Magnetic resonance imaging of the central skull base

The central skull base is an anatomically complex region whose foundation is the sphenoid bone. It includes the sphenoid sinus, clivus, and sella turcica, as well as adjacent soft tissues such as the cavernous sinuses and nasopharynx. The central skull base may be affected by pathologies intrinsic to the sphenoid bone or by processes that arise in adjacent soft tissue and extend centrally to affect the central skull base. In general, this region is optimally imaged with magnetic resonance scanning, although in some cases computed tomography can provide complementary information. In this review, we will discuss a variety of pathologies that can affect the central skull base, such as neoplasms, infections, trauma, congenital malformations, and a variety of miscellaneous pathologies. We will discuss processes that can mimic neoplasia, such as aggressive polyposis and chronic inflammatory disease. For each pathology we will review clinical and imaging findings.     

Two-dimensional finite element modelling of the neonatal head

Electrical impedance tomography (EIT) could allow the early diagnosis of infant brain injury following birth asphyxia. The purpose of this work was to determine the effect of variations in skull, scalp or cerebrospinal fluid (CSF) resistivity, as these vary in clinical conditions and could degrade image quality. These factors were investigated using finite element models of the adult and neonatal head. The results suggest that there is a wide range over which the resistivity of the neonatal skull has little effect on the sensitivity to a central impedance change. The scalp and CSF appear to shunt current away from the brain; when their resistivity was decreased from normal values, this shunting effect increased and caused a decrease in sensitivity to a central resistance change. The resistivity of neonatal skull has not, to our knowledge, been directly measured and will anyway vary within and between individuals; this work suggests that EIT will be relatively insensitive to variations in neonatal skull impedance.     

颅骨修补材料的选择及其评价

背景:对颅骨修复材料的分类、性质及其在颅骨修补和塑形中的应用和相关并发症的处理进行归纳总结.方法:第一作者应用计算机检索PubMed数据库(http://www.ncbi.nlm.nih.gov/PubMed),检索关键词"codubix,synmesh,bone cement",限定语言种类为"English";同时检索CNKI数据库(www.cnki.net/index.htm),检索关键词"颅骨修补材料,钛网,骨水泥",限定语言种类为中文.选择文章内容与颅骨修补材料种类、材料学特性、组织相容性及其应用效果相关,同一领域文献则选择近期发表或发表在权威杂志文章.排除重复及较陈旧的文献.共纳入26篇文献.结果:骨水泥组织相容性好但不易被吸收,只应用于部分颅骨的修补.经过对比发现钛因其良好的生物相容性可与颅骨结合,使其应用得到了进一步研究,具备较好的应用前景,但也存在很多不足之处.随着生物工程研究的不断深入,骨组织工程、软骨组织工程等研究的深入将会为颅骨修补材料的开拓提供更广阔的前景.结论:颅骨缺损修补材料有很多种,文内只介绍了其中应用较广泛的一些,结合临床实际工作,修补材料选择时要结合患者的病情、经济条件、当地的设备及技术水平等.若经济条件允许情况下,应首选纯钛网及钛钉,因术中塑形方便,不需处理骨窗缘即可固定,且并发症极少,不影响术后X射线检查,手感良好,均匀美观.自体骨及骨水泥应用时,应注意减少相应的并发症,及时有效的处理,也会获得良好的效果.     

Correlation of ultrasound phase with physical skull properties

Noninvasive treatment of brain disorders using focused ultrasound (US) requires a reliable model for predicting the distortion of the field due to the skull using physical parameters obtained in vivo. Previous studies indicate that control of US phase alone is sufficient for producing a focus through the skull using a phased US array. The present study concentrates on identifying methods to estimate phase distortion. This will be critical for the future clinical use of noninvasive brain therapy. Ten ex vivo human calvaria were examined. Each sample was imaged in water using computerized tomography (CT). The information was used to determine the inner and outer skull surfaces, thickness as a function of position, and internal structure. Phase measurement over a series of points was obtained by placing a skull fragment between a transducer and a receiver with the skull normal to the transducer. Correlation was found between the skull thickness and the US phase shift. A linear fit of the data follows that predicted by a homogeneous skull when average speed of sound 2650 m/s was used. Large variance (SD = 60 degrees, mean = 50 degrees ) indicates the additional role of internal bone speed and density fluctuations. In an attempt to reduce the variance, the skull was first studied as a three-layer structure. Next, density-dependent bone speed fluctuation was introduced to both the single-layer and three-layer models. It was determined that adjustment of the mean propagation speeds using density improves the overall phase prediction. Results demonstrate that it is possible to use thickness and density information from CT images to predict the US phase distortion induced by the skull accurately enough for therapeutic aberration correction. In addition, the measurements provide coefficients for phase dependence on skull thickness and density that can be used in clinical treatments.     

