Tag: Computed tomography

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Clinical Significance and Utility of Early Postoperative Computed Tomography Scan Head after Brain Surgery

Neurosurgery 98:810–817, 2026

This prospective single-center study assesses the clinical value of routine early (within 6 hours) postoperative CT scans in 339 adults after intracranial surgery, correlating immediate neurological status with CT findings and resulting management changes. Results show 97.3% had only expected postoperative changes, 2.7% had hematoma without mass effect, and none required surgical intervention; only six patients had medical management altered.

The authors conclude that routine early CT provides minimal benefit for extubated, neurologically stable or expected-deficit patients and advocate selective imaging for clinical deterioration or unreliable examinations, highlighting cost, radiation, and logistical considerations particularly relevant to resource-limited settings.

Aim Evaluate whether an early postoperative head CT within 6 hours after intracranial surgery changes patient management and assess its clinical utility.

Design/setting Single-center prospective cohort of 339 intracranial surgery patients; all received CT within 6 hours and were grouped clinically as no deficit, expected deficit, or unexpected deficit.

CT classification Imaging findings were categorized as postoperative changes only, operative site hematoma without mass effect, or hematoma with mass effect (with management options: no change, medical change, or surgery).

Key findings (imaging) 97.3% (330/339) showed postoperative changes only; 2.7% (9/339) had operative site hematoma without mass effect; 0% had hematoma with mass effect.

Key findings (management impact) 98.2% (333/339) had no change in management based on early CT; 1.8% (6/339) had a change in medical management; 0% required surgical intervention.

Neurological status distribution Postoperatively, 90.9% had no fresh deficit, 7.1% had an expected deficit, and 2.1% had an unexpected deficit.

Association signal Patients with unexpected neurological deficits were more likely to have abnormal CT findings (reported OR 6.22, wide CI, P = .193, not statistically significant).

Bottom line Early postoperative CT offers minimal benefit for extubated patients with no or expected deficits; CT should be reserved for clinical deterioration or unreliable neurological examination.

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Predicting Intracranial Pressure Levels: A Deep Learning Approach Using Computed Tomography Brain Scans

Neurosurgery 98:256–268, 2026

This clinical study evaluates deep learning models that predict whether intracranial pressure (ICP) exceeds 15 mm Hg from brain CT scans, integrating demographic and Glasgow Coma Scale data into image inputs. Four 3D architectures—including MobileNetV2 3D and DenseNet201 3D—were trained on 578 paired CT–ICP cases with preprocessing, augmentation, and explainability via class activation maps.

Results show MobileNetV2 3D achieved the best generalization (AUC 0.883, recall 81.8%), with demographic embedding improving performance; limitations include single-center data, class imbalance, and lack of external validation, and authors recommend multicenter expansion and refined region-specific feature extraction before clinical deployment.

Intracranial Pressure (ICP) Risk: Elevated ICP is a critical, potentially fatal condition requiring rapid diagnosis and intervention, but current gold-standard invasive monitoring methods carry risks and are not always feasible in emergency settings.

Noninvasive ICP Assessment Challenge: Existing noninvasive methods (e.g., CT-based qualitative markers) lack sufficient accuracy and reliability for routine emergency use, highlighting the need for improved approaches.

Deep Learning Solution: Four deep learning models were trained on a custom dataset of 578 paired brain CT scans, demographic information, and Glasgow Coma Scale (GCS) scores to classify whether ICP exceeds 15 mm Hg, addressing the gap in noninvasive, rapid ICP estimation.

Data Integration Innovation: Demographic and GCS data were embedded and merged with CT imaging, creating a multimodal input that improved model performance compared to imaging-only approaches.

Best Model Performance: The MobileNetV2 3D model with demographic data achieved the highest test AUC of 88.3% and recall of 81.8%, outperforming other architectures and showing promise for high-sensitivity emergency applications.

Explainability: Class Activation Maps (CAMs) were used to visualize which regions of the brain CT scans influenced model predictions, enhancing transparency and interpretability of the AI system.

Limitations: The study’s main limitations include a relatively small, single-center dataset with class imbalance, lack of external/multicenter validation, and potential inconsistencies due to timing mismatches between CT and ICP measurements.

Clinical Impact & Future Directions: This AI approach could reduce reliance on invasive monitoring and accelerate ICP triage in neurocritical care; further multicenter studies, prospective validation, and expansion to multiclass classification are needed for clinical deployment.

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Are the Umbilicus and Iliac Crests Truly at the Level of L4 to L5? A Computed Tomography-Based Study of Surface Anatomy of the Anterior Lumbar Spine

International Journal of Spine Surgery, Vol. 18, No. 6, 2024, pp. 660–666

This study aimed to determine whether the iliac crests are truly at the level of L4 to L5, accounting for patient demographic and anthropometric characteristics.

