Pneumosinus dilatans in anterior skull base meningiomas

INTRODUCTION

Skull base meningiomas are often missed on non-contrast CT or MR examinations due to their close proximity to bone and low lesion to brain contrast. The purpose of this study is to illustrate that pneumosinus dilatans can be an indicator of anterior skull base meningiomas.

METHODS

A retrospective search of the radiology information system and picture archiving and computing system database was performed. Search terms were "meningioma" in association with "pneumosinus dilatans." Medical records and imaging studies were reviewed independently by two experienced neuroradiologists and were read in consensus. We recorded the patient age at the time of discovery of the meningioma, main presenting symptom(s), location of the tumor, and imaging characteristics. We also performed a comparative literature search for pneumosinus dilatans and its association with meningiomas.

RESULTS

Ten patients (six women; four men) were identified in whom a meningioma of the anterior skull base was associated with a pneumosinus dilatans. Three patients had multiple meningiomas, so a total of 14 intracranial tumors were identified. Mean age at discovery was 59 years with an age range of ± 20years. All meningiomas were diagnosed by MRI and/or CT.

CONCLUSION

Pneumosinus dilatans can be a helpful sign to indicate the presence of a meningioma of the anterior skull base.

Bilateral Meckel's cave amyloidoma: a case report

Primary solitary amyloidoma of Meckel's cave is rare, and a bilateral location is even more rare. To the best of our knowledge, only 12 cases in the literature have described such a primary lesion, including one case of bilateral involvement of Meckel's cave. We report here on the case of a 57-year-old woman presenting with pseudotumor masses involving both Meckel's caves and responsible for trigeminal neuropathy. The final diagnosis of amyloidoma was made on the basis of histological examination of surgical biopsy specimens.

Trauma of the spine and spinal cord: imaging strategies

Traumatic injuries of the spine and spinal cord are common and potentially devastating lesions. We present a comprehensive overview of the classification of vertebral fractures, based on morphology (e.g., wedge, (bi)concave, or crush fractures) or on the mechanism of injury (flexion-compression, axial compression, flexion-distraction, or rotational fracture-dislocation lesions). The merits and limitations of different imaging techniques are discussed, including plain X-ray films, multi-detector computed tomography (MDCT), and magnetic resonance imaging (MRI) for the detection. There is growing evidence that state-of-the-art imaging techniques provide answers to some of the key questions in the management of patients with spine and spinal cord trauma: is the fracture stable or unstable? Is the fracture recent or old? Is the fracture benign or malignant? In summary, we show that high-quality radiological investigations are essential in the diagnosis and management of patients with spinal trauma.

Functional MRI of the cervical spinal cord on 1.5 T with fingertapping: to what extent is it feasible?

INTRODUCTION

Until recently, functional magnetic resonance imaging (fMRI) with blood oxygen level-dependent (BOLD) contrast, was mainly used to study brain physiology. The activation signal measured with fMRI is based upon the changes in the concentration of deoxyhaemoglobin that arise from an increase in blood flow in the vicinity of neuronal firing. Technical limitations have impeded such research in the human cervical spinal cord. The purpose of this investigation was to determine whether a reliable fMRI signal can be elicited from the cervical spinal cord during fingertapping, a complex motor activity. Furthermore, we wanted to determine whether the fMRI signal could be spatially localized to the particular neuroanatomical location specific for this task.

METHODS

A group of 12 right-handed healthy volunteers performed the complex motor task of fingertapping with their right hand. T2*-weighted gradient-echo echo-planar imaging on a 1.5-T clinical unit was used to image the cervical spinal cord. Motion correction was applied. Cord activation was measured in the transverse imaging plane, between the spinal cord levels C5 and T1.

RESULTS

In all subjects spinal cord responses were found, and in most of them on the left and the right side. The distribution of the activation response showed important variations between the subjects. While regions of activation were distributed throughout the spinal cord, concentrated activity was found at the anatomical location of expected motor innervation, namely nerve root C8, in 6 of the 12 subjects.

