Craniotomy Area Research Articles

HyperMRI: hyperspectral and magnetic resonance fusion methodology for neurosurgery applications

PurposeMagnetic resonance imaging (MRI) is a common technique in image-guided neurosurgery (IGN). Recent research explores the integration of methods like ultrasound and tomography, among others, with hyperspectral (HS) imaging gaining attention due to its non-invasive real-time tissue classification capabilities. The main challenge is the registration process, often requiring manual intervention. This work introduces an automatic, markerless method for aligning HS images with MRI.MethodsThis work presents a multimodal system that combines RGB-Depth (RGBD) and HS cameras. The RGBD camera captures the patient’s facial geometry, which is used for registration with the preoperative MR through ICP. Once MR-depth registration is complete, the integration of HS data is achieved using a calibrated homography transformation. The incorporation of external tracking with a novel calibration method allows camera mobility from the registration position to the craniotomy area. This methodology streamlines the fusion of RGBD, HS and MR images within the craniotomy area.ResultsUsing the described system and an anthropomorphic phantom head, the system has been characterised by registering the patient’s face in 25 positions and 5 positions resulted in a fiducial registration error of 1.88 ± 0.19 mm and a target registration error of 4.07 ± 1.28 mm, respectively.ConclusionsThis work proposes a new methodology to automatically register MR and HS information with a sufficient accuracy. It can support the neurosurgeons to guide the diagnosis using multimodal data over an augmented reality representation. However, in its preliminary prototype stage, this system exhibits significant promise, driven by its cost-effectiveness and user-friendly design.

Middle meningeal artery patency after surgical evacuation for chronic subdural hematoma.

Chronic subdural hematoma (CSDH) often requires surgical evacuation, but recurrence rates remain high. Middle meningeal artery (MMA) embolization (MMAE) has been proposed as an alternative or adjunct treatment. There is concern that prior surgery might limit patency, access, penetration, and efficacy of MMAE, such that some recent trials excluded patients with prior craniotomy. However, the impact of prior open surgery on MMA patency has not been studied. A retrospective analysis was conducted on patients who underwent MMAE for cSDH (2019-2022), after prior surgical evacuation or not. MMA patency was assessed using a six-point grading scale. Of the 109 MMAEs (84 patients, median age 72 years, 20.2% females), 58.7% were upfront MMAEs, while 41.3% were after prior surgery (20 craniotomies, 25 burr holes). Median hematoma thickness was 14mm and midline shift 3mm. Hematoma thickness reduction, surgical rescue, and functional outcome did not differ between MMAE subgroups and were not affected by MMA patency or total area of craniotomy or burr-holes. MMA patency was reduced in the craniotomy group only, specifically in the distal portion of the anterior division (p = 0.005), and correlated with craniotomy area (p < 0.001). MMA remains relatively patent after burr-hole evacuation of cSDH, while craniotomy typically only affects the frontal-distal division. However, MMA patency, evacuation method, and total area do not affect outcomes. These findings support the use of MMAE regardless of prior surgery and may influence future trial inclusion/exclusion criteria. Further studies are needed to optimize the timing and techniques for MMAE in cSDH management.

Comparative anatomical analysis between lateral supraorbital and minipterional approaches.

The pterional craniotomy, described by Yasargil and Fox in 1975, constitutes the most traditional and important surgical access in vascular neurosurgery. Minimally invasive alternatives include the minipterional (MP) and lateral supraorbital (LSO) craniotomies, which avoid complications such as injury to the frontal branch of the facial nerve, temporal muscle dysfunction, depression of the craniotomy site, frontal sinus opening, and cosmetically unacceptable outcomes. We evaluated and compared the exposures provided by MP and LSO craniotomies through quantitative measurements of the surgical exposure area around the circle of Willis and parasellar regions, as well as angular and linear exposures of the internal carotid artery (ICA) bifurcation, middle cerebral artery (MCA), midpoint of the anterior communicating artery, and tip of the basilar artery (BA). Seven fresh cadavers were dissected at the São Paulo Medical Examiner's Office, SP, and three at the skull base laboratory of Weill Cornell Medical College, New York, USA. The craniotomies were performed sequentially, initially with the LSO craniotomy followed by the MP. After the craniotomy, the surgical exposure area, craniotomy area, and angular exposures in the horizontal and vertical axes were determined. The MP craniotomy provided better angular exposure for the ipsilateral MCA, while the LSO craniotomy and BA provided better vertical axis exposures. The LSO craniotomy provided better angular exposure in the vertical axis for the midpoint of the anterior communicating artery and contralateral ICA bifurcation. Regarding surgical exposure and craniotomy area, there were no statistically significant differences. The MP craniotomy offers a significantly larger surgical exposure compared to the LSO craniotomy, with specific advantages regarding angular exposure to important neurovascular structures. This study provides important quantitative data to guide the choice between these minimally invasive access techniques in vascular neurosurgery.

