Magnetic resonance imaging results can affect therapy decisions in hyperacute stroke care.

BACKGROUND: Despite some limitations, a perfusion/diffusion mismatch can provide a working estimate of the ischemic penumbra in hyperacute stroke and has successfully been used to triage patients. PURPOSE: To evaluate whether the addition of magnetic resonance imaging (MRI) to clinical and non-contrast computed tomography (CT) data alters diagnosis and choice of therapy. MATERIAL AND METHODS: We retrospectively analyzed clinical records, and CT and MRI data fully available in 97 of 117 patients. Upon clinical examination and CT, a diagnosis and treatment path was scored and compared to treatment path after addition of MRI data. The MRI protocol included T2-weighted images, diffusion-weighted images (DWI), and perfusion-weighted images (PWI), and MR angiography (MRA). RESULTS: MRI data were acquired in less than 15 min. In 20 of 97 patients (21%), the diagnosis changed after MRI. In 25 of 97 patients (26%), the presumptive treatment plan was changed after MRI evaluation. Thirteen patients had their treatment changed from thrombolytic to nonthrombolytic therapy. Three patients were changed from nonthrombolytic to intraarterial (IA) thrombolysis. In one patient, treatment was changed from intravenous (IV) to IA thrombolysis, and in five patients it was changed from IA to IV thrombolysis. In two patients, systemic heparin was added to antiplatelet therapy. CONCLUSION: The expansion of the acute stroke protocol to include MRI altered the therapy plan in 26% of our patients. The utility of MRI, shown here to improve patient stratification into best-treatment options, demonstrates the value of using MRI to optimize care in hyperacute stroke patients.

Good clinical outcome in a patient with a large CT scan hypodensity treated with intra-arterial urokinase after an embolic stroke.

Hypodense regions demonstrated by CT within 6 hours of the onset of stroke may reflect irreversibly damaged tissue, and some have suggested that patients with such findings should be spared the risks of thrombolytic therapy since they are unable to benefit from it. We report here a patient with a low-density area demonstrated by CT less than 6 hours after onset of symptoms who improved dramatically after successful intra-arterial thrombolysis.

Potential pitfalls of magnetic resonance imaging in the diagnosis of avascular necrosis.

Magnetic resonance (MR) imaging and radionuclide (RN) bone scans were performed in two patients with collagen vascular disease (CVD) to evaluate hip pains. In both patients RN bone scans demonstrated decreased radioactivity in the femoral heads, whereas, MR imaging was normal. Because early changes of avascular necrosis (AVN) frequently present as decreased radioactivity in the femoral head, special attempts were made to detect this decreased activity using pinhole collimator imaging. The diagnosis of AVN was confirmed surgically by venous pressure measurements. Abnormal RN bone scans representing decreased flow due to vasculitis in patients with CVD, may be more sensitive in the diagnosis of AVN before structural changes can be detected on MR studies.

The "aortic nipple" as a sign of impending superior vena caval syndrome.

The development of dilatation of the left superior intercostal vein ("aortic nipple") on chest radiographic studies can be used as a clue to impending superior vena caval syndrome. Two cases are described in which detection of an "aortic nipple" on chest roentgenograms predated the clinical syndrome by seven to ten weeks. Since superior vena caval syndrome is a medical emergency, recognition of signs such as this which may significantly predate the "full-blown" syndrome have far-reaching implications in the care of patients.

Magnetic resonance imaging of ischemic bowel in rabbit model.

Acute mesenteric ischemic bowel disease is a common yet complex disorder with high morbidity and mortality rates predominantly caused by delayed diagnosis. We examined the role of magnetic resonance imaging (MRI) in the early detection of small bowel ischemia using the rabbit model. Surgical ligation of the appropriate arterial vascular supply to the ileum of 10 rabbits produced the ischemic compromise. The animals were imaged at different time intervals after the arterial occlusion. Multislice, T1 and T2-weighted images were obtained in axial and coronal planes. Abnormal findings of the dearterialized segment of bowel were visualized as early as 45 minutes after vascular occlusion. The findings consisted of: (1) bowel wall thickening, (2) two- to three-fold increase in signal intensity from bowel on T2-weighted images, and (3) isointensity or slightly increased signal intensity within the bowel wall on T1-weighted images. MRI appears to be a sensitive, noninvasive technique for the early detection of bowel ischemia in the rabbit animal model.

