Intraoperative imaging in a comprehensive neuronavigation environment for minimally invasive brain tumour surgery

BACKGROUND

Development of an image-guided operation theatre offering multimodal information for mini-invasive neurosurgical brain tumour operations.

METHODS

A multi-purpose resistive low-field MR scanner with on-off capability, was installed in a radio frequency-shielded operating room with in-room control panel and display. Intraoperative ultrasound imaging with Doppler mode as needed is used to provide check-up image data between intraoperative MR-imaging sessions. Cortical stimulation and registration are performed during awake craniotomies. The neuronavigation systems are customised arm-based and passive optical. The navigation systems show the positions of the ultrasound probe, cortical stimulation electrode, biopsy needles, endoscope and other instruments on the intraoperative MR-images.

FINDINGS

Since 1999, 70 patients (mean age 47, range 3-88 years) have been operated with intraoperative MR-guidance (including 10 tumour biopsies, 56 resections). Twenty-one patients (mean age 46, range 16-67 years) underwent awake craniotomy and tumour resection secured with cortical stimulation and usually preoperative fMR-imaging. The present operating environment offered useful multimodal information for surgery of brain tumours in critical locations. Surgical mortality was 0%, morbidity included 3 (4.3%) infections and 2 (2.9%) permanent hemiparesis. Further removal of tumour was continued in 17 cases (57%) out of the 30 cases where intraoperative MR imaging was used for controlling completeness of the resection.

Cost of migration: invasion of malignant gliomas and implications for treatment

Tumors of glial origin consist of a core mass and a penumbra of invasive, single cells, decreasing in numbers towards the periphery and still detectable several centimeters away from the core lesion. Several decades ago, the diffuse nature of malignant gliomas was recognized by neurosurgeons when super-radical resections using hemispherectomies failed to eradicate these tumors. Local invasiveness eventually leads to regrowth of a recurrent tumor predominantly adjacent to the resection cavity, which is not significantly altered by radiation or chemotherapy. This raises the question of whether invasive glioma cells activate cellular programs that render these cells resistant to conventional treatments. Clinical and experimental data demonstrate that glioma invasion is determined by several independent mechanisms that facilitate the spread of these tumors along different anatomic and molecular structures. A common denominator of this cellular behavior may be cell motility. Gene-expression profiling showed upregulation of genes related to motility, and functional studies demonstrated that cell motility contributes to the invasive phenotype of malignant gliomas. There is accumulating evidence that invasive glioma cells show a decreased proliferation rate and a relative resistance to apoptosis, which may contribute to chemotherapy and radiation resistance. Interestingly, interference with cell motility by different strategies results in increased susceptibility to apoptosis, indicating that this dynamic relationship can potentially be exploited as an anti-invasive treatment paradigm. In this review, we discuss mechanisms of glioma invasion, characteristics of the invasive cell, and consequences of this cellular phenotype for surgical resection, oncologic treatments, and future perspectives for anti-invasive strategies.

Early-postoperative magnetic resonance imaging in glial tumors: prediction of tumor regrowth and recurrence

OBJECTIVE

This study investigated the value of early-postoperative magnetic resonance (EPMR) imaging in the detection of residual glial tumor and investigated the role of EPMR for the prediction of tumor regrowth and recurrence.

METHODS AND MATERIALS

We retrospectively analyzed pre- and post-operative magnetic resonance imaging results from 50 adult patients who underwent surgical treatment for supratentorial glial tumor. There were glioblastoma multiforme in 25 patients, astrocytoma (grades II and III) in 11 patients, oligodendroglioma (grades II and III) in 9 patients, and oligoastrocytoma (grades II and III) in 5 patients. EPMR imaging was performed within 24 h after surgery. EPMR findings were compared with the neurosurgeon's intraoperative estimation of gross tumor removal. Patterns of contrast enhancement at the resection site, in residual and developing tumor tissue and blood at the resection site were evaluated on EPMR and in follow-up studies. 'Residual tumor' was defined as contrast enhancing mass at the operative site on EPMR. 'Regrowth' was defined as contrast enhancing mass detected on follow-up in the same location as the primary tumor. 'Recurrence' was defined as appearance of a mass lesion in the brain parenchyma distant from the resection bed during follow-up.

