Intraoperative Electrostimulation Research Articles

The third branch of the superior longitudinal system.

One of the major associative fiber pathways in the brain is the superior longitudinal system. This review discusses the current knowledge gained from studies on the third branch of the superior longitudinal system (SLS) regarding its anatomy, functional role in healthy individuals, results from lesion-symptom mapping studies and intraoperative electrostimulation studies. The results of these studies clearly indicate that the third branch of the SLS is a distinct pathway, as seen both from a functional and anatomical perspective. The third branch of the SLS should be distinguished from the long segment of the arcuate fasciculus, that courses along its trajectory but seems implicated in different functions. Moreover, these studies also provide substantial evidence that the right and left third branch of the SLS have different functional roles. Finally, a hypothesis for an integrated anatomo-functional model is proposed, that describes three subcomponents of the third branch of the superior longitudinal system.

Comparison of Diffusion Signal Models for Fiber Tractography in Eloquent Glioma Surgery–Determination of Accuracy Under Awake Craniotomy Conditions

Fiber tractography (FT) has become an important noninvasive tool to ensure maximal safe tumor resection in eloquent glioma surgery. Intraoperatively applied FT is still predominantly based on diffusion tensor imaging (DTI). However, reconstruction schemes of high angular resolution diffusion imaging data for high-resolution FT (HRFT) are gaining increasing attention. The aim of this prospective study was to compare the accuracy of sophisticated HRFT models compared with DTI-FT. Ten patients with eloquent gliomas underwent surgery under awake craniotomy conditions. The localization of acquisition points, representing deteriorations during intraoperative electrostimulation (IOM) and neuropsychological mapping, were documented. The offsets of acquisition points to the respective fiber bundle were calculated. Probabilistic Q-ball imaging (QBI) and constrained spherical deconvolution (CSD)-FT were compared with DTI-FT for the major language-associated fiber bundles (superior longitudinal fasciculus [SLF] II-IV, inferior fronto-occipital fasciculus, and inferior longitudinal fasciculus/medial longitudinal fasciculus). Among 186 offset values, 46% were located closer than 10 mm to the estimated fiber bundle (CSD, 36%; DTI, 40% and QBI, 60%). Moreover, only 10 offsets were further away than 30 mm (5%). Lowest mean minimum offsets (SLF, 7.7 ± 7.9 mm; inferior fronto-occipital fasciculus, 12.7 ± 8.3 mm; inferior longitudinal fasciculus/medial longitudinal fasciculus, 17.7 ± 6.7 mm) were found for QBI, indicating a significant advantage compared with CSD or DTI (P < 0.001), respectively. No significant differences were found between CSD-FT and DTI-FT offsets (P= 0.105), albeit for the compound SLF exclusively (P < 0.001). Comparing HRFT techniques QBI and CSD with DTI, QBI delivered significantly better results with lowest offsets and good correlation to IOM results. Besides, QBI-FT was feasible for neurosurgical preoperative and intraoperative applications. Our findings suggest that a combined approach of QBI-FT and IOM under awake craniotomy is considerable for best preservation of neurological function in the presented setting. Overall, the implementation of selected HRFT models into neuronavigation systems seems to be a promising tool in glioma surgery.

Intraoperative electrostimulation for awake brain mapping: how many positive interference responses are required for reliability?

