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Molecular imaging of gliomas with PET: Opportunities and limitations

Neuro-Oncology 13(8):806–819, 2011. doi:10.1093/neuonc/nor054

Neuroimaging enables the noninvasive evaluation of glioma and is considered to be one of the key factors for individualized therapy and patient management, since accurate diagnosis and demarcation of viable tumor tissue is required for treatment planning as well as assessment of treatment response. Conventional imaging techniques like MRI and CT reveal morphological information but are of limited value for the assessment of more specific and reproducible information about biology and activity of the tumor. Molecular imaging with PET is increasingly implemented in neuro-oncology, since it provides additional metabolic information of the tumor, both for patient management as well as for evaluation of newly developed therapeutics.Different molecular processes have been proposed to be useful, like glucose consumption, expression of amino acid transporters, proliferation rate, membrane biosynthesis, and hypoxia. Thus, PET might help neuro-oncologists gain further insights into tumor biology by “true molecular imaging” as well as understand treatment-related phenomena. This review describes the method of PET acquisition as well as the tracers used to image biological processes in gliomas. Furthermore, it considers the clinical impact of PET on the use of currently available radiotracers, which were shown to be potentially valuable for discrimination between neoplastic and nonneoplastic tissue, as well as on tumor grading, determinination of treatment response, and providing an outlook toward further developments.

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Preoperative Evaluation of Unruptured Cerebral Aneurysms by Fast Imaging Employing Steady- State Acquisition Image

Neurosurgery 69:412–420, 2011 DOI: 10.1227/NEU.0b013e318213431e

In aneurysm surgery, understanding the microanatomy around the aneurysm such as perforating arteries and cranial nerves is mandatory.

OBJECTIVE: To assess the usefulness in determining the microanatomy around the cerebral aneurysms by the use of fast imaging employing steady-state acquisition (FIESTA) images of magnetic resonance imaging preoperatively, in addition to computed tomography and digital subtraction angiography.

METHODS: Between October 2006 and June 2009, 123 patients with 140 unruptured cerebral aneurysms were treated in our institution. Eighty-two patients were assessed with FIESTA by the operators on the workstation of the magnetic resonance image before surgical clipping of the aneurysms. The small vessels and cranial nerves were confirmed intraoperatively before or after obliteration of the aneurysms.

RESULTS: Sensitivities and specificities of FIESTA imaging were 100% in detecting hypothalamic artery around anterior communicating artery aneurysms, oculomotor nerve attachment to the posterior communicating artery aneurysm domes, and anterior choroidal artery adhesion to the posterior communicating artery aneurysms. This technique was also useful for predicting adhesion between the aneurysm and adjacent main trunks or perforators. Although the specificity was 100%, sensitivity was 56% in detecting vessel adhesion around the middle cerebral aneurysms. This technique can provide limited information in large aneurysms or aneurysms located in minimal cerebrospinal fluid space. The overall outcomes of the patients included 120 excellent recoveries, 1 moderate deficit, 1 severe deficit, and 1 persistent vegetative state according to the Glasgow Outcome Scale.

CONCLUSION: By giving information on the minute anatomical structure around the aneurysm, FIESTA can contribute to thorough preoperative evaluations of cerebral aneurysms.

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Thromboembolic Complications After Neuroform Stent-Assisted Treatment of Cerebral Aneurysms: The Duke Cerebrovascular Center Experience in 235 Patients With 274 Stents

Neurosurgery 69:369–375, 2011 DOI: 10.1227/NEU.0b013e31821bc49c

The Neuroform Stent has facilitated the endovascular treatment of wide-necked cerebral aneurysms. It is unknown which factors pose risks of thromboembolic events after stent placement.

OBJECTIVE: This series is the largest single-center study reporting on the incidence of and factors influencing thromboembolic complications after Neuroform stent placement.

METHODS: A total of 235 patients were treated with 274 Neuroform stents. The thromboembolic event rate was determined by imaging or clinical evidence of cerebrovascular accident within 90 days of stent placement; for patients with incomplete follow-up through chart review, telephone interviews were conducted. Analyses were performed to investigate patient factors that may be associated with stroke.

RESULTS: Most aneurysms were unruptured; 30 patients (12.8%) presented with acute subarachnoid hemorrhage. Twelve patients of the 224 with follow-up (5.4%, 95% confidence interval: 2.4%-8.3%) demonstrated imaging or clinical evidence of a new thromboembolic event within 90 days of stent placement. There was a 3.1% thromboembolic rate for unruptured aneurysms and a 20% rate in patients with subarachnoid bleed. Hemorrhage was significantly associated with having a thromboembolic event (P = .002). There was a trend toward an increased thromboembolic event rate for patients with hypertension (P = .07). Larger stent caliber was significantly associated with a decreased thromboembolic event rate (P = .032).

CONCLUSION: Our results suggest that the thromboembolic event rate associated with Neuroform stent use is low in unruptured aneurysms. In ruptured aneurysms, the complication rate is high, possibly partly related to restricted use of antiplatelet therapy. Stent size and hypertension may be associated with the risk of stroke, but additional studies are needed to confirm their significance.

