Deep Brain Stimulation (DBS) is a neurosurgical procedure involving the implantation of a medical device, similar to a pacemaker, to deliver controlled electrical impulses to specific brain targets. This therapy manages disabling motor symptoms associated with movement disorders, such as Parkinson’s disease, essential tremor, and dystonia, when medication is ineffective or causes problematic side effects. DBS works by modulating abnormal electrical signals, often resulting in significant symptomatic improvement. However, as an invasive brain surgery, DBS carries potential risks and complications that prospective patients should understand.
Immediate Surgical Complications
The immediate risks of DBS are tied to the physical act of brain surgery and the insertion of electrode leads. These complications are infrequent but can be severe, occurring during or shortly after the operation. The primary acute risk is intracranial hemorrhage, or bleeding in the brain, which occurs if the electrode trajectory encounters a blood vessel.
Symptomatic hemorrhages, causing observable neurological deficits, are reported in 0.5% to 2% of cases. This bleeding can lead to a stroke, causing weakness, sensory loss, or other neurological problems, and is the most common cause of morbidity related to the surgery. Infection is another serious concern, with risks ranging from 1% to 5% at the incision site or within the brain. Infections often require prolonged antibiotics and the complete removal of the implanted hardware. General surgical risks, such as adverse reactions to anesthesia, seizures, or temporary confusion, are also possible postoperatively.
Hardware and Device-Related Issues
Complications can arise from the physical components of the DBS system, including the electrodes (leads), the extension wire, and the Implantable Pulse Generator (IPG) or battery pack. These hardware issues can manifest months or years after implantation, with overall rates reported between 5% and 20% long-term.
Mechanical Issues
One common issue is lead migration, where the electrode shifts from its optimal position, reducing the therapeutic effect or inducing side effects. Mechanical failure, such as a fracture or breakage of the lead or extension wire, interrupts the electrical signal and requires surgical replacement.
Skin and Battery Issues
The skin overlying the hardware, particularly the IPG, can become thin or eroded, increasing the risk of infection and potentially exposing the device. Furthermore, the IPG battery life is finite, requiring an additional, less invasive surgery for replacement when the charge depletes. This recurring procedure is necessary for the long-term continuation of the therapy.
Stimulation-Induced Adverse Effects
The most common side effects are those directly caused by the electrical current delivered to the brain, known as stimulation-induced adverse effects. These effects depend highly on the precise location and intensity of the stimulation, as the current can spread to unintended nearby neural pathways. Adjustments to the stimulation settings can often eliminate these unwanted movements.
Motor and Speech Effects
Motor symptoms are frequently observed, such as involuntary muscle contractions (tonic contractions) or the worsening of existing movement issues like dyskinesia, often occurring if the stimulation amplitude is too high. Speech difficulties, particularly dysarthria or slurred speech, are common, especially with bilateral stimulation in certain brain targets. The current can affect corticobulbar fibers involved in speech control, leading to reduced clarity or volume.
Sensory and Neuropsychiatric Effects
Sensory changes, such as paresthesia (a feeling of tingling or numbness in the limbs or face), can occur if the electrical field reaches adjacent sensory pathways. Neuropsychiatric effects are also recognized, including changes in mood, such as the development or worsening of depression or anxiety, and alterations in impulse control or behavior. Cognitive changes, such as problems with memory or word-finding, may also emerge. Importantly, these stimulation-induced side effects are almost always reversible and manageable by adjusting the device parameters.
Management and Resolution Strategies
The resolution of DBS side effects relies on a collaborative, multidisciplinary approach involving the neurosurgeon, neurologist, and programmer. For stimulation-induced effects, the first intervention is reprogramming the IPG settings. This non-invasive adjustment involves altering parameters like voltage, frequency, or pulse width, or changing the active electrode contact to reshape the electrical field. Newer technologies, such as directional leads, allow for more precise steering of the current, reducing the likelihood of stimulating unwanted areas.
If the problem relates to implanted hardware, such as a lead fracture, migration, or erosion, surgical intervention is necessary. A migrated lead may require revision surgery to reposition it, while mechanical failure or severe infection necessitates removal and replacement of the affected component. For cognitive or mood changes, medication adjustments (to existing Parkinson’s or psychiatric drugs) are often made alongside device reprogramming. The goal of this ongoing management is to find the optimal balance between maximum symptom control and minimal side effects.