Calculating the Tumor Volumes in Vestibular Schwannomas: Are the ABC/2 and Volumetric Methods Comparable?

Presbycusis and Hearing Preservation in Observed Vestibular Schwannomas

OBJECTIVE

We reviewed a cohort of patients with untreated sporadic vestibular schwannoma (VS) and examined the relationship between high-frequency hearing loss (HFHL) in the non-VS ear and long-term hearing outcomes in the VS-affected ear. We hypothesized that the progression of HFHL is associated with accelerated hearing decline in sporadic VS.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary center.

PATIENTS

We studied 102 patients with sporadic VS diagnosed from 1999 to 2015 with ≥5 years of observation (median, 6.92; interquartile range, 5.85-9.29). Sixty-six patients had AAO-HNS class A/B hearing at presentation and were included in analysis.

INTERVENTIONS

Audiometry, serial magnetic resonance imaging for observation of VS.

MAIN OUTCOME MEASURES

Four-frequency pure tone average (PTA) and word recognition scores (WRS) in the VS-affected ear. Decline in high-frequency PTA (average of thresholds at 4000, 6000, and 8,000 Hz) was defined as ≥10 dB during the study period. Decline in WRS was defined as ≥10%.

RESULTS

Compared with those without, patients with progressive HFHL in the non-VS ear were more likely to experience a decline in WRS in the VS ear (80% vs. 54%, p = 0.031). However, the same group showed no difference (52% vs. 41%, p = 0.40) in decline in PTA of the VS ear.

CONCLUSIONS

Patients with observed VS who experience progressive HFHL in the non-VS ear are more likely to experience significant declines in speech understanding in the VS-affected ear over time. Patients with a history of presbycusis may have an increased risk of losing serviceable hearing because of sporadic VS.

Reduction of sporadic and neurofibromatosis type 2-associated vestibular schwannoma growth in vitro and in vivo after treatment with the c-Jun N-terminal kinase inhibitor AS602801

OBJECTIVE

Vestibular schwannomas (VSs) are benign nerve sheath tumors that result from mutation in the tumor suppressor gene NF2, with functional loss of the protein merlin. The authors have previously shown that c-Jun N-terminal kinase (JNK) is constitutively active in human VS cells and plays a central role in their survival by suppressing accumulation of mitochondrial superoxides, implicating JNK inhibitors as a potential systemic treatment for VS. Thus, the authors hypothesized that the adenosine 5'-triphosphate-competitive JNK inhibitor AS602801 would demonstrate antitumor activity in multiple VS models.

METHODS

Treatment with AS602801 was tested in primary human VS cultures, human VS xenografts, and a genetic mouse model of schwannoma (Postn-Cre;Nf2flox/flox). Primary human VS cell cultures were established from freshly obtained surgical tumor specimens; treatment group media was enriched with AS602801. VS xenograft tumors were established in male athymic nude mice from freshly collected human tumor. Four weeks postimplantation, a pretreatment MRI scan was obtained, followed by 65 days of AS602801 (n = 18) or vehicle control (n = 19) treatment. Posttreatment MRI scans were used to measure final tumor volume. Tumors were then harvested. Finally, Postn-Cre;Nf2flox/flox mice were treated with AS602801 (n = 10) or a vehicle (n = 13) for 65 days. Posttreatment auditory brainstem responses were obtained. Dorsal root ganglia from Postn-Cre;Nf2flox/flox mice were then harvested. In all models, schwannoma identity was confirmed with anti-S100 staining, cell proliferation was measured with the EdU assay, and cell death was measured with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. All protocols were approved by the local institutional review board and Institutional Animal Care and Use Committees.

RESULTS

Treatment with AS602801 decreased cell proliferation and increased apoptosis in primary human VS cultures. The systemic administration of AS602801 in mice with human VS xenografts reduced tumor volume and cell proliferation. Last, the AS602801-treated Postn-Cre;Nf2flox/flox mice demonstrated decreased cell proliferation in glial cells in the dorsal root ganglia. However, AS602801 did not significantly delay hearing loss in Postn-Cre;Nf2flox/flox mice up to 3 months posttreatment.