RESULTS

Nineteen patients showed no evidence of residual tumor, regrowth, or recurrence on EPMR or any of the later follow-up radiological examinations. EPMR identified 20 cases of residual tumor. Follow-up showed tumor regrowth in 10 patients, and tumor recurrence in 1 case. EPMR showed contrast enhancement of the resection bed in 45 of the 50 patients. Four of the 20 residual tumors showed a thick linear enhancement pattern, and the other 16 cases exhibited thick linear-nodular enhancement. No thin linear enhancement was observed in the residual tumor group. Nine of the 10-regrowth tumors showed a thick linear-nodular enhancement pattern, and one exhibited thin linear enhancement in EPMR. For predicting regrowth tumor EPMR sensitivity was 91%, specificity was 100%, positive predictive value 1; negative predictive value was 0.9375.

CONCLUSION

EPMR, depending on the surgical site enhancement pattern, is a valuable means of demonstrating residual tumors, and can be used to predict possible regrowth after surgery.

Intraoperative Nutzung eines offenen Mittelfeld-MRT während der chirurgischen Therapie zerebraler Gliome

The aim of the present study was to evaluate the effectiveness of intraoperative MRI guidance in achieving more gross-total resection in case of primary brain tumors. We studied 12 patients with low-grade glioma and 19 patients with high-grade glioma who underwent surgery within a vertically open 0.5 T MR system. After initial imaging, the resection was stopped at the point in which the neurosurgeon considered the resection complete by viewing the operation field. At this time, intraoperative MRI was repeated ("first control") to identify any residual tumor. Areas of tumor-suspected tissue were localized and resected, with the exception of tissue adjacent to eloquent areas. Final imaging was carried out before closing the craniotomy. Comparison of "first control" and final imaging revealed a decrease of residual tumor volume from 32% to 4.3% in low-grade gliomas, and from 29% to 10% in high-grade gliomas. Intraoperative MRI allows a clear optimization of microsurgical resection of both low-grade and high-grade gliomas.

Preoperative magnetic source imaging for brain tumor surgery: a quantitative comparison with intraoperative sensory and motor mapping

OBJECT

The aim of this study was to compare quantitatively the methods of preoperative magnetic source (MS) imaging and intraoperative electrophysiological cortical mapping (ECM) in the localization of sensorimotor cortex in patients with intraaxial brain tumors.

METHODS

Preoperative magnetoencephalography (MEG) was performed while patients received painless tactile somatosensory stimulation of the lip, hand, and foot. The early somatosensory evoked field was modeled using a single equivalent current dipole approach to estimate the spatial source of the response. Three-dimensional magnetic resonance image volume data sets with fiducials were coregistered with the MEG recordings to form the MS image. These individualized functional brain maps were integrated into a neuronavigation system. Intraoperative mapping of somatosensory and/or motor cortex was performed and sites were compared. In two subgroups of patients we compared intraoperative somatosensory and motor stimulation sites with MS imaging-based somatosensory localizations. Mediolateral projection of the MS imaging source localizations to the cortical surface reduced systematic intermodality discrepancies. The distance between two corresponding points determined using MS imaging and ECM was 12.5 +/- 1.3 mm for somatosensory-somatosensory and 19 +/- 1.3 mm for somatosensory-motor comparisons. The observed 6.5 mm increase in site separation was systematically demonstrated in the anteroposterior direction, as expected from actual anatomy. In fact, intraoperative sites at which stimulation evoked the same patient response exhibited a spatial variation of 10.7 +/- 0.7 mm.

CONCLUSIONS

Preoperative MS imaging and intraoperative ECM show a favorable degree of quantitative correlation. Thus, MS imaging can be considered a valuable and accurate planning adjunct in the treatment of patients with intraaxial brain tumors.

Photoirradiation therapy of experimental malignant glioma with 5-aminolevulinic acid

OBJECT

Accumulation of protoporphyrin IX (PPIX) in malignant gliomas is induced by 5-aminolevulinic acid (5-ALA). Because PPIX is a potent photosensitizer, the authors sought to discover whether its accumulation might be exploited for use in photoirradiation therapy of experimental brain tumors, without injuring normal or edematous brain.

