Preoperative assessment of eloquence in neurosurgery: a systematic review

BACKGROUND AND OBJECTIVES

Tumor location and eloquence are two crucial preoperative factors when deciding on the optimal treatment choice in glioma management. Consensus is currently lacking regarding the preoperative assessment and definition of eloquent areas. This systematic review aims to evaluate the existing definitions and assessment methods of eloquent areas that are used in current clinical practice.

METHODS

A computer-aided search of Embase, Medline (OvidSP), and Google Scholar was performed to identify relevant studies. This review includes articles describing preoperative definitions of eloquence in the study's Methods section. These definitions were compared and categorized by anatomical structure. Additionally, various techniques to preoperatively assess tumor eloquence were extracted, along with their benefits, drawbacks and ease of use.

RESULTS

This review covers 98 articles including 12,714 participants. Evaluation of these studies indicated considerable variability in defining eloquence. Categorization of these definitions yielded a list of 32 brain regions that were considered eloquent. The most commonly used methods to preoperatively determine tumor eloquence were anatomical classification systems and structural MRI, followed by DTI-FT, functional MRI and nTMS.

CONCLUSIONS

There were major differences in the definitions and assessment methods of eloquence, and none of them proved to be satisfactory to express eloquence as an objective, quantifiable, preoperative factor to use in glioma decision making. Therefore, we propose the development of a novel, objective, reliable, preoperative classification system to assess eloquence. This should in the future aid neurosurgeons in their preoperative decision making to facilitate personalized treatment paradigms and to improve surgical outcomes.

A Preoperative Scoring System to Predict Function-Based Resection Limitation Due to Insufficient Participation During Awake Surgery

BACKGROUND

Failure in achieving a function-based resection related to the insufficient patient's participation is a drawback of awake surgery.

OBJECTIVE

To assess preoperative parameters predicting the risk of patient insufficient intraoperative cooperation leading to the arrest of the awake resection.

METHODS

Observational, retrospective, multicentric cohort analysis enrolling 384 (experimental dataset) and 100 (external validation dataset) awake surgeries.

RESULTS

In the experimental data set, an insufficient intraoperative cooperation occurred in 20/384 patients (5.2%), leading to awake surgery failure in 3/384 patients (ie, no resection, 0.8%), and precluded the achievement of the function-based resection in 17/384 patients (ie, resection limitation, 4.4%). The insufficient intraoperative cooperation significantly reduced the resection rates (55.0% vs 94.0%, P < .001) and precluded a supratotal resection (0% vs 11.3%, P = .017). Seventy years or older, uncontrolled epileptic seizures, previous oncological treatment, hyperperfusion on MRI, and mass effect on midline were independent predictors of insufficient cooperation during awake surgery ( P < .05). An Awake Surgery Insufficient Cooperation score was then assessed: 96.9% of patients (n = 343/354) with a score ≤2 presented a good intraoperative cooperation, while only 70.0% of patients (n = 21/30) with a score >2 presented a good intraoperative cooperation. In the experimental data set, similar date were found: 98.9% of patients (n = 98/99) with a score ≤2 presented a good cooperation, while 0% of patients (n = 0/1) with a score >2 presented a good cooperation.

CONCLUSION

Function-based resection under awake conditions can be safely performed with a low rate of insufficient patient intraoperative cooperation. The risk can be assessed preoperatively by a careful patient selection.

Atlas of Nervous System Vascular Malformations: A Systematic Review

Vascular malformations are frequent in the head and neck region, affecting the nervous system. The wide range of therapeutic approaches demand the correct anatomical, morphological, and functional characterization of these lesions supported by imaging. Using a systematic search protocol in PubMed, Google Scholar, Ebsco, Redalyc, and SciELO, the authors extracted clinical studies, review articles, book chapters, and case reports that provided information about vascular cerebral malformations, in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 385,614 articles were grouped; using the inclusion and exclusion criteria, three of the authors independently selected 51 articles about five vascular cerebral malformations: venous malformation, brain capillary telangiectasia, brain cavernous angiomas, arteriovenous malformation, and leptomeningeal angiomatosis as part of Sturge–Weber syndrome. We described the next topics—“definition”, “etiology”, “pathophysiology”, and “treatment”—with a focus on the relationship with the imaging approach. We concluded that the correct anatomical, morphological, and functional characterization of cerebral vascular malformations by means of various imaging studies is highly relevant in determining the therapeutic approach, and that new lines of therapeutic approaches continue to depend on the imaging evaluation of these lesions.