CONCLUSIONS

The data suggest that JNK inhibition with AS602801 suppresses growth of sporadic and neurofibromatosis type 2-associated VSs. As such, AS602801 is a potential systemic therapy for VS and warrants further investigation.

Functional Outcomes and Postoperative Cerebral Venous Sinus Thrombosis after Translabyrinthine Approach for Vestibular Schwannoma Resection: A Radiographic Demonstration of Anatomic Predictors

Introduction While regarded as an effective surgical approach to vestibular schwannoma (VS) resection, the translabyrinthine (TL) approach is not without complications. It has been postulated that postoperative cerebral venous sinus thrombosis (pCVST) may occur as a result of injury and manipulation during surgery. Our objective was to identify radiologic, surgical, and patient-specific risk factors that may be associated with pCVST.

Methods The Institutional Review Board (IRB) approval was obtained and the medical records of adult patients with VS who underwent TL craniectomy at University Hospitals Cleveland Medical Center between 2009 and 2019 were reviewed. Demographic data, radiographic measurements, and tumor characteristics were collected. Outcomes assessed included pCVST and the modified Rankin score (mRS).

Results Sixty-one patients ultimately met inclusion criteria for the study. Ten patients demonstrated radiographic evidence of thrombus. Patients who developed pCVST demonstrated shorter internal auditory canal (IAC) to sinus distance (mean: 22.5 vs. 25.0 mm, p = 0.044) and significantly smaller petrous angles (mean: 26.3 vs. 32.7 degrees, p = 0.0045). Patients with good mRS scores (<3) appeared also to have higher mean petrous angles (32.5 vs. 26.8, p = 0.016). Koos' grading and tumor size, in our study, were not associated with thrombosis.

Conclusion More acute petrous angle and shorter IAC to sinus distance are objective anatomic variables associated with pCVST in TL surgical approaches.

Dorsal Root Ganglion Volumetry by MR Gangliography

BACKGROUND AND PURPOSE

Dorsal root ganglion MR imaging (MR gangliography) is increasingly gaining clinical-scientific relevance. However, dorsal root ganglion morphometry by MR imaging is typically performed under the assumption of ellipsoid geometry, which remains to be validated.

MATERIALS AND METHODS

Sixty-four healthy volunteers (37 [57.8%] men; mean age, 31.5 [SD, 8.3] years) underwent MR gangliography of the bilateral L4-S2 levels (3D-T2WI TSE spectral attenuated inversion recovery-sampling perfection with application-optimized contrasts by using different flip angle evolution, isotropic voxels = 1.1 mm³, TE = 301 ms). Ground truth dorsal root ganglion volumes were bilaterally determined for 96 dorsal root ganglia (derivation cohort) by expert manual 3D segmentation by 3 independent raters. These ground truth dorsal root ganglion volumes were then compared with geometric ellipsoid dorsal root ganglion approximations as commonly practiced for dorsal root ganglion morphometry. On the basis of the deviations from ellipsoid geometry, improved volume estimation could be derived and was finally applied to a large human validation cohort (510 dorsal root ganglia).

RESULTS

Commonly used equations of ellipsoid geometry underestimate true dorsal root ganglion volume by large degrees (factor = 0.42-0.63). Ground truth segmentation enabled substantially optimizing dorsal root ganglion geometric approximation using its principal axes lengths by deriving the dorsal root ganglion volume term of [Formula: see text]. Using this optimization, the mean volumes of 510 lumbosacral healthy dorsal root ganglia were as follows: L4: 211.3 (SD, 52.5) mm³, L5: 290.7 (SD, 90.9) mm³, S1: 384.2 (SD, 145.0) mm³, and S2: 192.4 (SD, 52.6) mm³. Dorsal root ganglion volume increased from L4 to S1 and decreased from S1 to S2 (P < .001). Dorsal root ganglion volume correlated with subject height (r = . 22, P < .001) and was higher in men (P < .001).

