Posterior reversible encephalopathy and Guillain-Barré syndrome in a single patient: coincidence or causative relation?

We report 62-year-old female patient with coincident posterior reversible encephalopathy syndrome (PRES) and Guillain-Barré syndrome (GBS). The first presentation of PRES was a generalised tonic-clonic seizure. A risk factor for PRES was acute arterial hypertension. The diagnosis of PRES was established by MRI (magnetic resonance imaging) and hypertension was treated with labetalol 800mg daily followed by regression of symptoms of PRES. Two days after the seizure the first motor signs of GBS presented with a weakness in both upper arms. The diagnosis of GBS was finally established 6 days after the seizure by clinical evolution, lumbar puncture and electrophysiological findings. After treatment of GBS with intravenous immunoglobulins (IVIg), antihypertensive therapy could be phased out and finally stopped. The patient was discharged after 25 days without any medication. At that time she was completely recovered from PRES and recovering well from GBS. The acute arterial hypertension, the provoking factor of PRES, was probably caused by an autonomic dysfunction in the context of GBS before motor signs of GBS were present but we speculate also that there are other GBS related factors playing a role in PRES. This hypothesis is based on the relatively high coincidence of these two rare syndromes which appears from a review of the literature. One other possible mechanism can be the influence of cytokines, produced in the context of a GBS, on the permeability of blood brain barrier.

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.

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.

The postsurgical lumbosacral spine. Magnetic resonance imaging evaluation following intervertebral disk surgery, surgical decompression, intervertebral bony fusion, and spinal instrumentation.

It should be clear to those who perform and interpret medical images of the spine following one or more forms of surgical therapy that the images are often difficult to interpret in part because of the superimposition of the original disease process, alteration engendered by the surgery, or a complication of the surgical procedure. Although long-term experience in this area is helpful in regard to improving interpretive skills, certain sequela can be predicted regardless of the interpreter's background. Once the normal or expected postsurgical findings are understood, the subtle and gross changes that depart from these observations can be analyzed better. The importance of a high level of competence in the domain of post-therapeutic neurodiagnostic imaging is in the knowledge that the patient returning for restudy may be acutely in distress or even in medical danger (e.g., postoperative spondylitis). In fact, the clinical presentation posttherapeutically may well be more severe or dire than was observed pretherapeutically. An indepth appreciation of the broad range of clinicoradiologic possibilities as presented [figure: see text] here should place the medical imaging physician in an excellent position to provide an experienced diagnostic evaluation in the patient presenting with recurrent or new signs and symptoms following any one of the spectrum of possible spinal surgical procedures.

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.

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.

Hereditary neuromuscular diseases.

This article presents the actual classification of neuromuscular diseases based on present expansion of our knowledge and understanding due to genetic developments. It summarizes the genetic and clinical presentations of each disorder together with CT findings, which we studied in a large group of patients with neuromuscular diseases. The muscular dystrophies as the largest and most common group of hereditary muscle diseases will be highlighted by giving detailed information about the role of CT and MRI in the differential diagnosis. The radiological features of neuromuscular diseases are atrophy, hypertrophy, pseudohypertrophy and fatty infiltration of muscles on a selective basis. Although the patterns and distribution of involvement are characteristic in some of the diseases, the definition of the type of disease based on CT scan only is not always possible.

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.

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.

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.

Influence of user-defined parameters on diffusion tensor tractography of the corticospinal tract.

This study discusses the influence of user-defined parameters on fiber tracking results obtained from a standard deterministic streamline tractography algorithm. Diffusion tensor imaging with fiber tractography was performed in five healthy volunteers. A region of interest was highlighted in the ventral part of the pons at the level of the middle cerebellar peduncle. The parameters studied were angle threshold, fractional anisotropy threshold, step length and number of seed samples per voxel. Changes in fiber tracts were described for increasing values per parameter. Increasing the angle threshold resulted in more and longer fibers. A higher fractional anisotropy threshold resulted in decreased length and fiber tracts that were not representative. Increasing the step length decreased the fiber continuity and altered its position. A higher number of seed samples per voxel resulted in a higher fiber tract density. When interpreting diffusion tensor images, the reader should understand the influence of user-defined settings on the results, and should be aware of the inter-dependency of fiber tracking parameters.

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.

New developments in the neuroradiological diagnosis of craniocerebral trauma.

