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PubMed2002

Influence of the lateral ventricles and irregular skull base on brain kinematics due to sagittal plane head rotation.

Two-dimensional physical models of the human head were used to investigate how the lateral ventricles and irregular skull base influence kinematics in the medial brain during sagittal angular head dynamics. Silicone gel simulated the brain and was separatedfrom the surrounding skull vessel by paraffin that provided a slip interface between the gel and vessel. A humanlike skull base model (HSB) included a surrogate skull base mimicking the irregular geometry of the human. An HSBV model added an elliptical inclusion filled with liquid paraffin simulating the lateral ventricles to the HSB model. A simplified skull base model (SSBV) included ventricle substitute but approximated the anterior and middle cranial fossae by a flat and slightly angled surface. The models were exposed to 7600 rad/s2 peak angular acceleration with 6 ms pulse duration and 5 deg forced rotation. After 90 deg free rotation, the models were decelerated during 30 ms. Rigid body displacement, shear strain and principal strains were determined from high-speed video recorded trajectories of grid markers in the surrogate brains. Peak values of inferior brain surface displacement and strains were up to 10.9X (times) and 3.3X higher in SSBV than in HSBV. Peak strain was up to 2.7X higher in HSB than in HSBV. The results indicate that the irregular skull base protects nerves and vessels passing through the cranial floor by reducing brain displacement and that the intraventricular cerebrospinal fluid relieves strain in regions inferior and superior to the ventricles. The ventricles and irregular skull base are necessary in modeling head impact and understanding brain injury mechanisms.

Biomechanical Phenomena↗
PubMed1997

The developing anterior skull base: CT appearance from birth to 2 years of age.

PURPOSE: To describe the normal CT appearance of the developing anterior skull base in children 24 months of age and younger. METHODS: A retrospective review of the CT examinations of a healthy population of 61 subjects newborn through 24 months of age was performed. Two investigators independently reviewed the examinations, making measurements and observations regarding the length of the skull base, ossification pattern, and development of the crista galli, perpendicular plate of the ethmoid bone, and fovea ethmoidalis. RESULTS: At birth, the anterior skull base is largely cartilaginous. Ossification begins in the roof of the ethmoidal labyrinth laterally and spreads toward the midline. By 6 months of age, 50% of the anterior skull base has completely ossified. This percentage steadily increases over the first 2 years of life, and by 24 months, 84% of the anterior skull base is completely ossified, with a cartilaginous gap anteriorly in the region of the foramen cecum, the residual unossified portion. Ossification of the crista galli and perpendicular plate of the ethmoid bone begins around 2 months of age, shows a steady increase in ossification to 14 months of age, then increases little to 24 months of age. The fovea ethmoidalis begins development by 6 months of age, with the anterior portion the most developed in 82% of the population. CONCLUSION: The timing and pattern of ossification we observed differ somewhat from that reported in prior radiologic and anatomic studies, with the earliest bony bridging of the ethmoidal complex to the crista galli seen as early as 2 months of age. Development of the anterior skull base follows a predictable and orderly pattern that is important for understanding how to avoid errors in interpreting CT examinations through this region.

Age Distribution↗
PubMed1995

Genetics of familial and non-familial skull base tumours.

Many tumours of the skull base, including schwannomas, paragangliomas, meningiomas and anterior pituitary tumours occur both as sporadic tumours and in clear cut familial syndromes. These cancers' highly penetrant dominantly inherited syndromes have proven to be a rich resource for locating tumour genes, most of which are of the tumour suppressor type. Recently, the gene for type 2 neurofibromatosis (NF2) was isolated by the technique of positional cloning. The NF2 gene has now been demonstrated to be involved in the pathogenesis of both familial and non-familial vestibular schwannomas as well as meningiomas. The presence of inactivating mutations within this gene suggests that it acts as a tumour suppressor and the mechanism has been shown to comply with a 'two hit' mutation model. Hereditary tumours constitute a small proportion of all cases, but evidence from studies of tumours such as vestibular schwannoma and meningioma have shown that their genes are also relevant to the much more common non-familial forms of the same tumour. This paper briefly describes the approach to locating tumour genes, and reviews our current knowledge regarding the chromosomal location and function of genes responsible for familial tumours involving the skull base. The genetic mechanisms of tumourigenesis are discussed as are the prospects for the development of novel forms of diagnosis and treatment.