KEY WORDS: Cerebral aneurysms, Neuroform stent, Stent-assisted aneurysm coiling, Stent thrombosis, Thromboembolic complications

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Safety of microvascular decompression for trigeminal neuralgia in the elderly

J Neurosurg 115:202–209, 2011. DOI: 10.3171/2011.4.JNS101924

Microvascular decompression (MVD) offers an effective and durable treatment for patients suffering from trigeminal neuralgia (TN). Because the disorder has a tendency to occur in older persons, the risks of surgical treatment in the elderly have been a topic of recent interest. To date, evidence derived from several small retrospective and a single prospective case series has suggested that age does not increase the complication rate associated with surgery. Using a large national database, the authors aimed to study the impact of age on in-hospital complications following MVD for TN.

Methods. Using the Nationwide Inpatient Sample (NIS) for the 10-year period from 1999 to 2008, the authors selected all patients who underwent MVD for TN. The primary outcome of interest was the in-hospital mortality rate. Secondary outcomes of interest were cardiac, pulmonary, thromboembolic, cerebrovascular, and wound complications as well as the duration of hospital stay, total hospital charges, and discharge location. An elderly cohort of patients was first defined as those 65 years of age and older and then redefined as those 75 years and older.

Results. A total of 3273 patients who underwent MVD for TN were identified, having a median age of 57 years. Within this sample, 31.5% were 65 years and older and 10.7% were 75 years and older. The in-hospital mortality rate was 0.68% for patients 65 years or older (p = 0.0087) and 1.16% for those 75 years or older (p = 0.0026). In patients younger than 65 years, the in-hospital mortality rate was 0.13% (3 deaths among 2241 patients). As analyzed using the chi-square test (for both 65 and 75 years as the age cutoff) and the Pearson rank correlation coefficient, the risk of cardiac, pulmonary, thromboembolic, and cerebrovascular complications was higher in older patients (that is, those 65 and older and those 75 and older), but the risks of wound complications and CNS infection were not. The risk of any in-hospital complication occurring in a patient 65 years and older was 7.36% (p < 0.0001) and 10.0% in those 75 years and older (p < 0.0001). There was no difference in the total hospital charges associated with age. The duration of the hospital stay was longer in older patients, and the likelihood of discharge home was lower in older patients.

Conclusions. Microvascular decompression for TN in the elderly population remains a reasonable surgical option. However, based on data from a large national database, authors of the present study suggest that complications do tend to gradually increase in tandem with an advanced age. While age does not act as a risk factor in isolation, it may serve as a convenient surrogate for complication rates. The authors hope that this information can be of use in guiding older patients through decisions for the surgical treatment of TN.

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Comparative Morphological Analysis of the Geometry of Ruptured and Unruptured Aneurysms

Neurosurgery 69:349–356, 2011 DOI: 10.1227/NEU.0b013e31821661c3

The risk of aneurysm rupture appears to be related to multiple factors such as topology, morphology, size, perianeurysmal environment, and blood flow hemodynamics.

OBJECTIVE: To evaluate aneurysm morphology and to quantitatively compare the volumetric parameters between ruptured and unruptured aneurysms from our clinical database at the UCLA Medical Center.

METHODS: Novel algorithms that automatically compute aneurysm geometry were tested on the basis of voxel data obtained from angiographic images, and measurements of aneurysm morphology were automatically recorded. We studied a total of 50 aneurysms (25 ruptured and 25 unruptured) with sizes ranging from 3 to 26 mm. To compare the geometric characteristics between ruptured and unruptured groups, we examined measurements, including volume and surface area, and the ratios of these measurements to the minimal bounding sphere around each aneurysm.

RESULTS: More than 65% of ruptured aneurysms had a ratio of aneurysm volume to bounding sphere volume (AVSV) of > 0.5. More than 70% of ruptured aneurysms had a ratio of aneurysm surface to bounding sphere surface (AASA) of < 1. A trend differentiating ruptured and unruptured aneurysms was observed in AVSV (P = .07) and AASA (P = .04). Classification and regression trees analysis showed 68% correct classification with rupture for AVSV and 70% for AASA.

CONCLUSION: By comparing aneurysm geometry with the bounding sphere, we found a trend associating the ratios of aneurysm volume and surface area with rupture. These geometric parameters may be useful for understanding the influence of morphology on the risk of aneurysm rupture.

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Cost-effectiveness of transforaminal lumbar interbody fusion for Grade I degenerative spondylolisthesis

J Neurosurg Spine 15:138–143, 2011. DOI: 10.3171/2011.3.SPINE10562

Transforaminal lumbar interbody fusion (TLIF) for spondylolisthesis-associated back and leg pain is associated with improvement in pain, disability, and quality of life. However, given the rising health care costs associated with spinal fusion procedures and varying results of recent cost-utility studies, the cost-effectiveness of TLIF remains unclear. The authors set out to assess the comprehensive costs of TLIF at their institution and to determine its cost-effectiveness in the treatment of degenerative spondylolisthesis.

Methods. Forty-five patients undergoing TLIF for Grade I degenerative spondylolisthesis–associated back and leg pain after 6–12 months of conservative therapy were included. The authors assessed the 2-year back pain visual analog scale (VAS) score, leg pain VAS score, Oswestry Disability Index, and total back-related medical resource utilization, missed work, and health-state values (quality-adjusted life years [QALYs], calculated from EQ-5D with US valuation). Two-year resource use was multiplied by unit costs based on Medicare national allowable payment amounts (direct cost), and patient and caregiver workday losses were multiplied by the self-reported gross-of-tax wage rate (indirect cost). The mean total 2-year cost per QALY gained after TLIF was assessed.