Angular deformities and forearm function.

Angular deformities were created in cadaver forearms at proximal, middle, and distal third levels of the radius and ulna separately, and at middle and distal third levels of both bones, to determine the corresponding limitations of pronation and supination. The ranges of pronation and supination were recorded using a rotational motion measurement apparatus instrumented with a 360 degrees goniometer. These experimental results were compared to data obtained from clinical and radiographic examination of 105 patients with similar residual deformities following treatment of fractures by nonsurgical means, to evaluate the accuracy of the experimental model and to determine if loss of rotational motion could be predicted based on radiographic findings. With cadaver forearms, on the average, angulation of 10 degrees of the radius or ulna in coronal or sagittal planes limited pronation and supination by less than 24 degrees, whereas angulation of 10 degrees of both the radius and the ulna limited pronation and supination by less than 18%. Comparison of experimental results with clinical findings showed that, despite the errors involved in measuring forearm deformities in patients using biplanar radiographs, the experimental results predicted the clinical loss of pronation and supination to within 17% for the fractures of the radius, and within 8% accuracy for the fractures of the ulna.

Postoperative evaluation for intracranial recurrence of medulloblastoma: MR findings with gadopentetate dimeglumine.

PURPOSE: To characterize the gadopentetate dimeglumine-enhanced MR features of recurrent medulloblastoma. METHODS: The postsurgical gadopentetate dimeglumine-enhanced MR images of 48 patients (206 head examinations) with prior resection of medulloblastoma were retrospectively evaluated for enhancement in the brain parenchyma, meninges (dura, pia-arachnoid), and ventricles. RESULTS: Nineteen patients had recurrent tumor as determined by clinical course and positive imaging studies. Seventeen patients with recurrent disease had intracranial enhancement predominating in the pia-arachnoid (63%) or as a focal nodular brain lesion (26%). Three of these patients also had intraventricular metastases. None of the clinically healthy patients had these findings. One patient had recurrent tumor presenting within the fourth ventricle. Only 3 of 8 intraventricular lesions observed in the 4 patients initially enhanced with gadopentetate dimeglumine. Another patient with recurrent disease had extensive skeletal metastases without involvement of the central nervous system. Dural enhancement was observed in patients both with (42%) and without (38%) recurrent tumor. CONCLUSION: The MR findings of pia-arachnoidal or focal nodular brain enhancement are highly specific in the diagnosis of recurrent medulloblastoma. Pia-arachnoidal or focal brain enhancement were also the most frequent patterns associated with recurrent tumor. Dural enhancement alone is not a reliable indicator of recurrent medulloblastoma. Not all intraventricular metastases enhance with gadopentetate dimeglumine, and careful evaluation for nonenhancing lesions within the ventricles should be made on postoperative MR examinations.

Use of the delayed mask for improved demonstration of aneurysms on intraarterial DSA.

PURPOSE: We retrospectively explored the use of the delayed mask technique for intraarterial digital subtraction angiography (IADSA) to demonstrate the anatomy of aneurysm necks. METHODS: The delayed mask technique was utilized in 22 patients who had craniotomies for aneurysms demonstrated at angiography. The operative notes were compared to the angiographic findings of both the traditionally masked IADSA and the delayed mask IADSA. In addition, an in vitro model was constructed to examine the relationship between the size of the aneurysm neck and the ability to indirectly define its anatomy by demonstrating the flow jet. RESULTS: In 12 of 22 cases, the delayed mask technique demonstrated a systolic jet that was not demonstrated by traditional subtraction techniques. In nine of 12 cases, the delayed mask technique gave more specific information regarding the size, location, and orientation of the aneurysm neck. CONCLUSION: The delayed mask technique can add important information regarding the anatomy of aneurysm without adding time or risk to the procedure.

Deceptively normal MR in early infantile Krabbe disease.

The authors present two cases of 5-month-old children with early infantile Krabbe disease studied by CT and MR. Both infants had characteristic CT scans for the disease consisting of symmetric hyperdensity involving the cerebellum, thalami, caudate, corona radiata, and brain stem. One of the infants had a deceptively normal initial MR examination, with dramatic progression of the white-matter disease over the following 4 months.