Minimally Invasive Approaches in the Surgical Treatment of Intracranial Meningiomas: An Analysis of 54 Cases.

Intracranial meningiomas, being a fairly common disease in the population, often require surgical treatment, which, in turn, can completely heal the patient. The localization of meningiomas often influences treatment even if they are asymptomatic. By modernizing approaches to surgical treatment, it is possible to minimize intra- and postoperative risks, while achieving complete removal of the tumor. One of these methods is minimally invasive neurosurgery, the development of which in recent years allows it to compete with standard surgical methods. The purpose of this study was the objectification of minimally invasive approaches, such as the calculation of the craniotomy area and the ratio of craniotomy area to the resected tumor volume. The retrospective study consisted of a group of 54 consecutive patients who were operated on in our neurosurgery clinic specialized on minimally invasive neurosurgery. Preoperative planning was carried out using the Surgical Theater visualization platform. Using this system, the tumor volume and craniotomy surface area were calculated. During the analysis, the symptoms before and after the surgery, classification of tumors, postoperative complications, further treatment and follow-up results were assessed. Twelve (22.2%) patients were men and 42 (77.8%) were women. The mean age of the group was 64.2 years (median 67.5). The craniotomy area ranged from 202 to 2,108 mm² (mean 631 mm²). Tumor volume ranged from 0.85 to 110.1 cm3 (mean 21.6 cm3). The craniotomy size of minimally invasive approaches to the skull base was 3-5 times smaller than standard approaches. Skull base meningiomas accounted for 19 cases (35.2%), convexity meningiomas for 26 cases (48.1%), and falx and tentorium meningiomas for 9 cases (16.7%). Three complications were reported: postoperative hemorrhage, CSF leakage, and ophthalmoplegia. Relapse was detected in 2 patients with a mean follow-up of 26.3 months (median 20). Minimally invasive approaches in the surgical treatment of intracranial meningiomas reduce the possibility of operating trauma by several times; they are safe and sufficient for complete removal of the tumor.

Preventing Post-incisional Dural Shrink in Craniotomy: Introducing the "Roll-up Technique".

Dural dryness makes suturing difficult during dural closure after craniotomy. In this case, dural plasty is often performed using a membrane taken from the surrounding tissue (e.g., fascia or periosteum) or an artificial replacement membrane. Herein, we introduce our novel "roll-up technique" to reduce the utilization of substitute membranes and explore its effectiveness in dural closure. We retrospectively examined the medical records of 50 patients who underwent craniotomy for the first time for supratentorial intracranial lesions between 2015 and 2022. Furthermore, we divided them into two groups: (1) the conventional technique group, which consisted of patients in whom the dura mater was flipped after incision and protected with a moistened gauze (n = 23), and (2) the roll-up technique group, which consisted of patients in whom the dura mater was incised in a U shape, rolled up, and protected with a moist gauze (n = 27). After surgery, we compared the success rates of primary closure, operating time, craniotomy area, and percentage of complications (e.g., cerebrospinal fluid [CSF] leakage or infection) between the groups. Dural closure without dural substitutes using the roll-up technique had a higher success rate than that using the conventional technique (26/27 [96.3%] cases vs. 14/23 [60.9%] cases; P = 0.003). Postoperative CSF leakage or infection did not occur, and no statistically significant difference was observed in the operating time between the groups (P = 0.247). The roll-up technique for dural closure may effectively prevent post-incisional dural shrink after craniotomy.

