Showing papers in "American Journal of Neuroradiology in 1998"

MR volumetric analysis of the human entorhinal, perirhinal, and temporopolar cortices.

Abstract: PURPOSE Our purpose was to investigate the normal volumes of the human entorhinal, perirhinal, and temporopolar cortices on MR imaging studies using a customized program. METHODS We designed a protocol in which the volumes of the entorhinal, perirhinal, and temporopolar cortices were determined from coronal MR images using anatomic landmarks defined on the basis of cytoarchitectonic analyses of 49 autopsy cases. MR volumetry of these cortical areas was performed in 52 healthy volunteers. RESULTS The overall mean volumes were 1768 +/- 328 mm3/1558 +/- 341 mm3 (right/left) for the entorhinal cortex, 2512 +/- 672 mm3/2572 +/- 666 mm3 for the perirhinal cortex, and 2960 +/- 623 mm3/3091 +/- 636 mm3 for the temporopolar cortex. The right entorhinal cortex was 12% larger than the left. The volume of the temporopolar cortex was reduced bilaterally by 13% in the older age group compared with younger subjects, while the volumes of the entorhinal and perirhinal cortices were unaffected by age. There were no differences between men and women in the volumes of any of the three cortices. CONCLUSION Our method provides a tool by which to measure volumes of the entorhinal, perirhinal, and temporopolar cortices on coronal MR images.

Clinical experience with diffusion-weighted MR in patients with acute stroke.

Abstract: PURPOSE Our purpose was to evaluate the clinical efficacy, sensitivity, and specificity of echo-planar diffusion-weighted MR imaging in patients with acute infarction. METHODS We retrospectively analyzed 194 cases of acute ischemic stroke diagnosed clinically within 24 hours of onset and studied with echo-planar diffusion-weighted MR imaging. Examinations were considered to be positive for infarction when an increase in signal was noted on images acquired at a high b value but absent on images with a low b value. A final clinical diagnosis of acute stroke was used as the standard of reference. A subset of 48 patients scanned within 6 hours was also analyzed. RESULTS Diffusion-weighted MR imaging studies were positive in 133 of 151 cases of infarction (88% sensitivity) and negative in 41 of 43 cases with no infarction (95% specificity). Two cases identified as positive on diffusion-weighted images had nonischemic diagnoses (1.5% false-positive rate). Diffusion-weighted imaging had a positive predictive value of 98.5% and a negative predictive value of 69.5%. Use of T2-weighted sequences as well as diffusion-weighted imaging produced no false-positive findings. Of the negative scans, 69.5% corresponded to transient ischemic attacks or infarcts (mostly small brain stem infarcts). When only cases scanned within 6 hours of onset were considered, the sensitivity rose to 94% and the specificity to 100%. CONCLUSION Despite bias due to dependence between diffusion-weighted imaging and the final diagnosis, this analysis suggests high sensitivity and specificity for echo-planar diffusion-weighted imaging in the diagnosis of acute cerebral infarction, although negative scans did not rule out an ischemic pathogenesis.

Prediction of neuromotor outcome in perinatal asphyxia: evaluation of MR scoring systems.

Abstract: PURPOSE We developed a scoring system for the assessment of perinatal asphyxia as depicted on MR images. METHODS Four scoring systems were derived to evaluate MR images obtained in asphyxiated neonates: the basal ganglia (BG) score, the watershed (W) score, the combined basal ganglia/watershed (BG/W) score, and the sum of the BG and W scores, the summation (S) score. In addition, three MR sequences, T1-weighted, first-echo T2-weighted, and second-echo T2-weighted, were assessed for each patient for each scoring system. Neuromotor examinations were performed at ages 3 and 12 months, and cognitive development was tested at age 12 months. Statistical analysis was then performed to test the relationship between the MR scores and the outcome scores. RESULTS The BG/W score, obtained with the first-echo T2-weighted sequence, was the most useful overall score for predicting neuromotor outcome at 3 and 12 months and cognitive outcome at 12 months. T1-weighted and first-echo T2-weighted sequences showed a stronger association with outcome in patients imaged during the first postnatal week, whereas second-echo T2-weighted sequences showed a stronger association with outcome in patients imaged during the second postnatal week. CONCLUSION It appears that, with the use of the BG/W score, MR imaging discriminates accurately between patients with good and poor neuromotor and cognitive outcome at 3 and 12 months. In terms of our scoring systems, the first-echo T2-weighted sequence appears to discriminate best between patients with good and poor 3- and 12-month outcomes. Proper use of the imaging sequences and scoring systems described in this article can increase the knowledge base upon which treatment decisions are made in asphyxiated neonates.

Diffusion-weighted MR imaging in hypertensive encephalopathy: clues to pathogenesis.

Abstract: PURPOSE Hypertensive encephalopathy, a complex of cerebral disorders, including headache, seizures, visual disturbances, and other neurologic manifestations, is associated with a variety of conditions in which blood pressure rises acutely. It has been ascribed to either exuberant vasospasm with ischemia/infarction or breakthrough of autoregulation with interstitial edema. Diffusion-weighted MR imaging may be used to determine whether the edema in hypertensive encephalopathy is cytotoxic or vasogenic in origin. METHODS Diffusion-weighted imaging was performed using the double line scan diffusion imaging technique on a 1.5-T MR system. Seven patients with hypertensive encephalopathy were imaged within 1 day of the onset of their symptoms. Apparent diffusion coefficient maps as well as low and high b-factor images were acquired. The two-tailed paired Student9s t-test was used to compare the apparent diffusion coefficients in edematous brain regions with those of normal white matter. RESULTS In all cases the apparent diffusion coefficient maps of the patients with hypertensive encephalopathy showed increased signal in regions corresponding to increased T2 signal on standard T2-weighted (low b-factor) images. Quantitative apparent diffusion coefficients in regions of abnormal T2 signal were 1.36 +/- 0.14 microm2/ms, compared with 0.80 +/- 0.05 microm2/ms in normal white matter. Diffusion-weighted (high b-factor) T2-weighted images did not show abnormal signal. CONCLUSION Diffusion-weighted MR imaging shows that the edema in hypertensive encephalopathy is of vasogenic origin and does not represent ischemia or infarction. This finding may have therapeutic implications.

