Intracerebral microdialysis during deep brain stimulation surgery.
BACKGROUND
This report describes the use of microdialysis in conjunction with deep brain stimulation (DBS) surgery to assess extracellular levels of neurotransmitters within the human basal ganglia (BG). Electrical stimulation of the subthalamic nucleus (STN) is an efficacious treatment for advanced Parkinson's disease, yet the mechanisms of STN DBS remain poorly understood. Measurement of neurotransmitter levels within the BG may provide insight into mechanisms of DBS, but such an approach presents technical challenges.


METHODS
After microelectrode recordings confirmed location of STN, a custom microdialysis guide cannula was inserted. A CMA (Stockholm, Sweden) microdialysis probe was then positioned to the same depth as the microrecording electrode in STN or 2mm inferiorly to record in the substantia nigra. The catheter was perfused at a rate of 2.0 microL/min with a sterile mock CSF solution and samples of extracellular fluid were collected at regular intervals. Dialysate samples were analyzed using high-pressure liquid chromatography (HPLC) detection procedures for quantitation of glutamate, gamma-aminobutyric acid (GABA), and dopamine.


RESULTS
Levels of neurotransmitters were reliably identified in dialysate samples using HPLC. By monitoring concentrations of glutamate, GABA and dopamine, we were able to demonstrate what seemed to be a steady state baseline within approximately 30 min.


CONCLUSIONS
Microdialysis during DBS surgery is a feasible method for assessing levels of glutamate, GABA and dopamine within the human BG. Obtaining a steady state baseline of neurotransmitter levels appears feasible, thus making future studies of intraoperative microdialysis during DBS meaningful.
Kilpatrick
Michaux
M
Department of Neurological Surgery, Gaston Memorial Hospital, Gastonia, NC, USA.
Church
Ephraim
E
Danish
Shabbar
S
Stiefel
Michael
M
Jaggi
Jurg
J
Halpern
Casey
C
Kerr
Marie
M
Maloney
Eileen
E
Robinson
Michael
M
Lucki
Irwin
I
Krizman-Grenda
Elizabeth
E
Baltuch
Gordon
G
D002404:Catheterization; D002851:Chromatography, High Pressure Liquid; D046690:Deep Brain Stimulation; D004298:Dopamine / Q000378:metabolism; D045604:Extracellular Fluid / Q000378:metabolism; D005240:Feasibility Studies; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D017551:Microdialysis / Q000295:instrumentation / Q000379:methods*; D008839:Microelectrodes; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods*; D019635:Neurosurgical Procedures / Q000295:instrumentation / Q000379:methods*; D013378:Substantia Nigra / Q000378:metabolism*; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D004298:Dopamine