The purpose of this study was to characterize the reproducibility of language trials within and between brain mapping sessions. Brain mapping and baseline testing data from 200 adult patients who underwent resection of left-hemisphere tumors were evaluated. Data from 11 additional patients who underwent a second resection for recurrence were analyzed separately to investigate reproducibility over time. In all cases, a specific protocol of electrostimulation brain mapping with a controlled naming task was used to detect language areas, and the results were statistically compared with preoperative and intraoperative baseline naming error rates. All patients had normal preoperative error rates, controlled for educational level and age (mean 8.92%, range 0%-16.25%). Intraoperative baseline error rates within the normal range were highly correlated with preoperative ones (r = 0.74, p < 10-10), although intraoperative rates were usually higher (mean 13.30%, range 0%-26.67%). Initially, 3 electrostimulation trials were performed in each cortical area. If 2 of 3 trials showed language interference, 1 or 2 additional trials were performed (depending on results). In the main group of 200 patients, there were 82 single interferences (i.e., positive results in 1 of 3 trials), 227 double interferences (2/3), and 312 full interferences (3/3). Binomial statistics revealed that full interferences were statistically significant (vs intraoperative baseline) in 92.7% of patients, while double interferences were significant only in 38.5% of patients, those with the lowest error rates. On further testing, one-third of the 2/3 trials became 2/4 trials, which was significant in only one-quarter of patients. Double interference could be considered significant for most patients (> 90%) when confirmed by 2 subsequent positive trials (4/5). In the 11 patients who were operated on twice, only 26% of areas that tested positive in the initial operation tested positive in the second and showed the same type of interference and the same current threshold (i.e., met all 3 criteria). Electrostimulation trials in awake brain mapping produced graded patterns of positive reproducibility levels, and their significance varied with the baseline error rates. The results suggest that caution is warranted when 2 of 3 trials are positive, although the need for additional trials depends on the individual patients' baseline error rates. Reproducibility issues should be considered in the interpretation of data from awake brain mapping.

New insights into the neural network mediating reading processes provided by cortico-subcortical electrical mapping.

To ascertain the neural network mediating reading using intraoperative electrostimulation. A cortical and axonal intraoperative electrical mapping of reading processes was achieved in seven patients who underwent awake surgery for a left occipitotemporal glioma. We performed resection cavity overlapping and superimposition with a diffusion tensor imaging-based white matter atlas. We assessed the relationship between the location of resection cavities and the occurrence of reading impairments of regular, irregular, and pseudowords. Intraoperative stimulation of the left posterior inferior temporal cortex (ITCp) elicited reading disturbances. Subcortical stimulation at the anterior portion of the visual word form area (VWFA) induced addressed phonology (irregular words reading) disturbances. Subcortical stimulation of the connection between VWFA and the posterior segment of the arcuate fascicle (AFp) induced both addressed and assembled phonology (irregular and pseudowords reading) disturbances. Postoperative assessment showed that resection of the posterior portion of the inferior longitudinal fascicle (ILFp), connecting the visual cortex to VWFA, induced long-term and global reading impairment. Resection of the terminations of left AFp in the ITCp-induced irregular and pseudowords reading disturbances with no impairment of regular words reading. Resection of the anterior portion of ILF did not induce reading impairment. Our data support an inner posterior-to-anterior hierarchical coding of letter strings in the VWFA and a crucial role of the left ILFp to provide visual inputs to the VWFA. Furthermore, we suggest that the AFp is involved in an interactive feedback system between visual and nonvisual information, recruited when reading irregular and pseudowords.

Segmental anatomy of the vastus lateralis: guidelines for muscle-sparing flap harvest.

The vastus lateralis muscle is a versatile donor site for pedicled and free flaps that, despite great potential, remains unpopular. Although the muscle is classically described as a single belly, evidence exists for a more complex morphology. The aim of this study was to investigate the segmental anatomy of the vastus lateralis muscle and the feasibility of selective flap harvest. Ten cadaveric lower limbs were investigated. Muscular partitions were identified according to morphologic architecture, vascular supply, and nerve supply; guidelines for selective flap harvest were described. Twenty-three segmental vastus lateralis (n = 14) or chimeric anterolateral thigh-vastus lateralis flaps (n = 9) were raised based on neurovascular segmental supply, and used as noninnervated free flaps for reconstruction of moderate and large defects of the head and neck, trunk, or lower limbs. Intraoperative electrostimulation was used to confirm segmental innervation. Lower limb function was evaluated through the Lower Extremity Functional Scale. The authors clearly identified three anatomical partitions, which receive a constant segmental neurovascular supply, and two aponeuroses. The authors successfully applied the proposed guidelines for flap harvesting to all 23 patients. Intraoperative electrostimulation confirmed functional integrity of both the flap and the spared partitions. All muscle flaps survived. Donor-site morbidity was negligible, with comparable mean preoperative and postoperative Lower Extremity Functional Scale values (67.7 versus 67.4; p > 0.05). This study provides detailed knowledge on the morphologic and neurovascular anatomy of the vastus lateralis muscle, which supports the authors' guidelines for selective flap harvesting. The technique described is safe and minimizes surgical damage.

