Johan Van Goethem

MR angiography of the intracranial vessels: technical aspects and clinical applications

Evaluation of the intracranial circulation provides valuable information in the diagnosis and prognosis of various intracranial abnormalities and may influence patient management. Technical advances in magnetic resonance angiography (MRA) have improved the accuracy of this technique in various clinical situations, such as aneurysms, arterial and venous steno-occlusive diseases, vascular malformations, inflammatory arterial diseases, preoperative assessment of the patency of dural sinuses, and congenital vascular abnormalities. In many centers, MRA has replaced conventional digital subtraction angiography in screening for intracranial vascular disease, because of its non-invasive and non-ionizing character. Several MRA techniques have been developed for the imaging of the intracranial vascular system, such as time-of-flight MRA (TOF MRA), phase-contrast MRA (PC MRA), and more recently contrast-enhanced MRA (CE MRA). In the evaluation of steno-occlusive disease, the three-dimensional (3D) TOF-MRA technique is recommended for arterial evaluation, and the 2D TOF or 2D PC-MRA technique for venous evaluation. For the evaluation of aneurysms and arteriovenous malformations (AVMs), we recommend the 3D CE-MRA technique, especially dynamic sequences in case of AVM. In this review, the technical aspects, limitations, and optimization of these MRA techniques will be discussed together with their indications in intracranial disease.

A tracking-based diffusion tensor imaging segmentation method for the detection of diffusion-related changes of the cervical spinal cord with aging

To compare region of interest (ROI)‐based and diffusion tensor tractography (DTT)‐based methods for evaluating diffusion properties of the spinal cord as a function of age.

Imaging in spinal trauma

Because it may cause paralysis, injury to the spine is one of the most feared traumas, and spinal cord injury is a major cause of disability. In the USA approximately 10,000 traumatic cervical spine fractures and 4000 traumatic thoracolumbar fractures are diagnosed each year. Although the number of individuals sustaining paralysis is far less than those with moderate or severe brain injury, the socioeconomic costs are significant. Since most of the spinal trauma patients survive their injuries, almost one out of 1000 inhabitants in the USA are currently being cared for partial or complete paralysis. Little controversy exists regarding the need for accurate and emergent imaging assessment of the traumatized spine in order to evaluate spinal stability and integrity of neural elements. Because clinicians fear missing occult spine injuries, they obtain radiographs for nearly all patients who present with blunt trauma. We are influenced on one side by fear of litigation and the possible devastating medical, psychologic and financial consequences of cervical spine injury, and on the other side by pressure to reduce health care costs. A set of clinical and/or anamnestic criteria, however, can be very useful in identifying patients who have an extremely low probability of injury and who consequently have no need for imaging studies. Multidetector (or multislice) computed tomography (MDCT) is the preferred primary imaging modality in blunt spinal trauma patients who do need imaging. Not only is CT more accurate in diagnosing spinal injury, it also reduces imaging time and patient manipulation. Evidence-based research has established that MDCT improves patient outcome and saves money in comparison to plain film. This review discusses the use, advantages and disadvantages of the different imaging techniques used in spinal trauma patients and the criteria used in selecting patients who do not need imaging. Finally an overview of different types of spinal injuries is given.

Brainstem hemorrhage in descending transtentorial herniation (Duret hemorrhage)

Objectives: To review clinical and radiological findings in patients with Duret hemorrhages and to discuss the pathophysiology and differential diagnosis of these lesions. Patients and methods: We reviewed the case records of four patients with Duret hemorrhages who had been admitted to the neurological intensive care unit with supratentorial mass lesions. Results: Descending transtentorial and subfalcine herniations were present in all cases. Three patients were admitted with acute subdural hematoma and one with intraparenchymal hemorrhage. Computed tomography revealed the presence of blood in the mesencephalon and upper pons. Three patients died; one survived with severe disabilities. Discussion: Duret hemorrhages are typically located in the ventral and paramedian aspects of the upper brainstem (mesencephalon and pons). The pathophysiology of Duret hemorrhage remains under debate: arterial origin (stretching and laceration of pontine perforating branches of the basilar artery), versus venous origin (thrombosis and venous infarction). Multifactorial causation seems likely. Conclusion: Duret hemorrhages are delayed, secondary brainstem hemorrhages. They occur in craniocerebral trauma victims with rapidly evolving descending transtentorial herniation. Diagnosis is made on computed tomography of the brain. In most cases the outcome is fatal. On the basis of our observations we believe that arterial hypertension and advanced age are risk factors for the development of Duret hemorrhage.

