Intraoperative MRI and adjuvant radiosurgery

The Simpson Grading: Is It Still Valid?

The Simpson Grade was introduced in the era of limited resources, outdated techniques, and rudimentary surgical and imaging technologies. With the advent of modern techniques including pre- and post-operative imaging, microsurgical and endoscopic techniques, advanced histopathology and molecular analysis and adjuvant radiotherapy, the utility of the Simpson Grade scale for prognostication of recurrence after meningioma resection has become less useful. While the extent of resection remains an important factor in reducing recurrence, a subjective naked-eye criteria to Grade extent of resection cannot be generalized to all meningiomas regardless of their location or biology. Achieving the highest Simpson Grade resection should not always be the goal of surgery. It is prudent to take advantage of all the tools in the neurosurgeons’ armamentarium to aim for maximal safe resection of meningiomas. The primary goal of this study was to review the literature highlighting the Simpson Grade and its association with recurrence in modern meningioma practice. A PubMed search was conducted using terms “Simpson”, “Grade”, “meningioma”, “recurrence”, “gross total resection”, “extent of resection” “human”. A separate search using the terms “intraoperative imaging”, “intraoperative MRI” and “meningioma” were conducted. All studies reporting prognostic value of Simpson Grades were retrospective in nature. Simpson Grade I, II and III can be defined as gross total resection and were associated with lower recurrence compared to Simpson Grade IV or subtotal resection. The volume of residual tumor, a factor not considered in the Simpson Grade, is also a useful predictor of recurrence. Subtotal resection followed by stereotactic radiosurgery has similar recurrence-free survival as gross total resection. In current modern meningioma surgery, the Simpson Grade is no longer relevant and should be replaced with a grading scale that relies on post-operative MRI imaging that assess GTR versus STR and then divides STR into > or <4−5 cm3, in combination with modern molecular-based techniques for recurrence risk stratification.

Long-term outcome of Simpson IV meningioma resection: Would it improve with adjuvant SRS?

OBJECTIVE

Subtotal meningioma resection (STR) is often performed to minimize surgical morbidity. Nevertheless, only a few studies have reported on patient outcome after STR. We studied the long-term outcome of SIV (Simpson grade IV) resection and identified predictive factors of overall survival (OS), progression-free survival (PFS) and time to progression (TTP).

METHODS

A retrospective analysis was performed on 68 patients who underwent SIV resection of meningioma (grade I) from 2004 to 2010. Data were collected from clinical, surgical and pathology records and radiological imaging. Long-term outcomes were evaluated at least 10 years after surgery.

RESULTS

Permanent morbidity was 11.8%, 30-day mortality 2.9% and progression rate 50.0% for a median follow-up duration of 126.6 months. Median TTP was 86.2 months. Adjuvant SRS was the only significant factor associated with longer PFS (p = 0.0052) and TTP (p = 0.0079). Higher age (p = 0.0022), KPS (p = 0.0182), postoperative ECOG score (p = 0.0182) were reliable predictors of shortened OS and aSRS (p = 0.0445) was reliable predictor of longer OS.

CONCLUSION

STR in intracranial meningioma is still viable and often the only treatment option available in high-risk patients or high-risk tumors. Although surgical morbidity and mortality are high, the OS rate was 85.3% at 5 years and 79.4% at 10 years. Because of the considerable progression rate and rather a long term OS the adjuvant SRS should be considered following SIV resection.

Intraoperative MRI for the microsurgical resection of meningiomas close to eloquent areas or dural sinuses: patient series

BACKGROUND

Meningiomas are the most commonly encountered nonglial primary intracranial tumors. The authors report on the usefulness of intraoperative magnetic resonance imaging (iMRI) during microsurgical resection of meningiomas located close to eloquent areas or dural sinuses and on the feasibility of further radiation therapy.