Characteristics of donor vessels and cerebral blood flow in the chronic phase after combined revascularization surgery for moyamoya disease

ObjectiveThis study aimed to analyze whether the development of donor vessels after combined revascularization surgery for moyamoya disease (MMD) is related to cerebral blood flow (CBF) changes. MethodsWe retrospectively reviewed the charts of 11 adult (12 hemispheres) and 13 pediatric (19 hemispheres) patients who underwent combined revascularization in our department. The total vessel cross-sectional area (TVA) was the sum of the cross-sectional areas of the superficial temporal, middle meningeal, and deep temporal arteries imaged using time-of-flight magnetic resonance angiography. The ipsilateral relative CBF (RCBF) on the brain surface in the craniotomy area was calculated by single-photon emission computed tomography. ΔTVA and ΔRCBF were defined as the preoperative and postoperative ratios of TVA and RCBF, and their correlations were analyzed in adult and pediatric patients. ResultsThe TVA and RCBF showed a significant increase after surgery, regardless of the age group. However, there was no significant correlation between ΔTVA and ΔRCBF in either the adult or pediatric groups. While the adult group exhibited significantly higher ΔRCBF values compared to the pediatric group (p < 0.01, r = −0.44), the ΔTVA values were higher in the pediatric group compared to the adult group (p = 0.06). ConclusionsIn the chronic phase after combined revascularization surgery for MMD, the development of measurable TVA of donor vessels does not necessarily correlate with an increase in CBF around the craniotomy area.

Impact of craniotomy area on improvement of cerebral blood flow in combined revascularization surgery for moyamoya disease

To investigate factors associated with improvements in cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) after combined revascularization surgery for moyamoya disease, with special attention to the size of craniotomy. We retrospectively analyzed 35 hemispheres in 27 patients with adult and older pediatric moyamoya disease. CBF and CVR were measured separately in the MCA and ACA territories from acetazolamide-challenged single-photon emission computed tomography before and after 6 months postoperatively, and associations with various factors were analyzed. Postoperative CBF improved in patients with lower preoperative blood flow in both ACA and MCA territories. Postoperative CVR improved in 32 of 35 patients (91.4%) in the MCA territory and in 30 of 35 patients (85.7%) in the ACA territory, with more prominent improvement in the MCA territory than in the ACA territory (MCA territory 29.7% vs ACA territory 21.1%, p=0.015). Craniotomy area did not correlate with postoperative CBF and only MCA territory was associated with good (≥30%) CVR improvement (odds ratio 9.33, 95% confidence interval 1.91-45.6, p=0.003). Postoperative CBF improved in adult and older pediatric cases, reflecting preoperative CBF. Postoperative CVR improved in most cases, although the degree of improvement was more prominent in the MCA territory than in the ACA territory, suggesting a contribution of the temporal muscle. Large craniotomy area was not associated with improved blood flow in the ACA territory and should be applied prudently.