METHODS

Thirty rats underwent craniotomy and were randomized to the following groups: 1) photoirradiation of cortex (200 J/cm2, 635-nm argon-dye laser); 2) photoirradiation of cortex (200 J/cm2) 6 hours after intravenous administration of 5-ALA (100 mg/kg body weight); 3) cortical cold injury for edema induction; 4) cortical cold injury with simultaneous administration of 5-ALA (100 mg/kg body weight) and photoirradiation of cortex (200 J/cm2) 6 hours later; or 5) irradiation of cortex (200 J/cm2) 6 hours after intravenous administration of Photofrin II (5 mg/kg body weight). Tumors were induced by cortical inoculation of C6 cells and 9 days later, magnetic resonance (MR) images were obtained. On Day 10, animals were given 5-ALA (100 mg/kg body weight) and their brains were irradiated (100 J/cm2) 3 or 6 hours later. Seventy-two hours after irradiation, the brains were removed for histological examination. Irradiation of brains after administration of 5-ALA resulted in superficial cortical damage, the effects of which were not different from those of the irradiation alone. Induction of cold injury in combination with 5-ALA and irradiation slightly increased the depth of damage. In the group that received irradiation after intravenous administration of Photofrin II the depth of damage inflicted was significantly greater. The extent of damage in response to 5-ALA and irradiation in brains harboring C6 tumors corresponded to the extent of tumor determined from pretreatment MR images.

CONCLUSIONS

Photoirradiation therapy in combination with 5-ALA appears to damage experimental brain tumors selectively, with negligible damage to normal or perifocal edematous tissue.

Long-term follow-up in managing anaplastic astrocytoma by multimodality approach with surgery followed by postoperative radiotherapy and PCV-chemotherapy: phase II trial

Overall survival and progression-free survival after 5 and 10 years of 31 patients with malignant glioma treated by a combination of surgery, postoperative radiotherapy, and chemotherapy with a PCV regimen (procarbazine, CCNU [lomustine] and vincristine) is described. Parameters were evaluated by age at diagnosis, gender, ethnic origin, pre- and postsurgery Karnofsky Performance Status (KPS) score, limit and amount of surgical resection, histopathologic type, number of chemotherapy courses, time between surgery and radiotherapy, response to combined therapy, and dosage and type of radiotherapy. Progression-free survival was 29% at 24 months and 22% at 60 and 120 months. Overall survival was 47%, 36%, and 36% after 24, 60, and 120 months, respectively. Favorable prognostic factors for survival in univariate analysis were pre- and postoperative KPS (> or =70; p = 0.015; p = 0.0025, respectively), age of patients (<40; p = 0.01), number of chemotherapy cycles (> or =6; p = 0.02), and radiation dose (> or =60 Gy; p = 0.0015). The only significant prognostic factors for overall survival in a stepwise multivariate analysis were irradiation dose (p = 0.0001), number of chemotherapy cycles (p = 0.001), and preoperative KPS (p = 0.05); for progression-free survival it was number of chemotherapy cycles (p = 0.004). Survival was not affected by excision size, radiation method, histopathologic type of tumor, gender, ethnic origin, or time lapsed between surgery and irradiation.

Interventional and intraoperative magnetic resonance imaging

The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of imaging to guide minimally invasive therapy. The program combines interventional and intraoperative magnetic resonance imaging (MRI) with high-performance computing and novel therapeutic devices. In clinical practice the multidisciplinary program provides for the investigation of a wide range of interventional and surgical procedures. The Signa SP 0.5 T superconducting MRI system (GE Medical Systems, Milwaukee, WI) has a 56-cm-wide vertical gap, allowing access to the patient and permitting the execution of interactive MRI-guided procedures. This system is integrated with an optical tracking system and utilizes flexible surface coils and MRI-compatible displays to facilitate procedures. Images are obtained with routine pulse sequences. Nearly real-time imaging, with fast gradient-recalled echo sequences, may be acquired at a rate of one image every 1.5 s with interactive image plane selection. Since 1994, more than 800 of these procedures, including various percutaneous procedures and open surgeries, have been successfully performed at Brigham and Women's Hospital (Boston, MA).

A multivariate analysis of 416 patients with glioblastoma multiforme: prognosis, extent of resection, and survival

OBJECT

The extent of tumor resection that should be undertaken in patients with glioblastoma multiforme (GBM) remains controversial. The purpose of this study was to identify significant independent predictors of survival in these patients and to determine whether the extent of resection was associated with increased survival time.