Differentiating recurrent tumor from radiation necrosis: time for re-evaluation of positron emission tomography?

Abstract: Our purpose was to evaluate the ability of FDG PET to differentiate recurrent tumor from posttherapy radiation necrosis. METHODS: MR images, PET scans, and medical records of 84 consecutive patients with a history of a treated intracranial neoplasm were evaluated retrospectively. In all patients, recurrent tumor or radiation necrosis was suggested by clinical or MR findings. Metabolic activity of the PET abnormality was compared qualitatively with normal contralateral gray and white matter. RESULTS: PET findings were confirmed histologically in 31 patients. With contralateral white matter as the standard of comparison, the PET scan sensitivity and specificity were found to be 86% and 22%, respectively. With contralateral gray matter as the reference standard, the sensitivity and specificity became 73% and 56%, respectively. Overall, nearly one third of the patients would have been treated inappropriately in either scheme had the PET scan been the sole determinant of therapy. CONCLUSION: Our data suggest that the ability of FDG PET to differentiate recurrent tumor from radiation necrosis is limited. Both false-positive and false-negative PET scan results contributed to unacceptably low sensitivity and specificity values.

Patterns of lesion development in multiple sclerosis: longitudinal observations with T1-weighted spin-echo and magnetization transfer MR.

Abstract: PURPOSE We evaluated the appearance of enhancing multiple sclerosis (MS) lesions on unenhanced T1-weighted MR images and the natural course of enhancing MS lesions on serial unenhanced T1-weighted and magnetization transfer (MT) MR images. METHODS One hundred twenty-six enhancing lesions were followed up monthly for 6 to 12 months to determine their signal intensity on unenhanced T1-weighted and MT MR images. At the time of initial enhancement, the size of the lesion and the contrast ratio of enhancement were calculated for each enhancing lesion. During follow-up, the contrast ratio on the corresponding unenhanced T1-weighted image was measured, and an MT ratio (MTR) was calculated. RESULTS Twenty-five enhancing lesions (20%) appeared isointense and 101 lesions (80%) appeared hypointense relative to normal-appearing white matter on unenhanced T1-weighted images. During 6 months of follow-up, four MR patterns of active lesions were detected: initially isointense lesions remained isointense (15%); initially isointense lesions became hypointense (5%, most of which reenhanced); initially hypointense lesions became isointense (44%); and initially hypointense lesions remained hypointense (36%). MTR was significantly lower for hypointense lesions as compared with isointense lesions at the time of initial enhancement. For lesions that changed from hypointense to isointense, MTR increased significantly during 6 months of follow-up. Multiple regression analysis showed that strongly decreased MTR at the time of initial enhancement and enhancement duration of more than one scan were predictive of a hypointense appearance on unenhanced T1-weighted images at 6 months9 follow-up. Ring enhancement was found to be the only (weak) predictor of persistently hypointense signal intensity. CONCLUSION Most enhancing lesions appear slightly to significantly hypointense on unenhanced T1-weighted images. Although most hypointensities are reversible, only those lesions that fail to recover on unenhanced T1-weighted and MT images may have considerable irreversible structural changes.

CSF spaces in idiopathic normal pressure hydrocephalus : Morphology and volumetry

Abstract: PURPOSE Idiopathic normal pressure hydrocephalus (NPH) is an important cause of dementia in the elderly; however, idiopathic NPH is often difficult to differentiate from normal aging and vascular dementias in which brain atrophy with ventricular dilatation (hydrocephalus ex vacuo or central atrophy) is present. To elucidate the distinctive features of the distribution of CSF in idiopathic NPH, we used MR imaging to investigate the morphologic features and volume of the CSF space in patients with idiopathic NPH compared with those with other dementias. METHODS We assessed the size of four CSF compartments (the ventricle, basal cistern, sylvian space, and suprasylvian subarachnoid space) in 11 shunt-responsive patients with idiopathic NPH by semiquantitative and volumetric analyses of coronal T1-weighted MR images. The results were compared with those in 11 age- and sex-matched patients with Alzheimer disease and in 11 patients with vascular dementia. RESULTS In patients with idiopathic NPH, the CSF volume was significantly increased in the ventricles and decreased in the superior convexity and medial subarachnoid spaces as compared with patients with other dementias. The sylvian CSF volume in patients with idiopathic NPH was significantly greater than in patients with Alzheimer disease. The volume of the basal cistern was comparable among the three groups. In several patients with idiopathic NPH, focally dilated sulci were observed over the convexity or medial surface of the hemisphere. CONCLUSION Our results indicate that findings of enlarged basal cisterns and sylvian fissures and of focally dilated sulci support, rather than exclude, the diagnosis of shunt-responsive idiopathic NPH and suggest that this condition is caused by a suprasylvian subarachnoid block.

Follow-up study after intracranial percutaneous transluminal cerebral balloon angioplasty.

