Every procedure or even medical treatment has the potential to offer certain complications or side effects. Deep Brain Stimulation Surgery is perceived as safe but still has its own set of difficulties. The complications can be divided into three categories, complications related to surgery, complications related to hardware, and stimulation-related side effects. There is a concern among many patients about the implant and reactions to the implant. The hardware used for DBS is a very inert material and does not cause any allergic reaction in the body. The pacemakers that are implanted, have been implanted for other purposes, e.g. cardiac causes, for the past 30 to 40 years without giving any major cause of concern. There are no reports that show the risk of rejection of the hardware. Let us examine the associated complications in detail.
1. Surgical Complications
The most common complication is post-operative confusion. It ranges anywhere from 3 to 8% of patients depending on the series that is being examined. Post-operative confusion occurs because of the electrode insertion into the brain. It is more common in elderly patients than in younger patients. Post-operative confusion is temporary. However, it is important to take good care during the period of confusion so that the patient does not end up having any aspiration pneumonia. Usually, the post-operative confusion clears within 2 to 3 days. But in some cases, it can be prolonged up to a week or 10 days also.
The next common complication in surgery is vasovagal attack. This is a transient fainting attack that the patient may experience during the fixation of the surgical frame which is used for localizing the target. Once again, this can be avoided by proper hydration of the patient before surgery and making sure that the patient is explained about the procedure in detail before putting the stereotactic frame on the patient’s head.
The 3rd most common complication is bleeding; depending upon the series examined, it can range from 0.6% to 7%. The risk of bleeding can be minimized by proper planning of the surgery and preparation of the patient. One of the research papers published in the Neuromodulation Journal showed that the risk of bleeding decreased as the surgical team experience improved. The risk of bleeding was high in the first 200 cases, and there was no incidence of bleeding in the last 200 cases in the report.
Post-operative seizure is one of the other complications which is very rarely seen but can occur. There is no way you could prevent this and if it occurs, it is not of significant concern, as it can be controlled with medical management.
2. Hardware Complications
The most common complication in this category is infection. This ranges from 5 to 6% depending on the series of reports examined. No fixed condition causes an increase in infection. However, old-age, frail skin and trauma at the site of the pacemaker are a few of the common causes reported to be associated with infection. Other hardware complications include erosion over the connector site, fracture of the lead, or misplacement or migration of the leads. These complications can be minimized by careful handling of the implants at the time of surgery. It has been shown that the rate of this complication is very low in centers with a high level of expertise.
3. Stimulation-related Complications
These complications are similar to that seen as medication side effects. It means that they are reversible and are part and parcel of stimulation, which also improves patients’ clinical condition. One of the common stimulation-related side effects includes behavioral changes. This occurs because of the motivation of the limbic component of the subthalamic nucleus. This is completely reversible and can be reversed by changing the contact points on the electrode by just moving the stimulation away from the limbic subthalamic nucleus. The other side effect that is seen in approximately 3 to 4% of patients, is depression. Usually, subthalamic nucleus stimulation improves depression in most patients. However, in a select group of patients, it increases depression or brings in de novo depression. If the clinician is aware of this, he will try to control this by again steering away the current from the limbic part of the STN. Patients undergoing DBS of STN for Parkinson’s disease have reported weight gain. This is a welcome thing, as these patients were initially losing weight before the surgery. However in some patients once again this can become a little bothersome and can be avoided by changing the parameters of stimulation. One more complication is related to speech. Many people express deterioration of speech after subthalamic nucleus stimulation. Once again this is due to the current spread and it can be minimized by changing the contact point or altering the programming parameters of the pacemaker to minimize the side effect.
How Common Are Such Complications In DBS?
The incidence of surgical complications is highly diverse in the literature and includes cerebral hemorrhage (0%-10%), stroke (0%-2%), infection (0%-15%), lead erosion without infection (1%-2.5%), lead fracture (0%-15%), lead migration (0%-19%), and mortality (0%-4.4%). There was agreement that the prevalence of symptomatic cerebral hemorrhage is probably less than 2% for most institutions. Lead fracture and migration are probably significantly less common now because of technological advancements. Although there is universal agreement that using perioperative antibiotics is essential, the most frequently reported major surgical complication is hardware infection. However, there is little agreement on how to lower the risk of deep brain stimulation surgery side effects.
Although there aren’t any conclusive facts, it was generally agreed that advanced age and patient comorbidities increase risk, but these factors shouldn’t disqualify anyone from consideration, and in most centers, these have not proved to be a major concern. It was generally agreed that the surgical team’s experience plays a significant role in reducing the risk of surgical problems.