CONCLUSIONS

Dorsal root ganglion volumetry by measuring its principal geometric axes on MR gangliography can be substantially optimized. By means of this optimization, dorsal root ganglion volume distribution was estimated in a large healthy cohort for the clinically most relevant lumbosacral levels, L4-S2.

Simple Ways to Estimate Meningioma Volume: Can ABC- and SH-Derived Methods Be Used in Clinical Practice Reliably?

Background

There is a clinical demand for rapid estimation of meningioma volumes. Our objective was to assess the accuracy of three ABC-derived and three SH-derived formula methods on volume estimation of meningiomas.

Methods

The study group comprised 678 patients treated at our department for histopathologically proven intracranial meningiomas. For each patient, tumor volumes were independently measured using six formula methods as well as planimetry. Maximum tumor diameter and ellipsoidity were also recorded. Volumes were compared using descriptive statistics, correlation analysis, and consistency analysis.

Results

Among all methods assessed, 2/3SH and 1/2ABC outperformed the others. No significant differences were found between volumes obtained by the two methods and those of planimetry (p > 0.05). Spearman rank-correlation coefficients (r _s ) were 0.99 for both methods (p < 0.01), and ICC were 0.99 and 0.98, respectively. In Bland-Altman plot, most data points lay inside the limit of agreement. Overall, 2/3SH overestimated tumor volumes by 1.29%, and estimation errors in 93.66% cases were within 20%; 1/2ABC overestimated tumor volumes by 5.36%, and estimation errors in 93.51% cases were within 30%. The performance of 2/3SH and 1/2ABC in small-volume meningiomas was slightly worse, especially for 1/2ABC. Correlations between ellipsoidity and percentage errors of 2/3SH and 1/2ABC were weak (r _s  = -0.06 and -0.24, respectively). Despite a significant correlation between maximum tumor diameter and planimetric volume (r _s  = -0.96), volumes could vary significantly for a given diameter.

Conclusions

Formula methods 2/3SH and 1/2ABC can estimate meningioma volumes with decent accuracy. Compared with the 1/2ABC method, the 2/3SH method showed slightly better performance, especially in small-volume meningiomas. Ellipsoidity is not a suitable parameter to predict estimation error, and maximum tumor diameter is not a reliable surrogate for actual meningioma volume.

Simplifying Tumor Volume Estimation from Linear Dimensions for Intra-Cranial Lesions Treated with Stereotactic Radiosurgery

Aims:

This study aims to derive simple yet robust formula(s) for the calculation of cranial tumor volume using linear tumor dimensions in anterioposterior (AP), mediolateral (ML) and craniocaudal (CC) directions and also propose a reproducible methodology for tumor dimension measurements.

Materials and Methods:

Magnetic resonance images (MRI) of 337 patients planned for Gammaknife Stereotactic Radiosurgery for different types of brain tumors were analyzed using Leksell Gamma Plan (LGP) software. Tumor volume in three dimensional was outlined and maximum tumor diameters were measured in three orthogonal directions AP, ML, and CC on the MRI. Formulas were derived to calculate tumor volume from AP, ML, and CC diameters using linear regression technique. An agreement between the calculated volume and standard volume observed from LGP software was determined using Bland Altman (B-A) plot. A comparison was made between the volume calculated using traditionally used formula of ellipsoid, standard volume obtained from LGP software and volume calculated from formulas derived in the present study.

Results:

The tumors were divided into two categories based on their size for better volume prediction. The tumors having product of their diameters in the range 0–2.5cc were called “small tumors” and the formula proposed for their volume estimation (V = 1.513) × (AP × ML × CC) + 0.047 ) was found to predict the tumor volume with an average bias of 0.0005cc. For “large tumors,” having product of diameters in the range 2.5–36cc, the proposed formula (V = 0.444 × (AP × ML × CC) + 0.339 ) predicted the tumor volume with an average bias of 0.007cc.

Conclusions:

The two formulas proposed in the study are more accurate as compared to the commonly used formula that considers the tumors as ellipsoids. The methodology proposed in the study for measurement of linear tumor dimensions is simple and reproducible.

