Intracranial complications from isolated sphenoid sinusitis are rare but nevertheless demonstrate both a high morbidity and mortality. We herein report a case of a pituitary abscess secondary to sphenoid sinusitis in a 12-year-old boy. This patient presented with an acute onset of moderate fever and headache, followed by progressive right ptosis. An emergency endoscopic endonasal sphenoidotomy with sinus drainage and postoperative antibiotic therapy resulted in a satisfactory recovery.
Summary: We describe a case of a 63-year-old man with chronic-contained rupture of an abdominal aortic aneurysm at the site of prior graft repair of the aneurysm. Initially misinterpreted as osteomyelitis on the basis of CT findings, this chronic-contained rupture of the abdominal aorta eroding the vertebrae was preoperatively diagnosed at MR imaging and confirmed at surgery. A conventional angiogram failed to show the pseudoaneurysm. Owing to a major difference in the management of a contained aortic aneurysm rupture versus that for osteomyelitis, MR imaging with CT or MR angiography is recommended before any operative or invasive procedure.
To the Editor: We appreciate the analysis of and commentary1 on our recently published manuscript, "Microsurgical Anatomy of the Vertical Rami of the Superior Longitudinal Fasciculus: An Intraparietal Sulcus Dissection Study,"2 from Koutsarnakis et al.3 At the outset, we commend the authors on the rigor and detail of their recent work describing the complexity and vitality of the subcortical region underlying the superior parietal lobule and periatrial region. With respect to the comments by Koutsarnakis et al,3 their concerns fall into two general categories: The subcortical impact of the more posterior trajectory: May violate the inferior fronto-occipital fasciculus (IFOF) which may be more of an issue on the dominant hemisphere. A longer distance to the target The port corridor: The smaller and longer corridor may be restrictive for larger and more vascular lesions. COMMENT 1: POSTERIOR TRAJECTORY AND IMPACT ON THE SUBCORTICAL NETWORK (IFOF) The first issue raised by the authors is the selection of the posterior trajectory on the IFOF. In an effort to increase the safety of accessing subcortical parietal lobe lesions, as well as using this as a corridor en route to the ventricular trigone, we have chosen a more posterior trajectory at the intraparietal sulcus (IPS)-parietooccipital sulcus (POS) point ("Kassam-Monroy point"). The authors have commented that posteriorly tilting the trajectory may potentially damage the posterior portion of the IFOF which is a part of the ventral semantic pathway. They contend that this may increase language-related morbidity, especially in the dominant hemisphere. They specifically mentioned that in Figure 2C, which depicts anatomic dissections, the fibers of the IFOF have been resected along the posterior part of the IPS, en route to the ventricular trigone. Figure 2C, however, was not meant to be an exact representation of the surgical approach. Rather, the purpose of Figure 2C was to demonstrate a layer-by-layer dissection from the U-fibers to the callosal fibers and to illustrate the anatomic relationship between the IFOF, parieto-thalamic fibers, and the callosal fibers with the atrium. In the computer simulation, shown in the video included in the manuscript, we demonstrate the parafascicular layered dissection shown in the cadaveric dissection. Although the authors' observation is correct, the IFOF was intentionally resected in the cadaveric dissections to reveal the tapetum and the ventricular atrium posteriorly, it was done so for illustrative purposes, not to replicate the actual surgical approach. Figure 2C was constructed to demonstrate a sequential layer-by-layer panoramic and anatomic view of the parietal corridor, and guide the reader in understanding the relative position of the pertinent fibers as the surgeon travels from the surface en route to the atrium. The computer simulation allows for a "fly-by" view which is recreated in the cadaveric models via sequential fiber dissections, thus requiring the dissection of the IFOF. However, in clinical application, the surgical trajectory mimics the computer simulation, which is purposefully designed to parallel the fibers of the IFOF so as not to transect them. Figure 2C illustrates the "white-matter fiber" framework that sequentially surrounds the IPS-POS complex en route to the atrium, with the notion that pre-existing knowledge of the relative position of IFOF may be important when choosing the particular corridor, as it is in proximity to this trajectory and thus a key consideration in defining the parafascicular trajectory (see below). In addition, in the manuscript, we have described in detail the relative importance of the IFOF in the context of this subcortical framework and in relation to the IPS-POS complex: "This point we have termed the IPS-POS (Kassam-Monroy) Point and permits entry into a parafascicular zone leading to the atrium. This zone lies between SLF-II (laterally), and the projection fibers and SLF-I (medially), transecting the forceps major and extending superior and parallel to the oblique fibers of the MdLF-IPL and IFOF. Accessing the posterior third of the IPS in this fashion thus avoids the Vr." Explicitly, the port does not transect the IFOF but runs parallel to it, traversing fibers between IFOF