OBSERVATIONS

Six patients benefited from this approach. The mean follow-up period after surgery was 3.3 (median 3.2, range 2.1–4.6) years. Five patients had no postoperative neurological deficit, of whom two with preoperative motor deficit completely recovered. One patient with preoperative left inferior limb deficit partially recovered. The mean interval between surgery and radiation therapy was 15.8 (median 16.9, range 1.4–40.5) months. Additional radiation therapy was required in five cases after surgery. The mean preoperative tumor volume was 38.7 (median 27.5, range 8.6–75.6) mL. The mean postoperative tumor volume was 1.2 (median 0.8, range 0–4.3) mL. At the last follow-up, all tumors were controlled.

LESSONS

The use of iMRI was particularly helpful to (1) decide on additional tumor resection according to iMRI findings during the surgical procedure; (2) evaluate the residual tumor volume at the end of the surgery; and (3) judge the need for further radiation and, in particular, the feasibility of single-fraction radiosurgery.

Intraoperative imaging in the neurosurgery operating theatre: A review of the most commonly used techniques for brain tumour surgery

INTRODUCTION

New intraoperative imaging techniques, which aim to improve tumour resection, have been implemented in recent years in brain tumour surgery, although they lead to an increase in resources. In order to carry out an update on this topic, this manuscript has been drafted by a group from the Sociedad Española de Neurocirugía (Spanish Society of Neurosurgery).

MATERIAL AND METHODS

Experts in the use of each one of the most-used intraoperative techniques in brain tumour surgery were presented with a description of the technique and a brief review of the literature. Indications for use, their advantages and disadvantages based on clinical experience and on what is published in the literature will be described.

RESULTS

The most robust intraoperative imaging technique appears to be low- and high-field magnetic resonance imaging, but this is the technique which results in the greatest expenditure. Intraoperative ultrasound navigation is portable and less expensive, but it provides poorer differentiation of high-grade tumours and is observer-dependent. The most-used fluorescence techniques are 5-aminolevulinic acid for high-grade gliomas and fluorescein, useful in lesions which rupture the blood-brain barrier. Last of all, intraoperative CT is more versatile in the neurosurgery operating theatre, but it has fewer indications in neuro-oncology surgery.

CONCLUSIONS

Intraoperative imaging techniques are used with increasingly greater frequency in brain tumour surgery, and the neurosurgeon should assess their possible use depending on their resources and the needs of each patient.

Planned Subtotal Resection of Vestibular Schwannoma Differs from the Ideal Radiosurgical Target Defined by Adaptive Hybrid Surgery

OBJECTIVE

To retrospectively compare ideal radiosurgical target volumes defined by a manual method (surgeon) to those determined by Adaptive Hybrid Surgery (AHS) operative planning software in 7 patients with vestibular schwannoma (VS).

METHODS

Four attending surgeons (3 neurosurgeons and 1 ear, nose, and throat surgeon) manually contoured planned residual tumors volumes for 7 consecutive patients with VS. Next, the AHS software determined the ideal radiosurgical target volumes based on a specified radiotherapy plan. Our primary measure was the difference between the average planned residual tumor volumes and the ideal radiosurgical target volumes defined by AHS (dRV_AHS-planned).

RESULTS

We included 7 consecutive patients with VS in this study. The planned residual tumor volumes were smaller than the ideal radiosurgical target volumes defined by AHS (1.6 vs. 4.5 cm³, P = 0.004). On average, the actual post-operative residual tumor volumes were smaller than the ideal radiosurgical target volumes defined by AHS (2.2 cm³ vs. 4.5 cm³; P = 0.02). The average difference between the ideal radiosurgical target volume defined by AHS and the planned residual tumor volume (dRV_AHS-planned) was 2.9 ± 1.7 cm³, and we observed a trend toward larger dRV_AHS-planned in patients who lost serviceable facial nerve function compared with patients who maintained serviceable facial nerve function (4.7 cm³ vs. 1.9 cm³; P = 0.06).

CONCLUSIONS

Planned subtotal resection of VS diverges from the ideal radiosurgical target defined by AHS, but whether that influences clinical outcomes is unclear.

