Tag: trajectory

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Outcome prediction following lumbar disc surgery: a longitudinal study of outcome trajectories, prognostic factors, and risk models

J Neurosurg Spine 42:33–42, 2025

This study aimed to 1) describe the 2-year postoperative trajectories of leg pain and overall clinical outcome after surgery for radiculopathy, 2) identify the preoperative prognostic factors that predict trajectories representing poor clinical outcomes, and 3) develop and internally validate multivariable prognostic models to assist with clinical decision-making.

METHODS This retrospective cohort study included patients enrolled in the Canadian Spine Outcomes and Research Network who were diagnosed with lumbar disc pathology and radiculopathy and had undergone lumbar discectomy at one of 18 spine centers. Potential outcome predictors included preoperative demographic, health-related, and clinical prognostic factors. Clinical outcomes were 1) 2-year univariable latent trajectories of leg pain intensity (numeric pain rating scale) and 2) overall outcomes comprising multivariable trajectories showing the combined postoperative courses of leg and back pain intensity (numeric pain rating scale) together with pain-related disability (Oswestry Disability Index). Each outcome model identified a subgroup of patients classified as experiencing a poor outcome based on minimal change in their clinical status after surgery. Multivariable risk model performance and internal validity were evaluated with discrimination and calibration statistics based on bootstrap shrinkage with 500 resamplings.

RESULTS The authors included data from 1142 patients (47.6% female). The trajectory models identified 3 subgroups based on the patients’ postoperative courses of pain or disability: 88.6% of patients in the leg pain model and 71.9% in the overall outcome model experienced a good-to-excellent outcome. The models classified 11.4% (leg pain outcome) and 28.2% (overall outcome) of patients as experiencing a poor clinical outcome, which was defined as minimal improvement in pain or disability after surgery. Eleven individual demographic, health, and clinical factors predicted patients’ poor leg pain and overall outcomes. The performance of the multivariable risk model for leg pain was inadequate, while the overall outcome model had acceptable discrimination, calibration, and internal validity for predicting a poor surgical outcome.

CONCLUSIONS Patients with lumbar radiculopathy experience heterogeneous postoperative trajectories of pain and disability after lumbar discectomy. Individual preoperative factors are associated with postoperative outcomes and can be combined within a multivariable risk model to predict overall patient outcome. These results may inform clinical practice but require external validation before confident clinical implementation.

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Retrosigmoid transhorizontal fissure approach to lateral pontine cavernous malformation

J Neurosurg 136:205–214, 2022

The retrosigmoid (RS) approach is a classic route used to access deep-seated brainstem cavernous malformation (CM). The angle of access is limited, so alternatives such as the transpetrosal presigmoid retrolabyrinthine (TPPR) approach have been used to overcome this limitation. Here, the authors evaluated a modification to the RS approach, horizontal fissure dissection by using the RS transhorizontal (RSTH) approach.

METHODS Relevant clinical parameters were evaluated in 9 patients who underwent resection of lateral pontine CM. Cadaveric dissection was performed to compare the TPPR approach and the RSTH approach.

RESULTS Five patients underwent the TPPR approach, and 4 underwent the RSTH approach. Dissection of the horizontal fissure allowed for access to the infratrigeminal safe entry zone, with a direct trajectory to the middle cerebellar peduncle similar to that used in TPPR exposure. Operative time was longer in the TPPR group. All patients had a modified Rankin Scale score ≤ 2 at the last follow-up. Cadaveric dissection confirmed increased anteroposterior working angle and middle cerebellar peduncle exposure with the addition of horizontal fissure dissection.

CONCLUSIONS The RSTH approach leads to a direct lateral path to lateral pontine CM, with similar efficacy and shorter operative time compared with more extensive skull base exposure. The RSTH approach could be considered a valid alternative for resection of selected pontine CM.

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Modified unilateral approach for mid-third giant bifalcine meningiomas: resection using an oblique surgical trajectory and falx window

Acta Neurochirurgica (2019) 161:327–332

Utilizing the shortest available trajectory is the norm for excision of meningiomas. However, such an approach for the mid-third/central falcine meningiomas risks the adjoining draining veins and eloquent cortex. A larger size and bilaterality of such tumors adds to the surgical challenge. Herein, we report the surgical nuances of a modified unilateral approach in patients operated for giant bilateral symmetrical mid-third falcine meningiomas.

Methods Five such patients were operated. The clinico-radiologic data was studied at presentation and at the follow-up. The meningiomas were subclassified into those that were located in the anterior and posterior half of the central falx, and their surgical trajectory was chosen accordingly. The tumor was excised through an oblique anterior or a posterior trajectory instead of directly working over the major draining veins and eloquent brain. The falx was incised to create a surgical window and access the tumor on the contralateral side.

Results Four patients had meningiomas in the anterior half and one in the posterior half of central falx. Simpson excision was grade II in four patients. One patient showed small residual tumor and underwent stereotactic radiosurgery. The overall mean follow-up of the patients was 9.2 months. All the patients had good clinical outcome.

Conclusions Giant bifalcine meningiomas can be safely resected through a unilateral approach. Falx opening serves as a window to remove the tumor from the contralateral side. An oblique trajectory rather than an end-on access to these tumors minimizes the risk of venous and cortical injury.

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Optimal entry point for endoscopic colloid cyst resection

Endoscopic approach to colloid cysts

J Neurosurg 121:790–796, 2014

An optimal entry point and trajectory for endoscopic colloid cyst (ECC) resection helps to protect important neurovascular structures. There is a large discrepancy in the entry point and trajectory in the neuroendoscopic literature.

Methods. Trajectory views from MRI or CT scans used for cranial image guidance in 39 patients who had undergone ECC resection between July 2004 and July 2010 were retrospectively evaluated. A target point of the colloid cyst was extended out to the scalp through a trajectory carefully observed in a 3D model to ensure that important anatomical structures were not violated. The relation of the entry point to the midline and coronal sutures was established. Entry point and trajectory were correlated with the ventricular size.

Results. The optimal entry point was situated 42.3 ± 11.7 mm away from the sagittal suture, ranging from 19.1 to 66.9 mm (median 41.4 mm) and 46.9 ± 5.7 mm anterior to the coronal suture, ranging from 36.4 to 60.5 mm (median 45.9 mm). The distance from the entry point to the target on the colloid cyst varied from 56.5 to 78.0 mm, with a mean value of 67.9 ± 4.8 mm (median 68.5 mm). Approximately 90% of the optimal entry points are located 40–60 mm in front of the coronal suture, whereas their perpendicular distance from the midline ranges from 19.1 to 66.9 mm. The location of the “ideal” entry points changes laterally from the midline as the ventricles change in size.

Conclusions. The results suggest that the optimal entry for ECC excision be located at 42.3 ± 11.7 mm perpendicular to the midline, and 46.9 ± 5.7 mm anterior to the coronal suture, but also that this point differs with the size of the ventricles. Intraoperative stereotactic navigation should be considered for all ECC procedures whenever it is available. The entry point should be estimated from the patient’s own preoperative imaging studies if intraoperative neuronavigation is not available. An estimated entry point of 4 cm perpendicular to the midline and 4.5 cm anterior to the coronal suture is an acceptable alternative that can be used in patients with ventriculomegaly.

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