Results. Compared with preoperative health states reported after at least 6 months of medical management, a significant improvement in back pain VAS score, leg pain VAS score, and Oswestry Disability Index was observed 2 years after TLIF, with a mean 2-year gain of 0.86 QALYs. The mean ± SD total 2-year cost of TLIF was $36,836 ± $11,800 (surgery cost, $21,311 ± $2800; outpatient resource utilization cost, $3940 ± $2720; indirect cost, $11,584 ± $11,363). Transforaminal lumbar interbody fusion was associated with a mean 2-year cost per QALY gained of $42,854.

Conclusions. Transforaminal lumbar interbody fusion improved pain, disability, and quality of life in patients with degenerative spondylolisthesis–associated back and leg pain. The total cost per QALY gained for TLIF was $42,854 when evaluated 2 years after surgery with Medicare fees, suggesting that TLIF is a cost-effective treatment of lumbar spondylolisthesis.

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Meta-Analysis of Hemorrhagic Complications From Ventriculostomy Placement by Neurosurgeons

Neurosurgery 69:255–260, 2011 DOI: 10.1227/NEU.0b013e31821a45ba

Ventriculostomy placement is an important diagnostic and therapeutic tool for neurosurgeons. Multiple authors have presented retrospective series of patients evaluating periprocedure hemorrhage.

OBJECTIVE: We performed a meta-analysis of existing studies to determine a more accurate rate of hemorrhage.

METHODS: A MEDLINE and PubMed search was performed to find all studies of 25 or more patients conducted since 1970 that found a hemorrhagic complication rate from placement of a ventriculostomy. Studies in which a non-neurosurgeon placed the ventriculostomy and studies involving premature infants were excluded.

RESULTS: Sixteen studies were used to obtain data from 2428 ventriculostomy procedures. Hemorrhage was found after 203 procedures, and 52 of these hemorrhages were deemed significant by the authors. The cumulative rate of hemorrhage was 7.0% (95% confidence interval: 4.5%-9.4%), with P , .05. The cumulative rate of significant hemorrhage was 0.8% (95% confidence interval: 0.2%-1.4%) with P , .05.

CONCLUSION: Based on our meta-analysis, the overall hemorrhagic complication rate from ventriculostomy placement by neurosurgeons is approximately 7%. The rate of significant hemorrhage from ventriculostomy placement is approximately 0.8%. Further prospective studies are warranted to better address this question.

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Frameless deep brain stimulation using intraoperative O-arm technology

J Neurosurg 115:301–309, 2011. DOI: 10.3171/2011.3.JNS101642

Correct lead location in the desired target has been proven to be a strong influential factor for good clinical outcome in deep brain stimulation (DBS) surgery. Commonly, a surgeon’s first reliable assessment of such location is made on postoperative imaging. While intraoperative CT (iCT) and intraoperative MR imaging have been previously described, the authors present a series of frameless DBS procedures using O-arm iCT.

Methods. Twelve consecutive patients with 15 leads underwent frameless DBS placement using electrophysiological testing and O-arm iCT. Initial target coordinates were made using standard indirect and direct assessment. Microelectrode recording (MER) with kinesthetic responses was performed, followed by microstimulation to evaluate the side-effect profile. Intraoperative 3D CT acquisitions obtained between each MER pass and after final lead placement were fused with the preoperative MR image to verify intended MER movements around the target area and to identify the final lead location. Tip coordinates from the initial plan, final intended target, and actual lead location on iCT were later compared with the lead location on postoperative MR imaging, and euclidean distances were calculated. The amount of radiation exposure during each procedure was calculated and compared with the estimated radiation exposure if iCT was not performed.

Results. The mean euclidean distances between the coordinates for the initial plan, final intended target, and actual lead on iCT compared with the lead coordinates on postoperative MR imaging were 3.04 ± 1.45 mm (p = 0.0001), 2.62 ± 1.50 mm (p = 0.0001), and 1.52 ± 1.78 mm (p = 0.0052), respectively. The authors obtained good merging error during image fusion, and postoperative brain shift was minimal. The actual radiation exposure from iCT was invariably less than estimates of exposure using standard lateral fluoroscopy and anteroposterior radiographs (p < 0.0001).

Conclusions. O-arm iCT may be useful in frameless DBS surgery to approximate microelectrode or lead locations intraoperatively. Intraoperative CT, however, may not replace fundamental DBS surgical techniques such as electrophysiological testing in movement disorder surgery. Despite the lack of evidence for brain shift from the procedure, iCT-measured coordinates were statistically different from those obtained postoperatively, probably indicating image merging inaccuracy and the difficulties in accurately denoting lead location. Therefore, electrophysiological testing may truly be the only means of precisely knowing the location in 3D space intraoperatively. While iCT may provide clues to electrode or lead location during the procedure, its true utility may be in DBS procedures targeting areas where electrophysiology is less useful. The use of iCT appears to reduce radiation exposure compared with the authors’ traditional frameless technique.