Growth Patterns of Residual Tumor in Preoperatively Growing Vestibular Schwannomas

Objectives  To analyze growth of residual vestibular schwannoma (VS) following incomplete tumor resection and determine the influence of residual location and size. Design  Retrospective case note and scan review. Setting  Tertiary skull base unit. Participants  Patients with residual tumor following primary surgery for medium and large unilateral growing vestibular schwanomas between 2006 and 2009. Main Outcome Measures  Location of residual VS and post-operative growth, comparing those with more (>5%) or less than 5% of tumor residual (<5%). Results  Fifty-two patients had visible residual tumor left behind at surgery. Twenty had < 5% and 32 had > 5% residual. The residual growth rates were 38% overall, 20% in < 5%, and 50% in > 5% residuals. There was no significant difference in growth rates at different residual locations. Median follow-up was 6.4 years. Conclusions  There is a greater risk of regrowth of residuals > 5%. All positions of residual tumor can regrow, and the preoperative tumor size plays a role in this. Further data is needed to confirm if residual tumor in the fundus is less likely to grow.

Follow-up and long-term outcome of nonfunctioning pituitary adenoma operated by transsphenoidal surgery with intraoperative high-field magnetic resonance imaging

BACKGROUND

Intraoperative MRI (iMRI) increases gross total resection (GTR) rates in transsphenoidal surgery; however, long-term follow-up data is lacking. The objective is to assess the outcome of patients with nonfunctioning pituitary adenomas (NFA) at a mean follow-up of > 5 years.

METHODS

Patients with NFA operated in a single institution with resection control by a 1.5 T intraoperative magnetic resonance imaging (iMRI) scanner and no previous pituitary surgery were included. Microscopical transsphenoidal approaches with optional endoscopy were used. The iMRI was chosen for spacious suprasellar or retrosellar and/or invasive tumours. IMRI-scans were made if GTR or if nonresectable remnants were presumed. The patients had a full neuroradiological, endocrinological and ophthalmological follow-up at the institution.

RESULTS

Eighty-five patients (67 % male;55 ± 14 years) with a follow-up of 5.6 ± 1.9 years were included. The initial GTR rate on iMRI was 44 %. In 83 %, further resections were possible, resulting in a final GTR rate of 66 %. In invasive tumours, the GTR rate was increased by 29 %. The detection of remnants by iMRI had high sensitivity and specificity (100 %), as opposed to endoscopy (21 %;78 %). During follow-up, four (7 %) tumours recurred and 14 (64 %) remnants grew. The recurrence and regrowth rate were 0.013 and 0.114 patients/years, respectively. Seventy-nine percent of the growing remnants were seen < 5 years postoperatively.

CONCLUSIONS

The use of iMRI for transsphenoidal resection leads to low recurrence rates. Even in case of invasive tumours, distinctly more patients show long tumour-free follow-ups. Tumour remnants detected by iMRI are at high risk to grow within 5 years after surgery.

Intraoperative high-field MRI for transsphenoidal reoperations of nonfunctioning pituitary adenoma

OBJECT

The loss of anatomical landmarks, frequently invasive tumor growth, and tissue changes make transsphenoidal reoperation of nonfunctioning pituitary adenomas (NFAs) challenging. The use of intraoperative MRI (iMRI) may lead to improved results. The goal of this retrospective study was to evaluate the impact of iMRI on transsphenoidal reoperations for NFA.

METHODS

Between September 2002 and July 2012, 109 patients underwent reoperations in which 111 transsphenoidal procedures were performed and are represented in this study. A 1.5-T Magnetom Sonata Maestro Class scanner (Siemens) was used for iMRI. Follow-up iMRI scans were acquired if gross-total resection (GTR) was suspected or if no further removal seemed possible.

