Background: General anesthetics-induced changes of electrical oscillations in the basal ganglia may render the identification of the stimulation targets difficult. The authors hypothesized that while sevoflurane anesthesia entrains coherent lower frequency oscillations, it does not affect the identification of the subthalamic nucleus and clinical outcome.
Methods: A cohort of 19 patients with Parkinson's disease with comparable disability underwent placement of electrodes under either sevoflurane general anesthesia (n = 10) or local anesthesia (n = 9). Microelectrode recordings during targeting were compared for neuronal spiking characteristics and oscillatory dynamics. Clinical outcomes were compared at 5-yr follow-up.
Results: Under sevoflurane anesthesia, subbeta frequency oscillations predominated (general vs. local anesthesia, mean ± SD; delta: 13 ± 7.3% vs. 7.8 ± 4.8%; theta: 8.4 ± 4.1% vs. 3.9 ± 1.6%; alpha: 8.1 ± 4.1% vs. 4.8 ± 1.5%; all P < 0.001). In addition, distinct dorsolateral beta and ventromedial gamma oscillations were detected in the subthalamic nucleus solely in awake surgery (mean ± SD; dorsal vs. ventral beta band power: 20.5 ± 6.6% vs. 15.4 ± 4.3%; P < 0.001). Firing properties of subthalamic neurons did not show significant difference between groups. Clinical outcomes with regard to improvement in motor and psychiatric symptoms and adverse effects were comparable for both groups. Tract numbers of microelectrode recording, active contact coordinates, and stimulation parameters were also equivalent.
Conclusions: Sevoflurane general anesthesia decreased beta-frequency oscillations by inducing coherent lower frequency oscillations, comparable to the pattern seen in the scalp electroencephalogram. Nevertheless, sevoflurane-induced changes in electrical activity patterns did not reduce electrode placement accuracy and clinical effect. These observations suggest that microelectrode-guided deep brain stimulation under sevoflurane anesthesia is a feasible clinical option.