Dawid Larysz

Modeling and biomechanical analysis of craniosynostosis correction with the use of finite element method

Craniosynostosis is a skull malformation because of premature fusing of one or more cranial sutures. The most common types of craniosynostosis are scaphocephaly (with the sagittal suture fused) and trigonocephaly (with the metopic suture fused). In this paper we describe and discuss how finite element analysis and three-dimensional modeling can be used for preoperative planning of the correction of craniosynostosis and for the postoperative evaluation of the treatment results. We used the engineering software MIMICS MATERIALISE to obtain three-dimensional geometry from computed tomography scans, and applied finite element method for the sake of biomechanical analysis. These simulations help to improve the surgical treatment, making it more accurate, safer, and faster.

Morphological, Hemodynamic, and Clinical Independent Risk Factors for Anterior Communicating Artery Aneurysms

Background and Purpose— The pathogenesis of cerebral aneurysms still raises some controversies. The aim of this study was to identify morphological, hemodynamic, and clinical independent risk factors for anterior communicating artery (ACoA) aneurysm development. Methods— Computed tomography angiography and transcranial color-coded sonography were performed in 77 patients with a nonbleeding ACoA aneurysm and in 73 controls. Symmetry of A1 segments of the anterior cerebral arteries, angles between A1 and A2 segments, tortuosity, diameter, mean velocity (Vm), pulsatility index, and volume flow rate in both A1 segments were determined. Moreover, all study participants completed a survey on their medical history. Multivariate backward stepwise logistic regression analysis was performed to identify independent risk factors for ACoA aneurysm development. Results— Smoking, hypertension, asymmetry of A1 segments, the angle between A1 and A2 segments, A1 segment diameter, Vm, pulsatility index, and volume flow rate turned out to be associated with the occurrence of ACoA aneurysms on univariate analysis. Multivariate analysis identified smoking (odds ratio, 2.036; 95% confidence interval, 1.277–3.245), asymmetry of A1 segments >40% (odds ratio, 2.524; 95% confidence interval, 1.275–4.996), pulsatility index (odds ratio, 0.004; 95% confidence interval, 0.000–0.124), and the angle between A1 and A2 segments ⩽100° (odds ratio, 4.665; 95% confidence interval, 2.247–9.687) as independent strong risk factors for ACoA aneurysm development. Conclusions— The risk of ACoA aneurysm formation is determined by several independent clinical, morphological, and hemodynamic factors. The strongest independent risk factors include smoking, asymmetry of A1 segments >40%, low blood flow pulsatility, and the angle between A1 and A2 segments ⩽100°.

Hypofractionated stereotactic radiotherapy for large or involving critical organs cerebral arteriovenous malformations

Abstract Background. The treatment of large arteriovenous malformations (AVMs) or AVMs involving eloquent regions of the brain remains a challenge. For inoperable lesions, observation, volume-staged radiosurgery or hypofractionated stereotactic radiotherapy (HFSRT) are proposed. The aim of our study was to assess the safety and efficiency of HFSRT for large AVMs located in eloquent areas of the brain. Materials and methods. An analysis of records of 49 patients irradiated for cerebral AVMs with a mean dose of 19.9 Gy (12-28 Gy) delivered in 2-4 fractions with planned gap (at least one week) between fractions. Actuarial obliteration rates and annual bleeding hazard were calculated using Kaplan-Meier survival analysis and life tables. Results. Annual bleeding hazard rates were 4.5% and 1.6% after one and two years of the follow-up, respectively. Actuarial total obliteration rates were 7%, 11%, and 21% and total response rate (total and partial obliterations) 22%, 41%, and 55% after one, two and three years of the follow-up, respectively. There was a trend towards larger total obliteration rate in patients irradiated with fraction dose ≥ 8 Gy and total dose > 21 Gy for lesions of volume ≤ 8.18 cm3 which was not observed in case of partial obliterations. Conclusions. HFSRT results with relatively low obliteration rate but is not associated with a significant risk of permanent neurological deficits if both total and fraction doses are adjusted to size and location of the lesion. Predictive factors for total and partial obliterations can be different; this observation, however, is not firmly supported and requires further studies.

