Prospective study of postoperative magnetic resonance imaging in patients with malignant gliomas.

PURPOSE: We studied the natural history of postoperative enhancement on magnetic resonance (MR) scans in patients with malignant glioma to determine the following: (1) when a postoperative MR scan most accurately shows residual enhancing tumor; and (2) whether repeated doses of the contrast agent gadopentetate dimeglumine (Gd-DTPA) were well tolerated. PATIENTS AND METHODS: Seventeen patients with malignant glioma underwent tumor resection; four (24%) had nonenhancing tumors preoperatively. Serial MR scans were performed on postoperative days 1, 3, 5, 7, 14, and 21 and were analyzed qualitatively and quantitatively. The evolution of enhancement and subacute hemorrhage were described and measured. A uniform schedule of postoperative dexamethasone administration was used in all but four patients (24%) (each required higher doses to maintain neurologic function). RESULTS: Nontumoral, marginal (i.e., postsurgical) enhancement, potentially mimicking residual tumor, developed in eight patients (53%), including tumors that were nonenhancing preoperatively, and was maximal from days 5 to 14. Tumor enhancement was optimally visualized on postoperative days 3 to 5. Nine of 10 patients (90%) with gross residual enhancing tumor showed an increase of enhancing tumor size during the study. Methemoglobin was detected at some time in all patients (100%) and was usually minor, but in six (35%) it interfered with residual tumor assessment. The 97 doses of Gd-DTPA, administered in 17 patients, were well tolerated. CONCLUSION: When accurate assessment of residual enhancing tumor is needed in patients with malignant glioma, an MR scan performed on postoperative days 3 to 5 should minimize the confounding effects of postsurgical enhancement and methemoglobin. The repeated administration of Gd-DTPA over several weeks is well tolerated.

How often are nonenhancing supratentorial gliomas malignant? A population study.

The presence of contrast enhancement in a brain tumor is often regarded as a sign of malignancy. The authors identified 314 patients with malignant and low-grade supratentorial glial neoplasms in an unselected population, 58 of which lacked contrast enhancement on preoperative neuroimaging. Nonenhancing gliomas were malignant in approximately one third of cases, especially in older patients. Histologic confirmation of the diagnosis is therefore important in all patients suspected of harboring a primary glial neoplasm.

Diffuse-variant tenosynovial giant cell tumor: a rare and aggressive lesion.

The diffuse-variant tenosynovial giant cell tumor is rare. Although it shares histologic features with the exclusively intra-articular pigmented villonodular synovitis and local tenosynovial giant cell tumor, its behavior differs dramatically, being locally very aggressive. We report a case of a diffuse-variant aggressive tenosynovial giant cell tumor that, although diploid by flow cytometry, demonstrated trisomy 7 and 5 as well as clonal rearrangements involving chromosomes 1, 3, and 15. These cytogenetic abnormalities may be markers for aggressive behavior and useful for directing treatment.

Three-dimensional time-of-flight MR angiography in the evaluation of intracranial aneurysms treated by endovascular balloon occlusion.

The authors share their experience with MRA in the assessment of cerebral aneurysms. Despite its limitations--spatial resolution, insensitivity to slow flow states, subacute thrombus artifacts--they believe the technique shows potential.

Use of the Alberta Stroke Program Early CT Score (ASPECTS) for assessing CT scans in patients with acute stroke.