Adenoma↗
PubMed2003

Secure flap fixation to bony tissue using an anchoring system in skull-base surgery.

The reconstruction of extensive skull-base defects using flap transfer decreases crucial postoperative complications. However, flap fixation to bony tissue is often difficult, especially if there is no soft tissue to pass sutures through, and unsteady flap fixation causes dead space formation or displacement of the transferred flap due to gravity. The authors used an anchoring system for secure flap fixation in seven cases with difficult flap fixation, using the conventional suturing technique. Anchors were inserted at strategic points in the bony tissue, and secure flap fixation was achieved in all cases. Postoperative CT scans showed no dead space formation, and major postoperative complications were not observed. The anchoring system can be buried in bony tissue with a thickness of more than 4 mm, and it enables reliable flap fixation and dead space obliteration. Although the cost is relatively high, the procedure is simple and lowers the risk of crucial postoperative complications in skull-base surgery.

Adolescent↗
PubMed2001

Skull base reconstruction and rehabilitation.

This article separates skull base reconstruction into the surgical procedures available for immediate reconstruction of a small base defect and the secondary rehabilitative procedures that may be performed at a later date, usually for functional or cosmetic needs.

Bone Transplantation↗
PubMed2000

Positive predictive values of selected clinical signs associated with skull base fractures.

BACKGROUND: The goal of this study was to determinate the positive predictive values of selected clinical signs for skull base fractures and associated intracranial lesions. METHODS EXPERIMENTAL DESIGN: Clinical and radiological data were collected prospectively for all patients with selected clinical signs of skull base fractures, and their admission criteria were: 1) recent head injury story; 2) presence of one or more of following clinical signs: unilateral or bilateral blepharohaematoma, bloody otorrhea, and Battle's sign. SETTING: Emergency service of a institutional hospital. PATIENTS: One hundred forty two patients with the selected clinical signs for skull base fracture. RESULTS: Frontal bone fractures were the most frequent in patients with selected clinical signs. Battle's sign (100%) and unilateral blepharohaematoma (90%) were the signs with higher positive predictive values for skull base fractures; bilateral blepharohaematoma (70%) and bloody otorrhea (70%) were those with less values. The positive predictive values of the selected signs for intracranial lesions (acute extradural haematoma, pneumocephalus, brain contusion, brain sweLling, and acute subdural haematoma) were: unilateral and bilateral blepharohaematoma with positive predictive values of 85% and 68%, respectively; Battle's sign was 66%; and bloody otorrhea was 46%. For patients at admission on the 13-15 Glasgow Coma Scale only, the positive predictive values for that intracranial lesions were: blepharohaematoma=78%; Battle's sign=66%; and bloody otorrhea=41%. CONCLUSIONS: Our data demonstrated that the selected signs of skull base fractures have high positive predictive values for the presence of skull fracture and intracranial lesions, even in those patients classified in the Glasgow Coma Scale between 13 and 15. This indicates that all patients with the selected clinical signs should be submitted to computerized tomography of skull and with bone window, with the aim to detect associated lesions.

Brain Edema↗
PubMed2000

Acute and long-term complications of therapeutic radiation for skull base tumors.

Acute toxicity from radiation of skull base tumors typically resolves spontaneously within days to weeks after completion of therapy. Long-term complications have a latency of months to years after radiation and are usually irreversible. The need to keep the probability of chronic toxicity at an acceptable level has determined the upper limits of radiation doses for the treatment of tumors. The threat of chronic toxicity thus affects the ability to control skull base tumors with radiation. Use of conformal radiation techniques with image guidance, allowing minimization of normal tissue volume receiving significant radiation doses and close regulation of doses to specific structures, provides a low probability of long-term complications. Such conformal techniques may result in improved tumor control by allowing delivery of higher radiation doses to the tumor while maintaining an acceptable level of risk for chronic toxicity. Symptoms resulting from chronic radiation toxicity are indistinguishable from those due to tumor progression. In most cases in which radiation is used to treat tumors throughout the body, symptoms developing months after radiation are secondary to tumor recurrence and not due to toxicity from radiation. Notable exceptions are pituitary hormonal dysfunction after radiation for pituitary adenoma and cranial neuropathy after radiosurgery for vestibular schwannoma. With the recent evolution in radiosurgery techniques involving MR imaging guidance, decreased single doses in SRS, and fractionation of radiation dose in SRT, the probabilities of vestibular schwannoma progression and cranial nerve toxicity are approximately equal. Even in the case of visual field deficit after radiation therapy for a pituitary macroadenoma (for which the probability of tumor mass progression is only 5%-10%), the cause of the deficit is more likely to be progressive tumor than radiation-induced neuropathy. Consequently, diagnosis of a late-term radiation complication must be made only after verifying that the tumor has not progressed.