Impaired cerebral vasoreactivity after embolization of arteriovenous malformations: assessment with serial acetazolamide challenge xenon CT.

Embolization of a portion of the nidus of an arteriovenous malformation not only may alter hemodynamics within the nidus, but also may change blood flow dynamics in adjacent normal vessels. Sequential acetazolamide-challenge xenon CT cerebral blood flow studies were performed in eight patients before and after embolization of arteriovenous malformations to assess the hemodynamic effects on the major vascular territories supplying the malformation. Acetazolamide is a potent cerebral vasodilator, and its administration combined with cerebral blood flow studies allows assessment of cerebral vasoreactivity. In seven of the eight patients, one or more parenchymal areas exhibited a normal cerebral blood flow augmentation response to acetazolamide before embolization, but diminished acetazolamide flow augmentation was seen after embolization, indicating abnormal vasoreactivity. We found that the decrease in vasoreactivity peaked 6-10 days after embolization. In one of the eight patients, a temporary delayed neurologic deficit developed during a period of impaired cerebral vasoreactivity following embolization. Our results suggest that embolization of an arteriovenous malformation can induce vasoreactivity changes in adjacent normal vessels. Because these changes appear to be somewhat time-dependent, an appropriate interval should be observed between embolization stages or before surgical resection of an arteriovenous malformation following embolization to allow hemodynamic equilibration to occur. Acetazolamide challenge combined with serial cerebral blood flow studies following embolization enables determination of this hemodynamic equilibration.

Diagnosis of ruptured intracranial dermoid cyst: value MR over CT.

The CT and MR findings of seven patients with pathologically proved ruptured dermoid cysts were reviewed to analyze the MR characteristics and to see if MR evaluation had significant advantages over CT. In six cases, both CT and MR identified fatty material in the CSF spaces. Hemorrhage complicated preoperative diagnosis in one case. Patterns of extraaxial fat distribution were as follows: intraventricular fat/CSF levels (three patients), generalized subarachnoid spread (six patients), and localized subarachnoid spread with sulcal widening (one patient). There was no correlation between fat distribution and clinical symptoms. MR showed the vascular involvement better than CT did in five of seven cases, and showed extension of the cysts into the skull base in two cases. Signal intensity of the solid mass was low on T1-weighted MR images and inhomogeneously high on T2-weighted images, which correlated pathologically with the presence of crystal cholesterol, hair, sebaceous glands, and epithelial cells in all cases. On MR, brain parenchyma showed little edema or other reaction to the masses, which were typically large. The value of MR over CT in the examination of ruptured dermoid cysts is the conspicuity of the extent of subarachnoid spread, involvement of the extraaxial structures, and evidence of vascular compromise, which can obviate angiography. MR had no advantage over CT in making the initial diagnosis of ruptured dermoid, but it would be the preferred preoperative study.

Malignant hemangioendothelioma (angiosarcoma) of the skull: plain film, CT, and MR appearance.

Hemangioendothelioma is a rare neoplasm of bone that uncommonly involves the skull. We present a case of grade III malignant hemangioendothelioma (also known as angiosarcoma) of the skull in a 13-year-old boy and describe the plain film, CT, and MR appearance of this neoplasm as well as its histopathology.

Benefits of perfusion MR imaging relative to diffusion MR imaging in the diagnosis and treatment of hyperacute stroke.

BACKGROUND AND PURPOSE: The development of thrombolytic agents for use with compromised cerebral blood flow has made it critical to quickly identify those patients to best treat. We hypothesized that combined diffusion and perfusion MR imaging adds vital diagnostic value for patients for whom the greatest potential benefits exist and far exceeds the diagnostic value of diffusion MR imaging alone. METHODS: The cases of patients with neurologic symptoms of acute ischemic stroke who underwent ultra-fast emergent MR imaging within 6 hours were reviewed. In all cases, automatic processing yielded isotropic diffusion images and perfusion time-to-peak maps. Images with large vessel distribution ischemia and with mismatched perfusion abnormalities were correlated with patient records. All follow-up images were reviewed and compared with outcomes resulting from hyperacute therapies. RESULTS: For 16 (26%) of 62 patients, hypoperfusion was the best MR imaging evidence of disease distribution, and for 15 of the 16, hypoperfusion (not abnormal diffusion) comprised the only imaging evidence for disease involving large vessels. For seven patients, diffusion imaging findings were entirely normal, and for nine, diffusion imaging delineated abnormal signal in either small vessel distributions or in a notably smaller cortical branch in one case. In all cases, perfusion maps were predictive of eventual lesions, as confirmed by angiography, CT, or subsequent MR imaging. CONCLUSION: If only diffusion MR imaging is used in assessing patients with hyperacute stroke, nearly one quarter of the cases may be incorrectly categorized with respect to the distribution of ischemic at-risk tissue. Addition of perfusion information further enables better categorizing of vascular distribution to allow the best selection among therapeutic options and to improve patient outcomes.