BACKGROUND AND PURPOSE: Clinicians are insecure reading CT scans by using the one-third rule for acute middle cerebral artery stroke (1/3 MCA rule) before treating patients with recombinant tissue plasminogen activator. The 1/3 MCA rule is a poorly defined volumetric estimate of the size of cerebral infarction of the MCA. A 10-point quantitative topographic CT scan score, the Alberta Stroke Program Early CT Score (ASPECTS), is described and illustrated. A sharp increase in dependence and death occurs with an ASPECTS of 7 or less. We describe how to use ASPECTS and why it works with CT scans obtained on all commonly used axial baselines. We also describe interobserver reliability among clinicians from different specialties and with different experience in reading CT scans in the context of acute stroke. METHODS: The six physicians who developed ASPECTS answered a questionnaire on precisely how they interpret and use ASPECTS. The ASPECTS areas as interpreted by these physicians were compared with one another and with standards in the literature. kappa statistics were used to assess the interobserver reliability of ASPECTS versus the 1/3 MCA rule. RESULTS: The exact methods of interpretation varied among the six individual observers, with either a 3:3 or 4:2 split on the specific questions. The overall interobserver agreement was good compared with that of the 1/3 MCA rule. Normal anatomic vascular and interobserver variations explain why ASPECTS can be applied with different CT axial baselines. CONCLUSION: ASPECTS is a systematic, robust, and practical method that can be applied to different axial baselines. Clinician agreement is superior to that of the 1/3 MCA rule.

Symptomatic hamartoma of the spinal cord associated with neurofibromatosis type 1. Case report.

The authors present a case in which a symptomatic hamartoma was found in the spinal cord of a patient with neurofibromatosis type 1 (NF-1). This 52-year-old woman presented with painful urinary incontinence. Magnetic resonance (MR) imaging revealed an intramedullary lesion within the lower thoracic spinal cord and conus medullaris, which was surgically removed. Pathological investigation showed a hamartomatous lesion consisting of glial cells, ganglion cells, abundant disoriented axons, and thin-walled vessels. This case provides a pathological correlate to the hamartomatous lesions demonstrated on MR imaging in patients with NF-1 and illustrates that these benign lesions may become symptomatic and require neurosurgical intervention.

Symptomatic hemorrhage after alteplase therapy not due to silent ischemia.

BACKGROUND: Stroke thrombolysis-related intracerebral hemorrhage may occur remotely from the anatomical site of ischemia. One postulated mechanism for this is simultaneous multiple embolization with hemorrhage into a "silent" area of ischemia. RESULTS: A patient suffered a disabling stroke affecting the right cerebral hemisphere. He was treated with intravenous alteplase and underwent extensive early imaging with multimodal MRI. Several hours after treatment he developed a brainstem hemorrhage despite having no evidence of ischemia on DWI MRI in the brainstem. CONCLUSION: Not all occurrences of remote ICH after stroke thrombolysis are secondary to multiple emboli with silent ischemia.

Correlation of neurologic dysfunction with CT findings in early acute stroke.

OBJECTIVE: To determine the frequency of early computed tomographic (CT) findings of ischemia and their relationship to symptom duration and neurologic dysfunction within 3 hours of ischemic stroke. METHODS: The CT scans of 39 acute stroke patients were evaluated for signs of early ischemic change within 3 hours of symptom onset and without knowledge of the patient's neurologic deficit or results of a 24 hour follow-up post-thrombolysis CT. Early CT signs of acute ischemic change or thromboembolism were hypoattenuation of the insular ribbon, obscuration of the lentiform nucleus, cortical hypodensity/effacement, and hyperdense middle cerebral artery sign. RESULTS: Signs of acute ischemic change were seen on the baseline scan in 25/39 patients (64%). Hypoattenuation of the insular ribbon was seen in 11 patients, obscuration of the lentiform nucleus in 13, cortical hypodensity/effacement in 13, and hyperdense middle cerebral artery sign in 7. The prevalence of early ischemic signs was directly associated with increasing neurologic disability at the time of presentation. No clear relationship existed between symptom duration and the presence of CT signs. CONCLUSIONS: Evidence of cerebral ischemia is frequently seen on CT within 3 hours of symptom onset. The degree of neurologic disability correlates with CT signs of ischemia.

Idiopathic hypertrophic pachymeningitis: a report of two patients and review of the literature.