and the Vr. While beyond the scope of this report, we have previously reported the concept of parafascicular surgery: specifically, the ability of the port to course at angles parallel to critical white matter tracts creating parafascicular corridor access to eloquent regions, including in the sensorimotor subcortical spaces.4,5 The authors also contend that the mid-entry point along the IPS is a safer option in avoiding damage to the IFOF. As previously mentioned, a more posterior trajectory does not increase the risk of damage of IFOF and Figure 2C was intended to provide a regional anatomic relationship of surrounding white matter fibers. In addition, moving the trajectory to the mid-entry point along the IPS may increase the risk of damage to the Vr that we describe here. The next subcortical issue raised by the authors was on the putative role of the Vr that we have proposed as an integrator of learning memory (motor, sensory, emotional, and visual). This is a valid point. We understand that, to date, there is no documented proof of the functional significance of the vertical rami fibers. We performed all of our cases under awake anesthesia with intraoperative neurocognitive and psychometric testing to somatotopically categorize changes based on real-time coordinates relative to these critical subcortical networks; it is based on this that we share our observations on the function of the Vr. Utilizing awake anesthesia, 3D tractography, and intraoperative neuronavigation and relating this fiber with nearby related fibers, and intraoperative neurocognitive testing are bringing us closer to establishing a definitive role of the Vr, which will require additional validation studies. COMMENT 2: RADIAL CORRIDOR The authors have commented that if the "access point along the sulcal length tilts more posteriorly towards the IPS-POS meeting point, the surgical corridor accomplished becomes deeper and steeper…Thus, by deepening the operative field, the working corridor becomes considerably narrower and bimanual surgical dexterity more demanding." The authors raise an important point that may be a critical determinant in corridor selection to access a lesion. In our clinical practice, we routinely preplan a trajectory and choose an appropriate trajectory, in consideration of neural, vascular, and osseous structures, with reproducibility. In our paradigm, the primary consideration is the subcortical tract anatomy and the concept of developing a parafascicular corridor, ie, a corridor that parallels the key fascicular anatomy of the region. Based on this, it is not necessarily desirable to choose the shortest trajectory to the target; rather, in our experience, the safest parafascicular trajectory may be longer than the traditional approach. In addition, we are able to simulate trajectories with the port; explicitly, the port system is available in different lengths (maximum length of 9 cm) and is able to reach a majority of deep-seated targets. In our experience, despite the longer length, the trajectory reported was feasible and ergonomic for the user facilitating standard microsurgical technique assuming that optical chain is designed to deliver light down this small corridor. Explicitly, in our experience, the use of the Robotically Operated Video Optical Telescopic microscope (ROVOT-m) facilitated bimanual dissection (see below). Therefore, to reiterate, the most important factor in determining the appropriate trajectory is the relative position of neural structures; in this case, the WMTs surrounding the IPS en route to the atrium of the ventricle. In addition, neuronavigation, used with the port, guides the cannulation in real-time, preventing deviation from the preplanned trajectory to avoid inadvertent injury to the fibers that are situated parallel to the sulcus. The next issue raised by the authors is the ability to work inside a 13.5-mm port effectively when resecting fibrous and vascular lesions, and the possible need to convert to an open corridor that would be facilitated by their 3-cm deep sulcal dissection. Again, while beyond the scope of this report, we have published over the past decade the ability to address large and complex lesions using this port system, including the ability to resect large deep-seated AVMs.6,7 We have found that the 13.5-mm diameter port allows for adequate ability to perform bimanual dissection and microsurgical technique; explicitly, traction-counter-traction, sharp and blunt capsular dissection and hemostasis with bipolar coagulation can be accomplished safely and effectively in an air medium, respecting the principles of microdissection technique. Currently, these tasks are greatly facilitated with the implementation of an integrated exoscopic robotically controlled visualization system, namely the ROVOT-m, which delivers parallel light and deep field of view with a high resolution through the 13.5-mm diameter cannula. Even though there may be a learning curve with the use of the ROVOT-m in conjunction with the port, and their corroborative technology, we believe that this has not been prohibitive in accomplishing safe and maximal resection even for fibrous and vascular lesions.6-8 In addition, all cases utilizing the IPS-POS corridor with this technology were performed using this trajectory and the ROVOT-m under awake conditions, without the need for conversion into a conventional approach. SUMMARY In