Case history:
We present a case of a 49 year old gentleman with a history of Parkinson’s disease and Writer’s cramp who had been prepared for DBS surgery. Subthalamic nucleus (STN) was targeted. Under stereotactic conditions, the procedure was started under local anesthesia with mild sedation. However, the patient became restless at this stage, and the procedure was converted to general anesthesia (GA). A Bi-spectral index (BIS) monitor was applied along with routine monitors. MER signals were obtained after anesthesia was tapered to obtain a BIS value of 60 on one side. The microelectrode recordings (MER) obtained was acceptable. On other side too, at a BIS value of 80-85, better MER signals were obtained.
Discussion:
To obtain optimal results from STN–DBS electrodes and avoid adverse effects, determining the accurate location of the surgical target is crucial. Concerns exist about the possible influence of anesthesia on testing and MER signals. MER results obtained during varying BIS values in the same patient revealed that in a higher BIS value, good MER signals were obtained closer to the target STN than during a lower BIS value state of the patient. Hemodynamic stability was maintained. Our case report support that during GA, MER signals are more accurate with a higher BIS value. Hence, it depends on the anesthesiologist to maintain an adequate degree of awakening in the patient under general anesthesia to help achieve optimal surgical results of targeting the STN, which was the purpose of this case report.