Abstract: BACKGROUND AND PURPOSE Our objective was to find the specific angiographic characteristics of atherosclerotic lesions that indicate suitability for intracranial percutaneous transluminal cerebral balloon angioplasty (PTCBA). METHODS Forty-two clinically symptomatic patients with 42 hemodynamically significant intracranial lesions (>70% stenosis) were treated by PTCBA between January 1992 and May 1996. Before treatment, the patients were assigned to three groups according to the angiographic characteristics of the lesions, as follows: type A, short (5 mm or less in length) concentric or moderately eccentric lesions less than totally occlusive; type B, tubular (5 to 10 mm in length), extremely eccentric or totally occluded lesions, less than 3 months old; and type C, diffuse (more than 10 mm in length), extremely angulated (>90 degrees) lesions with excessive tortuosity of the proximal segment, or totally occluded lesions, and 3 months old or older. The patients were followed up for a period of 1 month to 6 years to compare the results of PTCBA treatment among the three groups. Primary end points were death, stroke, or bypass surgery. RESULTS The clinical success rates for the type A, B, and C groups were 92%, 86%, and 33%, respectively. Cumulative risks of fatal or nonfatal ischemic stroke or ipsilateral bypass surgery in type A, B, and C groups were 8%, 26%, and 87%, respectively. The cumulative risk of 8% among patients in the type A group appeared to be smaller than in studies reported in the literature. CONCLUSION PTCBA for intracranial simple (type A) lesions yields a favorable clinical outcome for symptomatic patients.

The Size of Lymph Nodes in the Neck on Sonograms as a Radiologic Criterion for Metastasis: How Reliable Is It?

Abstract: PURPOSE A definition of cut-off points for nodal size is essential to determine whether cervical lymph nodes are metastatic or not Because the currently used size criteria are defined for random populations of patients with head and neck cancer, we set out to study whether these criteria are optimal for patients without palpable metastases in different levels of the neck We defined optimal size criteria for sonography by calculating the sensitivity and specificity of different size cut-off points METHODS We compared the sensitivity and specificity of different size cut-off points as measured on sonograms for various levels in the neck in a series of 117 patients with and 131 patients without palpable neck metastases RESULTS A minimum axial diameter of 7 mm for level II and 6 mm for the rest of the neck revealed the optimal compromise between sensitivity and specificity in necks without palpable metastases For all necks together (with and without palpable metastases), the criteria were 1 to 2 mm larger CONCLUSION Our findings indicate that the current sonographic size criteria used for random patient populations are not optimal for necks without palpable metastases, nor can the same cut-off points be used for all levels in the neck

Imaging patterns of neonatal hypoglycemia.

Abstract: PURPOSE Our purpose was to report the patterns of injury observed in five patients who suffered brain damage consequent to neonatal hypoglycemia. METHODS The imaging studies and clinical records of five patients with brain damage caused by neonatal hypoglycemia were reviewed retrospectively. Patterns of injury were compared with those described in the literature and those seen in neonatal hypoxic-ischemic injury. RESULTS Diffuse cortical and subcortical white matter damage was seen, with the parietal and occipital lobes affected most severely. Globus pallidus injury was present in one patient who had the most severe cortical injury. CONCLUSION We found a specific pattern of injury that correlates well with the sparse pathologic and imaging reports on neonatal hypoglycemia. We speculate that the patterns of damage are the result of regional hypoperfusion and excitatory toxicity with cell-type-specific injury.

Imaging of the peripheral nervous system: evaluation of peripheral neuropathy and plexopathy.

Abstract: Over the past decade, technical advances in MR imaging of the CNS have resulted in improved diagnosis and evaluation of encephalopathy, myelopathy, and cranial neuropathy. Parallel advances in imaging of the peripheral nervous system have not occurred, and the evaluation of peripheral neuropathy or plexopathy has relied principally on the patient’s clinical history and the neurologic examination, with relatively few requests for imaging studies. Routine CT and MR imaging have been useful to exclude mass lesions in the vicinity of a peripheral nerve, but there has not been an effective method for directly imaging the nerve (1, 2). Also, in the last decade, neurologic and orthopedic surgeons have become skilled in newer, more sophisticated microsurgical procedures to repair damaged nerves, and many of these surgeons have chosen to specialize in peripheral nerve treatment. For these reasons, noninvasive techniques are needed that improve the diagnostic accuracy of peripheral neuropathy and facilitate preoperative planning when surgery is contemplated. Currently, electrophysiological studies are widely used and have high sensitivity for detecting a conduction abnormality; however, they lack specificity and cannot display the anatomic detail needed for precise localization and treatment planning. High-resolution imaging of peripheral nerves potentially overcomes these limitations and, consequently, recent interest has focused on improved MR imaging techniques that use phased-array radiofrequency (RF) coil technology and rapid acquisition of imaging data (3–5).

Hemichorea-hemiballism: an explanation for MR signal changes.