our manuscript, we have proposed several important concepts in accessing the parietal subcortical region and the lateral ventricular atrium via the IPS-POS Point (Kassam-Monroy Point) creating a more posteriorly based trajectory: We have devised a more posteriorly based corridor along the IPS-POS point in order to avoid the vertical rami of the superior longitudinal fasciculus (SLF), which we believe may be of critical importance in preventing common parietal lobe dysfunctions, such as visuospatial agnosia, and constructional and visual apraxia.9,10 This corridor was founded on core anatomic principles and supported by collaborative technology, such as diffusion-tensor imaging (DTI). With this novel purpose-built corridor, we have been able to plan the surgical trajectory in all cases with the application of DTI, resulting in enhanced conspicuity of the critical white matter tracts along the corridor. We appreciate the authors' comments that the use of the BrainPath port system (Nico Corporation, Indianapolis, Indiana) is a useful and elegant technique in trans-sulcal entry. The port has the ability to be co-registered with magnetic resonance imaging/computed tomography/DTI, to allow for dynamic intraoperative neuronavigation at all times during surgery. Given the angle of incidence of the port to the U-fibers, the port does transect these fibers; however, the trajectory is created to optimize parallelity to the other key subcortical fibers. In this particular corridor, the parafascicular corridor is purposefully designed to create access with the 0.9-mm atraumatic tip of the port to optimize preservation of the SLF I and II, MdLF-IP, IFOF, corona radiata, and callosal fibers. The technique does not require dissecting down the 3 cm depth of the sulcus, as the authors suggest; rather, only 2 mm of dissection is needed along the depth to allow the port to cannulate the sulcus. We have personally performed over 500 such cannulations and have separately reported several serial series documenting the safety of this in multiple subgroups.6-8,11-15 This approach results in less damage to the white matter fibers, as compared to traditional methods, with the intent to displace rather than transect the fibers. This process is aided by the ability to utilize real-time intraoperative neuronavigation when passing the port through the sulcus. With respect to the IFOF in the dominant and nondominant hemisphere, we have analyzed a series of 10 cases performed by the senior author using this corridor and have not observed an alteration in language, independent of laterally (this series will be reported separately). Of note, with respect to the IFOF, given that all of our procedures are performed with the patient awake and with continuous detailed intraoperative neurocognitive and psychometric testing, we use real-time assays to identify semantic language deficits were they to occur. We thank the authors for their interest in our work, comments, and feedback, and commend them on their efforts in describing this surgically and anatomical complex area. Disclosures This research is supported by an award to the Aurora Research Institute by the Vince Lombardi Cancer Foundation. We would like to thank Nico Corporation, Carl Zeiss, Synaptive Medical, Stryker Medical, and Karl Storz for their donations that made our research possible in the Neuroanatomy Laboratory. Dr Kassam reports involvement in Synaptive Medical (consultant), KLS Martin (consultant), Medtronic (advisory board), and founder and CEO of Neeka Health, LLC. Mark Lindsey reports involvement in Neeka Health, LLC (consultant).
Objective The aim of this study is to determine feasibility of incorporating three-dimensional (3D) tractography into routine skull base surgery planning and analyze our early clinical experience in a subset of anterior cranial base meningiomas (ACM). Methods Ninety-nine skull base endonasal and transcranial procedures were planned in 94 patients and retrospectively reviewed with a further analysis of the ACM subset. Main Outcome Measures (1) Automated generation of 3D tractography; (2) co-registration 3D tractography with computed tomography (CT), CT angiography (CTA), and magnetic resonance imaging (MRI); and (3) demonstration of real-time manipulation of 3D tractography intraoperatively. ACM subset: (1) pre- and postoperative cranial nerve function, (2) qualitative assessment of white matter tract preservation, and (3) frontal lobe fluid-attenuated inversion recovery (FLAIR) signal abnormality. Results Automated 3D tractography, with MRI, CT, and CTA overlay, was produced in all cases and was available intraoperatively. ACM subset : 8 (44%) procedures were performed via a ventral endoscopic endonasal approach (EEA) corridor and 12 (56%) via a dorsal anteromedial (DAM) transcranial corridor. Four cases (olfactory groove meningiomas) were managed with a combined, staged approach using ventral EEA and dorsal transcranial corridors. Average tumor volume reduction was 90.3 ± 15.0. Average FLAIR signal change was -30.9% ± 58.6. 11/12 (92%) patients (DAM subgroup) demonstrated preservation of, or improvement in, inferior fronto-occipital fasciculus volume. Functional cranial nerve recovery was 89% (all cases). Conclusion It is feasible to incorporate 3D tractography into the skull base surgical armamentarium. The utility of this tool in improving outcomes will require further study.