Awake mapping for low-grade gliomas involving the left sagittal stratum: anatomofunctional and surgical considerations

Preserving function while optimizing the extent of resection is the main goal in surgery for diffuse low-grade glioma (DLGG). This is particularly relevant for DLGG involving the sagittal stratum (SS), where damage can have severe consequences. Indeed, this structure is a major crossroad in which several important fascicles run. Thus, its complex functional anatomy is still poorly understood. Subcortical electrical stimulation during awake surgery provides a unique opportunity to investigate white matter pathways. This study reports the findings on anatomofunctional correlations evoked by stimulation during resection for gliomas involving the left SS. Surgical outcomes are also detailed. The authors performed a review of patients who underwent awake surgery for histopathologically confirmed WHO Grade II glioma involving the left SS in the neurosurgery department between August 2008 and August 2012. Information regarding clinicoradiological features, surgical procedures, and outcomes was collected and analyzed. Intraoperative electrostimulation was used to map the eloquent structures within the SS. Eight consecutive patients were included in this study. There were 6 men and 2 women, whose mean age was 41.7 years (range 32-61 years). Diagnosis was made because of seizures in 7 cases and slight language disorders in 1 case. After cortical mapping, subcortical stimulation detected functional fibers running in the SS in all patients: semantic paraphasia was generated by stimulating the inferior frontooccipital fascicle in 8 cases; alexia was elicited by stimulating the inferior longitudinal fascicle in 3 cases; visual disorders were induced by stimulating the optic radiations in 5 cases. Moreover, in front of the SS, phonemic paraphasia was evoked by stimulating the temporal part of the arcuate fascicle in 5 patients. The resection was stopped according to these functional limits in the 8 patients. After a transient postsurgical worsening, all patients recovered to normal results on examination, except for the persistence of a right superior quadrantanopia in 5 cases, with no consequences for quality of life. The 8 patients returned to a normal social and professional life. Total or subtotal resection was achieved in all cases but one. The authors suggest that the use of intrasurgical electrical mapping of the white matter pathways in awake patients opens the door to extensive resection of DLGG within the left SS while preserving the quality of life. Further anatomical, clinical, radiological, and electrophysiological studies are needed for a better understanding of the functional anatomy of this complex region.

White matter architecture of the language network

AbstractThe relevance of anatomical connectivity for understanding of the neural basis of language was recognized in the 19th century, and yet this topic has only recently become the subject of wider research interest. In this paper, I review recent findings on white matter tracts implicated in language: the arcuate fasciculus, superior longitudinal fasciculus, extreme capsule, uncinate fasciculus, middle longitudinal fasciculus, inferior longitudinal fasciculus, and inferior fronto-occipital fasciculus. The reviewed findings on these tracts were reported in studies that used a variety of methods, from post-mortem dissection and diffusion imaging to intraoperative electrostimulation with awake surgery patients. The emerging picture suggests that there is currently no consensus with regard to the exact number and identity of the tracts supporting language, their origins, trajectories, and terminations, as well as their functional interpretation.

Brain mapping in tumors: Intraoperative or extraoperative?

In nontumoral epilepsy surgery, the main goal for all preoperative investigation is to first determine the epileptogenic zone, and then to analyze its relation to eloquent cortex, in order to control seizures while avoiding adverse postoperative neurologic outcome. To this end, in addition to neuropsychological assessment, functional neuroimaging and scalp electroencephalography, extraoperative recording, and electrical mapping, especially using subdural strip- or grid-electrodes, has been reported extensively. Nonetheless, in tumoral epilepsy surgery, the rationale is different. Indeed, the first aim is rather to maximize the extent of tumor resection while minimizing postsurgical morbidity, in order to increase the median survival as well as to preserve quality of life. As a consequence, as frequently seen in infiltrating tumors such as gliomas, where these lesions not only grow but also migrate along white matter tracts, the resection should be performed according to functional boundaries both at cortical and subcortical levels. With this in mind, extraoperative mapping by strips/grids is often not sufficient in tumoral surgery, since in essence, it allows study of the cortex but cannot map subcortical pathways. Therefore, intraoperative electrostimulation mapping, especially in awake patients, is more appropriate in tumor surgery, because this technique allows real-time detection of areas crucial for cerebral functions--eloquent cortex and fibers--throughout the resection. In summary, rather than choosing one or the other of different mapping techniques, methodology should be adapted to each pathology, that is, extraoperative mapping in nontumoral epilepsy surgery and intraoperative mapping in tumoral surgery.