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Ability of electromyographic monitoring to determine the presence of malpositioned pedicle screws in the lumbosacral spine: analysis of 2450 consecutively placed screws

J Neurosurg Spine 15:130–135, 2011.DOI: 10.3171/2011.3.SPINE101

Pedicle screws provide efficient stabilization along all 3 columns of the spine, but they can be technically demanding to place, with malposition rates ranging from 5% to 10%. Intraoperative electromyographic (EMG) monitoring has the capacity to objectively identify a screw breaching the medial pedicle cortex that is in proximity to a nerve root. The purpose of this study is to describe and evaluate the authors’ 7-year institutional experience with intraoperative EMG monitoring during placement of lumbar pedicle screws and to determine the clinical utility of intraoperative EMG monitoring.

Methods. The authors retrospectively studied 2450 consecutive lumbar pedicle screws placed in 418 patients from June 2002 through June 2009. All screws were inserted using a free-hand technique and anatomical landmarks, stimulated at 10.0 mA, and evaluated with CT scanning within 48 hours postoperatively. Medial pedicle screw breach was defined as having greater than 25% of the screw diameter extend outside of the pedicle, as confirmed on CT scanning or intraoperatively by a positive EMG response indicating a medial breach. The sensitivity and specificity of intraoperative EMG monitoring in detecting the presence of a medial screw breach was evaluated based on the following definitions: 1) true positive (a positive response to EMG stimulation confirmed as a breach intraoperatively or on postoperative CT scans); 2) false positive (positive response to EMG stimulation confirmed as a correctly positioned screw on postoperative CT scans); 3) true negative (no response to EMG stimulation confirmed as a correctly positioned screw on postoperative CT scans); or 4) false negative (no response to EMG stimulation but confirmed as a breach on postoperative CT scans).

Results. One hundred fifteen pedicle screws (4.7%) showed positive stimulation during intraoperative EMG monitoring. At stimulation thresholds less than 5.0, 5.0–8.0, and > 8.0 mA, the specificity of a positive response was 99.9%, 97.9%, and 95.9%, respectively. The sensitivity of a positive response at these thresholds was only 43.4%, 69.6%, and 69.6%, respectively. At a threshold less than 5.0 mA, 91% of screws with a positive EMG response were confirmed as true medial breaches. However, at thresholds of 5.0–8.0 mA or greater than 8.0 mA, a positive EMG response was associated with 89% and 100% false positives (no breaches), respectively.

Conclusions. When using intraoperative EMG monitoring, a positive response at screw stimulation thresholds less than 5.0 mA was highly specific for a medial pedicle screw breach but was poorly sensitive. A positive response to stimulation thresholds greater 5.0 mA was associated with a very high rate of false positives. The authors’ experience suggests that pedicle screws showing positive stimulation below 5.0 mA warrants intraoperative investigation for malpositioning while responses at higher thresholds are less reliable at accurately representing a medial breach

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Complications following decompression of Chiari malformation Type I in children: dural graft or sealant?

J Neurosurg Pediatrics 8:177–183, 2011. DOI: 10.3171/2011.5.PEDS10362

Posterior fossa decompression with duraplasty for Chiari malformation Type I (CM-I) is a common pediatric neurosurgery procedure. Published series report a complication rate ranging from 3% to 40% for this procedure. Historically, many dural substitutes have been used, including bovine grafts, human cadaveric pericardium, synthetic dura, and autologous pericranium. The authors hypothesized that a recently observed increase in complications was dependent on the graft used.

Methods. Between January 2004 and January 2008, 114 consecutive patients ≤ 18 years old underwent primary CM-I decompression using duraplasty. Records were retrospectively reviewed for short- and intermediate-term complications and operative technique, focusing on the choice of duraplasty graft with or without application of a tissue sealant.

Results. The average age of the patients was 8.6 years. The dural graft used was variable: 15 were treated with cadaveric pericardium, 12 with Durepair, and 87 with EnDura. Tisseel was used in 75 patients, DuraSeal in 12, and no tissue sealant was used in 27 patients. The overall complication rate was 21.1%. The most common complications included aseptic meningitis, symptomatic pseudomeningocele, or a CSF leak requiring reoperation. The overall complication rates were as follows: cadaveric pericardium 26.7%, Durepair 41.7%, and EnDura 17.2%; reoperation rates were 13%, 25%, and 8.1%, respectively. Prior to adopting a different graft product, the overall complication rate was 18.1%; following the change the rate increased to 35%. Complication rates for tissue sealants were 14.8% for no sealant, 18.7% for Tisseel, and 50% for DuraSeal. Nine patients were treated with the combination of Durepair and DuraSeal and this subgroup had a 56% complication rate.

Conclusions. Complication rates after CM-I decompression may be dependent on the dural graft with or without the addition of tissue sealant. The complication rate at the authors’ institution approximately doubled following the adoption of a different graft product. Tissue sealants used in combination with a dural substitute to augment a duraplasty may increase the risk of aseptic meningitis and/or CSF leak. The mechanism of the apparent increased inflammation with this combination remains under investigation.