Linked-read Sequencing Analysis Reveals Tumor-specific Genome Variation Landscapes in Neurofibromatosis Type 2 (NF2) Patients

HYPOTHESIS

We hypothesize that genomic variants including deletions, insertions, inversions, and tandem duplications beyond the changes in tumor suppressor NF2 gene affect gene expression of tumor-specific pathways in vestibular schwannomas (VS) patients with Neurofibromatosis type 2 (NF2), thus contributing to their clinical behavior.

BACKGROUND

Genomic variation could reconfigure transcription in NF2 transformation process. Therefore, genome-wide high-resolution characterization of structural variants (SV) landscapes in NF2 tumors can expand our understanding of the genes regulating the clinical phenotypes in NF2-associated VS.

METHODS

We performed whole-genome haplotype-specific structural variation analysis using synthetic linked reads generated through microfluidics-based barcoding of high molecular weight DNA followed by high-coverage Illumina paired-end whole-genome sequencing from 10 patients' tumors of different growth rates and their matching blood samples.

RESULTS

NF2 tumor-specific deletions and large SVs were detected and can be classified based on their association with tumor growth rates. Through detailed annotation of these mutations, we uncover common alleles affected by these deletions and large SVs that can be associated with signaling pathways implicated in cell proliferation and tumorigenesis.

CONCLUSION

The genomic variation landscape of NF2-related VS was investigated through whole-genome linked-read sequencing. Large SVs, in addition to deletions, were identified and may serve as modulators of clinical behavior.

Fractionated Stereotactic Radiotherapy for Cavernous Venous Malformations of the Orbital Apex

PURPOSE

The objective of this study was to investigate the efficacy and safety of fractionated stereotactic radiotherapy in the treatment of cavernous venous malformation of the orbital apex.

METHODS

The authors reviewed a prospective database from a single center of patients with cavernous venous malformation of the orbital apex who had treatment with fractionated stereotactic radiotherapy. The authors compared the symptoms, visual function and the size of the tumor pre- and posttreatment as well as reviewed the treatment details and the incidence of complications.

RESULTS

Six patients received treatment with fractionated stereotactic radiotherapy for cavernous venous malformation involving the orbital apex. The median age was 48 (range, 32-63), and 50% were female. Patients received a dose of 45 to 50.4 Gy in 1.8 to 2 Gy fractions. Median follow up was 33 months (range, 18-66 months). The average tumor volume reduction at posttreatment imaging after 12 months was 63%. All lesions reduced in size postradiotherapy and remained controlled for the duration of follow up. All patients who had proptosis or a visual field defect had an improvement in the symptoms posttreatment. There were no complications of the treatment.

CONCLUSION

Fractionated stereotactic radiotherapy appears to be a safe and effective management option for cavernous venous malformation of the orbital apex and leads to a sustained reduction of the volume of the lesion with associated improvement in symptoms and visual function.

Current Volumetric Models Overestimate Vestibular Schwannoma Size Following Stereotactic Radiosurgery

OBJECTIVE

Accurate volume assessment is essential for the management of vestibular schwannoma after stereotactic radiosurgery (SRS). A cuboidal approximation for volume is the standard surveillance method; however, this may overestimate tumor volume. We sought to evaluate several volumetric models and their suitability for post-SRS surveillance.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary referral center.

PATIENTS

We evaluated 54 patients with vestibular schwannoma before and after SRS.

INTERVENTION(S)

Gold-standard volumes were obtained by a radiation oncologist using contouring software. Volume was also calculated by cuboidal, ellipsoidal, and spherical formulae using tumor diameters obtained by a neuroradiologist.

MAIN OUTCOME MEASURE(S)

Percent error (PE) and absolute percent error (APE) were calculated. Paired t test evaluated bias, and the Bland-Altman method evaluated reproducibility. Linear regression evaluated predictors of model error.

