Epilepsy Lab Report

ANESTHESIA CONSIDERATIONS IN EPILEPSY SURGERY

INTRODUCTION:
Surgery for epilepsy requires a multidisciplinary approach from the neurosurgeon, the neurophysician, the neurophysiologist and the neuroanesthetist.
Epilepsy surgery poses significant challenges to the neuroanesthetist. The challenges are to provide optimal operating conditions, hemodynamic stability, monitored anesthesia care for awake craniotomy and rapid emergence for neurological assessment as well as avoidance of agents which interfere with intraoperative ECoG and cortical mapping.

PREOPERATIVE EVALUATION.
Many disorders are associated with epilepsy which must be evaluated and optimized preoperatively. Von Recklinghausen’s disease may comprise of intracranial tumor, compromised

Thiopentone and benzodiazepines are potent anticonvulsants1, 7.
Reports about the effects of propofol on ECoG are conflicting. In epileptic patients low doses of propofol activated electrocorticogram and high dose produce burst suppression8.
There has been a report of activation of epileptogenic foci after administering a bolus of propofol (2mg/kg, IV), in patients having history of intractable temporal lobe epilepsy which lasted for upto 7 minutes7.
Numerous studies have shown that propofol is safe for use in epilepsy surgeries.
During emergence from prolonged propofol infusion marked beta activity may obscure the EEG9. It does not interfere with ECoG if stopped 15 minutes prior to recording10.
Etomidate, methohexitol and ketamine can activate EEG activity when administered to patients with epilepsy surgery. These may help to localize the ictal foci. Intravenous ketamine activates either cortical EEG or clinical seizure activity in epileptics when >2 mg/kg is administered. Low bolus dose or infusion of opioids have no effect on spikes. Large bolus doses of synthetic opioids like fentanyl, sufentanil, alfentanil, remifentanil can activate inter-ictal spikes. Morphine has no proconvulsant effect. Meperidine can induce seizures due to its metabolite

General anesthesia
2. Awake craniotomy SURGERY UNDER GENERAL ANESTHESIA.
Identification of epileptogenic zone from which seizures originate and its excision without complications is the primary goal of epilepsy surgery. Anesthetic agents are known to alter ECoG activity and thus the role of anesthesiologist becomes important so that optimal waveforms are obtained for neurologist and neurosurgeon to perform resection. The challenge further lies in avoiding awareness during intraoperative ECoG and motor testing while keeping the influence of anesthetics to a minimum.
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The use of general anesthesia for resection of epileptogenic foci without brain mapping (anterior temporal lobectomy) or ECoG monitoring has similar anesthetic goals as most open craniotomy procedures.
Intraoperative monitoring depends on the type of surgery and extent of resection. Routine monitoring is usually sufficient in a majority of cases.
During cortical mapping or ECoG guided resection depth of anesthesia should be reduced.
Induction can be done with intravenous agents such as propofol and fentanyl. Total intravenous anesthesia using propofol or inhalational agents like isoflurane or desflurane can be safely used for maintenance of anesthesia as they do not show evidence of activation of