Brain↗
PubMed2000

[Gamma knife radiosurgery for skull base meningiomas: the treatment results and patient satisfaction expressed in answers to a questionnaire].

Skull base meningiomas can be treated by radiosurgery with low morbidity. We evaluated the effectiveness of gamma knife radiosurgery for skull base meningiomas. We also evaluated patient satisfaction through answers to a questionnaire. We treated 77 patients of skull base meningiomas using gamma knife radiosurgery from January 1994 to June 1998. Among these patients, 73 patients were able to be followed up from 6 to 60 months (average 25 months). The diagnosis was made by operations on 39 patients (53%), and on magnetic resonance imagings in 34 patients (47%). 21 patients (28.7%) had residual tumors after operations and 18 patients (24.3%) had recurrence after operations. 40% of neurological deficits occurred after previous operations and 20% of the patients were asymptomatic. The locations of the tumors were mainly the cavernous sinus region in 35 patients and the petroclival region in 20 patients. The tumor sizes were 8.6 to 58.3 mm (average 24.7 mm) and five cases of tumors with a mean diameter above 40 mm were treated by two-staged radiosurgery. Treatment volume was 0.3 to 31 ml (average 9.8 ml). The treatment dose was 8 to 16 Gy (average 11.2 Gy) at the tumor margin. The tumor decreased in size in 50 patients (68%) and was unchanged in 20 patients (28%) and we were able to achieve 96% tumor growth control. The clinical symptoms improved in 22 patients (30.1%) and were unchanged in 47 patients (64.4%) and only 4 patients (5.5%) showed deterioration. 50 patients (68%) felt clinical improvement and only 3 patients (4%) sensed deterioration. 58 patients (79%) were able to continue their previous work. Gamma knife radiosurgery has a very low morbidity rate and enables good tumor control, and patients with skull base meningiomas express satisfaction with the treatment results.

Adolescent↗
PubMed1995

Comparison of conventional and skull base surgical approaches for the excision of trigeminal neurinomas.

Trigeminal neurinomas have traditionally been excised through conventional approaches. Because symptomatic tumor recurrence exceeds 50% after conventional procedures, the authors evaluated the use of skull base approaches to achieve complete resection and a lower rate of symptomatic recurrence. Comparisons of skull base with conventional approaches to trigeminal neurinomas have been limited to small series with short-term follow-up periods. The authors reviewed their experiences with conventional (frontotemporal transsylvian, subtemporal-intradural, subtemporal-transtentorial, and suboccipital) and skull base (frontotemporal extradural-intradural, frontoorbitozygomatic, subtemporal anterior petrosal, and presigmoid posterior petrosal) surgical approaches for the excision of trigeminal neurinomas. In this paper they report the results of 15 patients with trigeminal neurinoma who underwent 27 surgical procedures between 1980 and 1990. Seventeen of the procedures used conventional and 10 used skull base approaches. All patients had tumors arising from Meckel's cave and the porus trigeminus either initially or on recurrence. Tumors located in the cavernous sinus recurred most frequently (83%); other tumors that recurred frequently were those located in Meckel's cave and the porus trigeminus (67%), and the posterior fossa (17%). The tumor extended into the anterolateral wall of the cavernous sinus in 38% of patients with cavernous sinus involvement. Tumor exposure and ease of dissection were superior with skull base approaches. Residual or recurrent tumors were found in 65% of patients following conventional approaches compared with 10% of patients following skull base approaches. Using skull base approaches, the surgeon was more accurate (90%) in estimating tumor excision than when using conventional approaches (43%). Perioperative complications were similar with both. The authors discuss the indications, advantages, and limitations of each approach. Based on anatomical considerations, they propose a strategy to best resect these tumors.