CONCLUSION

fMRI of the human cervical spinal cord on an 1.5-T unit detects neuronal activity related to a complex motor task. The location of the neuronal activation (spinal cord segment C5 through T1 with a peak on C8) corresponds to the craniocaudal anatomical location of the neurons that activate the muscles in use.

Spinal tumors

Spinal tumors are uncommon lesions but may cause significant morbidity in terms of limb dysfunction. In establishing the differential diagnosis for a spinal lesion, location is the most important feature, but the clinical presentation and the patient's age and gender are also important. Magnetic resonance (MR) imaging plays a central role in the imaging of spinal tumors, easily allowing tumors to be classified as extradural, intradural-extramedullary or intramedullary, which is very useful in tumor characterization. In the evaluation of lesions of the osseous spine both computed tomography (CT) and MR are important. We describe the most common spinal tumors in detail. In general, extradural lesions are the most common with metastasis being the most frequent. Intradural tumors are rare, and the majority is extramedullary, with meningiomas and nerve sheath tumors being the most frequent. Intramedullary tumors are uncommon spinal tumors. Astrocytomas and ependymomas comprise the majority of the intramedullary tumors. The most important tumors are documented with appropriate high quality CT or MR images and the characteristics of these tumors are also summarized in a comprehensive table. Finally we illustrate the use of the new World Health Organization (WHO) classification of neoplasms affecting the central nervous system.

Phase-contrast magnetic resonance angiography

Time of flight (TOF) and phase contrast (PC) magnetic resonance angiography (MRA) are two established magnetic resonance (MR) techniques that were described and developed in the 1980s. Both of these techniques usually do not involve the use of intravascular contrast, but rather exploit the intrinsic contrast provided by flowing blood to produce vascular signal. Bolus infused (gadolinium-enhanced) MR angiography was only introduced in 1993. PC-MRA uses the phase shifts introduced to nuclei with motion in the presence of a magnetic field gradient. A bipolar magnetic field gradient will induce a phase shift to nuclei moving along the gradient dependent on the velocity, as well as acceleration and higher order motion terms. More complex gradient waveforms enable sensitivity to specific motion terms such as velocity or acceleration. By constructing an image in which the intensity is proportional to the phase shift of the nuclei, it is possible to create an angiographic image related to the flow properties of blood (or other liquids such as cerebrospinal fluid). The PC-MRA is a powerful technique and allows for encoding of flow in one or many directions in such a way that the velocity sensitivity can be chosen depending on the vessel of interest. This technique also allows for quantification of flow velocity and flow rate, which is not generally available with other angiographic techniques.

MR angiography in steno-occlusive disease of the intracranial vessels

Technical advances in MR angiography (MRA) have improved the sensitivity and the accuracy of this technique in the evaluation of vascular stenoocclusive disease of the brain. In many centers, due to its non-invasive and non-ionizing character, MR angiography has already replaced conventional angiography for the screening of intracranial vascular disease. Several MRA techniques have been developed for imaging the intracranial vascular system, such as time-of-flight MRA (TOF-MRA), phased-contrast MRA (PC-MRA), and more recently contrast-enhanced MRA (CE-MRA).

Contrast enhancement in Lhermitte-Duclos disease of the cerebellum: correlation of imaging with neuropathology in two cases

Lhermitte-Duclos disease (LDD), also known as dysplastic gangliocytoma, is a rare cerebellar lesion. It has long been regarded as avascular. We report two patients with surgically proven LDD in whom contrast enhancement was observed on MRI. Neuropathological examination revealed proliferation of veins. We suggest that peripheral enhancement of LDD probably reflects vascular proliferation of the cerebellar venous draining system, and should be considered part of the imaging features of LDD.