SURG-15. MINIMALLY INVASIVE PREFRONTAL APPROACH FOR GLIOMAS: TECHNICAL DESCRIPTION AND ASSOCIATED COMPLICATIONS

Abstract INTRODUCTION Classical prefrontal approaches exposed the lateral surface of the frontal lobe. Minimally invasive (MI) approaches achieved to reduce soft tissue damage and craniotomy size without affecting tumor resection grade. This is associated with shorter hospital stays and faster return to preoperative daily activities. OBJECTIVE To describe the MI prefrontal glioma resection technique developed in our department and to analyze our surgical results. METHODS We performed a retrospective review of patients who underwent prefrontal lobe glioma (WHO grade II-IV) resection using an MI approach in 2016-2021 at the University of Miami Hospital. Re-surgery, biopsy-only patients, multicentric tumors, and patients with less than four months of follow-up were excluded. Demographic and clinical data were collected. A 4-5 cm linear incision is done, starting at 1 cm lateral to the sagittal suture and extending towards the superior temporal line. An ellipsoidal-shaped mini-craniotomy is performed. RESULTS Thirty-four patients were included. The mean age was 50.2 years old, with 20 male subjects. Twenty-two patients had high-grade gliomas (HGG) and 12 patients had low-grade gliomas (LGG). On average, patients were discharged 1.97 days after surgery. The mean craniotomy area was 15,5 cm2 (7-43 cm2). The mean tumor volume was 64,5 cm2 ( 9 -165.8 cm2). Two wound infections and one case of aseptic meningitis were observed in patients with craniotomies &amp;gt; 15 cm2, while the group with craniotomies &amp;lt; 15 cm2 had no perioperative complications. In the HGG group, a supramaximal resection (SMR) was achieved in 8 patients, 9 HGG patients had gross total resection (GTR) or near-total resection (NTR), and 5 patients had subtotal resection (STR). In the LGG, GTR was achieved in 10 patients and STR in 2 patients. CONCLUSION MI prefrontal approach for frontal gliomas is safe and feasible with minor complications, short hospital stay, and without sacrificing tumor resection volume.

Epidural grid, a new methodology of invasive intracranial EEG monitoring: A technical note and experience of a single center

IntroductionSubdural grid monitoring (SDG) has the advantage to provide continuous coverage over a larger area of cortex, direct visualization of electrode location and functional mapping. However, SDG can cause direct irritation of the cortex or postoperative headaches due to cerebrospinal fluid (CSF) leakage. Epidural grid monitoring (EDG) without opening the dura is thought to reduce the possibility of these complications. We report our experience with EDG. MethodsWe described our surgical technique of EDG in invasive intracranial electroencephalography (iEEG) monitoring. A retrospective review of 30 patients who underwent grid placement of iEEG between March 2019 and December 2020 was performed to compare SDG and EDG. ResultsOf the 30 patients, 10 patients underwent SDG and 20 patients underwent EDG. There was no difference in age between SDG and EDG groups (p = 0.13). Also, there was no difference in the number of grid electrodes, craniotomy size, number of electrodes per craniotomy area and postoperative complication rate (p = 0.32, 0.84, 0.58 and 0.40). However, the maximum number of electrodes that have been undermined from the bone margin was much higher in SDG group (SDG 4.6 ± 2.2 vs. EDG 2.0 ± 0.9; p = 0.001). The demand for postoperative analgesics was significantly lower in EDG group (SDG 13.4 ± 9.1 vs. EDG 4.1 ± 4.3; p = 0.012); and the demand for postoperative antiemetics also tended to be low (SDG 4.6 ± 3.6 vs. EDG 1.8 ± 1.6; p = 0.078). ConclusionsThere was no significant difference in craniotomy and electrode insertion between the two groups; however, the EDG group showed less postoperative headache and nausea. Though not in direct contact with the cortex, the quality of the electrophysiological signal received through the electrode in EDG is comparable to that of the SDG. The EDG enables to detect the onset of seizure and delineate the epileptogenic zone sufficiently. Moreover, functional mapping is possible with EDG. Therefore, EDG has the sufficient potential to replace SDG for monitoring of the lateral surface of brain.

Development of a New Image-Guided Neuronavigation System: Mixed-Reality Projection Mapping Is Accurate and Feasible.

Image-guided systems improve the safety, functional outcome, and overall survival of neurosurgery but require extensive equipment. To develop an image-guided surgery system that combines the brain surface photographic texture (BSP-T) captured during surgery with 3-dimensional computer graphics (3DCG) using projection mapping. Patients who underwent initial surgery with brain tumors were prospectively enrolled. The texture of the 3DCG (3DCG-T) was obtained from 3DCG under similar conditions as those when capturing the brain surface photographs. The position and orientation at the time of 3DCG-T acquisition were used as the reference. The correct position and orientation of the BSP-T were obtained by aligning the BSP-T with the 3DCG-T using normalized mutual information. The BSP-T was combined with and displayed on the 3DCG using projection mapping. This mixed-reality projection mapping (MRPM) was used prospectively in 15 patients (mean age 46.6 yr, 6 males). The difference between the centerlines of surface blood vessels on the BSP-T and 3DCG constituted the target registration error (TRE) and was measured in 16 fields of the craniotomy area. We also measured the time required for image processing. The TRE was measured at 158 locations in the 15 patients, with an average of 1.19±0.14 mm (mean±standard error). The average image processing time was 16.58 min. Our MRPM method does not require extensive equipment while presenting information of patients' anatomy together with medical images in the same coordinate system. It has the potential to improve patient safety.