Abstract: PURPOSE Some cases of hemichorea-hemiballism (HCHB) are associated with a hyperintense putamen on T1-weighted MR images, the cause of which remains unclear. Our purpose was to determine the cause and significance of these MR signal changes. METHODS We analyzed the clinical and neuroimaging findings in 10 patients with HCHB, focusing on locations of the hyperintense lesions on T1-weighted images, comparing them with those on CT scans, and evaluating their changes after years of follow-up. A biopsy was performed in one patient. RESULTS Seven patients had hyperglycemia and two had cortical infarcts. HCHB recurred in four patients. A hyperintense putamen preceded the occurrence of HCHB in two patients. T1-weighted MR images revealed hyperintense lesions limited to the ventral striatum in six patients. Hyperintense lesions extended to the level of the midbrain in one patient and persisted for as long as 6 years in another patient. T2-weighted MR images revealed slit-shaped cystic lesions in the lateral part of the putamina 2 to 6 years after the onset of symptoms in two patients. A biopsy specimen from the hyperintense putamen in one patient revealed a fragment of gliotic brain tissue with abundant gemistocytes. Proton MR spectroscopy of the specimen showed an increase in lactic acid, acetate, and lipids, and a decrease in N-acetylaspartate and creatine, suggesting the presence of pronounced energy depletion and neuronal dysfunction. CONCLUSION Gemistocytes are sufficient to explain the shortening of T1 relaxation time. Our investigation suggests that neurons in the ventral striatum and striatonigral pathway may play a critical role in generating ballism.

Neuroradiologic Findings in Children with Mitochondrial Disorders

Abstract: PURPOSE: We report the neuroradiologic findings in 25 children with various mitochondrial diseases. METHODS: Twenty-two children with a mitochondrial disorder had MR imaging of the brain and three children had CT studies. In all cases, the diagnosis was based on examination of muscle morphology, analysis of oxygen consumption and respiratory chain enzyme activity in isolated muscle mitochondria, and analysis of rearrangements of the mitochondrial DNA. RESULTS: Fifteen patients were found to have the classical syndromes of mitochondrial diseases. Four children had Kearns-Sayre syndrome, but only one had the typical neuroradiologic findings of basal ganglia and brain stem lesions, T2 hyperintensity of the cerebral white matter, and cerebellar atrophy; the others had nonspecific or normal findings. Eight patients had Leigh syndrome, and all showed changes in the putamina. Involvement of the caudate nuclei, globus pallidi, thalami, and brain stem was common, and diffuse supratentorial white matter T2 hyperintensity was seen in two of these patients. Three patients had mitochondrial encephalopathy with lactic acidosis and strokelike episodes (MELAS), with infarctlike lesions that did not correspond to the vascular territories. Ten children with complex I or IV deficiencies and abnormal muscle morphology had nonspecific imaging findings, such as atrophy and abnormal or delayed myelination. One patient with combined complex I and IV deficiency had extensive white matter changes. None of the patients with clinical encephalopathy had normal findings. CONCLUSION: MR imaging is helpful in the diagnosis of the classical mitochondrial diseases; however, nonspecific findings are common.

Thromboembolic Events Associated with the Treatment of Cerebral Aneurysms with Guglielmi Detachable Coils

Abstract: BACKGROUND AND PURPOSE: The purpose of this study was to document the prevalence, radiologic appearance, and treatment of thromboembolic events related to GDC embolization of cerebral aneurysms. METHODS: The clinical and radiologic records of all patients undergoing GDC treatment of intracranial aneurysms at our institution were reviewed. All cases in which unexpected complications occurred were selected. Those complications related to presumed thromboembolic events were analyzed. RESULTS: Of 59 patients (60 aneurysms) treated with GDCs, 17 (28%) experienced thromboembolic events. Seven patients had transient ischemic attacks and 10 had strokes. In 10 patients, the deficits occurred during or immediately after the procedure; in the rest, the complications were delayed. In six patients, all radiologic investigations were negative for infarction and in seven patients, CT scans showed new ischemic lesions. In four patients, MR imaging alone showed infarcts, and in four of nine patients who underwent subsequent angiography, acute ischemic findings were demonstrated. Eight patients were treated with volume expansion, eight with full heparinization, and one patient underwent intraarterial thrombolysis. Clinical outcome was excellent or good in 14 of 17 patients, with only three patients (5%) incurring permanent neurologic deficits. CONCLUSION: Thromboembolic events related to GDC treatment may be more common than has been reported in the literature. In our experience, this rate was 28%, with persisting deficits in 5%. These events can occur after uncomplicated procedures and may be unaccompanied by radiologic findings. Clinical outcome is usually favorable.

Cisplatin neurotoxicity presenting as reversible posterior leukoencephalopathy syndrome.

Abstract: Visual disturbance, hypertension, convulsions, and unconsciousness developed in a 70-year-old man after cisplatin chemotherapy and upper-limb amputation for osteosarcoma. MR imaging revealed bilateral reversible abnormalities in the occipital, parietal, and frontal white matter. Clinical and neuroradiologic features corresponded to reversible posterior leukoencephalopathy syndrome (RPLS), which some immunosuppressive and chemotherapeutic drugs have been reported to trigger. Cisplatin may be among these drugs. Our patient also had hypomagnesemia, which may have figured in the pathophysiology.

Dementia resulting from dural arteriovenous fistulas: the pathologic findings of venous hypertensive encephalopathy.

