Numerical investigation of unruptured middle cerebral artery bifurcation aneurysms: influence of aspect ratio.

An aneurysm is a disease condition, which is due to the pathological weakening of an arterial wall. These aneurysms are often found in various branch points and bifurcations of an artery in the cerebral circulation. Most aneurysms come to medical attention, either due to brain hemorrhages caused by rupture or found unruptured. To consider surgically invasive treatment modalities, clinicians need scientific methods such as, hemodynamic analysis to assess rupture risk. The arterial wall loses its structural integrity when wall shear stress (WSS) and other hemodynamic parameters exceed a certain threshold. In the present study, numerical simulations are carried out for unruptured middle cerebral artery (MCA) aneurysms. Three distinct representative sizes are chosen from a larger patient pool of 26 MCA aneurysms. Logically, these aneurysms represent three growth stages of any patient with similar anatomical structure. Simulations are performed to compare the three growth phases (with different aspect ratios) of an aneurysm and correlate their hemodynamic parameters. Simulations with patient specific boundary conditions reveal that, aneurysms with a higher aspect ratio (AR) correspond to an attendant decrease in both time-averaged wall shear stress (TAWSS) and spatial wall shear stress gradients (WSSG). Smaller MCAs were observed to have higher positive wall shear stress divergence (WSSD), exemplifying the tensile nature of arterial wall stretching. Present study identifies positive wall shear stress divergence (PWSSD) to be a potential biomarker for evaluating the growth of an aneurysm.

Analysis of Evolution of Hydrocephalus in Posterior Fossa Tumors and Validation Study of the Modified Canadian Preoperative Prediction Rule for Hydrocephalus in Children and Frankfurt Grading System for Prediction of Cerebrospinal Fluid Diversion in Adults with Posterior Fossa Tumors.

OBJECTIVE: We sought to analyze the evolution of hydrocephalus and enumerate its predictive factors in posterior fossa tumors in children and adults. We also validated the modified Canadian Preoperative Prediction Rule for Hydrocephalus (mCPPRH) and Frankfurt grading systems as tools to predict cerebrospinal fluid (CSF) diversion in children and adults, respectively. METHODS: A retrospective review of patients with posterior fossa tumors operated between 2012 and 2019 was performed. Clinical, radiologic, and operative data were obtained. Validation was performed for both scores via receiver operating characteristic (ROC) curves and evaluation of the area under the curve (AUC). RESULTS: We included 116 children and 343 adults in the study. Of the adults, 141 patients had intraaxial tumors and 172 had extraaxial tumors. The insertion of external ventricular drain (EVD), its duration, papilledema was noted to have significant influence on the need for permanent CSF diversion (P < 0.05) in children. The ROC for mCPPRH score was 0.659 (0.501-0.816), Age- 0.496 (0.334-0.658) and Evans index- 0.788 (0.654-0.922). In adults- Intraaxial tumours Age, Frankfurt score, duration of EVD, Diagnosis, Extent of resection and periventricular capping significant predictors and ROC age AUC 0.300 (0.193-0.407), Evans index 0.939 (0.888-0.990), and Frankfurt score 0.908 (0.853-0.964) (P < 0.05), whereas in extraaxial tumors Frankfurt grading, sex, duration of EVD, presence of perilesional edema and extent of resection (P < 0.05) ROC age AUC 0.439 (0.344-0.534), Evans index 0.941 (0.906-0.977), and Frankfurt score 0.847 (0.782-0.912). CONCLUSIONS: This is the first external validation study for the 2 predictive systems in use. mCPPRH demonstrated poor predictive accuracy, and Frankfurt grading system demonstrated good accuracy. EVD insertion and its duration was significantly predictive of the need for permanent CSF diversion.

Usefulness of flat detector CT (FD-CT) with biplane fluoroscopy for complication avoidance during radiofrequency thermal rhizotomy for trigeminal neuralgia.

INTRODUCTION: Trigeminal neuralgia (TN) is characterized by episodes of shooting pain in the areas innervated by one or more divisions of the trigeminal nerve. The initial treatment of TN is with drugs but the increased frequency and intensity of the neuralgic episodes often force the patient to seek alternative therapies. Microvascular decompression (MVD) and radiofrequency thermal lesioning of trigeminal rootlets (RFTR) offer close to the best results for TN. MVD has the disadvantage of being an open surgical procedure with its attendant risks and longer hospital stay, whereas RFTR is a short, 'day-care' procedure. However this latter procedure involves positioning of the RF needle in the area behind the trigeminal ganglion through the foramen ovale, which can pose significant challenges. OBJECTIVE: To use the fluoroscopic support of a biplane catheter laboratory to access the foramen, and flat detector CT to confirm the location of the tip of the RF needle in the optimal position. METHODS: Fifty-three patients with TN underwent RFTR under local anesthesia with conscious sedation. RESULTS: All patients reported pain relief with hypesthesia over the offending trigeminal division. In seven patients the needle tip required repositioning according to the CT images. Two patients each had loss of corneal reflex and abducens nerve palsy after the procedure. No other complications were seen. CONCLUSIONS: The superior view in two planes coupled with the anatomical confirmation of the position of the needle tip in the Meckel's cave during the rhizotomy reduces the need for multiple passages of the needle to access the foramen ovale and achieves accurate needle tip positioning. The technique increases the safety and precision of such treatments and helps to manage potential complications.