Parkinson’s disease (PD), a degenerative condition of the nervous system, is a movement disorder characterised by slowness of movement, resting tremor (shaking of limbs), rigidity (stiffness), and postural instability (imbalance).
Advanced Parkinson’s Disease Management:
Medical management remains the first line of treatment in patients with PD. Patients respond well to medications that temporarily replenish dopamine (L-dopa) or mimic the action of dopamine. However, as the disease duration increases, the requirement of L-dopa increases and the medical management of advanced Parkinson’s disease can be quite challenging.
The most troublesome effects of L-dopa as the disease advances, usually after several years of treatment, are an end-of-dose reduction in efficacy, the more precipitous “on-off” phenomenon, and the induction of involuntary “dyskinetic” movements. This is when patients are evaluated for Deep Brain Stimulation – a surgical procedure that helps people with advanced PD improve their quality of life.
Deep Brain Stimulation :
Deep Brain Stimulation involves applying high-frequency electrical stimulation to specific structures in the deep areas of the brain. Deep brain stimulation (DBS) surgery was first approved in 1998 to treat Parkinson’s disease (PD) tremor, then in 2002 for the treatment of advanced Parkinson’s symptoms. It is now widely accepted as an effective, safe, and standard treatment worldwide.
The procedure involves placing a thin metal electrode into one of several possible brain targets and attaching it to a computerised pulse generator, which is implanted under the skin in the chest below the clavicle.
In DBS surgery, electrodes are inserted into a specific area of the brain (generally the subthalamic nucleus STN or the Globus pallidus GPi), using MRI (magnetic resonance imaging) and recordings of brain cell activity during the procedure. This is the part of the procedure where the patient is awake. A second procedure is performed under General Anaesthesia (GA) to implant an IPS, impulse generator battery (like a pacemaker). The IPG is placed under the collarbone. The IPS provides an electrical impulse to a part of the brain involved in motor function.
Role of Deep Brain Stimulation in Parkinson’s Disease :
DBS is highly effective for patients who suffer from disabling tremors, wearing-off spells, and dyskinesias induced by medication. Although DBS significantly improves the quality of life in PD patients, it is not a cure and it does not slow PD progression. It gives a good quality of life for 10-15 years depending on the age and stage of PD when DBS was performed. Most people after undergoing DBS, experience a considerable reduction of their PD symptoms, and their medications can be greatly reduced. However, it does not improve speech or swallowing issues, thinking problems, or gait freezing.
Like all brain surgeries, DBS carries a small risk (<5%) of complications. It can be procedure-related (haemorrhage that may be silent or symptomatic, transient confusion, infection), device-related (breakage of leads), or stimulation related (usually eliminated by adjusting stimulation settings). This is often avoided with stringent patient selection criteria, meticulous planning, and strict asepsis during DBS surgery. A controller is given to patients who undergo DBS surgery to turn the device on or off.
DBS surgery does not cause any damage to healthy brain tissues or nerve cells. It only interrupts abnormal electrical signals from targeted areas in the brain. It is a reversible procedure unlike other procedures used in the treatment of PD like lesioning which involves irreversibly destroying tissues in a specific area of the brain.
Ideal PD Candidate for DBS :
The patient has had PD symptoms for at least five years.
S/he continues to have a good response to PD medications, especially carbidopa/levodopa, although the duration of response may be insufficient (Levodopa responsive).
Age group of 40-70 years.
The patient has “on/off” fluctuations despite regular medication dosing.
S/he is unable to tolerate PD medications due to side effects.
Tremors that are not well controlled with medication.
Severe dyskinesias.
The patient should be cognitively intact.
(The author, Dr. Sathwik R Shetty is a Consultant – Neurosurgery at Manipal Hospital.)