Abstract: PURPOSE: Dural arteriovenous fistulas (DAVFs) are acquired arteriovenous shunts located within the dura. The highly variable natural history and symptomatology of DAVFs range from subjective bruit to intracranial hemorrhage and are related to the lesion's pattern of venous drainage and its effect on the drainage of adjacent brain. We examined the prevalence and features of DAVFs in patients with progressive dementia or encephalopathy. METHODS: The records and radiologic studies of 40 consecutive patients with DAVFs treated at our institution were reviewed. RESULTS: Five (12.5%) of 40 consecutive patients with DAVFs had encephalopathy or dementia. In each patient, high flow through the arteriovenous shunt combined with venous outflow obstruction caused impairment of cerebral venous drainage. Hemodynamically, the result was widespread venous hypertension causing diffuse ischemia and progressive dysfunction of brain parenchyma. Results of CT or MR imaging revealed abnormalities in each patient, reflecting the impaired parenchymal venous drainage. Pathologic findings in one patient confirmed the mechanism of cerebral dysfunction as venous hypertension. The hemodynamic mechanism and resulting abnormality appeared identical to that seen in progressive chronic myelopathy resulting from a spinal DAVF (Foix-Alajouanine syndrome). Remission of cognitive symptoms occurred in each patient after embolization. CONCLUSION: Venous hypertensive encephalopathy resulting from a DAVF should be considered a potentially reversible cause of vascular dementia in patients with progressive cognitive deficits.

Differential aging of the human striatum: a prospective MR imaging study.

Abstract: Background and purpose Advancing age is associated with declines in motor function; understanding age-related changes in the basal ganglia, therefore, is imperative for comprehension of such functional changes. The purpose of this study was to examine the age, sex, and hemispheric differences in volume of the caudate nucleus, the putamen, and the globus pallidus. Methods In a sample of 148 healthy right-handed adults (18-77 years old) with no evidence of age-related motor disorders, we estimated the volume of the head of the caudate nucleus, the putamen, and the globus pallidus from MR images. Results The analyses revealed bilateral age-related shrinkage of the head of the caudate nucleus and the putamen in both sexes. In men, the age-related shrinkage of the caudate was stronger on the left, whereas, in women, the opposite trend was evident. In both sexes, age-related shrinkage of the right putamen was greater than of its left counterpart. The mild bilateral age-related shrinkage of the globus pallidus was observed only in men. In both sexes, we observed significant rightward asymmetry in the putamen, significant leftward asymmetry in the caudate, and no asymmetry in the globus pallidus. Conclusions Bilateral age-related shrinkage of the neostriatum is found in healthy adults. The shrinkage of the globus pallidus is less pronounced and may be restricted to men only.

Evaluation of High-Resolution CT and MR Cisternography in the Diagnosis of Cerebrospinal Fluid Fistula

Abstract: PURPOSE: We undertook this study to determine the accuracy of MR cisternography and plain high-resolution CT as a noninvasive alternative to CT cisternography in the diagnosis of CSF fistula in patients with clinically suspected CSF rhinorrhea. METHODS: Forty-five consecutive patients with clinically suspected CSF rhinorrhea were examined prospectively for CSF fistula with MR cisternography and plain high-resolution CT. Twenty-one patients also underwent CT cisternography. The MR imaging technique included 3-mm thin-section T1-weighted coronal sequences and fast spin-echo T2-weighted coronal, axial, and sagittal sequences in the supine position. The plain high-resolution CT study included 3-mm and sometimes 1- to 1.5-mm thin coronal sections in the prone position. Similar sequences were used after injecting nonionic contrast material intrathecally via lumbar puncture for the CT cisternographic study. The plain high-resolution CT and MR cisternographic studies were compared with results of CT cisternography; surgical findings were used as the standard of reference. RESULTS: Plain high-resolution CT successfully depicted the presence or absence of CSF fistula in 42 of 45 patients, whereas MR cisternography was correct in 40 patients. MR cisternography or plain high-resolution CT correctly showed the site(s) of CSF fistula leakage in 36 of the 38 cases proved surgically. The combined techniques also correctly indicated the absence of CSF leakage in seven cases, six of which were confirmed at CT cisternography. Both MR cisternography and high-resolution CT failed to definitively locate the CSF fistula in two patients. High-resolution CT was accurate in 93% of patients, whereas MR cisternography was accurate in 89% of patients. The combination of high-resolution CT and MR cisternography was accurate in 96% of patients. CONCLUSION: In the presence of clinically diagnosed CSF leakage, the combination of MR cisternography and plain high-resolution CT is highly accurate in locating the site and extent of CSF fistula and should be considered a viable noninvasive alternative to CT cisternography.

MR of hereditary hemorrhagic telangiectasia: prevalence and spectrum of cerebrovascular malformations.

Abstract: PURPOSE: Our goal was to describe the prevalence and types of cerebral vascular malformations (CVMs) seen with MR imaging in patients with hereditary hemorrhagic telangiectasia (HHT). METHODS: We reviewed retrospectively the brain MR images of 184 consecutive patients with HHT. Catheter angiography was performed in 17 patients with CVMs detected on MR images. RESULTS: MR imaging revealed 63 CVMs in 42 patients. Classic arteriovenous malformations (n = 10) had a conspicuous network of vessels with flow voids and enlarged adjacent pial vessels. Apparent venous malformations (n = 5) were best seen after administration of contrast material as a prominent vessel coursing through normal brain parenchyma. Indeterminate vascular malformations (n = 48) had a spectrum of appearances characterized by variable combinations of heterogeneous signal intensity, enhancement, or hemosiderin. Angiography in 17 patients revealed 47 CVMs. Forty-six were arteriovenous malformations (AVMs), including 25 CVMs not seen with MR imaging and 21 CVMs that by MR criteria included 8 AVMs and 13 indeterminate vascular malformations. Angiography confirmed 1 venous malformation seen with MR imaging but failed to detect 3 indeterminate lesions revealed by MR imaging. CONCLUSION: MR imaging of a large cohort of consecutive patients with HHT revealed a CVM prevalence of 23% (42/184). Most CVMs (48/63) have an atypical appearance for vascular malformations on MR images. Angiographic correlation suggests that MR imaging underestimates the prevalence of CVMs and that the majority of indeterminate CVMs, despite their variable MR appearance, are AVMs.