Trans-sulcal versus trans-parenchymal approach in supratentorial cavernomas. A multicentric experience

ObjectivesCavernous malformations (CM) are low-flow vascular lesions that can cause significant symptoms and neurological deficits. Different intraoperative surgical approaches have been developed. Aim of the present investigation is the comparison between the trans-sulcal approach (TS) and the trans-parenchymal neuronavigation-assisted approach (TPN) in a surgical series from two neurosurgical centers. The technique and clinical outcomes are discussed, with a specific focus on seizure outcome. Patients and methodsClinical and radiological data from two neurosurgical centers (“A. Gemelli” Hospital in Rome and A.O.U. Città della Salute e della Scienza in Turin) were retrospectively reviewed in order to evaluate the different outcome of TS and TPN approach for cavernous malformation treatment. ResultsA total of 177 patients underwent surgical intervention for supratentorial CM, 130 patients with TPN approach and 47 with TS approach. TS approach was associated with higher rate of seizure in early post-operative period both in epileptic patients (p < 0,001) and in patients without history of seizures before surgery (p = 0,002). Moreover, length of incision (p < 0,001), area of craniotomy (p < 0,001) and corticectomy (p < 0,001) were bigger in TS than in TPN approach. Brain contusion (p < 0,001) and fluid collection (p < 0,001) were more likely to be discovered after TS approach. ConclusionsTPN is a valuable approach for resection of CM. Minor complications are significantly lower in TPN approach when compared with TS approach. In addition, it is associated with lower rate of early post-operative seizure and shorter length of stay.

Large Craniotomy Increases the Risk of Minor Perioperative Complications in Revascularization Surgery for Moyamoya Disease

Larger craniotomy is expected to increase blood flow over a wider range after indirect revascularization. However, the optimal size of craniotomy has not been established. In this study perioperative complications in revascularization surgery for moyamoya disease are evaluated, focusing on craniotomy size. We retrospectively analyzed 87 hemispheres in 65 patients with moyamoya disease who had undergone revascularization surgery. Areas and types of craniotomy were classified as 1-piece craniotomy in the middle cerebral artery (MCA) territory (1-piece group) in 54 hemispheres (mean area of craniotomy, 40.6 ± 13.5 cm2); 2-piece craniotomy in the MCA territory with anterior cerebral artery (ACA) territory (2-piece group) in 16 hemispheres (mean area of craniotomy, 55.4 ± 12.0 cm2); and 1-piece craniotomy in both MCA and ACA territories (large group) in 17 hemispheres (mean area of craniotomy, 84.2 ± 11.0 cm2). Perioperative complication rates in each craniotomy group were analyzed. Perioperative complications occurred in 45 hemispheres (52%). Transient, moderate, and severe complications occurred in 38 hemispheres, 3 hemispheres, and 4 hemispheres, respectively. Complication rates in the 1-piece, 2-piece, and large groups were 41%, 63%, and 76%, respectively. Large craniotomy was associated with a significantly higher frequency of complications (P= 0.01). However, no significant difference was found among groups when limiting analysis to moderate and severe complications. Multivariate analysis showed large craniotomy as the only factor independently related to complications (odds ratio, 2.93; 95% confidence interval, 1.08-7.92; P= 0.034). Large craniotomy is associated with more frequent perioperative complications, especially transient symptoms.