METHODS

The authors retrospectively analyzed 416 consecutive patients with histologically proven GBM who underwent tumor resection at the authors' institution between June 1993 and June 1999. Volumetric data and other tumor characteristics identified on magnetic resonance (MR) imaging were collected prospectively.

CONCLUSIONS

Five independent predictors of survival were identified: age, Karnofsky Performance Scale (KPS) score, extent of resection, and the degree of necrosis and enhancement on preoperative MR imaging studies. A significant survival advantage was associated with resection of 98% or more of the tumor volume (median survival 13 months, 95% confidence interval [CI] 11.4-14.6 months), compared with 8.8 months (95% CI 7.4-10.2 months; p < 0.0001) for resections of less than 98%. Using an outcome scale ranging from 0 to 5 based on age, KPS score, and tumor necrosis on MR imaging, we observed significantly longer survival in patients with lower scores (1-3) who underwent aggressive resections, and a trend toward slightly longer survival was found in patients with higher scores (4-5). Gross-total tumor resection is associated with longer survival in patients with GBM, especially when other predictive variables are favorable.

Fluorescence-guided resection of glioblastoma multiforme by using 5-aminolevulinic acid-induced porphyrins: a prospective study in 52 consecutive patients

OBJECT

It has been established that 5-aminolevulinic acid (5-ALA) induces the accumulation of fluorescent porphyrins in glioblastoma multiforme (GBM), a phenomenon potentially exploitable to guide tumor resection. In this study the authors analyze the influence of fluorescence-guided resection on postoperative magnetic resonance (MR) imaging and survival in a series of patients who underwent surgery in the authors' department.

METHODS

Fifty-two consecutive patients with GBM received oral doses of 5-ALA (20 mg/kg body weight) 3 hours before induction of anesthesia. Intraoperatively, tumor fluorescence was visualized using a modified operating microscope. Fluorescing tissue was removed whenever it was considered safely possible. Residual enhancement on early postoperative MR imaging was quantified and related to each patient's characteristics to determine which factors influenced resection. Survival was analyzed using the Kaplan-Meier method and multivariate analysis was performed in which the Karnofsky Performance Scale (KPS) score, residual fluorescence, patient age, and residual enhancement on MR images were considered. Intraoperatively, two fluorescence qualities were perceived: solid fluorescence generally reflected coalescent tumor, whereas vague fluorescence mostly corresponded to infiltrative tumor. Complete resection of contrast-enhancing tumor was accomplished in 33 patients (63%). Residual intraoperative tissue fluorescence left unresected for safety reasons predicted residual enhancement on MR images in 18 of the 19 remaining patients. Age, residual solid fluorescence, and absence of contrast enhancement in MR imaging were independent explanatory factors for survival, whereas the KPS score was significant only in univariate analysis. No perioperative deaths and one case of permanent morbidity were encountered.

CONCLUSIONS

The observations in this study indicate the usefulness of 5-ALA-induced tumor fluorescence for guiding tumor resection. The completeness of resection, as determined intraoperatively from residual tissue fluorescence, was related to postoperative MR imaging findings and to survival in patients suffering from GBM.

Disappearance of tumor contrast on contrast-enhanced FLAIR imaging of cerebral gliomas

Contrast-enhanced fluid-attentuated inversion recovery (FLAIR) magnetic resonance (MR) imaging has shown to be a valuable diagnostic modality in the assessment of cerebral gliomas. In this study we report of a potential pitfall regarding the delineation of enhancing tumor parts on contrast enhanced FLAIR imaging. In a limited number of patients, the administration of gadolinium obscures the area of contrast enhancement on contrast enhanced FLAIR images. Therefore the delineation of the macroscopic tumor parts, which are of great importance for the treatment planning is substantially worsened.

Contrast optimization of fluid-attenuated inversion-recovery (FLAIR) MR imaging in patients with high CSF blood or protein content

After surgical resection of a brain tumor or infection of the cerebrospinal fluid (CSF), elevated levels of blood by-products or protein contaminations are seen in the patient's CSF spaces. In fast fluid-attenuated inversion-recovery (FLAIR) imaging CSF signal is nulled by an appropriate choice of the inversion recovery time TI to improve the contrast between tissue structures adjacent to CSF-filled volumes. With contaminated CSF, however, the longitudinal relaxation time T(1) may change significantly, which results in an incomplete suppression in the FLAIR images, if standard inversion times are used. In this work, a fast single-voxel T(1) measurement pulse sequence with integrated T(1) calculation that allows determination the optimal TI value in 15 sec is presented. The method was tested in five patients after surgical resection of a brain tumor, where FLAIR MRI with and without contrast agent was performed to identify remaining tumor fragments at the margin of the resection cavity.