Intracranial hemorrhage: principles of CT and MRI interpretation

Accurate diagnosis of intracranial hemorrhage represents a frequent challenge for the practicing radiologist. The purpose of this article is to provide the reader with a synoptic overview of the imaging characteristics of intracranial hemorrhage, using text, tables, and figures to illustrate time-dependent changes. We examine the underlying physical, biological, and biochemical factors of evolving hematoma and correlate them with the aspect on cross-sectional imaging techniques. On CT scanning, the appearance of intracranial blood is determined by density changes which occur over time, reflecting clot formation, clot retraction, clot lysis and, eventually, tissue loss. However, MRI has become the technique of choice for assessing the age of an intracranial hemorrhage. On MRI the signal intensity of intracranial hemorrhage is much more complex and is influenced by multiple variables including: (a) age, location, and size of the lesion; (b) technical factors (e.g., sequence type and parameters, field strength); and (c) biological factors (e.g., pO2, arterial vs. venous origin, tissue pH, protein concentration, presence of a blood-brain barrier, condition of the patient). We discuss the intrinsic magnetic properties of sequential hemoglobin degradation products. The differences in evolution between extra- and intracerebral hemorrhages are addressed and illustrated.

Amyloidoma of the skull base

We report a case of a primary amyloidoma of the skull base. Plain radiography and CT showed a lytic, highly destructive lesion with multiple scattered calcifications within. MR imaging revealed that the tumor was isoto hypointense to muscle on T1-weighted images and extremely hypointense on T2-weighted images. In contrast to two previous reports, marked enhancement after the administration of contrast material was absent. Bone amyloidomas are very rare and are frequently misinterpreted as chondrosarcomas.

The value of MRI in the diagnosis of postoperative spondylodiscitis

We evaluated the role of MRI in the diagnosis of postoperative spondylodiscitis. Spondylodiscitis is a serious complication of surgery, and the diagnosis frequently depends on a combination of clinical, laboratory and imaging findings. We compared the MRI findings in six patients with biopsy- or surgery-proven spondylodiscitis with those in 38 asymptomatic postoperative patients. Contrast enhancement and signal changes in the intervertebral disc or the vertebral endplates are not specific for spondylodiscitis, being also seen in the asymptomatic patients. However, absence of Modic type 1 changes, of contrast enhancement of the disc or of enhancing paravertebral soft tissues suggests that the patient does not have spondylodiscitis. MRI appears more useful for exclusion than for confirmation of postoperative spondylodiscitis.

Maxillo-facial trauma

Injuries to the facial bones, orbits and adjacent soft tissue structures are common. Despite the increasing safety precautions in modern cars, facial injury is very often caused by motor vehicle accidents. Severe trauma to the face is a strong indication for radiological investigation. In the patient with maxillo-facial trauma, the radiological exploration of should answer two major questions: do the fractures involve areas that may alter the physiologic function of the sinuses, mouth, nasal vault or orbit?, and will the fracture result in any cosmetically detectable abnormality? The goal of the radiological work-up is to define the number and exact location of the fractures, to determine if there is any depression, elevation, or distraction of the fracture fragments, and to assess concomitant soft tissue complications. In this article, we review the role of clinical evaluation, plain X-rays, computed tomography (CT) and magnetic resonance imaging (MRI). Imaging findings are correlated with anatomic and physiopathologic considerations. We present a practical classification system of facial trauma, with emphasis on trauma of the paranasal sinuses and facial bones (nasal and tripod fractures, Le Fort fractures) and orbits (foreign bodies, soft tissue and orbital wall injuries such as blow-in and blow-out-, lateral wall- and apical fractures). A third part focuses on trauma of the mandible and the temporomandibular joints.

Computer assisted E.N.T. surgery, a preliminary report

The Medivision Image Guided Surgery System was used in the E.N.T. Department of the Antwerp University Hospital in 10 different E.N.T. surgical procedures between October 1997 and February 1998. The authors report and discuss the procedure for computer assisted surgery in E.N.T. interventions, based on this preliminary experience, and conclude that computer assisted surgery has many useful applications in our speciality.

An unusual case of maxillary ameloblastoma

We report a case of malignant maxillar ameloblastoma. A review of literature is presented. The unusual clinical behavior and the non specific presentation on CT of our case are discussed.