RESULTS

All models overestimated volume compared with the gold standard. The cuboidal model was not reproducible before SRS (p < 0.001), and no model was reproducible after SRS (cuboidal p < 0.001; ellipsoidal p = 0.02; spherical p = 0.02). Significant bias was present before SRS for the cuboidal model (p < 0.001), and post-SRS for all models [cuboidal (p < 0.001), ellipsoidal (p < 0.02), and spherical (p = 0.005)]. Model error was negatively associated with pretreatment volume for the cuboidal (PE p = 0.03; APE p = 0.03), ellipsoidal (PE p = 0.03; APE p = 0.04), and spherical (PE p = 0.02; APE p = 0.03) methods and lost linearity post-SRS.

CONCLUSIONS

The standard cuboidal practice for following vestibular schwannoma tumor volume after SRS overestimates size. Ellipsoidal and spherical estimations have improved performance but also overestimate volume and lack reliability post-SRS. The development of other volumetric models or application of contouring software should be investigated.

Infectious Complications of Expanded Endoscopic Transsphenoidal Surgery: A Retrospective Cohort Analysis of 100 Cases

Objective  To identify perioperative factors that may predict postoperative cerebrospinal fluid (CSF) leak and meningitis following expanded endoscopic transsphenoidal surgery (EETS). Study Design  This is a retrospective study. This study was set at the Cedars-Sinai Medical Center, Los Angeles. A total of 78 patients who underwent EETS between January 2007 and November 2018 were participated. The main outcome measures were CSF leak and meningitis. Results  A total of 78 patients underwent a total of 100 EETS procedures; 17.9 and 10.3% of patients developed postoperative CSF leaks and meningitis, respectively. Out of eight, three patients with meningitis did not develop an observable CSF leak. The risk of developing meningitis in patients with a CSF leak was significantly higher than those without a leak, with an odds ratio (OR) of 11.48 (95% confidence interval, 2.33-56.47; p  = 0.004). Pituicytomas were significantly associated with meningitis compared with other pathologies. No other patient-specific factors were identified as risks for leak or meningitis, including method of skull base repair, sex, tumor volume, or body mass index, although there was a strong trend toward reduced CSF leak rates in patient with nasoseptal flaps used for skull base repair, compared with those without (9.5 vs. 25%). CSF protein was consistently elevated on the first CSF values obtained when meningitis was suspected. Conclusion  CSF leak and meningitis are common complications of expanded endonasal surgery No statistically significant risk factors for developing a postoperative leak other than the pathology of pituicytoma were identified, including method of skull base repair, although the use of a vascularized nasoseptal flap did trend toward a reduced CSF leak rate. CSF protein is the most sensitive marker for the presumptive diagnosis and timely treatment of meningitis.

Skull Base Enchondroma and Chondrosarcoma in Ollier Disease and Maffucci Syndrome

BACKGROUND

Maffucci syndrome (MS) and Ollier disease (OD) are rare diseases characterized by multiple benign enchondromas. The incidence of skull base (SB) enchondromas and the risk of malignant transformation remain unknown. Most SB lesions are asymptomatic, and surgical resection carries significant morbidity. Observation may be a reasonable strategy. We report our experience with observation of probable SB enchondromas in MS/OD patients.

METHODS

Retrospective review of OD/MS patients with cranial imaging between 1995 and 2018 at 1 institution.

RESULTS

14 patients were included: 3 with MS (21.4%) and 11 with OD (78.6%). The median age was 28 years (range, 11-74 years) and 57.1% were female. Extracranial chondrosarcoma was reported in 3 (21.4%) patients. Seven (50%) patients with SB enchondroma or chondrosarcoma were identified on initial imaging. In patients with SB lesions, the indications for imaging were headache (n=3), seizure (n=1), and diplopia (n=1); 2 cases were incidental findings. The most commonly involved structures were petroclival fissure (86%) and clivus (71%). Treatment included observation (6/7) and resection (1/7). Follow-up imaging was available for all SB lesions, with a mean interval of 50.7 months (range, 5-225 months) and was negative for progression in all patients.

CONCLUSIONS

Primary SB lesions in OD/MS patients frequently present in the petroclival junction. Cranial screening and close observation should be considered in MS/OD patients, given the increased risk of intra-axial intracranial tumors, de novo chondrosarcomas, or malignant degeneration of previously known lesions. In asymptomatic patients, observation appears to be a safe strategy in this cohort. Further case accumulation and follow-up are required to better understand the long-term outcomes.