Assessment of cerebral perfusion and arterial anatomy in hyperacute stroke with three-dimensional functional CT: early clinical results.

Abstract: PURPOSE Our purpose was to determine the clinical feasibility of quantitative three-dimensional functional CT in patients with hyperacute stroke. METHODS Twenty-two patients who underwent clinically indicated CT angiography were studied: nine patients had no stroke, eight had mature stroke, and five had hyperacute stroke (less than 3 hours since ictus). Maps were obtained of perfused cerebral blood volume (PBV), and CT angiograms were generated by using standard techniques. RESULTS Normal PBV values (mean +/- SEM) were 4.6 +/- 0.15% in the gray matter, 1.75 +/- 0.09% in the white matter, 2.91 +/- 0.20% in the cerebellum, 3.18 +/- 0.10% in the caudate, 2.84 +/- 0.23% in the putamen, 2.92 +/- 0.29% in the thalamus, and 1.66 +/- 0.03% in the brain stem. For patients with mature stroke, ischemic changes were visible on noncontrast, contrast-enhanced, and PBV scans. In patients with hyperacute stroke, ischemic changes were either absent or subtle before contrast administration, but became apparent on contrast-enhanced scans. Quantitative PBV maps confirmed reduced regional perfusion. CT angiograms in the hyperacute group showed occlusion of vessels in locations appropriate to the PBV deficits seen. CONCLUSION Quantitative three-dimensional functional CT is feasible for patients with hyperacute stroke. It is performed by using helical CT techniques, and yields measures of cerebrovascular physiological function, which are useful in this patient population.

Clinical utility of positron emission tomography with 18F-fluorodeoxyglucose in detecting residual/recurrent squamous cell carcinoma of the head and neck.

Abstract: PURPOSE: The use of positron emission tomography with 18 F-fluorodeoxyglucose (FDGPET) to detect residual/recurrent squamous cell carcinoma of the head and neck has been tested only in small groups of patients. Our purpose, therefore, was to evaluate the ability of this technique to detect the presence of tumor at both primary and nodal sites in a large cohort of patients. METHODS: All patients referred for PET scanning over a 2.5-year period with a question of residual or recurrent squamous cell carcinoma of the head and neck were identified. Thirty-five of 44 patients had sufficient follow-up to be meaningful to our analysis (range, 6 ‐33 months). PET scans were interpreted visually with knowledge of the clinical history and correlative anatomic imaging findings. Detection of disease involving primary and nodal sites was assessed independently. Additionally, because each patient had been referred in an attempt to resolve a specific clinical problem, the usefulness of PET in accurately addressing these questions was assessed. RESULTS: At the primary site, sensitivity and specificity for residual/recurrent disease were 100% and 64%, respectively; for nodal disease, sensitivity and specificity were 93% and 77%, respectively. In helping to resolve the clinical question being asked, the positive predictive value of the test result was 65% and the negative predictive value was 91%. CONCLUSION: The high sensitivity and negative predictive value of PET scanning in our cohort of patients suggest an important role for this technique in the care of patients with suspected residual/recurrent head and neck carcinoma. The lower figures obtained for specificity and positive predictive value reflect the fact that increased FDG uptake may be due to either tumor or inflammation.

Functional MR of frontal lobe activation: comparison with Wada language results.

Abstract: PURPOSE Our purpose was to determine the utility of functional MR imaging in conjunction with a word-generation paradigm in the assessment of language lateralization. METHODS Functional MR imaging and Wada testing for language lateralization was performed in patients with complex partial seizures during the performance of word-generation tasks. A language lateralization quotient was calculated from the number of activated pixels in the right and left hemispheres. A language laterality score was derived from the Wada results as the percentage of correct responses during right internal carotid artery injection minus the percentage of correct responses during left internal carotid injection. A correlation coefficient between the functional MR imaging results and the Wada language laterality scores was calculated. RESULTS In 13 patients, hemispheric dominance based on Wada testing was confirmed by functional MR imaging during silent word generation. The Wada laterality scores varied from 100 to -100 and the functional MR imaging scores varied from 100 to -10. The language lateralization scores determined by functional MR imaging correlated significantly with the language lateralization scores derived from Wada testing. CONCLUSION Functional MR imaging performed during word generation is an accurate method for lateralizing language function in patients with complex partial epilepsy.

Perineural Spread of Head and Neck Tumors: How Accurate Is MR Imaging?

Abstract: PURPOSE: Our aim was to determine the precision of MR imaging evaluation of perineural spread of head and neck tumors. METHODS: Nineteen patients had complete extirpation of head and neck tumors (10 squamous cell carcinomas, four adenoid cystic carcinomas, one poorly differentiated carcinoma, one salivary duct carcinoma, one mucoepidermoid carcinoma, one chordoma, and one meningioma) with histologic confirmation of perineural spread. Findings at presurgical contrast-enhanced MR imaging were compared with findings at pathologic examination. RESULTS: The sensitivity of MR imaging for detection of perineural spread was 95%; however, the sensitivity for mapping the entire extent of perineural spread fell to 63%. CONCLUSION: MR imaging may fail to depict microscopic foci of perineural tumor infiltration, leading to underestimation of the extent of perineural spread. Nevertheless, with careful analysis of foraminal architecture and MR enhancement patterns, one can reliably identify the presence if not the extent of perineural spread.

Proton MR spectroscopic findings correspond to neuropsychological function in traumatic brain injury.

