Igor Lima Maldonado, Christophe Destrieux, Eduardo Carvalhal Ribas, Bruna Siqueira de Abreu Brito Guimarães, Patrícia Pontes Cruz, and Hugues Duffau
The sagittal stratum is divided into two layers. In classic descriptions, the stratum sagittale internum corresponds to optic radiations (RADs), whereas the stratum sagittale externum corresponds to fibers of the inferior longitudinal fasciculus. Although advanced for the time it was proposed, this schematic organization seems simplistic considering the recent progress on the understanding of cerebral connectivity and needs to be updated. Therefore, the authors sought to investigate the composition of the sagittal stratum and to detail the anatomical relationships among the macroscopic fasciculi.
The authors performed a layer-by-layer fiber dissection from the superolateral aspect to the ventricular cavity in 20 cadaveric human hemispheres.
Diverse bundles of white matter were observed to contribute to the sagittal stratum and their spatial arrangement was highly consistent from one individual to another. This was the case of the middle longitudinal fasciculus, the inferior fronto-occipital fasciculus, the RADs, and other posterior thalamic radiations directed to nonvisual areas of the cerebral cortex. In addition, small contributions to the sagittal stratum came from the anterior commissure anteriorly and the inferior longitudinal fasciculus inferiorly.
A general model of sagittal stratum organization in layers is possible, but the composition of the external layer is much more complex than is mentioned in classic descriptions. A small contribution of the inferior longitudinal fasciculus is the main difference between the present results and the classic descriptions in which this bundle was considered to entirely correspond to the stratum sagittale externum. This subject has important implications both for fundamental research and neurosurgery, as well as for the development of surgical approaches for the cerebral parenchyma and ventricular system.
Vincent Costalat, Igor Lima Maldonado, Jean-François Vendrell, Carlos Riquelme, Paolo Machi, Charles Arteaga, Francis Turjman, Hubert Desal, Jacques Sedat, and Alain Bonafé
The limitations of the medical management of symptomatic intracranial arterial stenosis (SIAS) have encouraged the development of new strategies, such as endovascular treatment. In this study, the authors report and analyze a series of 63 endovascular procedures in which the Wingspan stent system was used.
Data from 60 patients presenting with refractory SIAS, treated in 5 French neurointerventional centers between September 2006 and August 2009, were retrieved. An angiogram was systematically obtained 6 months after the procedure and yearly thereafter. The clinical neurological status was assessed and reported using the modified Rankin scale at 1-month, 6-month, and 1-year follow-up visits.
A total of 63 stenotic lesions was treated. The mean age of the patients was 65.3 years, and the mean diameter of the stenosis was 80.2%. Technical success was achieved in 95.2% of cases. The overall incidence of procedural complications was 20.6%, with a 4.8% rate of permanent postoperative morbidity and death. In-stent restenosis (ISR)/occlusion occurred in 11 cases (17.4%), of which 10 were asymptomatic and 9 were detected less than 1 year from the endovascular treatment. In 1 case, the patient presented with a recurrent transient ischemic attack and was treated again with angioplasty. The mean follow-up was 13.2 months.
Endovascular treatment of SIAS demonstrates a moderate risk of neurological complication. Nevertheless, considering the critical natural history of severe refractory lesions, this may be considered the first alternative in cases of failed medical therapy. Technical failure, residual stenosis, or in-stent restenosis did not lead to systematic recurrent stroke in this series, which suggests the importance of plaque stabilization and neoendothelialization.
Igor Lima Maldonado, Sylvie Moritz-Gasser, Nicolas Menjot de Champfleur, Luc Bertram, Gérard Moulinié, and Hugues Duffau
Surgery in the left dominant inferior parietal lobule (IPL) is challenging because of a high density of somatosensory and language structures, both in the cortex and white matter. In the present study, on the basis of the results provided by direct cerebral stimulation in awake patients, the authors revisit the anatomofunctional aspects of surgery within the left IPL.
Fourteen consecutive patients underwent awake craniotomy for a glioma involving the left IPL. Intraoperative motor, sensory, and language mapping was performed before and during the tumor removal, at both the cortical and subcortical levels, to optimize the extent of resection, which was determined based on functional boundaries. Anatomofunctional correlations were performed by combining the results of intraoperative mapping and those provided by pre- and postoperative MR imaging.
At the cortical level, the primary somatosensory area (retrocentral gyrus) limited the resection anteriorly in all cases, at least partially. Less frequently, speech arrest or articulatory problems were observed within the parietal operculum (4 cases). The lateral limit was determined by language sites that were variably distributed. Anomia was the most frequent response (9 cases) at the posterior third of the superior (and/or middle) temporal gyrus. Posteriorly, less reproducible reorganized language sites were seldom observed in the posterior portion of the angular gyrus (2 cases). At the subcortical level, in addition to somatosensory responses due to stimulation of the thalamocortical pathways, articulatory disturbances were induced by stimulation of white matter in the anterior and lateral part of the surgical cavity (11 cases). This tract anatomically corresponds to the horizontal portion of the lateral segment of the superior longitudinal fascicle (SLF III). Deeper and superiorly, phonemic paraphasia was the main language disturbance (12 cases), elicited by stimulation of the posterosuperior portion of the arcuate fascicle. All these eloquent structures were surgically preserved. Despite slight cognitive disorders (working memory, writing, or calculation) in 6 cases, no patient retained a severe or a moderate postoperative deficit (except one with right hemianopia [mean follow-up 41.8 months]). Resection was total or near total in 9 patients and partial in 3 cases.
To the authors' knowledge, this is the first series dedicated to the surgery of gliomas involving the left IPL. Interestingly, a certain degree of interindividual variability was observed in the distribution of the cortical maps, especially for language. Therefore, it is suggested that no rigid pattern of resection can be considered within the left IPL, and that surgery in this region should be performed in awake patients to adapt the tumor removal to individual functional limits. Nonetheless, several landmarks have been regularly identified, especially at the subcortical levels (SLF III and arcuate fascicle); a better knowledge of these functional tracts could be helpful to optimize functional outcomes.