PURPOSE: We report the treatment and follow-up, including MRI, of two patients with idiopathic hypertrophic pachymeningitis and review the English language literature, with emphasis on management and outcome in this rare disorder. METHODS AND MATERIALS: The files of two patients were reviewed, with relevant histopathology and imaging (MRI). The first patient has been followed for sixteen years (the longest MRI-documented postoperative course reported for this condition) and the second for two years. The English language literature was reviewed, including a summary of all reported patients that have been followed with MRI or CT imaging. RESULTS: Despite extensive investigation, no underlying etiology was determined in either patient. Histopathological studies revealed a chronic inflammatory dural infiltrate in both patients, with granulomas in the first but not the second patient. The first patient underwent surgery twice and has remained stable for sixteen years, despite persistent neurologic deficits. The second patient was managed with dexamethasone after a surgical biopsy, and experienced complete resolution of all neurological deficits and abnormalities seen with MRI. CONCLUSIONS: Although prompt and extensive surgery has been recommended for this condition, the results from our second patient indicate that complete remission can be achieved in some patients with biopsy and steroid therapy. This also supports the view that autoimmune mechanisms underlie idiopathic hypertrophic pachymeningitis. The first patient illustrates that extensive laminectomies may be an effective therapeutic option but chronic discomfort may result. If extensive surgery must be performed, laminoplasty should be done because of the potential for reduced pain and improved long-term spinal stability.

Magnetic resonance diffusion weighted imaging in cerebral fat embolism.

The use of diffusion weighted imaging with apparent diffusion coefficient mapping in the diagnosis of cerebral fat embolism is shown here to demonstrate infarcts secondary to fat emboli more intensely than T2 weighted sequences 24 hours after the onset of symptoms. Embolic foci are hypointense on apparent diffusion coefficient mapping consistent with cytotoxic edema associated with cell death and restricted water diffusion. This technique increases the sensitivity for detecting cerebral fat embolism and offers a potentially important tool in its diagnosis.

Cervical spine tumors.

Magnetic resonance imaging is the central imaging modality for cervical spine neoplasms. The majority of extradural lesions are metastatic. Nerve sheath tumors are the most common intradural neoplasm, followed by meningioma. Intramedullary tumors are less common. This article reviews tumors according to this classification, with emphasis on clinical considerations and imaging techniques and findings.

MR imaging of neoplasms of the lumbar spine.

MR imaging has evolved as the primary modality for imaging spinal neoplasms; however, neoplasms must be distinguished from unusual appearances of degenerative lesions. This article reviews MR imaging findings of a variety of neoplastic lesions of the lumbar spine. For example, extradural, metastatic tumors are the most common; nerve sheath tumors are the most common intradural extramedullary tumors; and ependymoma accounts for most of the tumors arising from the filum terminale.

Multifocal white matter lesions.

There is a long differential diagnosis for multifocal white matter lesions on MR. The most common causes are prominent Virchow-Robin spaces, white matter ischemic change, and multiple sclerosis, but many other causes have been reported. Most of these are related to vascular or other demyelinating etiologies, but infectious/inflammatory disease, trauma, and neoplastic and other unusual causes may also be responsible. Typical imaging features of the more common multifocal white matter disorders are outlined, and the rarer causes are discussed briefly. An approach to imaging differential diagnosis is given, with emphasis on the differences between white matter ischemic lesions and multiple sclerosis.

Magnetic resonance imaging and computed tomography of cerebral vascular disease.

Magnetic resonance imaging has emerged as the primary modality in detection and characterization of cerebrovascular lesions. New applications of existing spin-echo and gradient-recalled echo techniques are described. Functional imaging techniques ranging from the characterization of macroscopic proton motion (diffusion-weighted MR imaging), rapid imaging of intravascular contrast transit times (perfusion MR imaging), fast-flow mapping (MR angiography), and in vivo metabolic assessment (MR spectroscopy) are discussed. CT scanning remains important as an initial screening examination, in identifying acute hemorrhage, and in demonstrating blood flow.