Assessing the volume of large cerebral arteriovenous malformations: Can the ABC/2 formula reliably predict true volume?

BACKGROUND

Outcomes of stereotactic radiosurgery in the treatment of cerebral arteriovenous malformations (AVMs) are volume-dependent. The ability to estimate AVM volume has significant value in guiding AVM management.

OBJECTIVE

To determine whether AVM volume measurement calculated from the ABC/2 formula is accurate compared to volume calculated by a computer-assisted planimetric method for large AVMs.

METHODS

Retrospective review of 42 intracranial AVMs >3 cm in diameter that underwent treatment with dose-staged hypofractionated stereotactic radiotherapy (HSRT) from 2001 to 2018. Two raters independently measured pre- and post-HSRT volumes using both the ABC/2 formula and computer-assisted planimetry in a blinded fashion. Inter-rater reliability was assessed by calculation of intra-class correlation coefficient (ICC). Absolute volumes and percent volume change following HSRT as determined using the two methods were compared using paired t-tests, linear regression, and Bland-Altman plot analyses.

RESULTS

The ICC between the 2 raters for planimetric and ABC/2 volumes was 0.859 and 0.799, respectively. ABC/2 volumes, 26.1 ± 26.6 cm³, were statistically smaller than planimetric volumes, 28.6 ± 27.1 cm³ (P = .008). Despite differences, the two methods were highly correlated (R² = 0.904, linear regression). The percent volume change following HSRT was significantly greater with the ABC/2 method than compared to planimetry (P = .009).

CONCLUSION

The ABC/2 and planimetric methods are reproducible for measuring cerebral AVM volumes. Although the ABC/2 method of volume estimation underestimates planimetric AVM volume, the high correlation between the two suggests utility of the ABC/2 method if one understands its limits, particularly with respect to estimating change in AVM volume after treatment.

A novel grading system for the prediction of the need for cerebrospinal fluid drainage following posterior fossa tumor surgery

OBJECTIVE

Prophylactic placement of an external ventricular drain (EVD) is often performed prior to resection of a posterior fossa tumor (PFT); however, there is no general consensus regarding the indications. The purpose of this study was to establish a novel grading system for the prediction of required CSF drainage due to symptomatic elevated intracranial pressure (ICP) after resection of a PFT to identify patients who require an EVD.

METHODS

The authors performed a retrospective analysis of data from a prospective database. All patients who had undergone resection of a PFT between 2012 and 2017 at the University Hospital, Goethe University Frankfurt, were identified and data from their cases were analyzed. PFTs were categorized as intraparenchymal (iPFT) or extraparenchymal (ePFT). Prior to resection, patients underwent EVD placement, prophylactic burr hole placement, or neither. The authors assessed the amount of CSF drainage (if applicable), rate of EVD placement at a later time point, and complication rate and screened for factors associated with CSF drainage. By applying those factors, they established a grading system to predict the necessity of CSF drainage for elevated ICP.

RESULTS

A total of 197 patients met the inclusion criteria. Of these 197, 70.6% received an EVD, 15.7% underwent prophylactic burr hole placement, and 29.4% required temporary CSF drainage. In the prophylactic burr hole group, 1 of 32 patients (3.1%) required EVD placement at a later time. Independent predictors for postoperative need for CSF drainage due to symptomatic intracranial hypertension in patients with iPFTs were preoperative hydrocephalus (OR 2.9) and periventricular CSF capping (OR 2.9), whereas semi-sitting surgical position (OR 0.2) and total resection (OR 0.3) were protective factors. For patients with ePFTs, petroclival/midline tumor location (OR 12.2/OR 5.7), perilesional edema (OR 10.0), and preoperative hydrocephalus (OR 4.0) were independent predictors of need for CSF drainage. According to our grading system, CSF drainage after resection of iPFT or ePFT, respectively, was required in 16.7% and 5.1% of patients with a score of 0, in 21.1% and 12.5% of patients with a score of 1, in 47.1% and 26.3% of patients with a score of 2, and in 100% and 76.5% of patients with a score ≥ 3 (p < 0.0001). The rate of relevant EVD complications was 4.3%, and 10.1% of patients were shunt-dependent at 3-month follow-up.