Methods: We measured the umbilicus and iliac crests relative to the lumbar spine using computed tomography of patients without spinal pathology, accounting for the influences of patient height, weight, body mass index (BMI), sex, race, and ethnicity.

Results: A total of 834 patients (391 men and 443 women) were reviewed. The location of the umbilicus relative to the lumbar spine demonstrated a unimodal distribution pattern clustered at L4, while the iliac crests were most frequently located from L4 to L5. Iliac crests were located above the L4 to L5 disc space 26.5% of the time. Iliac crests were located at the L4 to L5 disc space 29.8% of the time. No correlations were observed between the umbilicus and iliac crests with patient height, weight, or BMI. There was no difference in the location of the umbilicus with respect to patient sex, race, and ethnicity. The locations of the iliac crests were cephalad in women compared with men and in Hispanics compared with African American, Caucasian, and Asian patients.

Conclusions: The iliac crests were located above the level of the L4 to L5 disc space approximately 26% of the time. The umbilicus is most frequently at the level of the L4 vertebral body. Patient height, weight, and BMI do not influence the location of the umbilicus or the iliac crests relative to the lumbar spine. Patient sex and ethnicity influence the location of the iliac crests but not the umbilicus relative to the lumbar spine.

Clinical Relevance: Modern neurosurgical techniques require clearance of the iliac crests during anterior and anterolateral approaches. Understanding the level of the iliac crests is crucial in planning for transpsoas fusion approaches.

Level of Evidence: 2

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Artificial Intelligence for Automatic Analysis of Shunt Treatment in Presurgery and Postsurgery Computed Tomography Brain Scans of Patients With Idiopathic Normal Pressure Hydrocephalus

Neurosurgery 95:1329–1337, 2024

Ventriculo-peritoneal shunt procedures can improve idiopathic normal pressure hydrocephalus (iNPH) symptoms. However, there are no automated methods that quantify the presurgery and postsurgery changes in the ventricular volume for computed tomography scans. Hence, the main goal of this research was to quantify longitudinal changes in the ventricular volume and its correlation with clinical improvement in iNPH symptoms. Furthermore, our objective was to develop an end-to-end graphical interface where surgeons can directly drag-drop a brain scan for quantified analysis.

METHODS: A total of 15 patients with 47 longitudinal computed tomography scans were taken before and after shunt surgery. Postoperative scans were collected between 1 and 45 months. We use a UNet-based model to develop a fully automated metric. Center slices of the scan that are most representative (80%) of the ventricular volume of the brain are used. Clinical symptoms of gait, balance, cognition, and bladder continence are studied with respect to the proposed metric.

RESULTS: Fifteen patients with iNPH demonstrate a decrease in ventricular volume (as shown by our metric) postsurgery and a concurrent clinical improvement in their iNPH symptomatology. The decrease in postoperative central ventricular volume varied between 6 cc and 33 cc (mean: 20, SD: 9) among patients who experienced improvements in gait, bladder continence, and cognition. Two patients who showed improvement in only one or two of these symptoms had <4 cc of cerebrospinal fluid drained. Our artificial intelligence–based metric and the graphical user interface facilitate this quantified analysis.

CONCLUSION: Proposed metric quantifies changes in ventricular volume before and after shunt surgery for patients with iNPH, serving as an automated and effective radiographic marker for a functioning shunt in a patient with iNPH.

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Normative Measurements of L1–S1 Segmental Angulation, Disk Space Height, and Neuroforaminal Dimensions Using Computed Tomography

Neurosurgery 94:813–827, 2024

BACKGROUND AND OBJECTIVES: To establish normative anatomic measurements of lumbar segmental angulation (SA) and disk space height (DSH) in relation to neuroforaminal dimensions (NFDs), and to uncover the influence of patient demographic and anthropometric characteristics on SA, DSH, and NFDs.

METHODS: NFDs, SA, and anterior, middle, and posterior DSH were measured using computed tomography of 969 patients. NFDs were defined as sagittal anterior-to-posterior width, foraminal height, and area. Statistical analyses were performed to assess associations among SA, DSH, NFDs, and patient height, weight, body mass index, sex, and ethnicity.

RESULTS: SA and DSH measurements increased moving caudally from L1 to S1. Foraminal width decreased moving caudally from L1 to S1. Foraminal height and area demonstrated unimodal distribution patterns with the largest values clustered at L2–L3 on the right side and L3–L4 on the left. Significant differences in SA, DSH, and NFD measurements were observed based on the disk level. Inconsistent, marginal NFD differences were observed based on laterality. Across all disk levels, only weak-to-moderate correlations were observed between SA and DSH in relation to NFDs. Patient height, weight, and body mass index were only weakly associated with SA, DSH, and NFDs. Based on patient sex, significant differences were observed for SA, DSH, and NFD measurements from L1 to S1, with males demonstrating consistently larger values compared with females. Based on patient race and ethnicity, significant differences in SA and NFD measurements were observed from L1 to S1.

