The modern era of DBS began in 1987 when Alim Benabid published his paper reporting the use of ventral intermediate nucleus (Vim) stimulation for Parkinson’s Disease (PD).
Since then DBS has been used for PD, Dystonia, Essential tremor, psychiatric disorders, and Epilepsy. The last several years have been characterized by many emerging and new indications and new intracranial targets for DBS.
Of particular interest in the treatment for DBS are behavioral and psychiatric disorders, including Tourette’s syndrome, major depression, and obsessive-compulsive disorder (OCD).
Large centers prefer a multidisciplinary approach that will involve a neurologist, a neurosurgeon, a psychologist, a psychiatrist, and a nurse specialist.
A neurologist plays a central role in the candidate selection process by confirming the diagnosis in PD, and dystonia, He also assesses the severity of symptoms and disability, verifying responsiveness to medications using objective Scales, and instilling realistic patient expectations.
The neurosurgeon and the neurologist work closely to evaluate the benefits and risks of DBS. Together they share the responsibility for evaluating the degree of disability as well as discussing patient expectations. He will evaluate the surgical risks and carefully explain all details of the procedure to the patient and family. Possible complications related to the surgical procedure, the implanted device and the stimulation will also be discussed by the treating neurosurgeon.
The principal role of the psychiatrist is to identify and treat patients with underlying psychiatric conditions, especially those that may be worsened by DBS. Psychiatric screening as an important safety measure.
In the case of DBS for psychiatric conditions, the psychiatrist will evaluate in detail if the patient is a suitable candidate for surgery. His role will be from evaluation to being part of the surgical team during surgery and in post-DBS programming in these patients.
A Neuropsychologist is responsible for cognitive and behavioral testing for the patients undergoing DBS surgery. Neuropsychological testing is helpful in excluding patients with dementia. In addition, it can also be helpful for separating medication-induced encephalopathy from true dementia
Deep brain stimulation (DBS) involves a surgery that implants a device that sends signals to areas of the brain that are responsible for body movements.
Electrodes are placed deep within the brain depending on the symptoms being targeted, and these are connected to a stimulator device.
Electric pulses produced by a neurostimulator are used to regulate brain activity. This device resembles a heart pacemaker. The mechanism of DBS is likely not simply a matter of inhibition or excitation, rather it involves complex changes throughout the entire basal ganglia-thalamocortical network. So basically it’s a high frequency, pulsatile, mono or bi-polar electrical stimulation device that is placed stereotactically in a particular area of the brain with pinpoint accuracy.
Although there is an impression that younger patients have less surgical risk, no well-defined upper age limit has been set for DBS surgery. However, a majority of centers have arbitrarily utilized an upper age limit of 75 years.
MRI is recommended as part of the pre-surgical evaluation for DBS. MRI helps to exclude patients with atypical symptoms, moderate to severe cortical atrophy, significant vascular white matter changes, and structural lesions.
There may be an increased risk for surgery in those having uncontrolled diabetes, heart disease, pulmonary dysfunction and hypertension.
DBS can be safely performed in patients who have had prior ablative surgery for PD. However, we need to consider a few parameters such as the size of the previous lesion, lesion location, and responsiveness of symptoms to a levodopa challenge.
The procedure can be done with the patient being awake or under general anesthesia depending on the indication and the surgeon’s preference.
The Patient who will undergo a DBS surgery will have to be evaluated with an MRI, and other necessary investigations. The steps of the surgery will be as follows.
Every surgery comes with its share of risks. General complications include infection(2-4%), Hemorrhage(<3%), seizures(<1%), depression, hardware-related complications, misplaced leads(0-10%), Skin erosion, etc. However, it is a relatively safe procedure with minimal overall risk to life.
Additional surgery may be required for reasons such as breakage of the extension wire in the neck, wear and tear of parts beneath the skin,or removal of the device due to mechanical failure of the device or infection. Battery replacement depends on the type of battery used. For non-rechargeable batteries, the replacement may be needed once every 3-5 years. For the rechargeable batteries, the replacement may last for 12-25 years.
DBS has shown promising results in clinical trials when used to treat mood and cognitive disorders such as major depression and Obsessive-compulsive disorder(OCD). Electrodes are placed in specific targeted regions of the brain. Several areas have been identified as target sites for the treatment of refractory depression that is resistant to medical treatment.
Although the precise mechanism is not yet completely understood, DBS can target certain regions and circuits within the brain which may be responsible for some neuropsychiatric illnesses. Also, DBS is a reversible process and the advantage of adjustability. This will enhance the effectiveness of therapy and minimize side effects. Thus, DBS may offer a degree of hope for patients with severe and treatment-resistant neuropsychiatric illness such as depression and OCD
However more work is needed in the field of DBS for psychiatric symptoms currently.
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