MR Spectroscopic Evaluation of Brain Tissue Damage After Treatment for Pediatric Brain Tumors

PURPOSE The aim of this study was to evaluate the metabolic profile of uninvolved brain tissue after treatment for pediatric brain tumors. MATERIAL A group of 24 patients aged 4-18 years was analyzed after combined treatment for brain tumors. In this group, there were nine medulloblastomas, seven low-grade gliomas, three high-grade gliomas, two ependymomas and three children with conservatively treated diffuse brainstem gliomas. METHODS Short echo-time (TE = 30 ms) point-resolved spectra were acquired using a 2 T clinical scanner (Elscint Prestige). The ratios of signal intensities for N-acetylaspartate (NAA), choline (Cho), myo-inositol (mI), lactate (Lac), and lipids (Lip) were calculated using the creatine (Cr) signal as an internal reference. The spectra were acquired both from the tumor bed and from contralateral uninvolved brain tissue; only control spectra were analyzed. The first examination was made between the third and sixth month after therapy (24 spectra), the second examination occurred 8-12 months after treatment (15 spectra available), and the third was performed approximately 18 months after completion of therapy (eight spectra available). The results were compared using the t-test for dependent samples. RESULTS At all time points, the metabolite ratios showed alterations indicating brain tissue damage. The most important were the decrease of NAA/Cr and increase of Lac/Cr and Lip/Cr ratios. The mean NAA/Cr values were 0.91, 0.91, and 0.86, respectively, for the three examinations, while the Lac/Cr and Lip/Cr values were 1.66, 2.11, 1.19 and 12.24, 12.05, 5.69, respectively. Interestingly, in children with supratentorial tumors, a significant increase in NAA/Cr value was observed (from 0.82 to 1.11 in the first and second examinations, respectively; p = 0.0487), which may be indicative of neuronal function recovery. CONCLUSIONS MRS examinations of uninvolved brain tissue indicate long-lasting metabolic disturbances. However, the NAA/Cr ratio increase may be a sign of at least partial recovery of metabolic function of the brain.

The Incidence of Imaging Abnormalities after Stereotactic Radiosurgery for Cerebral Arteriovenous and Cavernous Malformations

OBJECTIVE The aim of the study was to evaluate the incidence of postirradiation imaging changes after stereotactic radiosurgery for arteriovenous malformations (AVM) and cerebral cavernous malformations (CCM). MATERIAL AND METHODS A group of 85 patients treated for arteriovenous malformations (62 patients, 73%) and cavernomas (23 patients, 27%) between October 2001 and December 2005 was analyzed. All patients were treated with stereotactic radiosurgery with doses ranging from 8-28 Gy. After the irradiation, magnetic resonance imaging (MRI) or computed tomography (CT) was performed at 6 to 12-month intervals to assess the effects of the treatment. The mean follow-up time for the whole group was 27.3 months; AVM group -- 26 months; CCM group -- 30.9 months. All the imaging data were carefully reviewed to identify the radiological symptoms of postradiosurgical damage. T2 or FLAIR hyperintensity, T1-hypointensity and contrast enhancement on MRI and the presence of hypodense areas and contrast enhancement on CT examinations were assessed. RESULTS Imaging abnormalities were found in 28 (33%) patients. The symptoms of postradiosurgical damage were observed in 21 (33.9%) patients in the AVM group and 7 (30.4%) patients in the CCM group. Radiological symptoms of radiation necrosis associated with neurological deterioration were identified in two patients with cavernomas, while no radiation necrosis was found in the AVM group. Patients in whom radiological signs of focal brain edema or gliosis existed were asymptomatic. CONCLUSIONS Radiological symptoms of postradiosurgical damage affected about one third of the irradiated patients, typically without any clinical manifestations. Patients irradiated for CCMs seem to be more prone to develop symptomatic postradiosurgical necrosis; this observation, however, requires further investigation.

Radiological findings in relation to the neurodevelopmental outcome in hydrocephalic children treated with shunt insertion or endoscopic third ventriculostomy

PurposeThe aim of the study was to compare the radiological indicators of effectiveness for hydrocephalus treatment in children operated on under the third year of age with the use of shunt insertion (SI) and endoscopic third ventriculostomy (ETV). The effectiveness was considered in terms of postoperative neurodevelopment in correlation to pre- and postoperative radiological findings.MethodsThe examined group consisted of 46 children operated on for hydrocephalus in the Division of Pediatric Neurosurgery in Katowice, Poland. There were 21 children treated with SI and 25 with ETV. The radiographic assessment was carried out on the basis of MRI and CT examinations with the use of a linear estimate known as frontal and occipital horn ratio (FOR). The FOR values were calculated for the entire group and in correlation to the treatment method and to the children neurodevelopment evaluated with The Denver Developmental Screening Test.ResultsNo differences were recognized between initial FOR value in terms of the postoperative children neurodevelopment. In the successful ETV-treated subgroup, the mean change in FOR was 0.05 and in the SI-treated subgroup, the mean change in FOR 0.13. The patients with BFOR >0.1, developed normally more often than those in whom BFOR was lower than 0.1.ConclusionsThe initial FOR value probably does not affect the postoperative developmental outcome. Long-term change in ventricles size after surgery can correlate with psychomotor development of hydrocephalic children. Presumably, there are no differences between two treatment options according to initial FOR values and to changes in FOR values.