CONCLUSION: This study describes 48 450 normative measurements of L1–S1 SA, DSH, and NFDs. These measurements serve as representative models of normal anatomic dimensions necessary for several applications including surgical planning and diagnosis of foraminal stenosis. Normative values of SA and DSH are not moderately or strongly associated with NFDs. SA, DSH, and NFDs are influenced by sex and ethnicity, but are not strongly or moderately influenced by patient anthropometric factors.

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Anterior-To-Psoas Approach Measurements, Feasibility, Non-Neurological Structures at Risk and Influencing Factors: A Bilateral Analysis From L1-L5 Using Computed Tomography Imaging

Operative Neurosurgery 25:52–58, 2023

Spinal fusion through the anterior-to-psoas (ATP) technique harbors several approach-related risks. We used abdominal computed tomography imaging to analyze the L1-L5 ATP fusion approach measurements, feasibility, degree of obstruction by non-neurological structures, and the influence of patient characteristics on ATP approach dimensions.

METHODS: The vascular window, psoas window, safe window, and incision line anterior and posterior margins for the ATP approach were measured on abdominal computed tomography imaging. The feasibility of approach and the presence of kidneys, ribs, liver, spleen, and iliac crests within the ATP approach were also measured. Correlation and regression models among radiographic measurements and patient age, height, weight, and body mass index (BMI) were analyzed as well as differences in approach measurements based on sex.

RESULTS: Safe window and incision line measurements were more accommodating for the left-sided vs right-sided ATP approach. At L4-5, the ATP approach was not feasible 18% of the time on the left side vs 60% of the time on the right side. The spleen was present 22%, 10%, and 3% of the time from L1-4, while the liver was present 56%, 30%, and 9% of the time. The iliac crests were not observed within ATP parameters. Patient age, height, weight, and BMI did not strongly correlate with approach measurements, although ATP dimensions did differ based on sex.

CONCLUSION: This study reports characteristics of the ATP approach including approach measurements, feasibility, non-neurological structures at risk, and influencing factors to approach measurements. While incision line measurements are larger for male patients compared with female patients at the lower lumbar levels, safe window sizes are similar across all levels L1-L5. The kidneys, ribs, spleen, and liver are potential at-risk structures during the ATP approach, although the iliac crests pose limited concern for ATP technique. Patient characteristics such as age, height, weight, and BMI do not markedly affect ATP approach considerations.

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The accuracy of 3D fluoroscopy (XT) vs computed tomography (CT) registration in deep brain stimulation (DBS) surgery

Acta Neurochirurgica (2020) 162:1871–1878

Stereotactic registration is the most critical step ensuring accuracy in deep brain stimulation (DBS) surgery. 3D fluoroscopy (XT) is emerging as an alternative to CT. XT has been shown to be safe and effective for intraoperative confirmation of lead position following implantation. However, there is a lack of studies evaluating the suitability ofXT to be used for themore crucial step of registration and its capability of being merged to a preoperative MRI. This is the first study comparing accuracy, efficiency, and radiation exposure of XT- vs CT-based stereotactic registration and XT/MRI merging in deep brain stimulation.

Methods Mean absolute differences and Euclidean distance between planned (adjusted for intraoperative testing) and actual lead trajectories were calculated for accuracy of implantation. The radiation dose from each scan was recorded as the dose length product (DLP). Efficiency was measured as the time between the patient entering the operating room and the initial skin incision. A one-way ANOVA compared these parameters between patients that had either CT- or XT-based registration.

Results Forty-one patients underwent DBS surgery—25 in the CT group and 16 in the XT group. The mean absolute difference between CT and XTwas not statistically significant in the x (p = 0.331), y (p = 0.951), or z (p = 0.807) directions. The Euclidean distance between patient groups did not differ significantly (p = 0.874). The average radiation exposure with XT (220.0 ± 0.1 mGy*cm) was significantly lower than CT (1269.3 ± 112.9 mGy*cm) (p < 0.001). There was no significant difference in registration time between CT (107.8 ± 23.1 min) and XT (106.0 ± 18.2 min) (p = 0.518).

Conclusion XT-based frame registration was shown to result in similar implantation accuracy and significantly less radiation exposure compared with CT. Our results surprisingly showed no significant difference in registration time, but this may be due to a learning curve effect.

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Neuroimaging of Intracerebral Hemorrhage

Neurosurgery 86:E414–E423, 2020

Intracerebral hemorrhage (ICH) accounts for 10% to 20% of strokes worldwide and is associated with high morbidity and mortality rates. Neuroimaging is indispensable for rapid diagnosis of ICH and identification of the underlying etiology, thus facilitating triage and appropriate treatment of patients.

The most common neuroimaging modalities include noncontrast computed tomography (CT), CT angiography (CTA), digital subtraction angiography, andmagnetic resonance imaging (MRI). The strengths and disadvantages of each modality will be reviewed.

