Anesthetic Considerations for Awake Craniotomy for Epilepsy ... - Vtr

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246 Erickson & Cole Fig. 1. Open craniotomy showing the cortical surface of a patient with bipolar stimulation using an Ojemann bipolar stimulator while testing appropriate neurologic function in an awake patient. Cortical labels shown include A (arm), F (face), and H (hand). (Courtesy of Fredric B. Meyer, MD.) aids are use to plan a linear trajectory from parietal surface to thalamus or structures near-thalamus, which avoids vasculature and ventricles. Once the styleted electrode lead is in place, microelectrode recordings (MERs) demonstrate changes in spontaneous neuronal firing as the electrode enters different nuclear or thalamic brain tissue. Recordings of both spontaneous neuronal discharge and changes in discharges with patient movement guide lead placement. Macrostimulation then begins and patients are observed for specific symptom amelioration and for adverse effects or unpleasant sensations resulting from stimulation. High-frequency stimulation (above 100 Hz) seems to improve symptoms whereas low frequencies have no effect. 113 The stylet is removed when satisfactory feedback is observed, and the lead is ready for tunneled connection to the pulse generator. Fig. 2. An awake patient is positioned supine in pinion and under surgical drapes awake and is undergoing motor testing of the left upper extremity. (Courtesy of Fredric B. Meyer, MD.)
PATIENT SELECTION AND PREOPERATIVE EVALUATION Epilepsy and Functional Neurosurgery 247 Fig. 3. An awake patient is positioned in a semisitting position with head in a Leksell head frame and under widely spread surgical drapes. A left-sided DBS electrode has been placed via a bur hole, and symptom relief (lack of tremor) is demonstrated in the outstretched right upper extremity during macrostimulation. For either procedure, attention should focus on issues critical for the awake patient, in particular, mental maturity and the airway. Good rapport between patient and anesthesiologist as well as among all members of the operating room team cannot be overemphasized in making the procedure as safe and smooth as possible (Box 2). The importance of selecting motivated, mature patients who are able to cope in a strange and stressful environment for an extended period of time is crucial. 114 Anxiety disorder, low tolerance for pain, or psychiatric disorders, such as schizophrenia, may preclude candidacy because there is little pharmacologic rescue that can be offered to awake patients, with their head fixed with penetrating pins within a stereotactic head holder, who has a psychological crisis, without sacrificing the entire awake technique. Screening may include tests of concentration or personality inventory aimed at discovering traits incompatible with cooperative performance in the operating room. Claustrophobia, if severe, may complicate positioning because usually surgical drapes must hang near the immobilized face and can cause a sense of smothering. Careful draping with a more open access to a patient’s face, or perhaps the intermittent use of cool air blown over the face, may minimize this fearful sensation. 115 Movement disorders may also compromise a motionless surgical field, although one case report describes the use of regional blocks to eliminate involuntary extremity movements in a patient with unilateral spontaneous movements. 116 The airway must also be carefully considered. Ease of mask airway, Mallampati score, intubation history, and other predictors of difficulty with laryngoscopy should be assessed with an eye to potential for obstruction, wheezing, or other compromise. Obesity, gastroesophageal reflux, and chronic cough or wheezing may be contraindications of an awake procedure, depending on severity. Airway factors affect planning
Page 1 and 2: Anesthetic Considerations for Awake
Page 3 and 4: Table 1 Indications and target area
Page 5: Epilepsy and Functional Neurosurger
Page 9 and 10: neurophysiologists, and speech path
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Page 15 and 16: Dexmedetomidine infusion without lo
Page 17 and 18: for DBS insertion, however, venous

Anesthetic Considerations for Awake Craniotomy for Epilepsy ... - Vtr

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