Cortical hypoxic-ischemic brain damage in shaken-baby (shaken impact) syndrome: value of diffusion-weighted MRI.

Shaken-baby syndrome (SBS) is a type of child abuse caused by violent shaking of an infant, with or without impact, and characterized by subdural hematomas, retinal hemorrhages, and occult bone fractures. Parenchymal brain lesions in SBS may be missed or underestimated on CT scans, but can be detected at an earlier stage with diffusion-weighted MRI (DW-MRI) as areas of restricted diffusion. We demonstrate the value of DW-MRI in a 2-month-old baby boy with suspected SBS. The pattern of diffusion abnormalities indicates that the neuropathology of parenchymal lesions in SBS is due to hypoxic-ischemic brain injuries, and not to diffuse axonal injury.

A diffusion tensor imaging group study of the spinal cord in multiple sclerosis patients with and without T2 spinal cord lesions

To examine the T2‐normal appearing spinal cord of patients with multiple sclerosis (MS) using diffusion tensor imaging.

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 interpreters 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.

Degenerative Disc Disease

The spinal column is a complex anatomical structure which is composed of vertebrae, intervertebral discs, and ligaments. All components undergo degenerative changes and morphologic alterations during life (Prescher 1998). In this chapter we shall focus our attention on the intervertebral discs, which are also referred to as “intervertebral fibrocartilages”; the two terms can be used interchangeably (Warwick and Williams 1973). From the axis (C2) to the sacrum, the intervertebral discs are situated between the upper and lower endplates of adjacent vertebral bodies. They constitute the principal connections between the vertebrae, and have two main functions: to serve as shock absorbers, and to allow movement of the spinal column. Movement at a single disc level is limited, but all of the vertebrae and discs combined allow for a significant range of motion (Inoue and Takeda 1975).

Diffusion tensor imaging provides an insight into the microstructure of meningiomas, high-grade gliomas, and peritumoral edema.

Objective Fractional anisotropy (FA) is a measure for the degree of microstructural organization. Several studies have used FA values to assess microstructural organization of brain tumors and peritumoral edema. The purpose of our study was to validate FA and apparent diffusion constant (ADC) values in the diagnosis of meningiomas versus high-grade glial tumors, with the focus on the ability of diffusion tensor imaging (DTI) to reveal tumor ultrastructure. Our hypothesis was that FA and ADC values significantly differ between high-grade gliomas and meningiomas, and in the peritumoral edema. Methods Diffusion tensor imaging values were obtained from 20 patients with meningiomas (21 tumors) and 15 patients with high-grade gliomas. Regions of interest were outlined in FA and ADC maps for solid-enhancing tumor tissue and peritumoral edema. Fractional anisotropy and ADC values were normalized by comparison to normal-appearing white matter (NAWM) in the contralateral hemisphere. Differences between meningiomas and high-grade gliomas were statistically analyzed. Results Meningiomas showed a significantly higher FA tumor/FA NAWM ratio (P = 0.0001) and lower ADC tumor/ADC NAWM ratio (P = 0.0008) compared to high-grade gliomas. On average, meningiomas also showed higher FA values in peritumoral edema than high-grade gliomas (P = 0.016). Apparent diffusion constant values of peritumoral edema for the 2 tumor groups did not differ significantly (P = 0.5). Conclusions Diffusion tensor imaging can be used to reveal microstructural differences between meningiomas and high-grade gliomas and may contribute toward predicting the histopathology of intracranial tumors. We advocate that diffusion tensor imaging should be included in the standard imaging protocol for patients with intracranial tumors.

Epilepsy and migraine in a patient with Urbach–Wiethe disease

We report the clinical, neuroradiological, and molecular genetic findings in a patient with lipoid proteinosis or Urbach-Wiethe disease. Interestingly, in this patient epilepsy and migraine were the symptoms leading to the diagnosis of the disease, contrary to most patients in whom skin abnormalities are the first recognized symptoms.