Was ist der „kraniosakrale Rhythmus“?

Craniosacral osteopathic therapists claim the existence of an autonomous rhythm of the cerebrospinal fluid which they call the primary respiratory mechanism. These movements have not yet been proven nor has the active motility of the skull bones within their sutures. However, there is no doubt about a passive motility of the skull up to old age. Movements perceived by CSO therapists are therefore not produced in the patient’s body. They are probably movements produced in the hands of the therapist by meditation and self-induced trance as an “energy wave” between his hands. Relations between this energy wave and the therapist’s pulse and breath have not been sufficiently investigated. There is a possible correlation on the level of wave crossings of different frequencies. The waves generated by the therapist are induced into the skull of the patient, who may either react with a passive movement or will show a resistance towards this wave induction due to a disturbed function of the skull sutures. The positive and reliable use of such information for therapeutic action by a therapist has not been proven despite knowledge of anatomy and biomechanics. Only if the observations related to CSO are soundly explained on a scientific level could this method be integrated into manual medicine.     

An investigation into the regulation of intra-cranial pressure and its influence upon the surrounding cranial bones

The aim of this study is to present a rational coherent hypothesis to explain the palpable involuntary movements of the cranium. The arterial and venous anatomy inside and around the skull and spinal column presents a complete vascular system with the capacity to regulate intra-cranial pressure to a level of equilibrium slightly higher than atmospheric pressure. Variations in cerebrospinal fluid (csf) pressure control the volume of blood draining through the cavernous sinus and hence into the inter-vertebral venous plexus in relation to the jugular vein. Stable intra-cranial pressure is maintained by a controlled release of venous blood through the inter-vertebral venous plexus (slow) and the jugular vein (fast) in the cavernous sinus. Any distortion of the skull from its healthy state will lead to reduced intra-cranial volume. The process of release from the state of compression has been interpreted as “cranial rhythm” but may be a mechanical adjustment increasing the internal volume of the skull, aided by the continual maintenance of stable intracranial pressure. This involuntary movement is capable of being assisted manually.     

A novel mounting device for attaching intracranial probes to the skull for use in experimental research models

A simple mount capable of securely holding a variety of intracranial probes to the skull was constructed from commonly available clinical consumables. Using this device the cerebral cortical blood flow of preterm lambs was measured using a laser Doppler flow probe, and cerebral pH and cortical electrical impedance were measured in newborn piglets using pH electrodes and Ag/AgCl wire electrodes. In both studies, the mount held the various probes for periods up to 6 h with no dislodgement or probe failure. The simple mount presented here can be adapted to a wide variety of intracranial probes and will hold them securely to the skull.     

A multi-shell algorithm to reconstruct EIT images of brain function

Electrical impedance tomography (EIT) may be used to image brain function, but an important consideration is the effect of the highly resistive skull and other extracerebral layers on the flow of injected current. We describe a new reconstruction algorithm, based on a forward solution which models the head as four concentric, spherical shells, with conductivities of the brain, cerebrospinal fluid, skull and scalp. The model predicted that the mean current travelling in the brain in the diametric plane for current injection from polar electrodes was 5.6 times less than if the head was modelled as a homogeneous sphere; this suggests that an algorithm based on this should be more accurate than one based on a homogeneous sphere model. In images reconstructed from computer-simulated data or data from a realistic saline-filled tank containing a real skull, a Perspex rod was localized to within 17% or 20% of the tank diameter of its true position, respectively. Contrary to expectation, the tank images were less accurate than those obtained with a reconstruction algorithm based on a homogeneous sphere. It is not yet clear if the theoretical advantages of this algorithm will yield practical advantages for head EIT imaging; it may be necessary to proceed to more complex algorithms based on numerical models which incorporate realistic head geometry. If so, this analytical forward model and algorithm may be used to validate numerical solutions.     

Three-dimensional sonography of prenatal skull base development.

OBJECTIVE: To explore longitudinally the development of the fetal skull base using three-dimensional (3D) sonography. METHODS: Serial 3D sonographic measurements of anterior skull base length, posterior cranial fossa length and skull base angle were made in 126 normal singleton pregnancies at 18-34 weeks of gestation. In a sub-study of 22 pregnancies, intraobserver variability was determined. Regression analysis for repeated measurements was performed by means of the random coefficients model. Results from an earlier publication on brain volume were extended to the total patient cohort. RESULTS: Measurements were technically successful in 69-94% of cases. The coefficient of variation for differences between repeated tests within women was 3.5-7.6% and between repeated analyses of the same recorded volume it was 3.0-5.1%. A statistically significant gestational age-related increase was established for both the anterior skull base length and the posterior cranial fossa length and the skull base angle showed a small but significant flexion of about 6 degrees . A higher increment in posterior cranial fossa length relative to anterior skull base angle was established. A significant quadratic relationship could be established for both anterior skull base length (P < 0.0001) and posterior cranial fossa length (P < 0.0001) but not for skull base angle, relative to brain volume. CONCLUSION: The reproducibility was acceptable for all fetal skull base measurements. The more pronounced growth in posterior cranial fossa length relative to anterior skull base length is influenced by brain growth. The small flexion of the skull base angle, however, may be caused by other factors. Published by John Wiley & Sons, Ltd.     