Occipital WHO grade II gliomas: oncological, surgical and functional considerations

Diffuse WHO grade II glioma (GIIG) involving the occipital lobe is a rare entity. Its surgical resection remains controversial as it implies inducing a permanent visual deficit. For the first time to our knowledge, we report a consecutive surgical series of patients who underwent an occipital lobectomy for an LGG invading visual structures. Six right-handed patients harboring a GIIG revealed by seizures (normal examination except a quadrantanopsia in one case) and located within the occipital lobe (4 left and 2 right tumors) were submitted to surgery. Before making this decision, the benefit-to-risk ratio of the resection was extensively discussed with the patient and his/her family, especially concerning the price to pay to remove the tumor, that is, to voluntarily generate a permanent hemianopsia. All the procedures were performed under awake condition using intraoperative electrostimulation, in order to pursue the resection until sensory-motor and/or language structures were encountered. An extensive occipital lobectomy was achieved in the six patients, with identification and preservation of sensory-motor pathways in the two cases with a right tumor and detection of language pathways in the four cases with a left tumor. The mean extent of resection was 93% (range: 91-100%). All patients experienced an expected postoperative deficit of the visual field (homonymous hemianopsia). Nonetheless, the six patients resumed a normal social and professional life (KPS at 90 in the 6 cases) with a mean follow-up of 58 months (range: 3-147 months)--with adjuvant treatment in three cases (in addition to a reoperation in two of them). Our findings suggest that, despite a definitive hemianopsia, an extensive surgical resection can be considered in the rare cases of occipital GIIG involving the primary visual structures, with patients able to maintain a normal life--except regarding the medico-legal problem of driving.

Is the human left middle longitudinal fascicle essential for language? A brain electrostimulation study

Human brain pathways required for language processing are poorly known. A new white matter tract in humans, the middle longitudinal fascicle, has recently been anatomically determined by diffusion tensor imaging and suggested to be essential for language. Our aim is to determine the importance of the middle longitudinal fascicle for language processing. This study is based on 8 patients with glioma resection at least involving the superior temporal gyrus of the left dominant hemisphere. Language is systematically examined pre- and postoperatively at 3 months. Intraoperative electrostimulation is used to map cortical and subcortical structures as functional boundaries of the glioma resection, including those essential for language processing. The resections are extensive (on average 62 ml, ranging from 21 to 111 ml) and include a large part of the middle longitudinal fascicle in all patients. Intraoperatively, no interference with picture naming is observed by electrostimulation of the middle longitudinal fascicle, while in all patients the inferior fronto-occipital fascicle is identified by eliciting semantic paraphasia as functional boundary. Postoperatively, no new permanent language deficits are detected by systematic language examination. Therefore, we suggest that the middle longitudinal fascicle may participate but is not essential for language processing.

Awake surgery for WHO Grade II gliomas within “noneloquent” areas in the left dominant hemisphere: toward a “supratotal” resection