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Transgressing the Ventricular Wall During Subthalamic Deep Brain Stimulation Surgery for Parkinson Disease Increases the Risk of Adverse Neurological Sequelae

Neurosurgery 69:294–300, 2011 DOI: 10.1227/NEU.0b013e318214abda

Deep brain stimulation (DBS) at the subthalamic nucleus (STN) is an effective treatment for the motor manifestations of advanced medically refractory Parkinson disease. Because of the medial location of the target, surgical trajectories to the STN may violate the ipsilateral lateral ventricle.

OBJECTIVE: To determine whether violating the ventricle during STN DBS surgery is associated with postoperative confusion.

METHODS: A retrospective chart review of all STN implantation procedures for Parkinson disease performed by 1 surgeon between January 2005 and September 2008 was performed. Postoperative magnetic resonance imaging was performed in all cases, and each scan was reviewed for evidence of ventricular wall violation. All charts were reviewed for postoperative confusion and/or increased length of hospital stay.

RESULTS: A total of 145 leads were implanted in 81 patients over 102 admissions. Fortythree patients underwent contemporaneous bilateral lead implantation; 23 underwent unilateral implantation; and 18 underwent staged bilateral implantation. The cases of 8 patients were complicated by postoperative confusion and increased length of stay. Sixteen magnetic resonance imaging scans demonstrated evidence of ventricular wall violation including all 8 patients with postoperative confusion. The relative risk of having postoperative confusion after traversing the ventricle is 87 (P , .001).

CONCLUSION: Violating the ventricular system during STN DBS surgery correlated significantly with postoperative altered mental status and subsequent increased length of hospital stay. This finding may explain why cognitive complications are observed more frequently in Parkinson disease patients undergoing DBS at the STN compared with the internal globus pallidus.

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Postoperative Magnetic Resonance Imaging Can Predict Neurological Recovery After Surgery for Cervical Spondylotic Myelopathy: A Prospective Study With Blinded Assessments

Neurosurgery 69:362–368, 2011 DOI: 10.1227/NEU.0b013e31821a418

Factors that can predict the recovery of cervical spondylotic myelopathy (CSM) patients postoperatively are of significant interest to physicians and patients and their families. Magnetic resonance imaging (MRI) scans are a common method of examination after surgery, and thus of interest as a predictor of outcome.

OBJECTIVE: To investigate whether findings on MRI at 6 months postoperatively could predict recovery at 1 year in CSM patients.

METHODS: In 52 consecutive prospective patients, MRI was performed preoperatively and 6 months postoperatively. T1 and T2 signal change (area, height, and segmentation) and spinal cord re-expansion were measured. Outcome measures evaluated at 1 year postoperatively were compared with preoperative values. Univariate and stepwise multiple regressions were undertaken.

RESULTS: Using univariate analysis, patients whose cord failed to re-expand had poorer outcome according to the modified Japanese Orthopedic Association score and Nurick score (P = .014) and grip test (P = .006) postoperatively. Stepwise multivariate regression showed lack of cord re-expansion to be predictive of prognosis postoperatively in the modified Japanese Orthopedic Association score (P = .013) and Berg Balance Scale (P = .014), and walking test (P = .011). Postoperative hyperintense T2 signal change was predictive of worse outcome on the Berg Balance Scale (P = .014) and walking test (P = .020), Nurick score (P = .001), and Short Form-36 scores (P = .020). In cases in which the T2 signal intensified, there was a poorer outcome on Nurick scores (P = .013), grip test (P = .017), and Short Form-36 scores (P = .030).

CONCLUSION: Findings on postoperative MRI at 6 months is of predictive value in determining outcomes in CSM patients. The persistence and type of T2 signal change and lack of re-expansion of the cord correlate with poorer recovery and likely reflect irreversible structural changes in the spinal cord.

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Segmental anatomy of cerebellar arteries: a proposed nomenclature

J Neurosurg 115:387–397, 2011.DOI: 10.3171/2011.3.JNS101413

The conceptual division of intracranial arteries into segments provides a better understanding of their courses and a useful working vocabulary. Segmental anatomy of cerebral arteries is commonly cited by a numerical nomenclature, but an analogous nomenclature for cerebellar arteries has not been described. In this report, the microsurgical anatomy of the cerebellar arteries is reviewed, and a numbering system for cerebellar arteries is proposed.

Methods. Cerebellar arteries were designated by the first letter of the artery’s name in lowercase letters, distinguishing them from cerebral arteries with the same first letter of the artery’s name. Segmental anatomy was numbered in ascending order from proximal to distal segments.

Results. The superior cerebellar artery was divided into 4 segments: s1, anterior pontomesencephalic segment; s2, lateral pontomesencephalic segment; s3, cerebellomesencephalic segment; and s4, cortical segment. The anterior inferior cerebellar artery was divided into 4 segments: a1, anterior pontine segment; a2, lateral pontine segment; a3, flocculopeduncular segment; and a4, cortical segment. The posterior inferior cerebellar artery was divided into 5 segments: p1, anterior medullary segment; p2, lateral medullary segment; p3, tonsillomedullary segment; p4, telovelotonsillar segment; and p5, cortical segment.

Conclusions. The proposed nomenclature for segmental anatomy of cerebellar artery complements established nomenclature for segmental anatomy of cerebral arteries. This nomenclature is simple, easy to learn, and practical. The nomenclature localizes distal cerebellar artery aneurysms and also localizes an anastomosis or describes a graft’s connections to donor and recipient arteries. These applications of the proposed nomenclature with cerebellar arteries mimic the applications of the established nomenclature with cerebral arteries.