颅骨生长性骨折的病理学基础和临床X线研究

本文报告１０例生长性颅骨骨折，对该病的形成机理、病理学基础、Ｘ线表现及其类型进行了探讨。该病的特征为骨折多见于额骨和顶骨，多发生于颅骨生长的活跃期，在骨折同时伴有硬脑膜和蛛网膜的破裂，随后硬脑膜缺损，骨折扩大形成一个颅骨缺损，伴随着骨折下方脑的挫伤和局限性脑肿胀，常致使头部局限性包块形成。局限性大脑损害可导致一组晚期的病理学后遗症改变包括：局限性脑萎缩、脑穿通或囊肿、局限性脑室扩大以及复杂的疤痕可累及硬脑膜、软脑膜、蛛网膜和大脑。除此之外，我们认为颅骨下硬脑膜的分离和局部缺血也可是颅骨生长性骨折的原因之一。     

不同手术方式治疗高血压脑出血的疗效比较

目的比较小骨窗开颅手术及CT定位微创引流手术治疗高血压基底节区出血的疗效。方法回顾性分析95例高血压脑出血的临床表现、手术方式及疗效。结果小骨窗开颅手术51例,CT引导血肿吸引44例。两组年龄、术前血压、血肿量、术前GCS评分及发病至手术时间均无明显差异（P〉0．05）。血肿清除量：小骨窗开颅手术组优于CT血肿吸引组（P〈0．05）;术后48h意识好转率小骨窗开颅手术组高于血肿吸引组（P〈0．05）;术后血肿继续增大者,CT引导血肿吸引组高于小骨窗开颅下手术组（P〈0．05）。结论小骨窗开颅手术清除血肿充分、止血彻底,疗效优于CT引导血肿吸引术。     

Radiological techniques in the examination of patients with headaches

It can be said that in the majority of headache patients who have a long typical history, a negative neurologic examination, and a noncontributory general physical examination, radiologic studies will probably not give further pertinent information. Nevertheless, in a sufficient number of these patients, the noninvasive and essentially atraumatic procedures of plain skull radiography, computed tomography, and (as indicated) echoencephalography and radionuclide brain scanning will provide a considerable amount of information pertinent to the clinical problem. Hospitalization for angiography and, on occasion, pneumoencephalography or other special procedures, will then become indicated for those patients in whom an abnormality is found in these screening procedures.     

Cranial sonography: anatomic and pathological correlation

Through the acoustic window of the anterior fontanelle, coronal and parasagittal sonograms of the infant and premature neonate are easily obtained. Supplementary axial images are obtained through the lateral skull vault. The normal anatomy of axial, coronal, and sagittal sonograms will be demonstrated by correlating normal infant brain images with cadaver brain slices at similar levels. The relevant anatomical structures will be identified and labeled. Pathological entities, i.e., intracerebral hemorrhage, brain tumors, arteriovenous malformations, hydrocephalus, and congenital malformation syndromes will be included. Neonatal ultrasound is an inexpensive, innocuous, and noninvasive technique for examining the brain of the newborn infant. It does not require sedation and can be performed either within the radiology department or in the newborn intensive care unit.     

颅底转移瘤的影像诊断

目的 本文分析１２例颅底转移瘤的ＣＴ和ＭＲ影像表现特征。方法 １２例经手术病理证实为转移瘤。男性７例,女性５例。９例ＭＲ检查;２例ＣＴ,ＭＲ检查;１例ＣＴ检查。结果 单发１０例;多发２例。８例转移瘤位于中颅窝;２例位于前颅窝;２例位于后颅窝。８例有不同程度颅底骨质破坏。结论 颅底转移瘤在ＣＴ和ＭＲ有一定特征性表现,但必须结合病史、年龄、是有原发恶性肿瘤手术史及颅骨受损情况及综合分析做出诊断。     

Validation of an in-silico modelling platform for outcome prediction in spring assisted posterior vault expansion