It has been demonstrated that an extensive resection (total or subtotal) may significantly increase the overall survival in patients with WHO Grade II gliomas (low-grade gliomas [LGGs]). Yet, recent data have shown that conventional MR imaging underestimates the spatial extent of LGG, since tumor cells were found up to 20 mm around MR imaging abnormalities. Thus, it was hypothesized that an extended resection with a margin beyond MR imaging-defined abnormalities-a "supratotal" resection-might improve the outcome of LGG. However, because of the frequent location of LGG within "eloquent" brain areas, it is often difficult to achieve such a supratotal resection. This could nevertheless be possible when LGGs involve "noneloquent" areas, even in the left dominant hemisphere. The authors report on their use of awake electrical mapping to tailor the resection according to functional boundaries, that is, to pursue the resection beyond MR imaging-defined abnormalities, until corticosubcortical eloquent structures are encountered. Their aim was to apply this reliable surgical technique to LGGs located not within eloquent areas but distant from eloquent areas, to take a margin around the LGG visible on MR imaging while preserving brain function. Fifteen right-handed patients with a total of 17 tumors underwent resection of WHO Grade II gliomas involving nonfunctional areas within the left dominant hemisphere. In all patients, seizures were the initial manifestation of the tumors. Awake surgery with intraoperative electrostimulation was performed in all cases. The resection was continued until the surgeon reached cortical and subcortical areas crucial for brain function, especially language, as defined by the intrasurgical electrical mapping. The extent of resection was evaluated on postoperative FLAIR-weighted MR images. Despite transient neurological worsening in 60% of cases, all patients recovered and returned to a normal life. Seizure control was obtained in all patients with a decrease of antiepileptic drug therapy. Postoperative MR imaging showed that total resection was achieved in all 17 tumors and supratotal resection in 15. The average volume of the postoperative cavity (36.8 cm(3)) was significantly larger than the mean preoperative tumor volume (26.6 cm(3)) (p = 0.009). Neuropathological examination confirmed the diagnosis of WHO Grade II glioma in all cases. The mean duration of postoperative follow-up was 35.7 months (range 6-135 months). Only 4 of 15 patients experienced recurrence (without anaplastic transformation); the average time to recurrence in these cases was 38 months; radiotherapy was performed 6 years after the relapse in 1 case; no other patients received any adjuvant treatment. This series was compared with a control group of 29 patients who had "only" complete resection: anaplastic transformation was observed in 7 cases in the control group but not in any case in the series of patients who underwent supracomplete resection (p = 0.037). Furthermore, adjuvant treatment was administered in 10 patients in the control group compared with 1 patient who underwent supracomplete resection (p = 0.043). These findings support the usefulness of awake surgery with intraoperative functional (language) mapping with the attempt to perform supratotal resection of LGGs involving noneloquent areas in the left hemisphere. Indeed, the extent of resection was significantly increased in all cases but 2, with no additional permanent deficit and with control of seizures in all patients. The goal of supracomplete resection is currently to delay the anaplastic transformation, even if it does not (yet) enable a cure.

Surgical anatomy of the prostate in the era of radical robotic prostatectomy

New insights in the anatomy of the prostate and the surrounding tissue evolve the technique of radical prostatectomy for the treatment of prostate cancer. Regarding the course of the erectile nerves along the prostate, recent studies confirmed the presence of parasympathetic pro-erectile nerve fibers at the anterolateral aspect of the prostate. Another study of intraoperative electrostimulation of those nerves confirmed an increase in intracavernosal pressure by stimulations between the 1 and 3 o'clock position. Therefore, it is very likely that these anterior nerve fibers have an effect on erectile function. Regarding the urethral sphincter in the male, a study showed no attachment of the external sphincter to the levator ani muscle, probably resulting in an absence of a levator ani support to the continence mechanism. The male urinary sphincter seems to be in isolation responsible for urinary continence. The nerve fibers at the anterolateral aspect of the prostate seem to participate in erectile function, which renders the concept of a high anterior release during nerve sparing beneficial. The isolated urinary sphincter mechanism results in the need to conserve as much urethral length as possible during radical prostatectomy to avoid urinary incontinence.

Gerstmann‘s syndrome: where does it come from and what does that tell us?

Josef Gerstmann was first to describe patients with a selective association of finger agnosia, left–right confusion, acalculia and agraphia. Traditionally, the syndrome he introduced has been taken to indicate left parietal lobe damage, but intraoperative electrostimulation studies have failed to generate all four symptoms from a single site in the parietal cortex. On the basis of recent functional and structural neuroimaging results in healthy adults, we propose that the selective association of symptoms in pure Gerstmann’s syndrome could instead be explained by a white matter lesion at a very specific location that results in intraparietal disconnection. This result has implications for our understanding of lesion-induced cognitive dysfunction. It suggests expanding the classical concept of disconnection from disruption along a single long-distance fiber tract to situations where a conjoint disruption of separate fiber tracts determines the clinical syndrome. Such situations will arise only if a lesion affects the specific location where these separate fiber tracts happen to touch or cross each other. Given the complexity of fiber pathways in the brain, it is obvious that this mechanism can account for the huge variability in how different symptoms group together in individual patients.