RESULTS

Surgery was performed for tumor persistence and regrowth in 26 (23%) and 85 (77%) patients, respectively. On the initial iMRI scans, GTR was confirmed in 19 (17%) patients. Remnants were located as follows: 65 in the cavernous sinus (71%), 35 in the suprasellar space (38%), 9 in the retrosellar space (10%). Additional resection was possible in 62 (67%) patients, resulting in a significant volume reduction and increased GTR rate (49%). The GTR rates of invasive tumors on initial iMRI and postoperative MRI (poMRI) were 7% and 25%, respectively. Additional remnant resection was possible in 64% of the patients. Noninvasive tumors were shown to be totally resected on the initial iMRI in 31% of cases. After additional resection for 69% of the procedures, the GTR rate on poMRI was 75%. Transcranial surgery to resect tumor remnants was indicated in 5 (5%), and radiotherapy was performed in 29 (27%) patients. After GTR, no recurrence was detected during a mean follow-up of 2.2 ± 2.1 years.

CONCLUSIONS

The use of iMRI in transsphenoidal reoperations for NFA leads to significantly higher GTR rates. It thus prevents additional operations and reduces the number of tumor remnants. The complication rates do not exceed the incidences reported in the literature for primary transsphenoidal surgery. If complete tumor resection is not possible, iMRI guidance can facilitate tumor volume reduction.

Intraoperative MRI and endocrinological outcome of transsphenoidal surgery for non-functioning pituitary adenoma

BACKGROUND

Transsphenoidal surgery guided by intraoperative MRI (iMRI) is related to higher rates of tumour resection. The influence of iMRI on endocrinological outcome is still unclear. This study evaluates the endocrinological outcome of iMRI-guided transsphenoidal surgery.

METHODS

A series of 60 patients operated by iMRI-guidance for inactive adenomas were matched to a previous series of 32 controls. The following factors were used for matching: gender; age; tumour volume; Hardy's grade; pituitary function; pituitary stalk configuration; stalk effect hyperprolactinemia; arterial hypertension; diabetes mellitus; smoking.

RESULTS

Total resection rates were higher in the iMRI group (85%) than in the control group (69%). Follow-up times were 3.2 ± 1.0 years in the iMRI group and 6.8 ± 4.1 years for controls. No patient in the iMRI group needed additional tumour treatment, as opposed to 13% of the controls. The rate of postoperative hypopituitarism was 29% in the iMRI and 45% in the control group. Predictors for new hypopituitarism in the iMRI group were age >65 years, Hardy's grade >2 tumours and hypertension. Recovery rates were 59% in the iMRI and 45% for controls. Predictors of better recovery rates were female gender and age <65 years. The following predictors lead to an endocrinological benefit of iMRI-guidance: Hardy's grade <3 tumours; age <65 years; no hypertension; non-smokers; dysfunction of two or three axes pre-operatively.

CONCLUSION

The use of iMRI in transsphenoidal surgery for non-functioning pituitary adenoma might lead to higher total resection rates. In our series, resection of remnants detected by iMRI was neither associated with higher incidences of postoperative hypopituitarism nor with lower recovery rates of pituitary axes.

Intraoperative magnetic resonance imaging and early prognosis for vision after transsphenoidal surgery for sellar lesions

Object

Sellar lesions with suprasellar extension may cause loss of visual acuity and visual field damage due to compression of the optic chiasm. Using intraoperative MR (iMR) imaging to detect symptomatic lesion remnants adjacent to the optic chiasm (that may be resected in the same procedure) may positively affect the functional outcome of patients with these lesions. The aim of this study was to evaluate the correlation between visual improvement and optic nerve decompression detected by iMR imaging in patients undergoing transsphenoidal resection of pituitary lesions.

Methods

A total of 32 patients (23 men and 9 women) who underwent transsphenoidal resection of sellar lesions causing visual impairment were included in this study. Tumor volume ranged from 0.9 cm3 to 55.7 cm3 (mean 9.8 ± 11.7 cm3). Preoperative assessment showed visual field damage in 31 patients (97%) and loss of visual acuity in 28 patients (88%). The latency period between the appearance of symptoms and transsphenoidal decompression was 14.9 ± 19.5 weeks.

