Deep Brain Stimulation

Deep brain stimulation is a specialized neurosurgical treatment option for patients suffering from a special group of neurological disorders called 'Movement Disorders'. Deep Brain Stimulation or DBS is an advanced procedure performed by neurosurgeons for treating patients who cannot achieve optimal results through conventional medical therapy alone.

Neurophysiology of Movement Disorders

Movement disorders refer to conditions associated with changes in specific areas of the nervous system which results in abnormal involuntary movements, slow or reduced movements. The two main areas of the brain which are affected in movement disorders are the basal ganglia and the sub-thalamic nucleus. The disorders are classified into various groups such as hypokinetic disorders (e.g.: Parkinsons), hyperkinetic disorders (e.g.: Huntington's disease), and Non-motor disorders (e.g.: Tourette's Syndrome and Obsessive Compulsive Disorders). When these nuclei start having abnormal electrical activity (discharging too much or too little), the patient experiences specific symptoms related to movement.

Indications for Deep Brain Stimulation

Deep brain stimulation is used for patients who usually suffer from movement disorders such as Parkinsons, tremors, and dystonia. It is called Deep Brain Stimulation because surgically placed electrodes are used to stimulate specific areas (nuclei) deep inside the brain. The most common nuclei commonly stimulated are the Globus Pallidus and the sub-thalamic nuclei.

The idea behind DBS is that it functions somewhat like a 'pacemaker' in the brain, periodically sending electrical signals to the specific nuclei, thereby modulating the effect of these nuclei. Hence, DBS is also called as neuromodulation therapy'. In DBS, specific electrical signals are sent to the abnormally functioning nuclei to reduce or increase their activity.

Components

There are three components of the Deep Brain Stimulation system. They are:

The Stimulating Electrodes

The IPG – Internal Pulse Generator (the pacemaker)

The Extension - connecting leads between the Electrode and IPG.

The IPD contains a battery pack which has to be replaced every 4 years. The IPG is programmed by the neurologist based on the specific disease condition of the patient, and the placement of DBS requires regular follow-ups for programming the IPG based on the disease condition, if needed.

Procedure

Specialized Brain Mapping technology is used to locate the specific nuclei which are suspected to be abnormally functioning. These nuclei are the 'target area' for DBS. A specially designed stereotaxic frame is attached to the patient's head which provides a three-dimensional reference system for the patient's brain and enables the neurosurgeon to precisely locate the nuclei or track the electrode tip during placement.

The procedure normally takes up to three hours and is performed by a neurosurgeon specially trained in the procedure. The surgery is called awake craniotomy since the patient is awake during the entire duration of the procedure so that his neurological functions can be assessed in real-time to see the 'before and after' results due to the electrode placement. Following the placement of the electrodes, the IPGs are implanted either during the time of the surgery or later on. Each brain is unique, and hence the IPGs have to be specially programmed and the settings have to be specific for each patient. This is usually done about 2 weeks after the electrode placement.

Clinical Results

It is not exactly known how DBS functions, but there have been marked clinical improvements for patients with Parkinson's disease, tremors, and dystonia. Although a large percentage of patients report significant improvement after DBS surgery, there is no guarantee that DBS will help every patient with movement disorder.

Patients with Parkinson's report 60-80% improvement in tremor and slowness of movement. Patients on an average report 50% improvement in their walking and balance following DBS. Others with dyskinesia (involuntary movements) report more than 80% improvement following DBS.

Complications

Although DBS on the whole has proven safe and effective, there is a possible 2-3% risk of intra-cranial hemorrhage and meningitis due to leakage of cerebro-spinal fluid. There is a 15% chance of developing infection due to the placement of the electrodes. There is a possibility that seizures may occur, if the tip of the electrode migrates, thereby stimulating other areas of the brain. However such findings have not been reported until now.

Future of DBS

Besides movement disorders, DBS has been used to chronic pain, and currently possibilities of using DBS for other cognitive disorders such as severe depression, obsessive compulsive disorder, eating behavioral disorders and drug addiction, are underway.

Parkinson's disease

A disease relating to a progressive degenerative disorder of the central nervous system, Parkinson's disease leads to shaking/tremor and difficulty in movement, walking, coordination etc. As the disease progresses, it could lead to cognitive and behavioral problems. In its advanced stages, this disease could lead to dementia. Parkinson's disease commonly occurs in people aged over 50. James Parkinson, a general practitioner in London was the first to describe the symptoms of the disease and thus the disease has taken the name Parkinson's disease.

The disease progresses gradually, initial symptoms might be just a tremor in the hands. Slowly the disease leads to slowing or freezing of movements. There is no complete cure for the disease. However there are treatments that can handle the symptoms of the disease. Parkinson's disease is also known as Parkinsonism.

Diagnosed as the most common movement disorder, Parkinson's disease is classified into three types based on the age of onset of the disease

Juvenile Parkinson's disease: Sets in before the age of 21. This kind is a rare occurrence.

Young-onset Parkinson's disease: The disease sets in between the age of 21 and 40. Reportedly common in East Asian countries.

Adult-onset Parkinson's disease: The most common and prevalent type of Parkinson's disease, the disease sets in after the age of 60. The symptoms aggravate with advancing age.

Causes for Parkinson's disease

Parkinson's disease sets in usually after the age of 50 and affects both men and women.

• The major cause of Parkinson's disease is attributed to the death of the dopamine-containing cells in the brain.
  
• Toxins present in the environment can also contribute to the death of dopamine cells in the brain thus causing the disease.
  
• Family history of the disease.
  

• Tremor sets in from the hands and gradually spreads over to the rest of the body.
  
• Rigid muscles, stiffness in the muscles, this limits movement and induces pain.
  
• Loss of automatic movements like swinging arms, blinking.
  
• Slowed motion – The disease restricts the voluntary movement of the body.
  
• Change in speech – Few people speak in a monotone; few have soft or rapid speech based on the severity of the condition.
  
• Impaired posture and balance – There could be problems in the posture and balance of a person.
  
• Dementia – This usually occurs in the advanced stages of the disease.
  

The physician asks for the medical history of the patient and does a neurological examination of the patient. Hand co-ordination, walking, etc are assessed through neurological examination.

Treating Parkinson's disease

• Medications to tackle the symptoms
  
• Physical therapy to increase muscle tone and strength
  
• Lifestyle changes like healthy diet, exercises, speech therapy, etc
  
• In a few cases surgery for deep brain stimulation, in this process they implant an electrode into the brain. This electrode in turn takes care of the stimulation of the brain.