DEEP BRAIN STIMULATION (DBS) IN PARKINSON’S DISEASE
Major Symptoms of Parkinson’s disease
Parkinson’s disease (PD) is a progressive neurological disease, characterised by tremors, rigidity, slowness of movements and postural imbalance. Though it is more common after the age of 40, people younger than 40 can also get affected (when it is known as young onset PD).
Other symptoms of PD include low volume speech (sometimes totally incomprehensible), expressionless face, reduced blink rate, reduced arm swing while walking, stooped posture, small handwriting (called micrographia), short-shuffling steps, tendency to fall forwards. Many people also have pain and aches in the affected limbs. Sleep disturbance and restless leg syndrome are common comorbid illnesses in people with PD. Severe memory impairment is NOT a feature of PD, however, in advance PD, mild memory impairment may occur in about 10% of patients. Similarly, loss of bladder control or erectile dysfunction is not a feature of PD. When these features are present, one should suspect multiple system atrophy (MSA).
Diagnosis of PD
The diagnosis of PD is still best made on the basis of clinical examination by an experienced neurologist (preferably trained in movement disorders, though not a must). PET and DaT scans are available to help in the diagnosis of PD, but they are not superior to a good clinical examination by an experienced neurologist.
Treatment of PD
Treatment of PD is still primarily medical and DBS is not the first option.
The most effective medicine is levodopa-carbidopa combination. If a patient does not respond to levodopa treatment, we should doubt the diagnosis (it may not be PD). Even though levodopa is the most effective medication, we should delay starting it by 2-3 years, to avoid side effects and lack of efficacy later on. Other medications in use are pramipexole, ropinirole, trihexiphenydyl, selegiline, rasagiline, amantadine, entacapone, safinamide, etc.
Role of Deep Brain Stimulation (DBS) surgery in PD
DBS was approved for PD in 2002. In the past 15 years, about 1,35,000 patients worldwide have undergone DBS for PD.
What does DBS surgery involve?
A neurosurgeon places the leads (thin wires) that carry electrical signals to specific areas of the brain. Then, the surgeon places a battery-run neurostimulator (like a pacemaker) under the skin of the chest.
The surgeon may use a programming device to adjust the settings. You may have a device, similar to a remote control, which allows you to turn the system on and off and check the battery. You may also be able to adjust the stimulation within options programmed by your doctor.
A neurologist initially evaluates a patient to determine whether he or she is the right candidate for DBS surgery. Then, further evaluations include brain imaging (MRI, CT, PET, etc), neuropsychological testing, UPDRS scoring, etc. Once the patient is found to be suitable for DBS, he is referred to the neurosurgeon.
Which patients are likely to benefit from DBS surgery?
1. The diagnosis of PD should be definite.
2. Patient has had PD for five years or more.
3. Patient continues to respond to levodopa, even though the response may or may not be good.
4. There are motor fluctuations, such as on-off phenomena, with or without dyskinesia.
5. Various medical treatments have not had desired benefit.
6. PD symptoms are severe enough to interfere with activities of daily living.
Which patients are NOT likely to benefit from DBS surgery?
1. Patients with atypical Parkinsonian symptoms,
2. Patients with multiple system atrophy (where bladder and sexual dysfunction are prominent symptoms),
3. Patients with progressive supranuclear palsy,
4. Patients with dementia or severe cognitive impairment,
5. Patients with unstable psychiatric illnesses,
6. Patients with advanced PD, who are confined to bed/wheelchair; despite being on medications,
7. Patients with NO response to levodopa therapy,
Who are the best candidates for DBS surgery in PD?
1. Excellent response to levodopa therapy,
2. Younger age,
3. Mild or no cognitive impairment,
4. Few or no axial (affecting neck or trunk) motor symptoms,
5. Absence of or well controlled psychiatric disease.
Are there any complications of DBS surgery?
DBS surgery is generally safe if performed by a trained group of specialists. However, complications may occur in upto 3% of patients, which include:
1. Bleeding (hemorrhage) in the brain,
4. Speech impairment
5. Erosion, migration or fracture of the lead,
What to expect after DBS surgery?
Most patients report a reduction in severity of symptoms after surgery. Tremors, dyskinesia, slowness all respond to the surgery.
PD medications, however, can not be stopped even after DBS. Most patients still need to take medications, however, at much lower doses.
The benefits are seen at five years after surgery, however, the effect tends to wane in later years.
DBS does not alter the disease progerssion, and disease continues to get worse even after DBS.
Is MRI safe after DBS?
Yes, MRI can be safely done after DBS surgery.
What is the cost of DBS surgery ?
The cost of surgery is approximately INR 9,00,000 to 10,00,000.
Dr Sudhir Kumar MD (Med) DM (Neuro)
Senior Consultant Neurologist
Apollo hospitals, Hyderabad