Imaging findings in diffuse axonal injury after closed head trauma

Even in patients with closed head trauma, brain parenchyma can be severely injured due to disruption of axonal fibers by shearing forces during acceleration, deceleration, and rotation of the head. In this article we review the spectrum of imaging findings in patients with diffuse axonal injuries (DAI) after closed head trauma. Knowledge of the location and imaging characteristics of DAI is important to radiologists for detection and diagnosis. Common locations of DAI include: cerebral hemispheric gray-white matter interface and subcortical white matter, body and splenium of corpus callosum, basal ganglia, dorsolateral aspect of brainstem, and cerebellum. In the acute phase, CT may show punctate hemorrhages. The true extent of brain involvement is better appreciated with MR imaging, because both hemorrhagic and non-hemorrhagic lesions (gliotic scars) can be detected. The MR appearance of DAI lesions depends on several factors, including age of injury, presence of hemorrhage or blood-breakdown products (e. g., hemosiderin), and type of sequence used. Technical aspects in MR imaging of these patients are discussed. Non-hemorrhagic lesions can be detected with fluid attenuated inversion recovery (FLAIR), proton-density-, or T2-weighted images, whereas gradient echo sequences with long TE increase the visibility of old hemorrhagic lesions.

MR of the brain in Sjögren-Larsson syndrome

Cerebral MR was performed in three patients with Sjögren-Larsson syndrome. In each case, a 1.5-T system was used, and the patient was under general anesthesia. The MR findings included confluent hyperintense white matter lesions in the periventricular and deep white matter of the centrum semiovale, with sparing of the subcortical U fibers. The topography of the white matter abnormalities correlated well with the clinical signs and symptoms.

Low cost MR imaging: medical and economic perspectives

A critical review of the potential applications, clinical usefulness and shortcomings of low field MR imaging with a view to cost control is provided.

Imaging findings in patients with failed back surgery syndrome

The incidence of low back pain and leg pain related to the spine is very high in the Western population. As a result of conservative treatment failure there are roughly 200,000 lumbar disk operations performed annually. Unsuccessful surgical outcome is known as the failed back surgery syndrome (FBSS). FBSS is a complex and poorly understood syndrome, with as many different imaging findings as different possible etiologic mechanisms. Still we believe some imaging aspects deserve special attention. Firstly it is of particular importance to correctly differentiate residual disk herniation from epidural scar tissue since disk herniation can be an indication for repeat intervention. Secondly when residual disk herniation is present, one should keep in mind that it is not necessarily responsible for the patients complaints. Thirdly, late nerve root enhancement should be considered as pathological. Finally one should be aware of the mechanical back stress that may develop as a result of discectomy. One of the consequences can be secondary foraminal stenosis which is probably one of the most common causes of FBSS.

Imaging of primary tumors and tumor-like conditions of the lumbosacral osseous spine

Primary tumors of the osseous spine are rare. This article illustrates some aspects of imaging of tumoral pathology of the osseous spine. Plain film and CT scan still remain the initial imaging modalities in the work-up of tumoral pathology of the osseous spine. MR imaging however has proven its potentials in the detection of lesions in areas with superimposing structures which hamper reliable reading of the plain films or in areas with a complex bony anatomy such as the sacrum. MR imaging is exquisite in determining the local extent of tumoral lesions and in defining the relationship to adjacent central nervous system structures. In some tumors or tumor-like lesions, MR imaging allows to make a correct tissue-related diagnosis or to strengthen the diagnosis made on plain film/CT observations. In other case MR imaging only has a role in staging or may have definitely no role at all.