The relationship between the area of decompressive craniectomy and normal pressure hydrocephalus after traumatic brain injury

Objective To analyze the effect of craniotomy area on the development of normal pressure hydrocephalus after decompressive craniotomy. Methods The clinical data of 34 patients with traumatic brain injury who underwent unilateral craniotomy from January 2012 to April 2018 at Department of Neurosurgery, Tangdu Hospital, Airforce Military Medical University were retrospectively analyzed. The effects of multiple factors on hydrocephalus, including the gender, age, Glasgow coma scale before craniotomy, open injury, extent of midline shift on CT before craniectomy, duration of operation, intracranial pressure after craniotomy, cerebrospinal fluid infection and craniotomy area were analyzed. Results Univariate analysis showed that the age (P=0.016), preoperative Glasgow coma scale (P=0.018), craniotomy area (P 0.05). It was also suggested by multiple logistic regression that craniotomy area (OR=1.138, 95% CI: 1.005-1.288, P=0.042) was an independent risk factor for hydrocephalus. Conclusion After decompressive craniotomy, the skull defect area may increase the risk of hydrocephalus. Key words: Craniocerebral trauma; Hydrocephalus, normal pressure; Decompressive craniectomy; Area size of craniectomy; Cerebrospinal fluid dynamics

Comparison between frontolateral approach and pterional approach in the surgical treatment of paraclinoid aneurysms

ObjectiveTo compare the pterional and frontolateral approach to determine the most effective route for paraclinoid aneurysm surgery. MethodsBetween June 2010 and December 2015, a total of 176 patients with paraclinoid aneurysm underwent surgical clipping, 96 through the pterional and 80 through the frontolateral approach. We analyzed the two groups and compared demographic, radiologic, and clinical variables including age, sex, aneurysm type,intraoperative rupture rates, operative time,anatomical obstacles,outcome and postoperative complications. ResultsThe 2 groups were comparable with respect to baseline characteristics. The mean operation time was also signifcantly shorter in frontolateral group than in the pterion group (204.3 min vs. 264.1 min, p < 0.05). Furthermore, the mean craniotomy area was much smaller in the frontolateral group (1255.4 mm2 vs. 2758.5 mm2, p < 0.05). No patient experienced rebleeding in either group. In the frontolateral group, the exploration allows enough room for intracranial manipulation with maximal protection of the brain and other intracranial structures. ConclusionThe frontolateral approach is a simple, reliable, and efficient procedure. The frontolateral approach could be a good alternative to the classic pterional approach for the treatment of paraclinoid aneurysms.

A method for the assessment of time-varying brain shift during navigated epilepsy surgery.

Image guidance is widely used in neurosurgery. Tracking systems (neuronavigators) allow registering the preoperative image space to the surgical space. The localization accuracy is influenced by technical and clinical factors, such as brain shift. This paper aims at providing quantitative measure of the time-varying brain shift during open epilepsy surgery, and at measuring the pattern of brain deformation with respect to three potentially meaningful parameters: craniotomy area, craniotomy orientation and gravity vector direction in the images reference frame. We integrated an image-guided surgery system with 3D Slicer, an open-source package freely available in the Internet. We identified the preoperative position of several cortical features in the image space of 12 patients, inspecting both the multiplanar and the 3D reconstructions. We subsequently repeatedly tracked their position in the surgical space. Therefore, we measured the cortical shift, following its time-related changes and estimating its correlation with gravity and craniotomy normal directions. The mean of the median brain shift amount is 9.64 mm ([Formula: see text] mm). The brain shift amount resulted not correlated with respect to the gravity direction, the craniotomy normal, the angle between the gravity and the craniotomy normal and the craniotomy area. Our method, which relies on cortex surface 3D measurements, gave results, which are consistent with literature. Our measurements are useful for the neurosurgeon, since they provide a continuous monitoring of the intra-operative sinking or bulking of the brain, giving an estimate of the preoperative images validity versus time.