Novel technologies such as dual-energy CT/CTA, rapid MRI techniques, near-infrared spectroscopy, and automated ICH detection hold promise for faster pre- and in-hospital ICH diagnosis that may impact patient management.

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Value of whole-body low-dose computed tomography in patients with ventriculoperitoneal shunts: a retrospective study

J Neurosurg 129:1598–1603, 2018

The gold standard for evaluation of ventriculoperitoneal (VP) shunt position, dislocation, or disconnection is conventional radiography. Yet, assessment with this modality can be challenging because of low image quality and can result in repetitive radiation exposure with high fluctuation in the radiation dose. Recently, CT-based radiation doses have been significantly reduced by using low-dose protocols. Thus, whole-body low-dose CT (LDCT) has become applicable for routine use in VP shunt evaluation. The authors here compared image quality and approximate radiation dose between radiography and LDCT in patients with implanted VP shunt systems.

METHODS Ventriculoperitoneal shunt systems have been investigated with LDCT scanning at the authors’ department since 2015. A consecutive series of 57 patients (70 investigations) treated between 2015 and 2016 was retrospectively assessed. A historical patient cohort that had been evaluated with radiography was compared with the LDCT patients in terms of radiation dose and image quality. Three independent observers evaluated projection of the valve pressure level and correct intraperitoneal position, as well as complete shunt projection, using a Likert-type scale of 1–5, where 1 indicated “not assessable” and 5 meant “assessable with high accuracy.” Descriptive statistics and the Mann-Whitney U-test were used for analysis.

RESULTS Twenty-seven radiographs (38.6%) and 43 LDCT scans (61.4%) were analyzed. The median dose-length product (DLP) of the LDCT scans was 100 mGy·cm (range 59.9–183 mGy·cm). The median total dose-area product (DAP) of the radiographic images was 3177 mGy·cm2 (range 641–13,833 mGy·cm2). The estimated effective dose (EED) was significantly lower with the LDCT scan (p < 0.001). The median EED was 4.93 and 1.90 mSv for radiographs and LDCT, respectively. Significantly better identification of the abdominal position of the distal shunt catheter was achieved with LDCT (p < 0.001). Simultaneously, significantly improved visualization of the entire shunt system was realized with this technique (p < 0.001). On the contrary, identification of the valve settings was significantly worse with LDCT (p < 0.001).

CONCLUSIONS Whole-body LDCT scanning allows good visualization of the distal catheter after VP shunt placement. Despite the fact that only a rough estimation of effective doses is possible in a direct comparison of LDCT and radiography, the data showed that shunt assessment via LDCT does not lead to greater radiation exposure. Thus, especially in difficult anatomical conditions, as in patients who have undergone multiple intraabdominal surgeries, have a high BMI, or are immobile, the use of LDCT shunt evaluation has high clinical value. Further data are needed to determine the value of LDCT for the evaluation of complications or radiation dose in pediatric patients.

 

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Use of the Airo mobile intraoperative CT system versus the O-arm for transpedicular screw fixation in the thoracic and lumbar spine

J Neurosurg Spine 29:397–406, 2018

Navigation-enabling technology such as 3D-platform (O-arm) or intraoperative mobile CT (iCT-Airo) systems for use in spinal surgery has considerably improved accuracy over that of traditional fluoroscopy-guided techniques during pedicular screw positioning. In this study, the authors compared 2 intraoperative imaging systems with navigation, available in their neurosurgical unit, in terms of the accuracy they provided for transpedicular screw fixation in the thoracic and lumbar spine.

METHODS The authors performed a retrospective analysis of clinical and surgical data of 263 consecutive patients who underwent thoracic and lumbar spine screw placement in the same center. Data on 97 patients who underwent surgery with iCT-Airo navigation (iCT-Airo group) and 166 with O-arm navigation (O-arm group) were analyzed. Most patients underwent surgery for a degenerative or traumatic condition that involved thoracic and lumbar pedicle screw fixation using an open or percutaneous technique. The primary endpoint was the proportion of patients with at least 1 screw not correctly positioned according to the last intraoperative image. Secondary endpoints were the proportion of screws that were repositioned during surgery, the proportion of patients with a postoperative complication related to screw malposition, surgical time, and radiation exposure. A blinded radiologist graded screw positions in the last intraoperative image according to the Heary classification (grade 1–3 screws were considered correctly placed).