Cerebral complications of murine monoclonal CD3 antibody (OKT3): CT and MR findings

Treatment of acute renal allograft rejection with mouse monoclonal antibody (OKT3) is associated with systemic and neurologic side effects. We describe cerebral abnormalities in a 13-year-old boy with steroid-resistant renal allograft rejection. After treatment with OKT3, an acute neurologic syndrome developed, including seizures, lethargy, and decreased mental function. CT and MR imaging revealed confluent cerebral lesions at the corticomedullary junction. Contrast-enhanced MR images showed patchy enhancement, indicating blood-brain barrier dysfunction. The diagnosis of OKT3-induced encephalopathy with cerebral edema and capillary leak syndrome was made. Although CT and MR findings are nonspecific, neuroradiologists should be aware of this condition in transplant patients treated with OKT3.

MRI after successful lumbar discectomy

Our aim was to establish the normal range of MRI findings after successful lumbar discectomy. We prospectively examined 34 consecutive patients with an excellent clinical outcome by MRI 6 weeks and 6 months after surgery. All examinations included sagittal and axial spin-echo (SE) T1-weighted images before and after intravenous gadolinium-DTPA and fast SE T2-weighted images. Contrast enhancement along the surgical tract was seen in all patients 6 weeks and 6 months after surgery. After 6 months minimal or no mass effect on the dural sac by epidural scar was seen. In 20% of patients there was recurrent disc herniation, with mass effect. Enhancing nerve roots were seen in 20% of patients 6 weeks postoperatively, and half of these were associated with recurrent disc herniation at the same side. None of these patients still showed nerve root enhancement 6 months after surgery. Postoperative MRI studies must be interpreted with great care since the features described in the failed back surgery syndrome are also found, to some extent, in asymptomatic postoperative patients.

Clinical usefulness of contrast-enhanced MP-RAGE of the brain

Our purpose was to evaluate the usefulness of a 3D T1-weighted gradient-echo sequence (MP-RAGE) in clinical practice. We prospectively examined 200 patients with a variety of neurological disorders and symptoms. We compared lesion conspicuity and contrast enhancement on MP-RAGE images with conventional gadolinium-enhanced spin-echo (SE) T1-weighted images. Both the original MP-RAGE data and the reformatted images were characterised by improved differentiation between grey and white matter. More lesions were found on the 3D series, in both patients with neoplastic and non-neoplastic disease. Contrast enhancement of small oedematous lesions affecting the white matter in demyelinating disease was less obvious. Multiplanar reformatting, which can be realised in any desired plane and surface rendering with sophisticated segmentation algorithms superbly displayed the underlying anatomical relationships between lesions and normal brain structures. Excellent spatial resolution, the absence of posterior fossa artefacts and equivalent contrast enhancement resulted in an increased number of space-occupying lesions being found on the MP-RAGE images. Thus contrast-enhanced MP-RAGE is an alternative to conventional SE imaging in the investigation of intracranial masses. Although the total number of lesions found in patients with demyelinating disease was significantly higher on MP-RAGE, demonstration of blood-brain-barrier breakdown in active lesions was less obvious.

Whiplash injuries: is there a role for imaging?

Whiplash describes the manner in which a head is moved suddenly to produce a sprain in the neck and typically occurs after rear-end automobile collisions. It is one of the most common mechanisms of injury to the cervical spine. Although considered by some to be a form of compensation neurosis, evidence suggests that whiplash injuries are real and that they are a potential cause of significant impairment. Symptoms of cervical whiplash injury include neck pain and stiffness, interscapular pain, arm pain and/or occipital headache, and many whiplash patients have persistent complaints. Cervical roentgenography and conventional or computed tomography (CT) may show dislocations, subluxations and fractures in severely traumatized patients, but often fail to determine or visualize the cause for a whiplash syndrome. Magnetic resonance imaging (MRI), however, is able to assess different types of soft-tissue lesions related to whiplash injuries. Dynamic imaging may show functional disturbances. More widespread use of flexion/extension views, high-resolution static MRI and especially dynamic MRI should improve the correlation between imaging findings and patients' complaints.

Parinaud's syndrome in a patient with multifocal glioma

We describe the clinical and neuroradiological findings in a 63-year-old man with Parinaud's syndrome. Magnetic resonance (MR) imaging showed a mass lesion within the quadrigeminal plate. Additional MR findings included a right frontoparietal subcortical lesion as well as periventricular white matter edema due to acute deterioration of hydrocephalus. On MR, the diagnosis of multifocal glioma was proposed. Neuropathological examination after resection of the supratentorial lesion revealed an oligodendroglioma, grade II.