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Awake surgery for WHO Grade II gliomas within “noneloquent” areas in the left dominant hemisphere: toward a “supratotal” resection

J Neurosurg 115:232–239, 2011. DOI: 10.3171/2011.3.JNS101333

It has been demonstrated that an extensive resection (total or subtotal) may significantly increase the overall survival in patients with WHO Grade II gliomas (low-grade gliomas [LGGs]). Yet, recent data have shown that conventional MR imaging underestimates the spatial extent of LGG, since tumor cells were found up to 20 mm around MR imaging abnormalities. Thus, it was hypothesized that an extended resection with a margin beyond MR imaging–defined abnormalities—a “supratotal” resection—might improve the outcome of LGG. However, because of the frequent location of LGG within “eloquent” brain areas, it is often difficult to achieve such a supratotal resection. This could nevertheless be possible when LGGs involve “noneloquent” areas, even in the left dominant hemisphere.

The authors report on their use of awake electrical mapping to tailor the resection according to functional boundaries, that is, to pursue the resection beyond MR imaging–defined abnormalities, until corticosubcortical eloquent structures are encountered. Their aim was to apply this reliable surgical technique to LGGs located not within eloquent areas but distant from eloquent areas, to take a margin around the LGG visible on MR imaging while preserving brain function.

Methods. Fifteen right-handed patients with a total of 17 tumors underwent resection of WHO Grade II gliomas involving nonfunctional areas within the left dominant hemisphere. In all patients, seizures were the initial manifestation of the tumors. Awake surgery with intraoperative electrostimulation was performed in all cases. The resection was continued until the surgeon reached cortical and subcortical areas crucial for brain function, especially language, as defined by the intrasurgical electrical mapping. The extent of resection was evaluated on postoperative FLAIRweighted MR images.

Results. Despite transient neurological worsening in 60% of cases, all patients recovered and returned to a normal life. Seizure control was obtained in all patients with a decrease of antiepileptic drug therapy. Postoperative MR imaging showed that total resection was achieved in all 17 tumors and supratotal resection in 15. The average volume of the postoperative cavity (36.8 cm3) was significantly larger than the mean preoperative tumor volume (26.6 cm3) (p = 0.009). Neuropathological examination confirmed the diagnosis of WHO Grade II glioma in all cases. The mean duration of postoperative follow-up was 35.7 months (range 6–135 months). Only 4 of 15 patients experienced recurrence (without anaplastic transformation); the average time to recurrence in these cases was 38 months; radiotherapy was performed 6 years after the relapse in 1 case; no other patients received any adjuvant treatment. This series was compared with a control group of 29 patients who had “only” complete resection: anaplastic transformation was observed in 7 cases in the control group but not in any case in the series of patients who underwent supracomplete resection (p = 0.037). Furthermore, adjuvant treatment was administered in 10 patients in the control group compared with 1 patient who underwent supracomplete resection (p = 0.043).

Conclusions. These findings support the usefulness of awake surgery with intraoperative functional (language) mapping with the attempt to perform supratotal resection of LGGs involving noneloquent areas in the left hemisphere. Indeed, the extent of resection was significantly increased in all cases but 2, with no additional permanent deficit and with control of seizures in all patients. The goal of supracomplete resection is currently to delay the anaplastic transformation, even if it does not (yet) enable a cure.

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Delta-aminolevulinic acid–induced protoporphyrin IX concentration correlates with histopathologic markers of malignancy in human gliomas: the need for quantitative fluorescence-guided resection to identify regions of increasing malignancy

Neuro-Oncology 13(8):846–856, 2011. doi:10.1093/neuonc/nor086

Extent of resection is a major goal and prognostic factor in the treatment of gliomas. In this study we evaluate whether quantitative ex vivo tissue measurements of d-aminolevulinic acid–induced protoporphyrin IX (PpIX) identify regions of increasing malignancy in low- and high-grade gliomas beyond the capabilities of current fluorescence imaging in patients undergoing fluorescence-guided resection (FGR).

Surgical specimens were collected from 133 biopsies in 23 patients and processed for ex vivo neuropathological analysis: PpIX fluorimetry to measure PpIX concentrations (CPpIX) and Ki-67 immunohistochemistry to assess tissue proliferation. Samples displaying visible levels of fluorescence showed significantly higher levels of CPpIX and tissue proliferation. CPpIX was strongly correlated with histopathological score (nonparametric) and tissue proliferation (parametric), such that increasing levels of CPpIX were identified with regions of increasing malignancy. Furthermore, a large percentage of tumor-positive biopsy sites (∼40%) that were not visibly fluorescent under the operating microscope had levels of CPpIX greater than 0.1 mg/mL, which indicates that significant PpIX accumulation exists below the detection threshold of current fluorescence imaging.

Although PpIX fluorescence is recognized as a visual biomarker for neurosurgical resection guidance, these data show that it is quantitatively related at the microscopic level to increasing malignancy in both low- and high-grade gliomas. This work suggests a need for improved PpIX fluorescence detection technologies to achieve better sensitivity and quantification of PpIX in tissue during surgery.

