Surgery of Tumors in the Eloquent Cortex

Educational Objectives

The goal of this program is to improve methods of surgery for patients with brain tumors. After hearing and assimilating this program, the clinician will be better able to:

1. Define the eloquent brain cortex and describe the significance of brain tumor location.

2. Distinguish the advantages and disadvantages of awake craniotomy (AC) vs craniotomy under general anesthesia.

3. Assess and evaluate recent pivotal trials of AC.

Summary

Definition of eloquent brain: areas of brain that, if removed or stimulated, result in loss of sensory processing or linguistic ability, weakness, paralysis, or visual change; refers to sensory cortex, motor cortex, language-related areas in temporal and frontal region, hypothalamus, thalamus, internal capsule, and brainstem; damage results in significant neurologic deficit; most neurosurgery literature focused on motor cortex and language-related areas

Significance of tumor location: recent study indicates that, after adjusting for other known prognostic factors, patients with tumors in close proximity to eloquent cortex typically have worse overall outcome and worse progression-free survival (PFS); confirmation of tumor close to eloquent area at time of surgery associated with shorter survival; in contrast, if mapping reveals tumor spared eloquent areas, patients have significantly longer survival

Surgery in eloquent cortex: advances improving understanding of anatomic and functional characteristics of surgical areas to prevent neurologic morbidity; enhanced imaging technologies continue to emerge; new developments in intraoperative techniques allow wider extent of resection and more aggressive approaches to tumors; mapping of motor and language pathways now well-established technology for allowing safe resection of intrinsic tumors

Craniotomy under general anesthesia (GA): image-guidance options — include magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI); neurophysiologic monitoring — choices include intraoperative somatosensory evoked potentials, phase reversal, and cortical stimulation; advantages — patient immobile; easier management of anesthetics, improved ventilation and oxygenation; easier to teach students; disadvantages — operating blindly, potentially causing damage; brain shift may render image-guidance inaccurate; fear of over-resection can lead to less aggressive surgery

Awake craniotomy (AC): imaging — same ability to integrate MRI and DTI technologies; advantages — direct and most accurate feedback comes from patient; can compensate for brain shift with ongoing live monitoring; possibly improved extent of resection by enabling surgeon to feel more confident; possibly improved outcome and survival; disadvantages — not for all patients (must stay calm); even most stoic patients unable to tolerate prolonged awake surgery, requiring surgeons to operate relatively quickly; brain can fungate through craniotomy; patient can develop respiratory problems; not suitable for lesions extending to skull base or involving larger vessels; intraoperative seizures can jeopardize monitoring and patient cooperation, and can interfere with resection

Imaging of eloquent cortex: functional MRI has sensitivity ≈81%, specificity ≈53% in identifying key cortical areas; can integrate DTI and magnetoencephalography; all imaging technologies combined still relatively imprecise; brain shift may change location of tumor or important structures

Extent of resection: greatest risk for tumor recurrence within 2 cm of contrast-enhancing rim on neuroimaging; studies have shown ≤50% chance of encountering tumor cells within 2 cm to 5 cm of tumor edge, and even 10% chance of tumor cells in contralateral side of brain; despite possible residual tumor cells, growing body of evidence suggests extent of resection correlates well with PFS and outcome

Cortical mapping strategies: identification of language and motor areas critical; depolarization of very focal areas of cortex elicits excitatory response within neurons; accuracy approaches 3 mm to 5 mm with modern bipolar stimulators; trend toward smaller incisions, more tailored approach with less exposure of brain; efficiency important, as most awake patients unable to tolerate >2 hr; recent study demonstrates that intraoperative identification of eloquent areas (ie, positive mapping) increases risk of postoperative neurologic deficits; variability in language area location exists between patients; study of temporal lobe resections showed area of language function located as close as 3 cm to temporal tip and as far away as 9 cm; intraoperative cortical and subcortical stimulation essential for precise and safe resection; if distance of resection margin >1 cm from nearest language site, significantly fewer permanent language deficits occur