Postmortem MRI of the brain with neuropathological correlation

We prospectively correlated in vitro MRI of the brain with the neuropathological findings in patients with suspected intracranial disease. In vitro MRI was performed on 91 consecutive formalin-fixed whole-brain specimens. In 60 cases, the images were correlated with the neuropathological findings (number of lesions, lesion boundaries, spread of oedema and type of lesions). As compared with neuropathology, MRI showed an equal number of lesions in 50 cases, more in 5, and less in 5 specimens, resulting in a sensitivity of 83.3%. The extent of perilesional oedema was better seen on in vitro MRI than on gross pathology. Microscopic extent of glial tumours was underestimated on both T2-weighted images and macroscopic examination. Neuropathology remains the reference study, since on in vitro MRI primary brain tumours, metastatic deposits and non-neoplastic space-occupying lesions cannot be differentiated. However, in our study MRI had a specificity of 76.6%. MRI of postmortem specimens is sensitive to focal brain lesions, and can focus the attention of the neuropathologist to abnormal regions.

Influence of magnetic field strength on T2* decay and phase effects in gradient echo MRI of vertebral bone marrow

OBJECTIVE

The goal of this study was twofold: first, to quantify the influence of magnetic field strength (B0) on T2* and T2susceptibility relaxation rates in vertebral bone marrow; and second, to determine the significance of in-phase/out-of-phase phenomena in GE MRI as a function of TEs at different B0 values.

MATERIALS AND METHODS

Magnetic resonance imaging of the spine was performed at 1.5, 1.0, and 0.2 T using a GE sequence (2D-FLASH) with variable TE. Vertebral body signal intensities were measured and plotted against TE values. These curves were used to calculate T2* decay of bone marrow at different B0 values.

RESULTS

At all field strengths, we observed exponential signal decay, modulated by a cosine function, the periodicity of which was proportional to B0. The T2* values of vertebral bodies were 9.7 +/- 1.8 ms at 1.5 T, 17.2 +/- 2.4 ms at 1.0 T, and 53 +/- 5 ms at 0.2 T. True T2 relaxation time (independent of field strength) was 62 +/- 4 ms. The T2susceptibility was 11.7 ms at 1.5 T, 24.8 ms at 1.0 T, and 585 ms at 0.2 T.

CONCLUSION

We conclude that at low B0, susceptibility effects become less important and T2* approaches true T2 relaxation.

Understanding chemical shift induced boundary artefacts as a function of field strength: influence of imaging parameters (bandwidth, field-of-view, and matrix size)

OBJECTIVE

To study the importance of chemical shift induced boundary artefact (CSA) at different field strengths and the implications for pulse sequence design with respect to receiver bandwidth (BW), field-of-view (FOV) and matrix size.

MATERIALS AND METHODS

A fat-water phantom was examined in MR systems of different field strength (1.5 T, 1.0 T and 0.2 T), using pulse sequences with different receiver BW, FOV, and matrix size. The chemical shift was quantified by measuring the width of the bright and dark misregistration rims seen at the planar fat-water interface. The measured chemical shift was compared with the theoretically calculated chemical shift.

RESULTS

Excellent correlations were found between predicted chemical shift and measurement results in our experiments. The width of the CSA (in millimetres) is directly proportional to field strength, inversely proportional to receiver BW and hence to the strength of the readout gradient, directly proportional to FOV, and inversely proportional to matrix size.

CONCLUSION

CSA occurs at all magnetic field strengths, but given a certain BW it is more pronounced at higher fields. Although the CSA in Hz is directly proportional to field strength, the visible CSA at low-field was slightly higher than theoretically expected. The relative lack of CSA in low-field strength images permits the application of narrow receiver BW sequences, resulting in increased signal to noise ratio.