Adolescent↗
PubMed2003

Interpositional carotid artery bypass strategies in the surgical management of aneurysms and tumors of the skull base.

Cerebral revascularization is an important component in the surgical management of complex skull base tumors and aneurysms. Patients who harbor complex aneurysms that cannot be clipped directly and in whom parent vessel occlusion cannot be tolerated may require cerebrovascular bypass surgery. In cases in which skull base tumors encase the carotid artery (CA) and a resection is desired, a cerebrovascular bypass may be necessary in planned CA occlusion or sacrifice. In this review the authors discuss options for performing high-flow anterograde interposition CA bypass for lesions of the skull base. The authors review three important bypass techniques involving saphenous vein grafts: the cervical-to-petrous internal carotid artery (ICA), petrous-to-supraclinoid ICA, and cervical-to-supraclinoid ICA bypass. These revascularization techniques are important tools in the surgical treatment of complex aneurysms and tumors of the skull base and cavernous sinus.

Anastomosis, Surgical↗
PubMed2006

Emergency surgery in a severe penetrating skull base injury by a screwdriver: case report and literature review.

BACKGROUND: Very few cases of severe penetrating injuries to the skull base with a seemingly innocuous object have been described in the literature. Of the cases reported, only ten involve a penetrating screwdriver. However, the choice of therapeutic management, whether it be emergency surgical or non-surgical removal of the penetrating object as well as the selected surgical approach remain quite controversial. CASE PRESENTATION: The authors describe the case of a severe penetrating skull base injury caused by a screwdriver, following an accidental fall from a ladder. The patient was admitted in Glasgow Coma Scale (GCS) 11 with a cerebrospinal fluid (CSF) leak in the right maxillary area. The tri-dimensional computerized tomography (3-D CT) scan revealed an oblique trajectory of the screwdriver shank through the skull base. The authors opted for an emergency surgical extraction of the object. A contra-lateral pterional approach was successfully performed and a two-year follow-up showed no neurological deficits. CONCLUSION: The reported case supports the choice of emergency surgical removal of the object in penetrating skull base injuries involving the anterior skull base with neurovascular lesions. Surgical aspects of the pterional approach, and in particular the left pterional approach as well as other cranio-facial approaches in severe penetrating skull base injuries are discussed.

Journal Article↗
PubMed2005

Radiologic assessment of maxillofacial, mandibular, and skull base trauma.

Cranio-maxillofacial injuries affect a significant proportion of trauma patients either in isolation or concurring with other serious injuries. Contrary to maxillofacial injuries that result from a direct impact, central skull base and lateral skull base (petrous bone) fractures usually are caused by a lateral or sagittal directed force to the skull and therefore are indirect fractures. The traditional strong role of conventional images in patients with isolated trauma to the viscerocranium is decreasing. Spiral multislice CT is progressively replacing the panoramic radiograph, Waters view, and axial films for maxillofacial trauma, and is increasingly being performed in addition to conventional films to detail and classify trauma to the mandible as well. Imaging thus contributes to accurately categorizing mandibular fractures based on location, into alveolar, mandibular proper, and condylar fractures-the last are subdivided into intracapsular and extracapsular fractures. In the midface, CT facilitates attribution of trauma to the categories central, lateral, or combined centrolateral fractures. The last frequently encompass orbital trauma as well. CT is the imaging technique of choice to display the multiplicity of fragments, the degree of dislocation and rotation, or skull base involvement. Transsphenoid skull base fractures are classified into transverse and oblique types; lateral base (temporal bone) trauma is subdivided into longitudinal and transverse fractures. Supplementary MR examinations are required when a cranial nerve palsy occurs in order to recognize neural compression. Early and late complications of trauma related to the orbit, anterior cranial fossa, or lateral skull base due to infection, brain concussion, or herniation require CT to visualize the osseous prerequisites of complications, and MR to define the adjacent brain and soft tissue involvement.