RESULTS A total of 1361 screws placed in 97 patients in the iCT-Airo group (503 screws) and in 166 in the O-arm group (858 screws) were graded. Of those screws, 3 (0.6%) in the iCT-Airo group and 4 (0.5%) in the O-arm group were misplaced. No statistically significant difference in final accuracy between these 2 groups or in the subpopulation of patients who underwent percutaneous surgery was found. Three patients in the iCT-Airo group (3.1%, 95% CI 0%–6.9%) and 3 in the O-arm group (1.8%, 95% CI 0%–4.0%) had a misplaced screw (Heary grade 4 or 5). Seven (1.4%) screws in the iCT-Airo group and 37 (4.3%) in the O-arm group were repositioned intraoperatively (p = 0.003). One patient in the iCT-Airo group and 2 in the O-arm group experienced postoperative neurological deficits related to hardware malposition. The mean surgical times in both groups were similar (276 [iCT-Airo] and 279 [O-arm] minutes). The mean exposure to radiation in the iCT-Airo group was significantly lower than that in the O-arm group (15.82 vs 19.12 mSv, respectively; p = 0.02).

CONCLUSIONS Introduction of a mobile CT scanner reduced the rate of screw repositioning, which enhanced patient safety and diminished radiation exposure for patients, but it did not improve overall accuracy compared to that of a mobile 3D platform.

 

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Prognostic Value of the Amount of Bleeding After Aneurysmal Subarachnoid Hemorrhage: A Quantitative Volumetric Study

SAH

Neurosurgery 77:898–907, 2015

Quantitative estimation of the hemorrhage volume associated with aneurysm rupture is a new tool of assessing prognosis.

OBJECTIVE: To determine the prognostic value of the quantitative estimation of the amount of bleeding after aneurysmal subarachnoid hemorrhage, as well the relative importance of this factor related to other prognostic indicators, and to establish a possible cut-off value of volume of bleeding related to poor outcome.

METHODS: A prospective cohort of 206 patients consecutively admitted with the diagnosis of aneurysmal subarachnoid hemorrhage to Hospital 12 de Octubre were included in the study. Subarachnoid, intraventricular, intracerebral, and total bleeding volumes were calculated using analytic software. For assessing factors related to prognosis, univariate and multivariate analysis (logistic regression) were performed. The relative importance of factors in determining prognosis was established by calculating their proportion of explained variation. Maximum Youden index was calculated to determine the optimal cut point for subarachnoid and total bleeding volume.

RESULTS: Variables independently related to prognosis were clinical grade at admission, age, and the different bleeding volumes. The proportion of variance explained is higher for subarachnoid bleeding. The optimal cut point related to poor prognosis is a volume of 20 mL both for subarachnoid and total bleeding.

CONCLUSION: Volumetric measurement of subarachnoid or total bleeding volume are both independent prognostic factors in patients with aneurysmal subarachnoid hemorrhage. A volume of more than 20 mL of blood in the initial noncontrast computed tomography is related to a clear increase in poor outcome risk.

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Cerebral Venous Sinus Thrombosis on Unenhanced CT

Cerebral Venous Sinus Thrombosis on Unenhanced CT

Neurosurg Q 2015;25:154–160

The aim of the study was to investigate computed tomography (CT) signs of cerebral venous sinus thrombosis (CVST), so as to increase clinicians’ awareness of CVST and improve the sensitivity of the diagnosis.

Materials and Methods: We retrospectively analyzed all the CVST cases primary diagnosed by CT and confirmed further by magnetic resonance imaging (MRI) or other clinical methods within the past 4 years in our institution. In total, 11 cases including 6 male and 5 female patients with a mean age of 31.0 years were studied. All patients had emergency CT examination for complaints of headache. The initial CT examinations were performed within 7 days after the onset in 7 cases and over 7 days in the other 4 cases. Six cases had continuous follow-up CT examinations, twice in 4 and 3 times in 2. The analysis items focus on the density change by measuring the CT values of involved venous sinuses in different phases, as well as indirect signs including venous infarction and hemorrhage. As a comparison, we measured CT values of normal venous sinuses in 40 healthy people with age ranging from 20 to 60 years.

Results: Of the patients with CT examinations performed within a week after the onset, 6 cases displayed uniform high density in related venous sinuses with a mean value of 72 HU. One week later, the densities declined slightly or reached isodensity with a mean value of 58 HU. The follow-up CT demonstrated the density changes of sinuses with the extension of the course of CVST, from high density gradually attenuating into mixed density, and into isodensity at last. During 7 to 10 days after the onset in 3 cases, the involved sinuses showed central high density with peripheral isodensity. A change of involved sinuses from high-density to isodensity occurring in different sites was found in 1 case on follow-up CT. Cortical vein thrombosis with secondary hemorrhage in 2 cases and CVST with subarachnoid hemorrhage in 2 cases were revealed in our study.

Conclusions: On CT, the CVST presented as the attenuation of the sinuses from high to isodensity with its resolution course. In the first week, the involved sinuses mainly appear as high density, then in 7 to 10 days decrease to mixed density as central high density and peripheral isodensity, and gradually to uniform isodensity at last. The secondary infarction and hemorrhage are important indirect signs of CVST. Understanding the abnormal density change of venous sinuses and intracerebral indirect signs on CT could improve our diagnostic sensitivity for CVST.

