Preoperative Work-up

• Extensive evaluation by the epilepsy neurology team usually involving detailed seizure and medication history, inpatient video-electroencephalogram (EEG) monitoring with recording of some seizures, neuropsychologic evaluation, magnetic resonance imaging, and other tests in specific cases (e.g., intracarotid amobarbital [Wada] test, magnetoencephalograph, single photon emission computed tomography, positron emission tomography) to determine both lateralization and intrahemispheric localization of seizure onset.
  
• In case of discordant or unclear findings, preoperative evaluation will also include invasive intracranial EEG recording (e.g., subdural strips and/or grids ± depth electrodes).
  
• Concordance of EEG and imaging findings implicating temporal lobe pathology portends better postoperative seizure-free outcome.
  
• Anticonvulsant medications are often tapered preoperatively to facilitate preoperative evaluation or if intraoperative recording is performed.

Anesthetic Issues

• Standard general anesthesia is most commonly used.
  
• Some centers employ awake craniotomy (especially for dominant temporal lobectomy) for two reasons:
  
  
  
  • The need to perform intraoperative functional cortical mapping
    
  • The desire to minimize drug-induced interference with intraoperative electrocorticography
  
  
• In such cases, the surgeon will be called upon to perform a scalp block with local anesthetic as well as dural infiltration as needed during the procedure.

• Standard scalp incision is a curvilinear or “question mark” shape extending from the superior border of the zygomatic arch just in front of the tragus above the auricle then superiorly and anteriorly to the hairline; this spares the frontalis branch of the facial nerve and can also be performed so as to preserve the superficial temporal artery.
  
• The temporalis muscle is incised and reflected inferiorly leaving an appropriate cuff, or may be elevated together with the skin as a musculocutaneous flap.
  
• A standard temporal craniotomy is fashioned to expose the superior temporal gyrus (STG) and middle temporal gyrus (MTG), with the superior margin 1 cm above the sylvian fissure (more frontal lobe is exposed if intraoperative electrocorticography will be performed).
  
• The inferior and anterior margins of the craniotomy are rongeured to reach the floor of the middle fossa and temporal pole.
  
• The dura is opened and reflected anteriorly.

Lateral Neocortical Removal

• The length of resection from the temporal pole (e.g., ~4.5 cm on the dominant side, ~5.5 cm on the nondominant side) is measured with a Cushing needle or other measuring device.
  
• The pia of the STG parallel to the sylvian fissure is coagulated, and also perpendicularly at the posterior resection margin down to the floor of the middle fossa
  
• The plane between the STG and the sylvian fissure is dissected subpially with a Penfield dissector or with the ultrasonic aspirator, protecting the middle cerebral artery (MCA) and its candelabra; this subpial dissection is carried down to the uncus inferomedially.
  
• Next step is identification of the ventricle, done by incising the temporal stem at the inferior Circular sulcus in the proper trajectory; an incision too medial may result in injury to the optic tract (producing a hemianopsia); an incision too lateral will result in missing the ventricle and arriving at the cortex over the floor of the middle fossa.
  
• Entry into the ventricle is confirmed by the appearance of bluish ependyma, choroid plexus, CSF, and/or view of the ventricular surface of the hippocampus.
  
• Disconnection of the neocortical block can be completed: first, a disconnection line is fashioned slightly oblique from the inferior circular sulcus and extended basally just lateral to the ventricle; second, dissection down to the arachnoid deep to the lateral neocortical gyri is accomplished with the ultrasonic aspirator to approximately the level of the collateral sulcus; third, the posterior margin of the neocortical incision can then be extended to join with the prior disconnection to the ventricle; lastly, the remaining arachnoid attachments of the neocortical block are cut, and it can be removed.

Mesial Resection

Dural Opening, Sylvian Fissure Dissection, and Entry into the Temporal Horn

• The dura is opened in semicircular fashion and reflected across the sphenoid ridge and orbit
  
• For transsylvian approach, the Sylvian fissure is opened from the carotid bifurcation through the MCA bifurcation and ~2.5 cm more distally, exposing the ascending M1 branch, the limen insulae, the anterior third of the insular cortex and associated M2 branches, and the mesial surface of the uncus and temporal pole. The positions of the lateral M2 branches–including temporopolar and anterior temporal arteries–are noted. The inferior circular sulcus is identified, which separates the temporal operculum from the insular cortex.
  
• An incision into the anterior temporal stem is made reaching back ~15 mm from the level of the limen insulae; opening of the temporal horn posteriorly is accomplished by carrying this incision ~12 to 15 mm down to the roof of the ventricle.
  
• Alternatively, the temporal horn may be found anteriorly after emptying the uncus and carrying the resection more posterior until the tip of the temporal horn is entered.
  
• For transcortical approach, the temporal horn may be entered via the MTG or by first opening the superior or middle temporal sulcus.
  
• A subtemporal approach to the lateral ventricle for SAH is another option.

Mesial Resection

• Patient brought to the intensive care unit and extubated when fully awake
  
• Resumption of preoperative anticonvulsant doses (or per epilepsy neurology service)
  
• Patient is monitored for seizures with attention to known preoperative semiology