Analysis of the risk factors for development of post-operative extradural hematoma after intracranial surgery

Objective. Post-operative extradural hematoma (EDH) is a relatively common complication in patients undergoing intracranial operations. The risk factors associated with the occurrence of EDH are not well described in the literature. The objective of this study was to identify the risk factors and the incidence of post-operative EDH adjacent and regional to the craniotomy or the craniectomy site. Method. This was a retrospective study of 24 (2.6% of total) patients who underwent extradural hematoma evacuation after primary intracranial supratentorial surgery between January 2005 and December 2011. During this period, 941 intracranial operations were performed. The control group (72 patients) was selected on the basis of having undergone the same pre-operative diagnosis and treatment within 2 months of the operations for the 24 hematoma patients. The Glasgow Coma Scale score and operation character (emergency or elective) of the hematoma and control group were individually matched to minimize pre-operative conditional bias. The ages of both groups were individually matched with similar ages within 10 years of each other to minimize age bias. Result. Univariate analysis showed that the significant pre-operative and intra-operative factors associated with post-operative EDH were an intra-operative blood loss of greater than 800 mL (p = 0.007), maximal craniotomy length of greater than or equal to 100 mm (p = 0.001), and craniotomy area of greater than or equal to 71.53 cm2 (p = 0.018). In multivariate analysis, intra-operative blood loss exceeding 800 mL (median of total patients) placed a patient at significantly increased risk for post-operative EDH. Conclusion. The data did not examine established risk factors for post-operative hematoma, such as thrombocytopenia, anti-coagulant and anti-platelet therapy, and a history of heavy alcohol consumption and/or tobacco intake. Recognizing the limitations of the study, large intra-operative blood loss and wide craniotomy area are implicated with an increased risk of post-operative EDH after intracranial surgery.

Frameless Nonstereotactic Image-Guided Surgery of Supratentorial Lesions: Introduction to a Safe and Inexpensive Technique

We describe a simple, safe, and inexpensive technique that through the comparison of three-dimensional (3D)-rendered magnetic resonance (MR) images and real anatomy allows us to navigate and remove brain lesions, including those without cortical appearance, by direct recognition of anatomical landmarks. Preoperative planning no longer requires the use of fiducials and can therefore be performed out a stereotactic setting. MR Digital Imaging and Communications in Medicine format scans of 93 patients were reconstructed using MRIcro freeware for their three-dimensional rendering (3DR). The main location of the lesions was rolandic or left temporal, and most of them were without cortical appearance (78%). The two-dimensional (2D) sets of images were processed by the software to perform a 3DR, thus obtaining a virtual model of the patient's head. Using the same 2D sets, the edges of the lesion's images were contoured by the region of interest (ROI) tool. In the next step, the ROI was projected onto the surface of the virtual model of the patient's head, thus helping to attain the best identification of the craniotomy area. MRIcro automatic segmentation function, the Brain Extraction Tool (BET), provides a clear 3DR of the cortical surface. We used BET to display gyri, sulci, and perilesional vessels to have further anatomical landmarks to guide the surgical approach. The lesions were accessed through an optimally suited craniotomy. The visual matching of the cortical surface with reconstructed 3D images of the cortex permitted a fast localization of cortical and subcortical lesions. The major limitation is the depth of a lesion deeper than 3 cm. In these cases, the use of frame-based or frameless techniques still seems safer and more advantageous. Conclusions: The shape recognition of the cortical landmarks was not biased by brain distortion because the sulci and cortical vessels almost always had a relationship to each other that was not modified by edema or cerebrospinal fluid leakage. This 3DR allows us to reconstruct a virtual anatomy in an easy, portable, and inexpensive way. In selected cases, this technique represents a valid and safe alternative to the use of costly neuronavigation tools and is potentially helpful in developing countries.

Increased strain levels and water content in brain tissue after decompressive craniotomy