Brain tumor resection: intraoperative monitoring with high-field-strength MR imaging-initial results

PURPOSE

To investigate the challenges and benefits of magnetic resonance (MR) imaging during brain tumor resection.

MATERIALS AND METHODS

A short-bore 1.5-T MR system equipped with echo-planar-capable gradients was used in resection of brain tumors in 30 patients. MR sequences and need for contrast material enhancement were determined on the basis of the targeted lesion. MR images were acquired before, during, and after surgery. Tissue obtained at biopsy or excised as a result of intraoperative MR findings was examined histopathologically.

RESULTS

MR images of enhancing lesions proved to be the most challenging to interpret intraoperatively, and relative enhancement at the resection cavity boundary was not specific for residual tumor. The ability to detect residual tumor intraoperatively resulted in a radiologically complete resection in 24 (80%) of 30 patients. The frequency of complications was low, and no untoward effects related to the MR environment were observed.

CONCLUSION

Intraoperative MR imaging provided valuable information on the completeness of resection, and resection progress was well demonstrated during surgery.

A mobile high-field magnetic resonance system for neurosurgery

OBJECT

The authors' goal was to place a mobile, 1.5-tesla magnetic resonance (MR) imaging system into a neurosurgical operating room without adversely affecting established neurosurgical management. The system would help to plan accurate surgical corridors, confirm the accomplishment of operative objectives, and detect acute complications such as hemorrhage or ischemia.

METHODS

The authors used an actively shielded 1.5-tesla magnet, together with 15 mtesla/m gradients, MR console computers, gradient amplifiers, a titanium, hydraulic-controlled operating table, and a radiofrequency coil that can be disassembled. The magnet is moved to and from the surgical field by using overhead crane technology. To date, the system has provided unfettered access in 46 neurosurgical patients. In all patients, high-definition T1- and/or T2-weighted images were rapidly and reproducibly acquired at various stages of the surgical procedures. Eleven patients underwent craniotomy that was optimized after preincision imaging. In four patients who harbored subtotally resected tumor, intraoperative MR imaging aided the surgeon in removing the remaining tumor. Interestingly, the intraoperative administration of gadolinium demonstrated a dynamic expansion of enhancement beyond the preoperative contrast contour in patients with malignant glioma. These zones of new enhancement proved, on examination of biopsy samples, to be tumor.

CONCLUSIONS

The authors have demonstrated that high-quality MR images can be obtained in the operating room within reasonable time constraints. Procedures can be conducted without compromising or altering traditional neurosurgical, nursing, or anesthetic techniques. It is feasible that within the next decade intraoperative MR imaging may become the standard of care in neurosurgery.

Accelerated fractionated proton/photon irradiation to 90 cobalt gray equivalent for glioblastoma multiforme: results of a phase II prospective trial

OBJECT

After conventional doses of 55 to 65 Gy of fractionated irradiation, glioblastoma multiforme (GBM) usually recurs at its original location. This institutional phase II study was designed to assess whether dose escalation to 90 cobalt gray equivalent (CGE) with conformal protons and photons in accelerated fractionation would improve local tumor control and patient survival.

METHODS

Twenty-three patients were enrolled in this study. Eligibility criteria included age between 18 and 70 years, Karnofsky Performance Scale score of greater than or equal to 70, residual tumor volume of less than 60 ml, and a supratentorial, unilateral tumor. Actuarial survival rates at 2 and 3 years were 34% and 18%, respectively. The median survival time was 20 months, with four patients alive 22 to 60 months postdiagnosis. Analysis by Radiation Therapy Oncology Group prognostic criteria or Medical Research Council indices showed a 5- to 11-month increase in median survival time over those of comparable conventionally treated patients. All patients developed new areas of gadolinium enhancement during the follow-up period. Histological examination of tissues obtained at biopsy, resection, or autopsy was conducted in 15 of 23 patients. Radiation necrosis only was demonstrated in seven patients, and their survival was significantly longer than that of patients with recurrent tumor (p = 0.01). Tumor regrowth occurred most commonly in areas that received doses of 60 to 70 CGE or less; recurrent tumor was found in only one case in the 90-CGE volume.