Adult↗
PubMed1997

Surgical approach to midline skull base tumors with olfactory preservation.

Through the frontal approach, a skull base tumor in the deep midline region is obscured by the cribriform plate. This paper demonstrates our experience of operating on seven patients with midline skull base tumors posterior to the cribriform plate using a technique of maintaining the olfactory-cribriform anatomy. Following a bifrontal craniotomy and an orbitonaso-glabellar osteotomy, a circumferential osteotomy of the cribriform plate and horizontal incision of the nasal mucosa permitted mobilization of the cribriform plate unit along with the frontal lobe, providing a wide exposure of the posterior midline area. Tumors were resected from the posterior nasopharynx, ethmoid sinus, sphenoid sinus, and upper portion of the clivus. The skull base defects were repaired with the bipedicled temporoparietal galeal flap. Two patients lost olfaction because of poor preservation of the nasal mucosa and intradural dissection of the olfactory bulb. Five patients showed complete recovery of olfaction in 8 weeks. None of the patients developed cerebrospinal fluid leakage, infection, or increased neurologic deficits. En bloc mobilization of the cribriform plate and the bipedicled temporoparietal galeal flap are very useful for the management of midline cranial base tumors posterior to the cribriform plate as long as the olfactory unit is not involved with tumors.

Adolescent↗
PubMed1999

Gamma knife surgery for skull base meningiomas. The effectiveness of low-dose treatment.

BACKGROUND: The surgical removal of skull base meningiomas has a high morbidity rate, even by modern microsurgical standards. We evaluated the results of gamma knife surgery for skull base meningiomas using a relatively low radiation dose for the tumor margins. METHODS: We reviewed 24 cases of skull base meningiomas during a 30-month period. The locations of the tumors were the petroclival region in 11 cases, the cavernous sinus region in 9 cases, and the cerebellopontine angle region in 4 cases. Eight patients (33%) had been operated on previously and fourteen patients (67%) had been treated by neuroimaging. The marginal doses for the tumors were 8 Gy to 15 Gy (median, 10.6 Gy). A large petroclival tumor 58 mm in diameter was treated with a staged treatment protocol with a 6-month interval between treatments. RESULTS: Tumor regression was observed in 46% of the patients imaged during the follow-up period (median, 17.1 months). No patients revealed tumor growth in the follow-up period (100% tumor control rate). Eleven patients (46%) had improved clinically by the time of the follow-up examinations. Preexisting cranial nerve deficit in one patient worsened because of radiation injury. CONCLUSION: Although a longer follow-up period is required, the relatively low minimum tumor radiation dose treatment for skull base meningiomas using a gamma knife seems to be an effective treatment with low morbidity.

Adult↗
PubMed1994

Experience in charged particle irradiation of tumors of the skull base: 1977-1992.

PURPOSE: To review the experience at University of California Lawrence Berkeley Laboratory in using charged particles to irradiate primary neoplasms of the skull base and those extending to the skull base from the nasopharynx and paranasal sinuses. METHODS AND MATERIALS: During the period from 1977 to 1992, 223 patients were irradiated with charged particles at the Lawrence Berkeley Laboratory for tumors either arising in or extending to the skull base, of whom 48 (22%) had recurrent lesions, either post previous surgery or radiotherapy. One hundred twenty-six patients had lesions arising in the cranial base, mostly chordoma (53), chondrosarcoma (27), paraclival meningioma (27) with 19 patients having other histologies such as osteosarcoma or neurofibrosarcoma. There were also 31 patients with primary or recurrent squamous carcinoma of the nasopharynx extending to the skull base, 44 patients with major or minor salivary gland tumors, mostly adenocarcinoma, and 22 patients with squamous carcinoma of the paranasal sinuses, all with cranial base extension. RESULTS: Local control and survival appeared improved in tumors arising in the skull base, following the ability with charged particles to deliver high doses (mean of 65 Gy-equivalent) with relative sparing of the adjacent normal tissues. The Kaplan-Meier 5-year local control was 85% for meningioma, 78% for chondrosarcoma, 63% for chordoma and 58% for other sarcoma. Follow-up ranged from 4-191 months with a median of 51 months. CONCLUSION: Charged particle radiotherapy is highly effective in controlling cranial base lesions which have have been partially resected. Better tumor localization with CT and MRI, improved 3-D treatment planning and beam delivery techniques have continued to reduce the level of serious complications and increase local control and survival.

