicine, chapter 10: Data Analysis and Mathematical Modeling of Human Tremor, pages 303–355. Springer, New York,2003.
[4] V.C. Anderson, K.J. Burchiel, P. Hogarth, J. Favre, and J.P. Hammerstad,Pallidal vs subthalamic nucleus deep brain stimulation in Parkinson’s disease. Arch Neurol, 62:554–560, 2005.
[5] R. Kumar, A.M. Lozano, E. Sime, and A.E. Lang, Long-term followup of thalamic deep brain stimulation for essential and parkinsonian tremor. Neurology, 61:1601–1604, 2003.



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