Abstract: BACKGROUND AND PURPOSE: Traumatic brain injury (TBI) causes substantial irreversible damage to neurons. Our aim was to investigate whether proton MR spectroscopic measures of diffuse cellular integrity were related to neuropsychological dysfunction after TBI. METHODS: Twelve patients with TBI (mean, 53 6 23 days postinjury) and 14 control subjects were included in the study using paired MR spectroscopy and neuropsychological assessment. N-acetylaspartate (NAA), creatine, and choline were measured in normal-appearing occipitoparietal white and occipital gray matter using short-echo quantitative spectroscopy. A composite measure of neuropsychological function was calculated from z-scored individual tests probing the major functional domains commonly impaired after head trauma. RESULTS: Patients with TBI displayed reduced NAA in white matter and elevated choline in gray matter, suggestive of neuronal injury and inflammation, respectively. NAA and creatine in white and gray matter were significantly associated with composite neuropsychological function and many individual neuropsychological tests. Gray matter choline, although abnormal, was not related to neuropsychological function. CONCLUSION: The concordance between neurometabolic levels and behavioral function supports the hypothesis that diffuse axonal injury is an important contributor to brain dysfunction after TBI. Traumatic brain injury (TBI) affects approximately 2 million people in the United States each year, and many of these individuals sustain subsequent longterm disability. Although CT and MR imaging provide anatomic information relevant for clinical management, quantitative measurements of lesion severity from these imaging techniques are only weakly related to neuropsychological dysfunction or gross outcome (1‐3). This difficulty likely stems from the fact that structural imaging techniques do not resolve the widespread cellular injury found in autopsy studies (4, 5).

Spontaneous intracranial hypotension: spinal MR findings

Abstract: We report three patients with spontaneous intracranial hypotension in whom spinal MR imaging revealed ventral extradural fluid collections that were centered at the cervicothoracic junction in two patients and extended throughout the entire spine in the third patient. These spinal fluid collections most likely resulted from the accumulation of CSF at the site of dural leakage. Knowledge of this association can be helpful in the selection of imaging studies to facilitate diagnosis and treatment.

Local intraarterial fibrinolysis of thromboemboli occurring during endovascular treatment of intracerebral aneurysm: a comparison of anatomic results and clinical outcome.

Abstract: PURPOSE: We describe our therapeutic strategy and correlate the anatomic results and clinical outcomes in patients who received immediate fibrinolytic therapy for thromboembolic complications occurring during endovascular treatment of an intracerebral aneurysm. METHODS: The medical records and angiographic examinations of 19 patients were reviewed. All endovascular procedures were performed with the patients under general anesthesia and fully heparinized. Thirteen patients received an intravenous bolus injection of aspirin. Thromboemboli occurred during catheterization or insertion of embolic material (Guglielmi detachable coils or mechanical detachable spirals) or in the first hours after the intervention. Clot distribution was within the MCA territory in 14 patients, the ACA in three patients, and the basilar trunk in two patients. A continuous intraarterial injection of urokinase was administered immediately, either superselectively distal to the thrombus or selectively within or closely proximal to the thrombus. In nine cases, chemical lysis was combined with mechanical clot fragmentation. Initial anatomic recanalization as well as clinical outcome at 3 months were evaluated. RESULTS: Ten patients showed complete recanalization and nine patients showed partial recanalization. Fourteen patients had a good clinical recovery. One patient was moderately disabled and two were severely disabled according to their scores on the Glasgcow outcome scale. Two patients died, one as a consequence of the preexisting subarachnoid hemorrhage and the other because of a large intracerebral hematoma that developed after fibrinolysis. Of the 14 patients with a good clinical outcome, nine exhibited complete recanalization and five partial recanalization. CONCLUSION: Pharmacological thrombolysis seems to be a safe and efficient therapy that facilitates the natural fibrinolytic process, increasing the rate of recanalization in thromboembolic events. Clot fragmentation and superselective drug infusion appear to improve the rate of recanalization. Complete recanalization increases the chance of a better clinical outcome; however, clinical outcome does not always correspond to recanalization and vice versa.

Power Doppler Sonography of Cervical Lymph Nodes in Patients with Head and Neck Cancer

Abstract: PURPOSE The purpose of this preliminary study was to evaluate the usefulness of power Doppler sonography in differentiating metastatic from nonmetastatic cervical lymph nodes in patients with cancer METHODS Histologically proved metastatic (n = 71) and nonmetastatic (n = 220) lymph nodes were examined with power Doppler sonography in 77 patients with head and neck cancer Power Doppler sonography was assessed for its ability to differentiate metastatic from nonmetastatic lymph nodes RESULTS Power Doppler sonography showed characteristic features of parenchymal blood flow signal in 59 (83%) of the 71 metastatic lymph nodes By contrast, only four (2%) of the 220 nonmetastatic nodes showed these power Doppler signals In addition, power Doppler sonography showed high levels of sensitivity (83%) and specificity (98%) in depicting metastatic lymph nodes, which were superior to the values (66% sensitivity and 92% specificity) obtained by applying size criteria (transverse to longitudinal ratio) However, a combination of the two criteria (parenchymal color signal and transverse to longitudinal ratio) improved diagnostic accuracy to 92% sensitivity and 100% specificity CONCLUSION Our preliminary findings suggest that the power Doppler criteria of no hilar flow, peripheral parenchymal nodal flow, and a transverse to longitudinal ratio of more than 065 together constitute a powerful tool for depicting metastatic lymph nodes in patients with cancer

Diagnosis of brain death using two-phase spiral CT.