Results

Intraoperative MR imaging was performed after the resection was believed to be complete, or if further tumor removal was not safely possible due to changed conditions in the surgical field. Complete resection was detected on these initial scans in 17 patients (53%). Partial resection was achieved in 9 patients (28%) and tumor debulking in 6 (19%). Additional resection was possible in 8 (53%) of these 15 patients. Four (50%) of these 8 cases had suprasellar remnants and the optic chiasm was subsequently decompressed. In 5 cases optimal decompression of the optic chiasm was not possible. On early follow-up within 1 month after surgery, overall improvement of visual field damage was observed in 27 patients (87%). In 23 patients (74%), the Goldmann perimetry demonstrated complete recovery. Improvement of visual acuity was noted in 24 patients (86%). Eighteen patients (64%) regained full visual acuity. Identification of a decompressed optic chiasm on iMR imaging was significantly correlated with visual field improvement (p = 0.0007; positive predictive value 0.96, 95% CI 0.81–0.99) and relief of visual acuity deficits (p = 0.0002; positive predictive value 0.96, 95% CI 0.79–0.99). Two patients needed transcranial procedures for symptomatic tumor remnants detected on iMR imaging.

Conclusions

Intraoperative MR imaging findings correlate with prognosis of visual deficits after transsphenoidal decompression of the anterior optic pathways. The use of iMR imaging may prevent revision surgery for unexpected symptomatic remnants.

The evolution of iMRI utilization for pediatric neurosurgery: a single center experience

From its inception intraoperative magnetic resonance imaging (ioMRI) was envisioned to have significant applications in neurosurgery in general and pediatrics specifically. Over the last 9 years we have noted a dramatic shift in our ioMRI usage from intracranial tumors to cerebrospinal fluid management and complex cysts. Here we present seven selected cases to illustrate lessons learned from our operative experience within the GE Signa SP/I open-configuration "double-doughnut" MRI. These cases including a ganglioglioma, ependymoma, and pilocytic astrocytoma tumor resection, as well as arachnoid cysts, complex cyst, and microabscess drainage reflect our current use of ioMRI in pediatric neurosurgical cases. Namely that ioMRI is optimal for (1) resection of small tumors with poorly differentiated tumor margins, (2) large tumors with mass effect, and (3) shunt or catheter placement requiring either extreme accuracy or intraoperative confirmation of catheter placement. We also comment on the legitimate limitations of this technology in certain operations. Additionally emphasized are cases in which ioMRI imaging drives operative decision making, highlighting the unique and unequaled abilities of this technology for a subset of pediatric neurosurgical cases.

Intraoperative magnetic resonance imaging: impact on brain tumor surgery

BACKGROUND

Refinements in the imaging of intracranial tumors assist neurosurgeons in maximizing resections in a safe manner. Intraoperative magnetic resonance imaging (iMRI) represents a recent addition to their therapeutic armamentaria.

METHODS

The authors reviewed the development of iMRI and describe their experience with iMRI-guided resection of intracranial tumors in 112 patients. The PoleStar N-10 iMRI system was used in this series.

RESULTS

Intraoperative imaging resulted in additional tumor removal in 40 (36%) of the patients. In another 35 (31%), imaging confirmed that the goals of surgery had been attained so potentially harmful dissection in and around the brain was avoided. For patients with lesions of the skull base, iMRI was possible in all but 2 patients who had a large body habitus. There was a decrease in length of hospital stay for patients who had surgery with iMRI. Lesion location did not play a role in this change. Brain tumor surgery was affected in 67% of patients. A potential for cost savings with iMRI was demonstrated.

CONCLUSIONS

Intraoperative imaging with MRI is the latest evolution in the increasing precision of neurosurgery. The advantages of this technology will make it a ubiquitous feature in the neurosurgical operating room.