Deep brain stimulation provides benefit when applied properly and the benefit should persist for decades. Configuring stimulation parameters to optimize benefit while avoiding side effects is paramount to prolonged success and patient satisfaction. Optimal stimulation requires precisely positioned electrodes into a specific location in the brain that is about the size of a pea. Therefore, surgical skill in electrode placement is the first step in success over the lifetime.
Applying adequate stimulation through an excellent positioned electrode is associated with lasting benefit and has less risk of causing symptoms to worsen right after surgery. However, stimulation induced side effects will occur if stimulation is not adjusted properly. Using a less than excellent electrode may lessen side effects but may also lead to less benefit and require more battery power to reach the beneficial areas. Skilled programming adjustments are the second link in success and happiness with DBS. Even well placed electrodes can be rendered ineffective if not programmed properly.
Typical and Reversible Stimulation Side Effects
Well positioned electrodes can cause reversible stimulation induced side effects that can include any of the following signs or symptoms: tingling, numbness, poor coordination, muscle tightness, muscle twitching or contraction, sense of heaviness, speech change, swallowing change, worse walking and balance, vision change, dizziness, nausea, hot flash, anxiety, depression, mania, impulsivity, mental fog, verbal fluency decline, minor shocks or electrical surges, pulsations, coarse tremoring and pain.
The good news is stimulation side effects are reversible by adjusting stimulation settings while maintaining benefit. Side effects do not lead to symptom improvement and therefore should be avoided.
Atypical Reversible and Irreversible Stimulation Side Effects
Poor or inadequate surgical planning or electrode placement can cause poor results and unintended persistent problems after surgery. New or worsening problems with walking, balance, muscle tightness, coordination, speech, mood and cognition can occur and may not be reversible. Applying stimulation using poorly positioned electrodes may cause or worsen these disabling symptoms.
The timeline of events is essential when investigating new or worsening problems after DBS surgery. Patients generally know when their body changed for the worse. If the change happened prior to activating stimulation, the surgical plan and awake intraoperative testing can be analyzed to discover any irregularities that may have led to worsening symptoms. If the change happened after adjusting stimulation, then the stimulation parameters may need further consideration. After the brain has healed from surgery, any decline in symptoms should be investigated and stimulation adjusted if indicated to eliminate side effects.
Stimulation should always work in the right patient with adequate electrode placement and proper stimulation settings. The skills and knowledge of the surgeon and programmer will set the bar for the success of DBS over the lifetime.