Accurate radiographic diagnosis is a cornerstone of the clinical management and outcome prediction of the head-injured patient. New technological advances, such as multi-detector computed tomography (MDCT) scanning and diffusion-weighted magnetic resonance imaging (MRI) have influenced imaging strategy. In this article we review the impact of these developments on the neuroradiological diagnosis of acute head injury. In the acute phase, multi-detector CT has supplanted plain X-ray films of the skull as the initial imaging study of choice. MRI, including fluid-attenuated inversion recovery, gradient echo T2* and diffusion-weighted sequences, is useful in determining the severity of acute brain tissue injury and may help to predict outcome. The role of MRI in showing diffuse axonal injuries is emphasized. We review the different patterns of primary and secondary extra-axial and intra-axial traumatic brain lesions and integrate new insights. Assessment of intracranial hypertension and cerebral herniation are of major clinical importance in patient management. We discuss the issue of pediatric brain trauma and stress the importance of MRI in non-accidental injury. In summary, new developments in imaging technology have advanced our understanding of the pathophysiology of brain trauma and contribute to improving the survival of patients with craniocerebral injuries.

3D time-of-flight MR angiography of the intracranial vessels: optimization of the technique with water excitation, parallel acquisition, eight-channel phased-array head coil and low-dose contrast administration.

The aim of this study is three folds: to compare the eight-channel phased-array and standard circularly polarized (CP) head coils in visualisation of the intracranial vessels, to compare the three-dimensional (3D) time-of-flight (TOF) MR angiography (MRA) techniques, and to define the effects of parallel imaging in 3D TOF MRA. Fifteen healthy volunteers underwent 3D TOF MRA of the intracranial vessels using eight-channel phased-array and CP standard head coils. The following MRA techniques were obtained on each volunteer: (1) conventional 3D TOF MRA with magnetization transfer; (2) 3D TOF MRA with water excitation for background suppression; and (3) low-dose (0.5 ml) gadolinium-enhanced 3D TOF MRA with water excitation. Results are demonstrating that water excitation is a valuable background suppression technique, especially when applied with an eight-channel phased-array head coil. For central and proximal portions of the intracranial arteries, unenhanced TOF MRA with water excitation was the best technique. Low-dose contrast enhanced TOF MRA using an eight-channel phased-array head coil is superior in the evaluation of distal branches over the standard CP head coil. Parallel imaging with an acceleration factor of two allows an important time gain without a significant decrease in vessel evaluation. Water excitation allows better background suppression, especially around the orbits and at the periphery, when compared to conventional acquisitions.

MR and CT imaging of paraspinal textiloma (gossypiboma).

This report describes two cases of textiloma (gossypiboma, foreign body granuloma). These so-called "cottonoids" (Codman, U.S.A.) were inadvertently left behind in the operation wound following spinal surgery for an intervertebral disk herniation. Both textilomas were located paraspinally. These relatively uncommon lesions should be differentiated from paraspinal tumors, as well as from other postoperative complications, such as scar formation. Although plain radiography generally gives a characteristic image due to a marking filament, the CT and especially MR findings are less well known.

Pattern recognition of degenerative disorders in the lumbar spine. Guidelines to MR image interpretation.

Interpreting MR images of the lumbar spine remains a formidable diagnostic challenge, especially in patients with degenerative changes. What are the pertinent findings? Which abnormalities are clinically relevant? Which changes should be viewed as normal aging? The purpose of this presentation is to present a standardized 7-step approach towards interpreting MR images of the degenerative lumbar spine.

Cervical spine fractures and soft tissue injuries.

Spinal cord injury is the major cause of quadriplegia and disability. Plain radiographs have a low sensitivity for identifying traumatic cervical spine lesions. Therefore trauma victims with plain films negative for cervical injury but with a high clinical suspicion of injury, or positive for cervical injury should undergo CT or MR for a more definitive evaluation of the cervical spine. Besides the higher sensitivity than plain radiography in detecting fractures, CT is also able to show soft-tissue abnormalities. MR is the definitive modality in assessing cervical soft-tissue injuries, especially in the evaluation of the spinal cord, intervertebral discs, and ligaments. It also allows differentiate spinal cord hemorrhage and edema, which may have a prognostic value. The role of medical imaging in the evaluation of whiplash injuries remains to be determined.

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.