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The Impact of Minimizing Brain Retraction in Aneurysm Surgery: Evaluation Using Magnetic Resonance Imaging

Neurosurgery 69:344–348, 2011 DOI: 10.1227/NEU.0b013e31821819a0

Recent advances in skull base and microsurgical techniques minimize the need for brain retraction.

OBJECTIVE: We studied the impact of such techniques in 36 patients (51 aneurysms) using magnetic resonance imaging (MRI).

METHODS: Preoperative and 24 hours postoperative MR imaging was performed in patients undergoing microsurgical clipping of intracranial aneurysms. Images were evaluated for parenchymal signal changes. During surgery, use and time of brain retraction were recorded. The degree of cortical injury was quantified using a 0 to 3 scale (grade 0 = normal surface; 1 = pial/arachnoidal damage; 2 = gray matter injury; 3 = contusion/necrosis).

RESULTS: Brain retraction by use of a brain spatula was used in all patients. Retraction times ranged from 14 to 290 minutes (mean, 84.1). Cortical surface changes were grade 0 in 86% and grade 1 in 14%; none showed grade 2 or 3 changes. In the postoperative MRI, 4 patients presented with parenchymal alterations, 4 with edema (11.1%), and 1 patient had additional contusion (2.8%). All lesions were confined to the temporal pole. The grade of cortical surface changes was not related to lesions found on MR imaging. No patients showed retraction-related neurological deficits.

CONCLUSION: The incidence of evident mechanical parenchymal injury (infarction or contusion) is very low when appropriate microsurgical and skull base techniques are used. Minor pia-arachnoid injury should nevertheless continue to be attended through future advances.

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Laparoscopic versus open insertion of the peritoneal catheter in ventriculoperitoneal shunt placement: review of 810 consecutive cases

J Neurosurg 115:151–158, 2011. DOI: 10.3171/2011.1.JNS101492

Traditional ventriculoperitoneal (VP) shunt surgery involves insertion of the distal catheter by minilaparotomy. However, minilaparotomy may be a significant source of morbidity during shunt surgery. Laparoscopic insertion of the distal catheter is an alternative technique that may simplify and improve the safety of shunt surgery.

Methods. The authors performed a retrospective review of hospital records of all patients undergoing new VP shunt insertion at a tertiary care center between 2004 and 2009. Patient characteristics and outcomes were compared between patients undergoing open or laparoscopic insertion of the distal catheter. Independent variables in the analysis included age, sex, race, body mass index, surgical technique, previous VP shunt placement, previous abdominal procedures, American Society of Anesthesiology (ASA) score, and indication for shunt placement. Dependent variables included the occurrence of shunt failure, cause of shunt failure, complications, length of stay (LOS), LOS after shunt placement, estimated blood loss, and operative time.

Results. The authors identified 810 patients who met the inclusion criteria; open or laparoscopic distal catheter insertion was performed in 335 and 475 patients, respectively. There were no significant differences between the groups regarding age, race, ASA score, or indication for shunt placement. The most common indication was hydrocephalus due to subarachnoid hemorrhage, followed by tumor-associated hydrocephalus, normal pressure hydrocephalus (NPH), and hydrocephalus due to trauma. The incidence of shunt failure was not statistically different between cohorts, occurring in 20.0% of laparoscopic and 20.9% of open catheter placement cases (p = 0.791). With analysis of causes of shunt failure, shunt obstruction occurred significantly more often in the open surgery cohort (p = 0.012). In patients with a known cause shunt obstruction, distal obstruction occurred in 35.7% of the open cohort obstructions and 4.8% of the laparoscopic cohort obstructions (p = 0.014). The relative risk of distal obstruction in open cases compared with laparoscopic cases was 7.50. Infections occurred in 8.2% of laparoscopic cases compared with 6.6% of open cases (p = 0.419). Within the NPH subgroup, the laparoscopically treated patients had significantly more overdrainage (p = 0.040), whereas those in the open cohort experienced significantly more shunt obstructions (p = 0.034). Laparoscopically treated patients had shorter operative times (p < 0.0005), inpatient LOS (p < 0.001), and inpatient LOS after VP shunt placement (p = 0.01) as well as less blood loss (p = 0.058).

Conclusions. To our knowledge this is the largest reported comparison of distal VP shunt catheter insertion techniques. Compared with minilaparotomy, the laparoscopic approach was associated with decreased time in the operating room and a decreased LOS. Moreover, laparoscopy was associated with fewer distal shunt obstructions. Laparoscopic shunt surgery is a viable alternative to traditional shunt surgery.

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Occult Spinous Process Fractures Associated With Interspinous Process Spacers

Spine 2011;36:E1080–E1085. DOI: 10.1097/BRS.0b013e318204066a

Biomechanical cadaveric studies have suggested adequate spinous process strength to support placement of interspinous process spacers (IPS). Postoperative spinous process fractures have been reported in one%—to 5.8% of patients in previous series based on routine biplanar radiographic evaluation. However, most fractures occur between the base and midportion of the spinous process in an area that is typically diffi cult to visualize on plain radiographs due to device design.