CONCLUSIONS

This novel grading system for the prediction of need for CSF drainage following resection of PFT might be of help in deciding in favor of or against prophylactic EVD placement.

Excellent accuracy of ABC/2 volume formula compared to computer-assisted volumetric analysis of subdural hematomas

Background

Subdural hematoma (SDH) is a common disease associated with high morbidity, which is becoming more prominent due to the increasing incidence. Decision for a surgical evacuation is made depending on the clinical appearance and the volume of SDH, wherefore it is important to have a simple ‘bedside’ method to measure and compare the volume of SDH.

Objective

The aim of the study was to verify the accuracy of the simplified ABC/2 volumetric formula to determine a valuable tool for the clinical practice.

Methods

Preoperative CT-scans of 83 patients with SDHs were used for the computer-assisted volumetric measurement via BrainLab® as well as the ABC/2 volumetric measurement. A = largest length (anterior to posterior) of the SDH; B = maximum width (lateral to midline) 90° to A; C = maximum height (coronal plane or multiplication of slices) of the hematoma. These measurements were performed by two independent clinicians in a blinded fashion. Both volumes were compared by linear regression analysis of Pearson and Bland-Altman regression analysis.

Results

Among 100 SDHs, 53% were under an 47% were over 100cm³ showing a well distribution of the hematoma sizes. There was an excellent correlation between computer-assisted volumetric measurement and ABC/2 (R² = 0.947, p<0.0001) and no undesirable deviation and trend were detected (p = 0.101; p = 0.777). A 95% tolerance region of the ratios of both methods was [0.805–1.201].

Conclusion

The ABC/2 method is a simple and fast bedside formula for the measurement of SDH volume in a timely manner without limited access through simple adaption, which may replace the computer-assisted volumetric measurement in the clinical and research area. Reason for the good accuracy seems to be the spherical form of SDH, which has a similarity to a half ellipsoid.

Vestibular schwannomas: Accuracy of tumor volume estimated by ice cream cone formula using thin-sliced MR images

PURPOSE

We estimated the volume of vestibular schwannomas by an ice cream cone formula using thin-sliced magnetic resonance images (MRI) and compared the estimation accuracy among different estimating formulas and between different models.

METHODS

The study was approved by a local institutional review board. A total of 100 patients with vestibular schwannomas examined by MRI between January 2011 and November 2015 were enrolled retrospectively. Informed consent was waived. Volumes of vestibular schwannomas were estimated by cuboidal, ellipsoidal, and spherical formulas based on a one-component model, and cuboidal, ellipsoidal, Linskey's, and ice cream cone formulas based on a two-component model. The estimated volumes were compared to the volumes measured by planimetry. Intraobserver reproducibility and interobserver agreement was tested. Estimation error, including absolute percentage error (APE) and percentage error (PE), was calculated. Statistical analysis included intraclass correlation coefficient (ICC), linear regression analysis, one-way analysis of variance, and paired t-tests with P < 0.05 considered statistically significant.

RESULTS

Overall tumor size was 4.80 ± 6.8 mL (mean ±standard deviation). All ICCs were no less than 0.992, suggestive of high intraobserver reproducibility and high interobserver agreement. Cuboidal formulas significantly overestimated the tumor volume by a factor of 1.9 to 2.4 (P ≤ 0.001). The one-component ellipsoidal and spherical formulas overestimated the tumor volume with an APE of 20.3% and 29.2%, respectively. The two-component ice cream cone method, and ellipsoidal and Linskey's formulas significantly reduced the APE to 11.0%, 10.1%, and 12.5%, respectively (all P < 0.001).

CONCLUSION

The ice cream cone method and other two-component formulas including the ellipsoidal and Linskey's formulas allow for estimation of vestibular schwannoma volume more accurately than all one-component formulas.