Crossed aphasia elicited by intraoperative cortical and subcortical stimulation in awake patients

Crossed aphasia (aphasia resulting from a right hemispheric lesion among right-handed patients) is rare. The authors describe for the first time transient crossed aphasia elicited by intraoperative electrostimulation of both cortex and white matter pathways in awake patients. Three right-handed adults underwent surgery for a right-sided glioma. Because slight language disorders occurred during partial seizures or were identified on preoperative cognitive assessment, with right activations detected on language functional MR imaging in 1 patient, awake craniotomy was performed using intraoperative cortico-subcortical electrical functional mapping. Transient language disturbances were elicited by stimulating discrete cortical areas (inferior frontal gyrus and posterior part of the superior temporal gyrus) and white matter pathways (inferior frontooccipital fasciculus and arcuate fasciculus). A subtotal resection was achieved in all cases, according to functional boundaries. Postoperatively, 1 patient experienced a transient dysphasia, which resolved after speech rehabilitation, with no permanent deficit. These original findings highlight the possibility of finding crucial cortico-subcortical language networks in the right hemisphere in a subgroup of atypical right-handed patients. These findings provide new insights into the neural basis of language, by underlining the role of the right inferior occipitofrontal fasciculus in semantics and that of the right arcuate fasciculus in phonology, and by supporting the hypothesis of a mirror organization between the right and left hemispheres. The authors suggest that, in right-handed patients, if language disturbances are detected during seizures or on presurgical neuropsychological assessment, especially when right activations are observed on language functional MR imaging, awake craniotomy with intraoperative language mapping should be considered.

Awake Mapping Optimizes the Extent of Resection for Low-Grade Gliomas in Eloquent Areas

Awake craniotomy with intraoperative electrical mapping is a reliable method to minimize the risk of permanent deficit during surgery for low-grade glioma located within eloquent areas classically considered inoperable. However, it could be argued that preservation of functional sites might lead to a lesser degree of tumor removal. To the best of our knowledge, the extent of resection has never been directly compared between traditional and awake procedures. We report for the first time a series of patients who underwent 2 consecutive surgeries without and with awake mapping. Nine patients underwent surgery for a low-grade glioma in functional sites under general anesthesia in other institutions. The resection was subtotal in 3 cases and partial in 6 cases. There was a postoperative worsening in 3 cases. We performed a second surgery in the awake condition with intraoperative electrostimulation. The resection was performed according to functional boundaries at both the cortical and subcortical levels. Postoperative magnetic resonance imaging showed that the resection was complete in 5 cases and subtotal in 4 cases (no partial removal) and that it was improved in all cases compared with the first surgery (P = .04). There was no permanent neurological worsening. Three patients improved compared with the presurgical status. All patients returned to normal professional and social lives. Our results demonstrate that awake surgery, known to preserve the quality of life in patients with low-grade glioma, is also able to significantly improve the extent of resection for lesions located in functional regions.

Is the left uncinate fasciculus essential for language?

Despite a better understanding of the anatomy of the uncinate fasciculus (UF), its function remains poorly known. Our aim was to study the exact role of UF in language, and the possible existence of parallel distributed language networks within the "ventral stream", underlaid by distinct subcortical tracts--namely the inferior occipito-temporal fasciculus (IOF) and UF.We report a series of 13 patients operated on awake for a glioma involving the left anterior temporal lobe or the orbitofrontal area. We used intraoperative electrostimulation, to perform accurate and reliable anatomofunctional correlations both at cortical and subcortical levels. Using postoperative MRI, we correlated these functional findings with the anatomical locations of the sites where language disturbances were elicited by stimulation.Intraoperative cortical stimulation found perilesional language sites in all cases. Subcortically, semantic paraphasia were induced in the 13 patients by stimulating the IOF, and phonological paraphasia were generated in 6 patients by stimulating the arcuate fasciculus. Interestingly, subcortical stimulation never elicited any language disturbances when performed at the level of the UF. Moreover, after a transient postoperative language deficit, all patients recovered, despite the removal of at least one part of the UF, as confirmed by control MRI.We suggest that UF is not systematically essential for language. It can be explained by the fact that the "semantic ventral stream" might be constituted by at least two parallel pathways, i. e. a direct pathway underlaid by the IOF, crucial for language semantics, and an indirect pathway subserved by UF, which can be functionally compensated. However, we have to underline the fact not all language functions can be probed during surgery, and that more sensitive tasks have now to be added.