Impacting the Treatment of Highly Eloquent Supratentorial Cerebral Cavernous Malformations by Noninvasive Functional Mapping-An Observational Cohort Study

BACKGROUND

Cerebral cavernous malformations (CCM) may cause cavernoma-related epilepsy (CRE) and intracranial hemorrhage (ICH). Functional mapping has shown its usefulness during the resection of eloquent lesions including the treatment of brain arteriovenous malformations.

OBJECTIVE

To evaluate the impact of noninvasive functional mapping on decision-making and resection of eloquently located CCM.

METHODS

Of 126 patients with intracranial cavernomas, we prospectively included 40 consecutive patients (31.7%) with highly eloquent CCM between 2012 and 2020. We performed functional mapping via navigated transcranial magnetic stimulation (nTMS) motor mapping in 30 cases and nTMS language mapping in 20 cases. Twenty patients suffered from CRE. CCM caused ICH in 18 cases.

RESULTS

We used functional mapping data including function-based tractography in all cases. Indication toward (31 cases) or against (9 cases) CCM resection was influenced by noninvasive functional mapping in 36 cases (90%). We resected CCMs in 24 cases, and 7 patients refused the recommendation for surgery. In 19 and 4 cases, we used additional intraoperative neuromonitoring and awake craniotomy, respectively. Patients suffered from transient postoperative motor or language deficits in 2 and 2 cases, respectively. No patient suffered from permanent deficits. After 1 yr of follow-up, anti-epileptic drugs could be discontinued in all patients who underwent surgery but 1 patient.

CONCLUSION

Surgery-related deficit rates are low even for highly eloquent CCM and seizure outcome is excellent. The present results show that noninvasive functional mapping and function-based tractography is a useful tool for the decision-making process and during microsurgical resection of eloquently located CCM.

Intraoperative brain mapping during awake surgery in symptomatic supratentorial cavernomas

BACKGROUND

Complete resection of symptomatic supratentorial cavernoma (SCA) and removal of the surrounding gliotic area is recommended to minimize the risk of persistent seizures or (re)bleeding. Surgery of SCA located in an eloquent area, can carry out severe postoperative neurological morbidity. We report a study aimed to assess feasibility, extent of resection and outcome after surgical removal of CA by cortico-subcortical intraoperative brain stimulation (ioBS) in the awake patient.

METHODS

Six patients diagnosed of symptomatic SCA located on an eloquent area and operated on while awake under local anaesthesia ioBS, were included. Preoperative planning included neuropsychologic assessment of language-related functions, sociocognitive functions and executive functions. Intraoperatively, we recorded the results achieved in the planned neuropsychological tasks when stimulation was applied (cortical and subcortical). Postoperative control 3D MRI was scheduled at 1 month after surgery to calculate extent of resection. Neuropsychological assessment at 6 months after surgery was performed in all cases.

RESULTS

Six patients (5 females, 1 male) aged 24-48 years were included in our study. Locations of the lesions were right insular (n=1), left insular (n=1), left temporo-insular (n=1), left temporal (n=2) and left frontal (n=1). In all patients, positive findings were obtained during ioBS. In 5 patients, complete surgical resection was achieved. Two patients had postoperative transient neurological deficits, one case of hemiparesis, one case of dysnomia, both cleared over a 6-month period. Clinical follow-up revealed that all patients experienced complete recovery from preoperative symptoms within a year and five patients with seizures showed marked improvement and eventually quit antiepileptic drugs. Neuropsychological assessment at 6 months provided normal results compared to preoperative baseline in all domains.

CONCLUSIONS

Our study suggests that ioBS in the awake surgery of symptomatic SCA located in eloquent areas, allows to increase the rate of complete resection, minimizing postoperative neurological and neuropsychological deficit, and improving postoperative seizures control.

Reactive astrocytes contribute to epileptogenesis in patients with cavernous angioma

OBJECTIVE

Patients with cavernous angioma (CA) often suffer from severe epilepsy, and surgical resection is often performed to attenuate these epileptic seizures. Several studies have suggested that surgical removal of the surrounding hemosiderin-pigmented tissues adjacent to CA achieves better seizure control than restricted lesionectomy. Pathological examination of the resected foci reveals not only hemosiderin pigmentation but also various degrees of inflammatory change, such as hemosiderin-laden macrophages, gliosis and fibrosis. However, there is some controversy regarding the epileptogenic potential of these regions due to the uncertain nature of the mechanisms contributing to these histopathological changes.

METHODS

To investigate the correlations between neuron hyperexcitability and evident pathological changes, we performed ex vivo flavoprotein fluorescence imaging using surgically resected epileptogenic foci surrounding CA. The mirror surfaces of the tissues used for the physiological experiment were also subjected to morphological examination.