CONCLUSIONS

A dose of 90 CGE in accelerated fractionation prevented central recurrence in almost all cases. The median survival time was extended to 20 months, likely as a result of central control. Tumors will usually recur in areas immediately peripheral to this 90-CGE volume, but attempts to extend local control by enlarging the central volume are likely to be limited by difficulties with radiation necrosis.

KRN8602 (MX2-hydrochloride): an active new agent for the treatment of recurrent high-grade glioma

PURPOSE

To assess the efficacy and toxicity of KRN8602 when administered as an intravenous bolus to patients with recurrent high-grade malignant glioma.

PATIENTS AND METHODS

Patients with recurrent or persistent anaplastic astrocytoma or glioblastoma multiforme who had not received recent chemotherapy or radiotherapy and were of good performance status (Eastern Cooperative Oncology Group score < or = 2) were treated with an intravenous bolus of 40 mg/m(2) KRN8602 every 28 days. Tumor responses were assessed radiologically and clinically after every second cycle of therapy. Treatment was continued until documented progression or a total of six cycles.

RESULTS

A median of three cycles (range, one to six cycles) of KRN8602 was administered to 55 patients, 49 of whom received at least two cycles and were, therefore, assessable for response. The overall response rate (disease stabilization or better) was 43% (95% confidence interval, 29% to 58%). There were three complete responses, one partial response, seven minor responses, and 10 patients with stable disease. The median time to progression was 2 months (range, 1.5 to 37 months) and overall survival was 11 months (range, 1.5 to 40 months). Neutropenia was the most common toxicity, although it was generally of brief duration, and there were only seven episodes of febrile neutropenia in 176 cycles delivered. Nonhematologic toxicity was mostly gastrointestinal (nausea and vomiting, diarrhea) and events were grade 2 or lower except for a single episode of grade 3 vomiting.

CONCLUSION

KRN8602 is an active new agent with minimal toxicity in the treatment of relapsed or refractory high-grade glioma. Further studies with KRN8602 in combination with other cytotoxics and in adjuvant treatment of gliomas are warranted.

Intraoperative MR imaging guidance for intracranial neurosurgery: experience with the first 200 cases

PURPOSE

To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for guidance in intracranial surgical procedures.

MATERIALS AND METHODS

A vertically oriented, open-configuration 0.5-T MR imager was housed in a sterile procedure room. Receive and transmit surface coils were wrapped around the patient's head, and images were displayed on monitors mounted in the gap of the magnet and visible to surgeons. During 2 years, 200 intracranial procedures were performed.

RESULTS

There were 111 craniotomies, 68 biopsies, 12 intracranial cyst evaluations, four subdural drainages, and five transsphenoidal pituitary resections performed with the intraoperative MR unit. In each case, the intraoperative MR system yielded satisfactory results by allowing the radiologist to guide surgeons toward lesions and to assist in treatment. In two patients, hyperacute hemorrhage was noted and removed. The duration of the procedure and the complication rate were similar to those of conventional surgery.

CONCLUSION

Intraoperative MR imaging was successfully implemented for a variety of intracranial procedures and provided continuous visual feedback, which can be helpful in all stages of neurosurgical intervention without affecting the duration of the procedure or the incidence of complications. This system has potential advantages over conventional frame-based and frameless stereotactic procedures with respect to the safety and effectiveness of neurosurgical interventions.

Cerebral gliomas and metastases: assessment with contrast-enhanced fast fluid-attenuated inversion-recovery MR imaging

The effect of contrast material on fast fluid-attenuated inversion-recovery (FLAIR) magnetic resonance images was evaluated for 16 patients with enhancing gliomas and 12 patients with cerebral metastases. Because of a marked T1 effect, fast FLAIR imaging provided a marked contrast enhancement, resulting in the highest tumor-to-background contrast ratio compared with standard imaging techniques.

Immediate postoperative CT contrast enhancement following surgery of cerebral tumoral lesions

PURPOSE

Our goal was to evaluate the immediate postoperative contrast enhancement behavior of cerebral lesions and to gain further information about contrast enhancement in patients under general anesthesia.