Anesthesia considerations for AC: experienced anesthesia team crucial; use midazolam for premedication; basic monitoring with arterial line and temperature probe; sedation with propofol at beginning of procedure (so patient does not hear, eg, sound of drill); use lidocaine gel for Foley to minimize potential discomfort; scalp ring block with 1% lidocaine with epinephrine mixed with bupivacaine (Marcaine); have intravenous methohexital or ice-cold saline available in case of seizures; use dexmedetomidine (Precedex) or remifentanil as needed for agitation, but important for patient to stay awake and cooperate

Technique: use lateral position for lesions in language-related areas and supine position for motor cortex lesions; allowing patients to telephone family during surgery often helpful; utilize minimal shaving; typical craniotomy exposing tumor and up to ≈1.5 cm around it; grids placed to locate sensory-motor cortex; cortical mapping started with low stimulus; 10 to 15 areas stimulated and positive sites marked with sterile number; monitor patient throughout with number counting, spontaneous speech, and motor activity

Pivotal studies of AC: large prospective trial in France of AC vs surgery under GA in patients with comparable supratentorial lesions found that in patients with tumors in eloquent cortex, those who underwent AC had significantly better neurologic outcome and quality of resection; MD Anderson study — 309 patients with tumors in or near eloquent cortex; achieved gross total resection in 64% and resection >85% of tumor in 77% of patients; eloquent areas identified in 65% of patients, of whom 21% had worsened neurologic deficits postoperatively, compared to only 9% who had negative mapping; at 1 mo 83% of patients overall showed improved or stable neurologic status, whereas 17% had new or worse deficits; at 3 mo only 7% had persistent deficits; extent of resection <95% also predicted worsening of neurologic status; elderly patients — formerly assumed that older patients unable to tolerate sedation and AC; large study of 334 young patients matched with 90 older patients (average age 71 yr); older patients had significantly more high-grade gliomas and brain metastases, but did not show significantly higher rates of mortality or complications; study demonstrates that AC well tolerated in older patients; psychologic sequelae — small study of 16 patients in Germany showed 44% of patients experienced repetitive distressing recollections and dreams related to AC surgery, similar to post-traumatic stress disorder

Complications: general surgical complications of bleeding, infection, wound healing problems, cosmetic issues, and pain and numbness in incisional area; location-specific complications may also occur, such as problems with speech and understanding, motor deficits, visual problems, and seizures; largest published study of AC (2007) — summarized 610 patients who underwent AC for supratentorial tumors; utilized intraoperative brain mapping in 511 cases; mapping identified positive areas in 22% and no eloquent cortex in 77% of patients; neurologic deficits occurred in 14% (range in literature 5% to >20%); deficits more common in patients with preoperative neurologic deficit or in whom mapping identified eloquent tissue; 5% suffered intraoperative seizures, and 2 required intubation and GA; small percentage developed wound complications or postoperative hematoma

Intraoperative seizures: serious event during AC; in recent study of 477 patients, 12% developed intraoperative seizures; seizures more common in younger patients, patients with tumor in frontal lobe, and patients with history of seizures; irrigate quickly with ice-cold saline until seizure and afterdischarges cease; giving sedation for seizure causes loss of awake examination; important to treat seizure rapidly before it generalizes

Questions and answers: AC and large tumors — speaker cites case of 28-yr-old man with large insular glioma with unexpected vascularity and density, requiring 6-hr surgery with large blood loss; in retrospect, speaker regrets doing as awake case, but patient did well; hyperventilation and mannitol helpful; such cases challenging; age differences in coping with AC — patient dependent; long-term psychologic sequelae unknown and likely underestimated; preoperative neuropsychologic testing — not done in majority of patients because of limited resources

Readings

Disclosures

In adherence to ACCME Standards for Commercial Support, Audio Digest requires all faculty and members of the planning committee to disclose relevant financial relationships within the past 12 months that might create any personal conflicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this lecture, members of the faculty and planning committee reported nothing to disclose.

Acknowledgements

Dr. Siomin spoke at the Second Annual Miami Neuro Symposium, held December 6-7, 2013, in Coral Gables, FL, and sponsored by Baptist Health South Florida, Continuing Medical Education.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

NE051901

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.

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