RESULTS

Hemosiderin-laden macrophages and many gemistocytic astrocytes were observed in the area adjacent to CA, where horizontal spreading excitations were detected significantly more frequently. Outside these areas, we found fine granular iron deposits and only a few fibrillary astrocytes, and weakly propagating excitations were detected. Furthermore, areas of enhanced activation were more clearly correlated with the glial proliferation index than with iron deposition.

CONCLUSION

These results suggest that the epileptogenesis in patients with CA may be based on a biological process, such as alteration of glial function, rather than direct chemical reactions involving iron deposition.

Cavernoma-related epilepsy in cavernous malformations located within the temporal lobe: surgical management and seizure outcome

OBJECTIVE

Cavernoma-related epilepsy (CRE) is a frequent symptom in patients with cerebral cavernous malformations (CCMs). Reports on surgical management and seizure outcome of epileptogenic CCM often focus on intracranial cavernoma in general. Therefore, data on CCMs within the temporal lobe are scarce. The authors therefore analyzed their institutional data.

METHODS

From 2003 to 2018, 52 patients suffering from CCMs located within the temporal lobe underwent surgery for CRE at University Hospital Bonn. Information on patient characteristics, preoperative seizure history, preoperative evaluation, surgical strategies, postoperative complications, and seizure outcome was assessed and further analyzed. Seizure outcome was assessed 12 months after surgery according to the International League Against Epilepsy (ILAE) classification and stratified into favorable (ILAE class I) versus unfavorable (ILAE classes II-VI).

RESULTS

Overall, 47 (90%) of 52 patients with CCMs located in the temporal lobe and CRE achieved favorable seizure outcome. Pure lesionectomy was performed in 5 patients, extended lesionectomy with resection of the hemosiderin rim in 38 patients, and anterior temporal lobectomy in 9 patients with temporal lobe CCM. Specifically, 36 patients (69%) suffered from drug-resistant epilepsy (DRE), 3 patients (6%) from chronic CRE, and 13 patients (25%) sustained sporadic CRE. In patients with DRE, favorable seizure outcome was achieved in 32 (89%) of 36 patients. Patients with DRE were significantly older than patients with CCM-associated chronic or sporadic seizures (p = 0.02). Furthermore, patients with DRE more often underwent additional amygdalohippocampectomy following the recommendation of presurgical epileptological evaluation.

CONCLUSIONS

Favorable seizure outcome is achievable in a substantial number of patients with epileptogenic CCM located in the temporal lobe, even if patients suffered from drug-resistant CRE. For adequate counseling and monitoring, patients with CRE should undergo a thorough pre- and postsurgical evaluation in dedicated epilepsy surgery programs.

Intraoperative brain mapping during awake surgery in symptomatic supratentorial cavernomas

BACKGROUND

Complete resection of symptomatic supratentorial cavernoma (SCA) and removal of the surrounding gliotic area is recommended to minimize the risk of persistent seizures or (re)bleeding. Surgery of SCA located in an eloquent area, can carry out severe postoperative neurological morbidity. We report a study aimed to assess feasibility, extent of resection and outcome after surgical removal of CA by cortico-subcortical intraoperative brain stimulation (ioBS) in the awake patient.

METHODS

Six patients diagnosed of symptomatic SCA located on an eloquent area and operated on while awake under local anaesthesia ioBS, were included. Preoperative planning included neuropsychologic assessment of language-related functions, sociocognitive functions and executive functions. Intraoperatively, we recorded the results achieved in the planned neuropsychological tasks when stimulation was applied (cortical and subcortical). Postoperative control 3D MRI was scheduled at 1 month after surgery to calculate extent of resection. Neuropsychological assessment at 6 months after surgery was performed in all cases.

RESULTS

Six patients (5 females, 1 male) aged 24-48 years were included in our study. Locations of the lesions were right insular (n=1), left insular (n=1), left temporo-insular (n=1), left temporal (n=2) and left frontal (n=1). In all patients, positive findings were obtained during ioBS. In 5 patients, complete surgical resection was achieved. Two patients had postoperative transient neurological deficits, one case of hemiparesis, one case of dysnomia, both cleared over a 6-month period. Clinical follow-up revealed that all patients experienced complete recovery from preoperative symptoms within a year and five patients with seizures showed marked improvement and eventually quit antiepileptic drugs. Neuropsychological assessment at 6 months provided normal results compared to preoperative baseline in all domains.

CONCLUSIONS

Our study suggests that ioBS in the awake surgery of symptomatic SCA located in eloquent areas, allows to increase the rate of complete resection, minimizing postoperative neurological and neuropsychological deficit, and improving postoperative seizures control.