METHOD

In the early postoperative period, CT scans with the without contrast medium were performed in 46 patients. The time interval between surgery and postoperative CT imaging ranged from 1 to 7.5 h (mean 4 h). Nineteen patients were under general anesthesia during CT investigation.

RESULTS

In the early postoperative period, contrast medium leakage into the tumor resection cavity was noted In 14 patients (30%). Another phenomenon that was observed was the appearance of a strong demarcation and distinct contrast of gray against white matter in 24 patients (52%). This characteristic, global contrast enhancement of the cerebral cortex, occurred in 17 of 19 patients (89%) investigated under general anesthesia.

CONCLUSION

In immediate postoperative CT scans, contrast medium leakage due to extravasation of contrast medium into the tumor resection cavity can be detected early. Moreover, a global contrast enhancement of the cerebral cortex can be detected as a frequent pattern in patients investigated under general anesthesia.

CT and MRI findings after stereotactic resection of brain lesions

OBJECTIVE

To describe postoperative CT and MRI findings and their time course in uncomplicated cases after stereotactic volumetric resections of brain lesions.

MATERIALS AND METHODS

One-hundred twenty-eight imaging studies (CT, 86; MRI, 42), performed 6 h to 2 years after 52 stereotactic operations, were retrospectively reviewed and analyzed in relation to time of surgery in cases without complications.

RESULTS

The extent of resection bed did not change during the first week after operation; reduction of size then began and continued up to 3-6 months. Mass effect and edema showed no changed during the first 4 days, then later regressed gradually. Pneumocephalus was found in 58% of cases in the first 3 weeks, but never later. Benign, surgically-induced enhancement appeared at the margins of encephalotomy and retractor at the end of the first postoperative week, became more prominent during the following weeks, and lasted up to 3-5 months. In the majority of cases enhancement prevented recognition of the residual tumor. Dural enhancement was observed at the craniotomy site very early after the operation and persisted up to 1 year. Meningeal enhancement over convexities was found in 44% of MRI studies.

CONCLUSION

Extent of the resection bed, mass effect, edema, and pneumocephalus show, in uncomplicated cases, a regular regression during the postoperative period. The time course of enhancement is complex and can be a source of diagnostic misinterpretation.

Intrinsic tumors of the insula: a prospective surgical study of 30 patients

Intrinsic insular tumors are frequently excluded from surgical treatment. The authors propose a more extensive approach to these lesions based on the results of this prospective series. From September 1993 to January 1995, 30 patients (18 males and 12 females; mean age 42 years) harboring benign (15 patients) or malignant (15 patients) tumors involving the insula underwent surgical treatment. The dominant and nondominant hemispheres were both affected in 15 cases. Two groups were defined on the basis of preoperative magnetic resonance (MR) imaging: 14 lesions were restricted to the insula and the corresponding opercula; the other 16 lesions also involved other mesocortical and/or allocortical areas. Most patients displayed only mild preoperative symptoms. The median score according to the Karnofsky performance scale was 90. Microsurgical removal was achieved via a transsylvian approach in nine cases and via a frontal and/or temporal approach in 21 cases. According to early postoperative MR imaging, complete tumor removal (100%) was seen in five patients, nearly complete (> 80%) in 21, and incomplete resection (50%-80%) in four patients. There was no operative mortality; 19 patients (63%) experienced immediate postoperative morbidity, including reduced performance. After a mean follow-up review of 8.5 months two of 21 patients suffered permanent deficits, accounting for an overall operative morbidity of 10%. At the mean time of review, three patients with Grade IV tumors had died of tumor recurrence. The authors conclude that low-grade intrinsic insular tumors, as well as Grade III tumors, can be removed with favorable results in the majority of patients. Surgery to excise glioblastomas should only be considered for patients with good preoperative performance and young age.