At present there is a debate on the effectiveness of the decompressive craniotomy (DC). Stretching of axons was speculated to contribute to the unfavourable outcome for the patients. The quantification of strain level could provide more insight into the potential damage to the axons. The aim of the present study was to evaluate the strain level and water content (WC) of the brain tissue for both the pre- and post-craniotomy period. The stretching of brain tissue was quantified retrospectively based on the computerised tomography (CT) images of six patients before and after DC by a non-linear image registration method. WC was related to specific gravity (SG), which in turn was related to the Hounsfield unit (HU) value in the CT images by a photoelectric correction according to the chemical composition of brain tissue. For all the six patients, the strain level showed a substantial increase in the brain tissue close to the treated side of DC compared with that found at the pre-craniotomy period and ranged from 24 to 55 % at the post-craniotomy period. Increase of strain level was also observed at the brain tissue opposite to the treated side, however, to a much lesser extent. The mean area of craniotomy was found to be 91.1 ± 12.7 cm(2). The brain tissue volume increased from 27 to 127 ml, corresponding to 1.65 % and 8.13 % after DC in all six patients. Also, the increased volume seemed to correlate with increased strain level. Specifically, the overall WC of brain tissue for two patients evaluated presented a significant increase after the treatment compared with the condition seen before the treatment. Furthermore, the Glasgow Coma Scale (GCS) improved in four patients after the craniotomy, while two patients died. The GCS did not seem to correlate with the strain level. We present a new numerical method to quantify the stretching or strain level of brain tissue and WC following DC. The significant increase in strain level and WC in the post-craniotomy period may cause electrophysiological changes in the axons, resulting in loss of neuronal function. Hence, this new numerical method provides more insight of the consequences following DC and may be used to better define the most optimal size and area of the craniotomy in reducing the strain level development.

Comparison between Lateral Supraorbital Approach and Pterional Approach in the Surgical Treatment of Unruptured Intracranial Aneurysms

ObjectiveThe lateral supraorbital (LSO) approach is a modified method of the classic pterional approach and it has advantages of short skin incision and small craniotomy compared with the pterional approach. This study was designed to compare the two approaches in the surgical treatment of unruptured intracranial aneurysms.MethodsWe retrospectively reviewed 122 patients with 137 unruptured intracranial aneurysms treated by clipping, from July 2009 to April 2011. Between August 2010 and April 2011, 61 patients were treated by clipping via the lateral supraorbital approach and the same number of patients treated by clipping via the pterional approach were retrospectively enrolled. We analyzed the two groups and compared demographic, radiologic and clinical variables.ResultsThe mean age of patients in the two groups was 54.6 years (LSO group) and 55.7 years (Pterion group). The mean duration of hospitalization was shorter in the LSO group than in the Pterion group (7.9 days vs. 9.0 days, p=0.125) and the mean operation time was also significantly shorter in the LSO group (117.1 minutes vs. 164.3 minutes, p<0.001). Furthermore, the mean craniotomy area was much smaller in the LSO group (1275.4 mm2 vs. 2858.9 mm2, p<0.001). The two groups showed similar distributions of aneurysm location and postoperative complications.ConclusionThe lateral supraorbital approach for the clipping of unruptured intracranial aneurysm could be a good alternative to the classic pterional approach.

Post-Traumatic Hydrocephalus after Decompressive Craniectomy: An Underestimated Risk Factor

The incidence of post-traumatic hydrocephalus (PTH) has been reported to be 0.7-51.4%, and we have frequently observed the development of PTH in patients undergoing decompressive craniectomy (DC). For this reason we performed a retrospective review of a consecutive series of patients undergoing DC after traumatic brain injury (TBI). From January 2006 to December 2009, 41 patients underwent DC after closed head injury. Study outcomes focused specifically on the development of hydrocephalus after DC. Variables described by other authors to be associated with PTH were studied, including advanced age, the timing of cranioplasty, higher score on the Fisher grading system, low post-resuscitation Glasgow Coma Scale (GCS) score, and cerebrospinal fluid (CSF) infection. We also analyzed the influence of the area of craniotomy and the distance of craniotomy from the midline. Logistic regression was used with hydrocephalus as the primary outcome measure. Of the nine patients who developed hydrocephalus, eight patients (89%) had undergone craniotomy with the superior limit <25 mm from the midline. This association was statistically significant (p = 0.01 - Fisher's exact test). Logistic regression analysis showed that the only factor independently associated with the development of hydrocephalus was the distance from the midline. Patients with craniotomy whose superior limit was <25 mm from the midline had a markedly increased risk of developing hydrocephalus (OR = 17). Craniectomy with a superior limit too close to the midline can predispose patients undergoing DC to the development of hydrocephalus. We therefore suggest performing wide DCs with the superior limit >25 mm from the midline.