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Relevance of early head CT scans following neurosurgical procedures

early CT postcranio

J Neurosurg 121:307–312, 2014

Early postoperative head CT scanning is routinely performed following intracranial procedures for detection of complications, but its real value remains uncertain: so-called abnormal results are frequently found, but active, emergency intervention based on these findings may be rare. The authors’ objective was to analyze whether early postoperative CT scans led to emergency surgical interventions and if the results of neurological examination predicted this occurrence.

Methods. The authors retrospectively analyzed 892 intracranial procedures followed by an early postoperative CT scan performed over a 1-year period at Rush University Medical Center and classified these cases according to postoperative neurological status: baseline, predicted neurological change, unexpected neurological change, and sedated or comatose. The interpretation of CT results was reviewed and unexpected CT findings were classified based on immediate action taken: Type I, additional observation and CT; Type II, active nonsurgical intervention; and Type III, surgical intervention. Results were compared between neurological examination groups with the Fisher exact test.

Results. Patients with unexpected neurological changes or in the sedated or comatose group had significantly more unexpected findings on the postoperative CT (p < 0.001; OR 19.2 and 2.3, respectively) and Type II/III interventions (p < 0.001) than patients at baseline. Patients at baseline or with expected neurological changes still had a rate of Type II/III changes in the 2.2%–2.4% range; however, no patient required an immediate return to the operating room.

Conclusions. Over a 1-year period in an academic neurosurgery service, no patient who was neurologically intact or who had a predicted neurological change required an immediate return to the operating room based on early postoperative CT findings. Obtaining early CT scans should not be a priority in these patients and may even be cancelled in favor of MRI studies, if the latter have already been planned and can be performed safely and in a timely manner. Early postoperative CT scanning does not assure an uneventful course, nor should it replace accurate and frequent neurological checks, because operative interventions were always decided in conjunction with the neurological examination.

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Brain Imaging in Chronic Epilepsy Patients After Depth Electrode (Stereoelectroencephalography) Implantation: Magnetic Resonance Imaging or Computed Tomography?

Depth electrode localization error

Neurosurgery 73:543–549, 2013

The accurate localization of depth electrodes in epilepsy surgery is important for correct interpretation of stereoelectroencephalography recordings and neurosurgical resection. Unfortunately, image quality in postimplantation magnetic resonance imaging (MRI) is degraded by metal artifacts. The registration of postimplantation computed tomography (CT) or MRI to preimplantation (artifact-free) MRI facilitates electrode imaging and optimal visualization of brain anatomy. However, registration errors negatively affect electrode localization accuracy.

OBJECTIVE: To compare the relative registration deviation between postimplantation CT and MRI with preimplantation MRI.

METHODS: Retrospectively, 14 pharmacoresistant epilepsy patients were included who underwent stereotactic insertion of multiple depth electrodes and preimplantation and postimplantation MRI and postimplantation CT. Postimplantation MRI and CT image sets were registered to preimplantation MRI. The registration error between the registered postimplantation MRI and CT was quantified by measuring the geometrical distance between the electrodes of the registered postimplantation CT and the postimplantation MRI.

RESULTS: The registration error of postimplantation imaging to preimplantation MRI was dependent on the algorithm used. After optimization, the smallest registration error was 1.22 6 0.29 mm (mean 6 SD) at the tip and 2.25 6 1.18 mm at the base of the electrode.

CONCLUSION: The good correspondence between the CT/MRI and the MRI/MRI registration suggests that either postimplantation MRI or CT is sufficient for accurate electrode localization. In case of postoperative morphological brain deformations, postimplantation MRI is still recommended.

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Accuracy and complications associated with the freehand C-1 lateral mass screw fixation technique

Accuracy and complications associated with the freehand C-1 lateral mass screw fixation technique

J Neurosurg Spine 18:372–377, 2013

The aims of this study were to evaluate a large series of posterior C-1 lateral mass screws (LMSs) to determine accuracy based on CT scanning findings and to assess the perioperative complication rate related to errant screw placement.

Methods. Accuracy of screw placement was evaluated using postoperative CT scans obtained in 196 patients with atlantoaxial instability. Radiographic analysis included measurement of preoperative and postoperative CT scans to evaluate relevant anatomy and classify accuracy of instrumentation placement. Screws were graded using the following definitions: Type I, screw threads completely within the bone (ideal); Type II, less than half the diameter of the screw violates the surrounding cortex (safe); and Type III, clear violation of transverse foramen or spinal canal (unacceptable).