Contribution of cortical and subcortical electrostimulation in brain glioma surgery: Methodological and functional considerations

The aim of brain glioma surgery is to maximize the quality of resection, while minimizing the risk of sequelae. Due to the frequent location of gliomas in "eloquent areas" and because of major interindividual anatomofunctional variability, the cortical functional organization, effective connectivity and potential for plasticity must be studied for each patient individually. Consequently, in addition to preoperative functional neuroimaging, intraoperative electrostimulation (IES) can be used, under general anesthesia for motor mapping or on awake patient for language and cognitive mapping. This is an easy, accurate, reliable, and safe technique of detection of both cortical and subcortical functionally essential structures. Thus, IES enables: (i) to study the individual cortical functional organization before any resection; (ii) to understand the pathophysiology of areas involved by gliomas; (iii) to map the subcortical structures along the resection, allowing a study of the anatomofunctional connectivity; (iv) to analyze the mechanisms of on-line short-term plasticity, using repeated IES; (v) to tailor the resection according to individual cortico-subcortical functional boundaries, enabling to optimize the benefit:risk ratio of surgery. Moreover, IES can be combined with perioperative functional neuroimaging, before and after surgery, to validate these noninvasive techniques and to better understand the short-term and long-term plasticity mechanisms based on functional cortical reshaping and connectivity changes. Such individual knowledge allows planning multiple-stages surgery. In conclusion, IES enables to increase the impact of surgery on the natural history of gliomas, to preserve the quality of life, and to better understand the dynamic functional anatomy of the brain.

Intraoperative electrostimulation objectifies the assessment of functional nerve preservation after mesorectal excision

To improve nerve-sparing surgery, intraoperative electrical stimulation of pelvic autonomic nerves (INS) has been proposed in urology, gynecology, and visceral surgery. The aim of this study was to assess the impact of INS while monitoring intravesical pressure on the accurate evaluation of pelvic autonomic nerve preservation (PANP) after mesorectal excision. It was sought to determine whether this confirmation is useful in the prediction of postoperative urinary function. Sixty-two patients with mesorectal exzision for rectal cancer were examined prospectively. PANP was assessed visually by the surgeon and with INS. Bladder function was evaluated by post voiding residual volume measurement, rate of recatheterization, rate of long-term urinary catheterisation, and the international prostatic symptom score with quality of life index. INS confirmed bilateral preservation of parasympathetic nerves in 46 patients (74%), and in 10 patients (16%) in at least one side. In six patients (10%), INS failed to confirm PANP. Eleven patients (18%) developed urinary symptoms postoperatively. INS results had a higher sensitivity than visual assessment by the surgeon (82 vs 46%). Values for specificity ranged at 90 and 92%, respectively. Accuracy of INS in predicting PANP was higher (88 vs 83%). The correlation between urinary function and the findings on INS was good (kappa-value: 0.65), correlation between urinary function and visual assessment by the surgeon was fair (kappa-value: 0.40). INS, while monitoring intravesical pressure, accurately predicts bladder function after mesorectal excision. It may provide further insight into pelvic autonomic nerve sparing techniques.

Accessory Nerve to Suprascapular Nerve Transfer to Restore Shoulder Exorotation in Otherwise Spontaneously Recovered Obstetric Brachial Plexus Lesions

A systematic follow-up of infants with an obstetric brachial plexus lesion of C5 and C6 or the superior trunk showing satisfactory spontaneous recovery of shoulder and arm function except for voluntary shoulder exorotation, who underwent an accessory to suprascapular nerve transfer to improve active shoulder exorotation, to evaluate for functional recovery, and to understand why other superior trunk functions spontaneously recover in contrast with exorotation. In 54 children, an accessory to suprascapular nerve transfer was performed as a separate procedure at a mean age of 21.7 months. Follow-up examinations were conducted before and at 4, 8, 12, 24, and 36 months after operation and included scoring of shoulder exorotation and abduction. Intraoperative reactivity of spinatus muscles and additional needle electromyographic responses were registered after electrostimulation of suprascapular nerves. Histological examination of suprascapular nerves was performed. Trophy of spinatus muscles was followed by magnetic resonance imaging scanning. The influence of perinatal variables and results of ancillary investigations on outcome were evaluated. Exorotation improved from 70 degrees to functional levels exceeding 0 degrees, except in two patients. Abduction improved in 27 patients, with results of 90 degrees or more in 49 patients. Electromyography at 4 months did not show signs of denervation in 39 out of 40 patients. Intraoperative electrostimulation of suprascapular nerves elicited spinatus muscle reaction in 44 out of 48 patients. Histology of suprascapular nerves was normal. Preoperative magnetic resonance imaging scans showed only minor wasting of spinatus muscles in contrast with major wasting after successful operations. An accessory to suprascapular nerve transfer is effective to restore active exorotation when performed as the primary or a separate secondary procedure in children older than 10 months of age. Contradictory spontaneous recovery of other superior trunk functions and integrity of suprascapular nerves, as well as absence of spinatus muscle wasting direct to central nervous changes are possible main causes for the lack of exorotation.