Female↗
PubMed1996

Skull base and calvarial deformities: association with intracranial changes in craniofacial syndromes.

PURPOSE: To analyze the skull and brain malformations in patients with craniofacial syndromes. METHODS: A retrospective analysis of imaging studies of 21 children with craniofacial anomalies (8 with Apert syndrome, 6 with Pfeiffer syndrome, 4 with Crouzon syndrome, 1 with Robert syndrome, 1 with Coffin-Lowry-syndrome, and 1 with Saethre-Chotzen syndrome) was carried out using CT (21 patients), MR imaging (9 patients), and MR venography (2 patients). A series of qualitative and quantitative assessments of the skull base and intracranial structures was performed. RESULTS: Skull base abnormalities were present in all patients. Intracranial abnormalities included ventriculomegaly, frank hydrocephalus, callosal anomalies, hypoplasia/absence of the septum pellucidum, hypoplasia/dysplasia of the hippocampus, dysplasias or distortions of the cerebral cortex, and parenchymal hemorrhage. The anomalies of the corpus callosum, septum pellucidum, and hippocampus appeared primary, whereas the others may have been the result of brain distortion by the calvarial anomaly. MR imaging was more useful than CT for evaluating brain abnormalities. In the two patients in whom it was performed, MR venography showed anomalies of the venous system, indicating that venous anomalies, possibly related to the skull base hypoplasia, may contribute to the intracranial abnormalities. CONCLUSION: A wide range of neuroimaging abnormalities are present in the craniofacial syndromes. Some of these are clearly primary, whereas others appear to be related to the small skull base and sutural synostoses. MR venography may prove useful in defining the cause of some of the associated anomalies.

Acrocephalosyndactylia↗
PubMedDate not supplied

[Surgery of the skull base and paranasal sinuses assisted by a computerized navigation system without external orientation support].

OBJECTIVE: To present a new concept in computer-assisted surgery for the base of the skull and paranasal sinuses using a frameless navigation system. METHOD AND MATERIALS: This system is based on computer tomography images, which are displayed online on a workstation monitor. Using specially mounted infrared instruments, the patient's anatomic landmarks are visualized on the monitor. This system does not require invasive markers because it uses a reference system fixed to the patient with a silicone maxillary splint. PATIENTS: From March 1997 to February 1998 we operated on 44 patients with this innovative system. RESULTS: The clinical accuracy of this system was 0.5 to 2 mm for surgery of the anterior skull base and 1 to 2.5 mm for the lateral skull base. There were no intraoperative complications. CONCLUSIONS: This computer-assisted surgical aid made it possible to carry out complex and difficult skull-base surgery with reasonable intraoperative safety. It also allowed development of new minimally invasive surgical approaches.

Chondroma↗
PubMed1998

Three-dimensional computed tomographic reconstruction: planning tool for surgery of skull base pathologies.

Three-dimensional (3-D) computed tomographic (CT) reconstruction of the skull base region has added a different perspective to the data set usually presented in axial or coronal slices. It simultaneously demonstrates the spatial relationship of bones, tumors, vessels, and ventricles in a single illustration. Forty-nine patients with skull base lesions (44 with neoplastic and 5 with vascular pathologies) were examined with a spiral CT and 3-D reconstruction prior to surgery. A scanner and a maximum of 95 mL of iodized contrast media were used to enhance either tumor or vessels according to the specific pathology. Preoperative 3-D reconstruction was performed. It rendered a spatial representation of the pathology using data similar to that usually acquired in routine preoperative diagnostics. Complex anatomy can be visualized with only a handful of pictures. It was possible to easily compare various surgical approaches to the lesion on the basis of the 3-D computer model and to simulate the surgeon's view. The short time span (1 h average) necessary for reconstruction and editing allows the application of this method as a routine preoperative procedure for selected skull base pathologies.

Adult↗