Methods. All patients underwent preoperative biplanar plain radiographs and computed tomography (CT) of the lumbar spine to confirm anatomy favorable for IPS placement and rule out fracture or spondylolysis. Postoperatively, all patients underwent repeat CT imaging within six months of surgery, biplanar radiographs at two weeks, six weeks, three months, six months, and one year. All studies were reviewed independently by a neuroradiologist and two orthopedic spine surgeons.

Results. Fifty implants (38 L4–5, 12 L3–4) were placed in 38 patients who completed follow-up and were included in final analysis. Three IPS designs were included (34 Medtronic X-STOP titanium, 8 X-STOP PEEK, 8 Lanx Aspen). Postoperative CT revealed 11 nondisplaced spinous process fractures in 11 patients (28.9% of patients, 22% of levels). Five fractures were associated with mild to moderate lumbar back pain and six fractures were asymptomatic. No patient reported a traumatic incident. No fracture was identifiable on plain radiographs. One fracture displaced during follow-up evaluation. Three patients underwent IPS removal and laminectomy. Three fractures healed by CT in one year. Overall, patients with fractures tended toward poorer outcomes by Zurich Claudication Questionnaire (ZCQ) (28.5% vs. 34.8% improvement in symptom severity, P=  0.496; 21.4% vs. 30.7% improvement in physical function, P = 0.199) and tended toward lower satisfaction rates (50% vs. 73.7%, P = 0.24) at one year compared to patients without fracture.

Conclusion. Interspinous process spacer surgery appears associated with a higher rate of early postoperative spinous process fracture than previously reported. In all cases, in this series, plain radiographs were inadequate to identify fractures because all fractures were initially minimal or nondisplaced, many patients were osteopenic, and the metallic wings of the devices often obscured fractures. Moreover, in most patients, fractures were associated with mild or no acute localized pain. This study suggests that unrecognized spinous process fracture may be responsible for a signifi cant number of patients who experience unsatisfactory outcome after IPS surgery. CT imaging is required to identify the vast majority of such fractures.

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Lateral supracerebellar transtentorial approach for petroclival meningiomas: operative technique and outcome

J Neurosurg 115:49–54, 2011. DOI: 10.3171/2011.2.JNS101759

The retrosigmoid intradural suprameatal approach with the patient in a semisitting position is an effective alternative to transpetrosal approaches for the treatment of petroclival meningiomas. The authors have made a simple modification to the retrosigmoid intradural suprameatal approach by using the lateral oblique position and preferentially dividing the tentorium with limited drilling of the suprameatal bone, which is termed the “lateral su- pracerebellar transtentorial approach.”

Methods. Twenty-six patients with petroclival meningiomas surgically treated via the lateral supracerebellar transtentorial approach were analyzed. All tumors had most of their bulk in the posterior fossa with some degree of extension into the middle fossa and/or Meckel cave. The patient is placed in the lateral oblique position, and a standard retrosigmoid craniotomy is performed. The tentorium medial to the trigeminal nerve is incised toward the free edge, which improves exposure to the petroclival region without extensive resection of the suprameatal petrous bone.

Results. Gross-total resection was achieved in 11 patients (42%). Ten patients (38%) underwent subtotal resection, and 5 patients (19%) underwent partial resection. There was no incidence of operative death, and the postoperative permanent morbidity rate was 15%. All patients except one did well postoperatively and were independent at the time of their last follow-up examinations.

Conclusions. The lateral supracerebellar transtentorial approach provides the simplest and safest access to the petroclival region. It offers an advantageous approach to petroclival meningiomas exclusively located in the posterior fossa with minimal extension into the Meckel cave and middle fossa.

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Superciliary Keyhole Approach for Small Unruptured Aneurysms in Anterior Cerebral Circulation

Neurosurgery 68[ONS Suppl 2]:ons300–ons309, 2011 DOI: 10.1227/NEU.0b013e3182124810

Neurovascular surgeons have been trying to find a solution to the problem of surgical invasiveness by applying minimally invasive keyhole approaches.

OBJECTIVE: To evaluate the feasibility and surgical outcomes of a superciliary keyhole approach for unruptured intracranial aneurysms (UIAs) as an alternative to a pterional approach.

METHODS: The authors report on a consecutive series of patients who underwent a superciliary approach for clipping UIAs smaller than 15 mm arising at the supraclinoid internal carotid artery (ICA), A1 segment, anterior communicating artery (ACoA), and M1 segment including the middle cerebral artery (MCA) bifurcation. The data were compared with a historical control group (n = 90) who underwent a pterional approach for UIAs.

RESULTS: A total of 120 aneurysms were successfully clipped in 102 patients with a mean age of 58 years. There was no direct mortality related to the surgery, and only 1 (1.0%) patient developed significant morbidity adversely affecting the Glasgow Outcome Scale score. The superciliary approach demonstrated statistically significant advantages over the pterional approach, including a shorter operative duration (mean, 120 min), no intraoperative blood transfusion, and extremely rare postoperative epidural hemorrhages. In addition, temporalis atrophy was rare and palsy of the frontalis persisting more than 6 months only occurred in 6 patients (5.9%) and was resolved within 2 years. The overall cosmetic outcome was excellent.

CONCLUSION: A superciliary approach can be a reasonable alternative to a pterional approach for small (,15 mm) UIAs arising at the supraclinoid ICA, A1, ACoA, and M1 segment including the MCA bifurcation.

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