Introduction: Access to the posterior fossa via the presigmoid or far lateral approaches often requires removal of segments of the occipital condyle (OC), resulting in a potential need for spinal fixation to prevent craniocervical instability and the need to locate the hypoglossal canal to prevent damage to the hypoglossal nerve. Organization of the relative relationships of osseous and neurovascular structures in this region may assist the surgeon in dictating the extent of resection of the OC.
PURPOSE To identify patterns of enhancement in the internal auditory canal (IAC) on MR studies after removal of an acoustic neuroma, including changes in those patterns with time; to evaluate signal and enhancement of the labyrinth; to differentiate normal postoperative findings from those suggesting residual tumor; and to describe MR hallmarks of surgical approaches. METHODS We reviewed the postoperative MR studies obtained in 36 patients who had had surgery for acoustic neuroma (101 images total). Four patterns of IAC enhancement were evaluated, as was labyrinthine signal intensity before and after contrast administration, changes in findings over time, and anatomic alterations caused by surgery. RESULTS All patients had enhancement of the IAC on the first postoperative study. In 30 patients, IAC enhancement remained the same or decreased over time. Seventeen patients had hyperintense cochlear signal and 15 had cochlear enhancement that decreased with time. Effects of retrosigmoid craniotomy, a translabyrinthine surgical approach, and middle fossa craniotomy were recognizable. CONCLUSION Linear enhancement in the IAC is probably normal after surgery. Nodular and masslike enhancement and any progressive enhancement may require close follow-up to monitor growth of residual tumor. Labyrinthine hyperintensity may reflect blood metabolites. An MR protocol is suggested for following up patients in the years after surgery.
Object The purpose of this study was to determine whether cerebral blood flow (CBF) measurements in acute stroke could be correlated with the subsequent development of cerebral edema and life-threatening brain herniation. Methods Twenty patients with aggressively managed acute middle cerebral artery (MCA) territory strokes who underwent xenon-enhanced computerized tomography (Xe-CT) CBF scanning within 6 hours of onset of symptoms were retrospectively reviewed. The relationship among CBF and follow-up CT evidence of edema and clinical evidence of brain herniation during the 36 to 96 hours following stroke onset was analyzed. Initial CT scans displayed abnormal findings in 11 patients (55%), whereas the Xe-CT CBF scans showed abnormal findings in all patients (100%). The mean CBF in the symptomatic MCA territory was 10.4 ml/100 g/minute in patients who developed severe edema compared with 19 ml/100 g/minute in patients who developed mild edema (p < 0.05). The mean CBF in the symptomatic MCA territory was 8.6 ml/100 g/minute in patients who developed clinical brain herniation compared with 18 ml/100 g/minute in those who did not (p < 0.01). The mean CBF in the symptomatic MCA territory that was 15 ml/100 g/minute or lower was significantly associated with the development of severe edema and herniation (p < 0.05). Conclusions Within 6 hours of acute MCA territory stroke, Xe-CT CBF measurements can be used to predict the subsequent development of severe edema and progression to clinical life-threatening brain herniation. Early knowledge of the anatomical and clinical sequelae of stroke in the acute phase may aid in the triage of such patients and alert physicians to the potential need for more aggressive medical or neurosurgical intervention.
A 28-year-old woman presented with left-sided frontotemporal headache lasting 6 wk. Head CT and MR imaging revealed a clival mass, which was interpreted as a chondrosarcoma. The lesion was removed at endoscopic endonasal surgery; histologic and immunohistochemical findings proved it to be neurenteric cyst. On CT scans, the lesion was lytic, with an intact cortex; it was uniformly hyperintense relative to gray matter on T1-weighted MR images and iso- to hypointense relative to CSF on T2-weighted MR images.