Statistical Analysis of Cranial Measurements - Determination of Indices for Assessing Skull Shape in Patients with Isolated Craniosynostosis

This paper presents a morphological analysis of the skull shape in infants under one year of age. Three-dimensional measurements were performed on models generated from images in Mimics software. Subsequently, a multivariate statistical analysis of the measured dimensions was performed to determine key indicators of the skull shape. Eventually it was developed the norms of skull indices for children up to one year of age. Regular values of these indices were compared with abnormal values measured in patients with isolated craniosynostosis. With the use of these indices it is possible to perform a quantitative evaluation of head deformity.

Application of 3D modeling and modern visualization technique to neurosurgical trigonocephaly correction in children

The attempt to a new methodology creation, supported neurosurgical correction of trigonocephaly by engineers is presented in this paper. Trigonocephaly is an example of skull deformity, that wrong influence on child physical and psychological development. Conventional procedures in such cases are connected with invasive operation. Up to now neurosurgeons during pre-operation planning of bones correction, based on their own knowledge and experience. Modeling in biomechanics connected with modern visualization methods give new possibilities of engineer support for medical procedures. Three-dimensional model of deformed skull was created on the basis of CT scans with use of Mimics software. The model was transformed to FEM and used for suitable shape of forehead bone determination. Material properties of modeled bones were assumed on the basis of experimental researches. The geometrical model was presented in 3-dimensional virtual reality. It helps to better imagine about the real shape of skull hidden under head skin and take the best decision how to operate the example of trigonocephaly.

Preoperative Planning of Surgical Treatment with the Use of 3D Visualization and Finite Element Method

This chapter describes a method of engineering support of preoperative planning of surgical procedures with the use of engineering tools, such as state-of-the-art software for medical image processing, or a finite element method. The procedure of pre-operative planning consists in matching individual cases of incision sites and directions, visualization and selection of areas for resection as well as planning the technique of implant positioning and fixation. Also, the final visualization of the result of the planned medical procedure can be performed. This paper presents procedural propositions in surgery planning in the cases of corrections of the head shape in patients with craniosynostosis, corrections of the chest deformity such as pigeon chest and stabilization of the lumbar spine. 3D models created on the basis of computer tomography (CT) or magnetic resonance imaging (MRI) enabled it to conduct a biomechanical analysis as well as an objective quantitative and qualitative virtual evaluation of the surgical procedure. Preoperative planning support gives the physician an opportunity to prepare for the operation in a better way, which results in the selection of the best possible variant of an operative technique, reduction of time of the surgical procedure and minimization of the risk of intraoperative complications.

Is Neuroradiological Imaging Sufficient for Exclusion of Intracranial Hypertension in Children? Intracranial Hypertension Syndrome Without Evident Radiological Symptoms

There are still many important questions about algorithms and clinical scenarios in the context of children with clinical intracranial hypertension symptoms (IHS) without radiological findings. Such conditions could appear in different clinical situations, including slit ventricle syndrome, overdrainage syndrome, normal volume hydrocephalus, or idiopathic intracranial hypertension. Many articles have defined specific treatment strategies for various forms of IHS, including ventriculoperitoneal shunting, medication for shunt-related migraine, steroids, and valve upgrades with antisiphoning devices or programmable systems. This study is an attempt to define the proper diagnostic procedures and treatment options for patients with various forms of IHS without evident neuroradiological findings. The authors discuss possible pathological mechanisms leading to IHS in the pediatric population. The authors present six children treated in their center. All of the children presented clinical manifestation of intracranial hypertension without evident neuroradiological findings in CT and/or MRI examinations. In three cases, the final diagnosis was slit ventricle syndrome; in two cases, normal volume hydrocephalus; in another case, idiopathic intracranial hypertension. The treatment options included short-term steroid (dexamethasone) administration and ventriculoperitoneal shunting using programmable systems. In one case of idiopathic intracranial hypertension, ICP monitoring was also performed. The authors discuss possible diagnostic and treatment strategies for the aforementioned cases. There are still many controversies about management of children with clinical symptoms of intracranial hypertension that are not confirmed in neuroimaging. It seems that our understanding of intracranial hypertension in the pediatric population is not nearly as sophisticated or complete as we might have imagined. Ventriculoperitoneal shunting with antisiphoning devices and/or short-term dexamethasone administration seem to be the best treatment options in these cases.