Abstract: PURPOSE The purpose of this study was to determine the utility of spiral CT in the diagnosis of brain death METHODS Spiral CT was evaluated prospectively in 14 brain-dead patients and in 11 healthy subjects A two-phase protocol was used Twenty seconds after intravenous injection of a nonionic iodinized contrast medium, the CT table was drawn through the gantry at a rate of 10 mm/s while scanning was in progress The second scanning phase was started automatically a mean of 54 seconds later, using the same parameters Opacification or absence of opacification of carotid, vertebral, and basilar arteries and intracerebral veins was ascertained for each image in both phases The diagnosis of brain death was confirmed by elecroencephalography (n = 7), angiography (n = 5), or both (n = 2) Statistical analysis with the Fisher exact test enabled us to compare the brain-dead patients with the healthy control subjects RESULTS In brain death, the pericallosal and terminal arteries of the cortex did not opacify during the two phases of spiral CT, whereas the superficial temporal arteries were always visible The internal cerebral veins, the great cerebral vein, and the straight sinus did not opacify, whereas the superior ophthalmic veins were visible on both sides 13 times For each vessel type, specificity was 100% for nonvascular opacification criteria on the right and left sides CONCLUSION Two-phase spiral CT can demonstrate the absence of intracerebral blood flow in brain death

Middle cerebral artery variations: duplicated and accessory arteries.

Abstract: PURPOSE: Our goal was to analyze the anatomic similarity between the duplicated middle cerebral artery (MCA) and the accessory MCA and their relationship to the early branches of the MCA. METHODS: We reviewed stereoscopic angiograms of duplicated MCAs in four patients and accessory MCAs in four patients with reference to the origin, size, and cortical supply of these anomalous vessels, along with the presence of perforating arteries and the recurrent artery of Heubner (RAH). RESULTS: The duplicated MCAs supplied the cortical territory of the temporopolar and the anterior temporal and/or middle temporal arteries. The accessory MCAs supplied the cortical territory of the orbitofrontal and/or prefrontal arteries. The duplicated MCAs had perforating arteries in three of four cases and coexisted with the RAH in three of four cases, whereas the main MCA had perforating arteries in all four cases. The accessory MCA had perforating arteries in all four cases and coexisted with the RAH in three of four cases, whereas the main MCA had perforating arteries in one of four cases. CONCLUSION: A consistent cortical supply by the duplicated MCA and the accessory MCA to the anterior temporal lobe and the anterior frontal lobe, respectively, and its similarity to the cortical supply by the early branches of the MCA suggest that development of duplicated and/or accessory MCAs is an anomalously early ramification of the early branches of the MCA. In 1962, Crompton (1) described the accessory middle cerebral artery (MCA), which included duplication of the MCA, and the anomalous vessel originating from the A1 portion of the anterior cerebral artery (ACA), which coursed parallel to the MCA. In 1973, Teal et al (2) proposed using the term MCA duplication to characterize the two vessels originating from the distal end of the internal carotid artery, and the term accessory MCA to describe the anomalous vessel originating from the ACA. We use Teal’s classification because it is widely accepted. Although there are several explanations for the duplicated MCA and the accessory MCA (3‐6), their embryologic origins are still an open question. The early branch of the MCA proximal to the bifurcation or the trifurcation supplies either the anterior temporal lobe or the anterior frontal lobe (7). We found a great similarity between the cortical territory of this early branch of the MCA and that of the duplicated or accessory MCA. This prompted us to review these anomalous vessels to postulate a theory as to their common origin. Knowledge of the anomalous ramification of the MCA is important for the surgical treatment of cerebral aneurysms (1, 8‐10) and for understanding the collateral blood supply in cerebral ischemia (11) associated with duplicated or accessory MCAs.

Dynamic susceptibility contrast MR imaging of regional cerebral blood volume in Alzheimer disease: A promising alternative to nuclear medicine

Abstract: BACKGROUND AND PURPOSE: The goal of our study was to evaluate the sensitivity and specificity for Alzheimer disease of semiquantitative dynamic susceptibility contrast (DSC) MR imaging as compared with results of qualitative single-photon emission computed tomography (SPECT) in the same patients and with previously published semiquantitative SPECT results. METHODS: Fifty subjects were studied: 19 patients with probable Alzheimer disease with moderate cognitive impairment, eight mildly impaired patients with possible or probable Alzheimer disease, 18 group-matched elderly healthy comparison subjects, and five elderly comparison patients with psychiatric diagnoses. Relative values of temporoparietal regional cerebral blood volume (rCBV) were measured as a percentage of cerebellar rCBV, and group classification was assessed with logistic regression. The DSC MR imaging results were compared with SPECT scans in these same subjects and with previously published semiquantitative SPECT data. RESULTS: Temporoparietal rCBV ratios were reduced 20% bilaterally in the patients with Alzheimer disease. Using left and right temporoparietal rCBV as index measures, sensitivity was 95% in moderately affected patients with Alzheimer disease and 88% in patients with mild cases. Specificity was 96% in healthy comparison subjects and in psychiatric comparison subjects. Sensitivity with DSC MR imaging was considerably better than with visual clinical readings of SPECT scans (74% in moderate and 50% in mild Alzheimer disease cases), and was similar to previous published SPECT temporoparietal measurements (90%). Specificity with SPECT was 100% visually and 87% based on previous temporoparietal measurements. CONCLUSIONS: DSC MR imaging of rCBV is promising as a safe, potentially lower-cost alternative to nuclear medicine imaging for the evaluation of patients with dementia.