Results. A total of 390 C-1 LMSs were placed, but 32 screws (8.2%) were excluded from accuracy measurements because of a lack of postoperative CT scans; patients in these cases were still included in the assessment of potential clinical complications based on clinical records. Of the 358 evaluable screws with postoperative CT scanning, 85.5% of screws (Type I) were rated as being in the ideal position, 11.7% of screws (Type II) were rated as occupying a safe position, and 10 screws (2.8%) were unacceptable (Type III). Overall, 97.2% of screws were rated Type I or II. Of the 10 screws that were unacceptable on postoperative CT scans, there were no known associated neurological or vertebral artery (VA) injuries. Seven unacceptable screws erred medially into the spinal canal, and 2 patients underwent revision surgery for medial screws. In 2 patients, unilateral C-1 LMSs penetrated the C-1 anterior cortex by approximately 4 mm. Neither patient with anterior C-1 penetration had evidence of internal carotid artery or hypoglossal nerve injury. Computed tomography scanning showed partial entry of C-1 LMSs into the VA foramen of C-1 in 10 cases; no occlusion, associated aneurysm, or fistula of the VA was found. Two patients complained of postoperative occipital neuralgia. This was transient in one patient and resolved by 2 months after surgery. The second patient developed persistent neuralgia, which remained 2 years after surgery, necessitating referral to the pain service.

Conclusions. The technique for freehand C-1 LMS fixation appears to be safe and effective without intraoperative fluoroscopy guidance. Preoperative planning and determination of the ideal screw insertion point, the ideal trajectory, and screw length are the most important considerations. In addition, fewer malpositioned screws were inserted as the study progressed, suggesting a learning curve to the technique.

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Accuracy of Postoperative Computed Tomography and Magnetic Resonance Image Fusion for Assessing Deep Brain Stimulation Electrodes

Neurosurgery 69:207–214, 2011 DOI: 10.1227/NEU.0b013e318218c7ae

Knowledge of the anatomic location of the deep brain stimulation (DBS) electrode in the brain is essential in quality control and judicious selection of stimulation parameters. Postoperative computed tomography (CT) imaging coregistered with preoperative magnetic resonance imaging (MRI) is commonly used to document the electrode location safely. The accuracy of this method, however, depends on many factors, including the quality of the source images, the area of signal artifact created by the DBS lead, and the fusion algorithm.

OBJECTIVE: To calculate the accuracy of determining the location of active contacts of the DBS electrode by coregistering postoperative CT image to intraoperative MRI.

METHODS: Intraoperative MRI with a surrogate marker (carbothane stylette) was digitally coregistered with postoperative CT with DBS electrodes in 8 consecutive patients. The location of the active contact of the DBS electrode was calculated in the stereotactic frame space, and the discrepancy between the 2 images was assessed.

RESULTS: The carbothane stylette significantly reduces the signal void on the MRI to a mean diameter of 1.4 6 0.1 mm. The discrepancy between the CT and MRI coregistration in assessing the active contact location of the DBS lead is 1.6 6 0.2 mm, P < .001 with iPlan (BrainLab AG, Erlangen, Germany) and 1.5 6 0.2 mm, P < .001 with Framelink (Medtronic, Minneapolis, Minnesota) software.

CONCLUSION: CT/MRI coregistration is an acceptable method of identifying the anatomic location of DBS electrode and active contacts.

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Intraoperative Computed Tomography for Deep Brain Stimulation Surgery: Technique and Accuracy Assessment

Neurosurgery 68[ONS Suppl 1]:ons114–ons124, 2011. DOI: 10.1227/NEU.0b013e31820781bc

The efficacy of deep brain stimulation (DBS) is highly dependent on the accuracy of lead placement.

OBJECTIVE: To describe the use of intraoperative computed tomography (iCT) to confirm lead location before surgical closure and to study the accuracy of this technique.

METHODS: Fifteen patients underwent awake microelectrode-guided DBS surgery in a stereotactic frame. A portable iCT scanner (Medtronic O-arm) was positioned around the patient’s head throughout the procedure and was used to confirm lead location before fixation of the lead to the skull. Images were computationally fused with preoperative magnetic resonance imaging (MRI), and lead tip coordinates with respect to the midpoint of the anterior commissure-posterior commissure line were measured. Tip coordinates were compared with those obtained from postoperative MRI.

RESULTS: iCT was integrated into standard frame-based microelectrode-guided DBS surgery with a minimal increase in surgical time or complexity. Technically adequate 2-dimensional and 3-dimensional images were obtained in all cases. Head positioning and fixation techniques that allow unobstructed imaging are described. Lead tip measurements on iCT fused with preoperative MRI were statistically indistinguishable from those obtained with postoperative MRI.

CONCLUSION: iCT can be easily incorporated into standard DBS surgery, replaces the need for C-arm fluoroscopy, and provides accurate intraoperative 3-dimensional confirmation of electrode tip locations relative to preoperative images and surgical plans. iCT fused to preoperative MRI may obviate the need for routine postoperative MRI in DBS surgery. Technical nuances that must be mastered for the efficient use of iCT during DBS implantation are described.