BackgroundSpring-Assisted Posterior Vault Expansion has been adopted at Great Ormond Street Hospital for Children, London, UK to treat raised intracranial pressure in patients affected by syndromic craniosynostosis, a congenital calvarial anomaly which causes premature fusion of skull sutures. This procedure aims at normalising head shape and augmenting intracranial volume by means of metallic springs which expand the back portion of the skull. The aim of this study is to create and validate a 3D numerical model able to predict the outcome of spring cranioplasty in patients affected by syndromic craniosynostosis, suitable for clinical adoption for preoperative surgical planning.MethodsRetrospective spring expansion measurements retrieved from x-ray images of 50 patients were used to tune the skull viscoelastic properties for syndromic cases. Pre-operative computed tomography (CT) data relative to 14 patients were processed to extract patient-specific skull shape, replicate surgical cuts and simulate spring insertion. For each patient, the predicted finite element post-operative skull shape model was compared with the respective post-operative 3D CT data.FindingsThe comparison of the sagittal and transverse cross-sections of the simulated end-of-expansion calvaria and the post-operative skull shapes extracted from CT images showed a good shape matching for the whole population. The finite element model compared well in terms of post-operative intracranial volume prediction (R² = 0.92, p < 0.0001).InterpretationThese preliminary results show that Finite Element Modelling has great potential for outcome prediction of spring assisted posterior vault expansion. Further optimisation will make it suitable for clinical deployment.     

Assessment of head injuries in a Minor Injuries Unit

Approximately one million patients in the UK present to hospitals each year with head injuries. Almost half are under 16 years of age. (Royal College of Surgeons of England 1999). The majority of patients who attend for treatment will be suffering from a minor head injury. It is stated that some 92% of these patients will have normal neurology (Klauber 1993) and most will be discharged into the care of a responsible adult with instructions and advice for further observation at home. Only 1% of patients attending with a head injury have a skull fracture (Ramrakha & Moore 1997). The aim of this article is to guide the practitioner into ensuring a consistent, evidence-based approach to the assessment of patients with head injury when they present at a Minor Injuries Unit. This includes timely, appropriate referral for further investigation and clinical intervention.     

Application of the Canadian CT head rules in managing minor head injuries in a UK emergency department: implications for the implementation of the NICE guidelines

Objective: : In 2002 a new protocol was introduced based on the Canadian CT rules. Before this the Royal College of Surgeons "Galasko" report guidelines had been followed. This study evaluates the effects of the protocol and discusses the impact of the implementation of the NICE head injury guidelines—also based on the Canadian CT rules.

Methods: A "before and after" study was undertaken, using data from accident and emergency cards and hospital notes of adult patients with head injuries presenting to the emergency department over seven months in 2001 and nine months in 2002. The two groups were compared to see how rates of computed tomography (CT), admission for observation, discharge, and skull radiography had changed after introduction of the protocol.

Results: : Head CT rates in patients with minor head injuries (MHI) increased significantly from 47 of 330 (14%) to 58 of 267 (20%) (p<0.05). There were also significantly increased rates of admission for observation, from 111 (34%) to 119 (45%). Skull radiography rates fell considerably from 33% of all patients with head injuries in 2001 to 1.6% in 2002, without any adverse effect.

Conclusions: This study shows that it is possible to replace the current practice in the UK of risk stratification of adult MHI based on skull radiography, with slightly modified versions of the Canadian CT rule/NICE guidelines. This will result in a large reduction in skull radiography and will be associated with modest increases in CT and admissions rates. If introduction of the NICE guideline is to be realistic, the study suggests that it will not be cost neutral.

     

Prenatal diagnosis of scalp cyst with spontaneous regression

Fetal scalp cysts are rare, and they may be easily misdiagnosed as meningoceles or encephaloceles. A 38-year-old pregnant woman was referred to our hospital for ultrasound examination, which revealed a small cyst above the skull with no defect in the skull. The cyst could not be seen on follow-up ultrasound examinations. After delivery, a three-dimensional CT scan of the head revealed no defect in skull and scalp. Fetal scalp cysts usually require surgical excision after birth, but can regress without any treatment.     

高压氧综合治疗鼻咽癌患者放射性脑损伤26例

INTRODUCTION Because nasopharynx is near to base of skull,radiation therapy might cause radiating brain injury that will influence patient's life quality.     

颅脑急症的影像学诊断

急诊医学是临床医学的一个较年轻的分支。以危急病人的迅速诊治和监护为主要目的。急诊影像学的任务则是发挥其内视诊的特点，尽可能迅速、准确地作出诊断和进行必要的介入性治疗。各种影像学手段中，应用于颅脑急症的主要有ＣＴ、头颅和脊柱平片、ＭＲＩ、ＵＳ和介入放射学处理。常见的颅脑急症有：颅脑损伤、抽搐与惊厥、昏迷、头痛和瘫痪等。