Three-dimensional time-of-flight MR angiography in the evaluation of cerebral aneurysms.

We review our preliminary experience with the use of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography (MRA) in the assessment of intra- and extracranial aneurysms. Six patients were examined: Five had intracranial aneurysms and one had a cervical carotid pseudoaneurysm. A 3D rephased gradient recalled echo pulse sequence and maximum intensity projection (MIP) reconstruction algorithm were used. Magnetic resonance angiography, spin echo MR, and conventional angiography were retrospectively reviewed with specific regard to individual vessel visualization, aneurysm depiction, and presence of artifact related to acquisition techniques or MIP reconstruction. All aneurysms were detected on MRA, and anatomical correlation with conventional angiography was excellent. Significant problems included loss of visualization of small vessels, intraluminal signal loss in large vessels, subacute thrombus simulating flow on MIP reconstructions, and limited projections obtainable with MIP techniques. Adequate MRA assessment of aneurysms can be obtained using a combination of T1-weighted spin echo images and 3D TOF MRA. Review of all components of the MRA is required. MRA may be useful in screening asymptomatic patients for intracranial aneurysms as well as in the follow-up of patients treated with balloon occlusion.

Aortic arch interruption associated with ruptured cerebral aneurysm.

The authors present a case of aortic arch interruption in an adult, an anomaly that was discovered coincidentally during angiography for ruptured cerebral aneurysm. The presentation in adulthood with rupture of the aneurysm and the successful surgical treatment of both abnormalities are unusual.

Trigeminal neuropathy: Gd-DTPA enhanced MR imaging.

A review of 17 patients with Gd-DTPA enhancing lesions of the trigeminal nerve (6 patients with benign tumors, 4 with inflammatory disease, 7 with malignant tumors) was conducted to determine if contrast enhanced MR imaging is superior to nonenhanced imaging and to identify imaging characteristics that aid in separating benign and malignant disease. Contrast enhanced imaging appears to be superior to nonenhanced imaging in patients with intrinsic fifth nerve lesions. Malignant lesions are suggested by enlarged, enhancing fifth nerves with irregular margins and benign lesions by minimal or no enlargement with smooth margins. Overlap of imaging findings between benign and malignant disease strongly suggests that follow-up imaging and clinical findings are of utmost importance. Gadolinium-enhanced MR imaging of the fifth nerve is recommended in patients with trigeminal sensory or motor deficits as well as those with atypical trigeminal neuralgia.

Recent advances in MR imaging/spectroscopy of cerebral ischemia.

Recent advances in high-resolution MR imaging and multinuclear spectroscopy have stimulated studies of the functional relationships between tissue hypoperfusion, cellular energy depletion, and brain edema associated with cerebral ischemia. The very slow (microns/sec) random translational motion of water protons in various brain tissues and intracranial fluid compartments can now be assessed with MR diffusion imaging. More slowly diffusing protons in ischemic tissues can be differentiated from normal parenchyma, CSF, and flowing blood, enabling the detection and localization of ischemic regions within minutes of the onset of stroke. Perfusion imaging "snapshots," obtained in as little as 25 msec with echoplanar MR methods, permit the evaluation of tissue washin/washout kinetics of contrast agents in the microvasculature, and thus the quantification of brain perfusion on a regional basis. Also, delineation of major intra- and extracranial arterial and venous structures with MR angiography, acquired with two- or three-dimensional Fourier transformation techniques, has enabled accurate noninvasive assessments of vascular occlusive disease. Finally, improvements in MR spectroscopic techniques have facilitated investigations of metabolic regulation and bioenergetics in experimental animal models of cerebral ischemia, as well as in stroke patients. Combined MR imaging and spectroscopy will likely play an important role in differentiating reversibly from irreversibly ischemic brain tissues and in the investigation of various neuroprotective pharmaceuticals.