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The clinical significance and optimal timing of postoperative computed tomography following cranial surgery

J Neurosurg 113:1021–1025, 2010. DOI: 10.3171/2009.11.JNS081048

This study was conducted to evaluate the value of postoperative CT scans in determining the probability of return to the operating room (OR) and the optimal time to obtain such scans to determine the effects of surgery.

Methods. Between January and December 2006 (12 months), all postoperative head CT scans obtained for 3 individual surgeons were reviewed. Scans were divided into 3 groups, which were determined by the preference of each surgeon: Group A (early scans—scheduled between 0 and 7 hours); Group B (delayed scans—scheduled between 8 and 24 hours); and Group C (urgent scans—ordered because of a new neurological deficit). The initial scans were reviewed and analyzed in 2 different fashions. The first was to analyze the efficacy of the scans in predicting return to the OR. The second was to determine the optimal time for obtaining a scan. The second analysis was a review of serial postoperative scans for expected versus unexpected findings and changes in the acuity of these findings over time.

Results. In 251 (74%) of 338 cases, the patients had postoperative head CT scans within 24 hours of surgery. Analysis 1 determined the percent of patients returning to the OR for emergency treatment based on postoperative scans: Group A (early)—133 patients, with 0% returning to the OR; Group B (delayed)—108 patients, with 0% returning to the OR; and Group C (urgent)—10 patients, with 30% returning to the OR (p < 0.05). Analysis 2 determined the optimal timing of postoperative scans and changes in scan acuity: Group A (early scan) had an 11% incidence of change in acuity on subsequent scans. Group B (delayed scan) had a 3% incidence of change in acuity on follow-up scans (p < 0.05).

Conclusions. Routine postoperative scans at 0–7 hours or at 8–24 hours are not predictive of return to the OR, whereas patients with a new neurological deficit in the postoperative period have a 30% chance of emergency reoperation based on CT scans. In addition, early postoperative scans (0–7 hours) fail to predict CT changes, which might evolve over time and may influence postoperative medical management.

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Extensions of the Sphenoid Sinus: A New Classification

Neurosurgery. 66(4):797-816, April 2010. doi: 10.1227/01.NEU.0000367619.24800.B1

The transsphenoidal approach has been extended in recent years from tumors of the sellar region to lesions involving other areas bordering the sphenoid sinus including the cavernous sinus, Meckel’s cave, middle cranial fossa, planum sphenoidal, suprasellar region, and clivus. The goal of this study was to examine various pneumatized extensions of the sphenoid sinus that may facilitate extended approaches directed through the sinus.

METHODS: The sphenoid sinus and its surrounding structures were examined in 18 cadaver heads, and the results were correlated with the findings from 100 computed tomography images of the sinus. The sellar type of the sphenoid sinus in which the pneumatization extended beyond the anterior sellar wall was further classified according to the various extensions of the sinus.

RESULTS: The sellar type of the sphenoid sinus was classified into the following 6 basic types based on the direction of pneumatization: sphenoid body, lateral, clival, lesser wing, anterior, and combined. The recesses and prominences, formed by pneumatization of the sinus, act as “windows” opening from the sinus in different areas of the cranial base and may facilitate minimally invasive access to lesions in the corresponding areas.

CONCLUSION: The variations in the extensions of pneumatization of the sphenoid sinus may facilitate entry into areas bordering the sphenoid sinus and play a role in the selection of a surgical approach to lesions bordering the sinus.

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Indications for Brain Computed Tomography and Hospital Admission in Pediatric Patients with Minor Head Injury

Pediatr Neurosurg 2009;45:262–270. DOI: 10.1159/000228984

Objectives: The aim of this study was to describe the characteristics of patients with a minor head injury (MHI) who were admitted to a pediatric emergency unit and to identify the clinical signs and symptoms that most reliably predict the need for cranial computed tomography (CCT) and hospital admission following MHI.

Methods: All patients were retrospectively evaluated according to age, gender, details of injury, presenting symptoms, physical examination findings, radiological investigations ordered and results, length of stay, outcome of the injury and hospitalization rates.

Results:The factors affecting indications for computed tomography and hospitalization were retrospectively analyzed in 916 patients – 585 males and 331 females, aged between 1month and 15 years (mean: 5.01 8 3.58 years), with MHI. A multivariate analysis revealed significant correlations between CCT abnormalities and Glasgow Coma Scale scores of 13 or 14, headache, posttraumatic amnesia, blurred vision, cephalohematomas, periorbital ecchymoses, otorrhea and abnormal neurological findings. CCT abnormalities were identified in 67 (19.8%) of the 338 CCT scans. Twenty of the 67 patients (29.9%) with CCT scan abnormality had no clinical signs. Of all cases, 125 (13.6%) were hospitalized, 617 (67.4%) were treated as outpatients, and 174 (19.0%) left the emergency department based on a personal decision.

Conclusion: Some clinical risk factors can be used as predictors of abnormalities in CCT scans following MHI, but the absence of such clinical findings does not exclude the possibility of intracranial injuries.

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