Radiation response and survival time in patients with glioblastoma multiforme

The determine the value of radiographically assessed response to radiation therapy as a predictor of survival in patients with glioblastoma multiforme (GBM), the authors studied a cohort of 301 patients who were initially treated according to uniform clinical protocols. All patients had newly diagnosed supratentorial GBM and underwent the maximum safe resection followed by external- beam radiation treatment (60 Gy in standard daily fractions or 70.4 Gy in twice-daily fractions of 160 cGy). The radiation response and survival rates were assessable in 222 patients. The extent of resection and the immediate response to radiation therapy were highly correlated with survival, both in a univariate analysis and after correction for age and Karnofsky performance scale (KPS) score in a multivariate Cox model (p< 0.001 for radiation response and p=0.04 for extent of resection). A subgroup analysis suggested that neuroimaging obtained within 3 days after surgery served as a better baseline for assessment of radiation response than images obtained later. Imaging obtained within 3 days after completion of a course of radiation therapy also provided valid radiation response scores. The impact of the radiographically assessed radiation response on survival time was comparable to that of age or KPS score. This information is easily obtained early in the course of the disease, may be of value for individual patients, and may also have implications for the design and analysis of trials of adjuvant therapy for GBM, including volume-dependent therapies such as radiosurgery or brachytherapy.

Early postoperative magnetic resonance imaging following nonneoplastic cortical resection

Postcraniotomy residual tumor is often determined by magnetic resonance (MR) imaging. Magnetic resonance changes that occur in the postoperative setting must be defined to ensure both the optimum timing of postoperative image acquisition and the accurate assessment of images for residual tumor. Postoperative changes in nontumor parenchyma have previously been described for computerized tomography but not for MR imaging. In the present study, 11 patients without intracranial neoplastic disease (six females and five males with a median age of 36 years) submitted to MR imaging 17 to 28 hours after undergoing temporal lobectomies for epilepsy. Four of the operations were performed with the patients under general anesthesia and seven under local anesthesia. Postoperative MR images (T1-weighted, T1-weighted gadolinium enhanced, and T2-weighted) were reviewed. Extraaxial fluid, air, or blood was present in all cases. Enhancement of the resection bed parenchyma occurred in seven (64%) of 11 patients. In three of the remaining four patients, assessment of parenchymal enhancement was obscured by extraaxial fluid collections. Dural enhancement occurred adjacent to the resection site in all of the cases and remotely in 73%. Eight (73%) of 11 patients displayed enhancement of the pia-arachnoid of the ipsilateral cerebral convexity, two (18%) of the contralateral convexity, and four (36%) of the pia-arachnoid overlying the cerebellum. Contrary to previous reports, contrast enhancement of nonneoplastic human brain parenchyma can occur postoperatively within 17 hours. Benign parenchymal contrast enhancement is usually linear in appearance; nonneoplastic dural and leptomeningeal enhancement can occur both adjacent to and distant from the surgical site. Extraaxial fluid collections can hinder MR evaluation of the resection bed.

Preoperative and postoperative follow-up in high-grade gliomas: comparison of transcranial color-coded real-time sonography and computed tomography findings

Twenty patients with high-grade gliomas were prospectively studied by pre- and postoperative transcranial color-coded real-time sonography (TCCS) and CT, to determine the sensitivity of TCCS in the identification of residual tumor and tumor regrowth. Each patient was subjected to preoperative and early postoperative CT (postoperative day 1) and TCCS examinations (postoperative days 6 to 8) and subsequent CT and TCCS follow-up examinations within a time interval of 6 weeks to 3 months. In eight patients, a total of 15 biopsy specimens were intraoperatively obtained from the wall of the resection cavity. Histological findings of intraoperative biopsy specimens showed that hyperechogenic areas adjacent to the resection cavity always contained residual tumor tissue. Early postoperative TCCS identified these hyperechogenic areas in 19 of 20 patients. In 12 patients, postoperative CT revealed contrast enhancement at the resection margin, indicating residual tumor. In these patients the extension of these hyperechogenic areas on TCCS exceeded the contrast-enhancing areas on CT by a mean of 58%. In eight patients, postoperative CT displayed no contrast enhancement along the border of resection. TCCS and histological findings indicated residual tumor in seven of these eight patients. The size of the hyperechogenic lesions identified by postoperative TCCS increased in time and follow-up examinations revealed that tumor regrowth arose from these hyperechogenic areas in all patients. In four patients, tumor regrowth was identified, on average 0.7 months earlier by TCCS than by CT. From these data we conclude that the sensitivity of TCCS in detection of residual tumor and tumor regrowth seems to be superior to CT. The value of TCCS requires further clarification by comparative studies including histology and MRI.