Radiological and Electrophysiological Detection of Nerve Roots Avulsion in Patients with Birth-Related Brachial Plexus Paralysis

Obstetrical trauma is one of the most common causes of traction injuries of the brachial plexus, with incidence varying between one and two per 1000 live births. This incidence remains stable despite improvement in obstetrical care because of increasing mean birth weight. The majority of the patients with obstetrical brachial plexus palsy recover spontaneously after conservative treatment, without any or with minor functional deficit. The rest of the children require microsurgical treatment, which recently, with the introduction of interposition nerve grafting and neurotization techniques, has significantly improved the prognosis of these patients. Outcomes of surgical treatment depend on the severity and localization of the brachial plexus lesion and also on the timing of surgery. The results of early microsurgical brachial plexus interventions are superior to late brachial plexus reconstructions or following secondary procedures dealing with established joint contractures and bone deformities. Root avulsion is the most severe type of obstetrical brachial plexus lesion, usually found following use of extreme force during a complicated delivery. Presence of an avulsion lesion implies devastating paralysis without possibility for spontaneous recovery, as well as associated spread of the traction force to neighboring spinal nerves or trunks. Therefore, clinical signs of root avulsion such as Horner sign and phrenic nerve palsy are considered strong indicators for brachial plexus exploration and reconstruction. However, the absence of these signs does not rule out root avulsion. Thus, poor spontaneous recovery necessitates accurate diagnostic between preganglionic and postganglionic lesions of the brachial plexus. Postganglionic lesions occur distally to the dorsal root ganglion at the level of the spinal nerve, trunks, or cords. Continuity usually can be restored with nerve repair or interposition nerve grafting. Preganglionic lesions occur proximal to the dorsal root ganglion, with irreversible loss of the original source of nerve fibers. Preganglionic lesions were once considered inoperable, but the use of neurotization procedures from other plexus donors or the use of extraplexus donor nerves has allowed the return of rewarding degree of function.1,2,3,4 Radiological studies such as cervical myelography, computed tomography myelography (CTM) and preoperative electrophysiological testing are commonly used in an effort to correctly pinpoint the brachial plexus lesion. However, there are some controversies regarding the place of all these methods in diagnostic of obstetrical brachial plexus lesions. Cervical myelography can indicate a sign that has a strong association with root avulsions; however, the signs can exist without root avulsion. Furthermore, large, contrast-enhancing pseudomeningoceles expanding along the cervical spine can overlap adjacent normal roots. The CTM allows more accurate assessment of the root and rootlets, but delineation of a level of avulsion on axial slides can be difficult because of discrepancy between the location of root exit zones from spinal cord segments and that of respective intervertebral foramina. The electrophysiology in obstetric brachial plexus lesions differs essentially from one in older patients. The electromyelography (EMG) in obstetric palsy is far too optimistic compared with the clinical picture.5 Others consider EMG unreliable and excluded it from their protocol for examination of the children with obstetrical brachial plexus paralysis, but some still use it with the condition that studies must be done by experienced electromyographer, and results must be interpreted expertly.6 This study was undertaken to determine the diagnostic value of plain myelography, CTM, and preoperative electrophysiology in patients with obstetrical brachial plexus paralysis. Data obtained from these studies will be correlated with intraoperative diagnosis on the basis of operative findings following exploration of these lesions, intraoperative electrostimulation, and histological studies of nerve biopsies.