Cost-effectiveness of emergency intraarterial intracerebral thrombolysis: a pilot study.

PURPOSE: To assess the clinical efficacy and cost-effectiveness of emergency thrombolysis as a treatment strategy for thromboembolic intracerebral events. METHODS: Thirty-four patients with symptoms suggestive of middle cerebral artery occlusion were included. Eight of these patients were treated with intraarterial urokinase. Effectiveness was determined by comparing the admission National Institutes of Health stroke score to the 24-hour National Institutes of Health stroke score. The cost and length of stay of both populations were derived and used as measures of direct cost. The likelihood of admission to extended care facilities and estimated length cost of admission was used as a measure of indirect cost. RESULTS: The control population became slightly worse, with a change in National Institutes of Health score of -0.5, whereas the treated population improved slightly, with a change in National Institutes of Health score of +5.12. Analysis of the direct costs data between the two populations revealed a slight increased mean for the treated population ($15,202) as compared with the control population ($13,478). The unpaired t test, however, revealed no significant cost difference between the two groups. By reducing the number of completed strokes by one third or by decreasing the severity by the same factor (as shown in our study), the likelihood of admission to an extended nursing facility also is decreased. The cost saving per patient from extended care facilities is approximately $3435. CONCLUSION: The emergency application of intraarterial thrombolysis with urokinase results in a statistically significant positive change in National Institutes of Health score by at least five points. A statistically significant benefit is realized through the use of intraarterial urokinase. A statistically insignificant additional cost is shown by this study. This insignificant cost is more than offset by the saved nursing home costs.

Treatment of arteriovenous malformations of the brain with combined embolization and stereotactic radiosurgery: results after 1 and 2 years.

Seven patients with large arteriovenous malformations (AVMs) of the brain were selected for combined therapy with particulate embolization, followed by radiosurgery of the residual nidus. The goal of embolization was to reduce the patient nidus to a size that facilitated successful stereotactic radiosurgery. Angiograms obtained 1 and 2 years after radiosurgery were evaluated for changes in nidus size, flow rate, and feeding and draining vessels. One year after stereotactic radiosurgery, one AVM was angiographically undetectable. Three other AVMs demonstrated a volume reduction of greater than 50%, in addition to decreased shunt speed and altered angioarchitecture at 1-year follow-up. At 2-year follow-ups, two of seven AVMs were cured, and an additional two of seven had a greater than 98% reduction in nidus volume. Although one patient experienced a transient deficit from embolotherapy, none of our patients suffered a new neurologic deficit or a hemorrhage during the follow-up period. Our data support the efficacy of combined embolotherapy and radiosurgery for definitive therapy of selected large AVMs of the brain.

Use of acetazolamide-challenge xenon CT in the assessment of cerebral blood flow dynamics in patients with arteriovenous malformations.

Arteriovenous malformations (AVMs) may cause symptoms related to a reduction of cerebral blood flow (CBF) to surrounding brain parenchyma. To evaluate this compromise of hemodynamic reserve (commonly referred to as steal phenomenon), we used acetazolamide challenge and stable-xenon CT (Xe/CT). Baseline Xe/CT studies in 13 patients with AVMs were followed by an acetazolamide challenge to the vascular reserve. Blood flow maps were quantitated by using region-of-interest (ROI) software. ROI findings were categorized into four groups on the basis of the presence or absence of normal baseline CBF and presence or absence of normal augmentation of CBF. ROIs were designated as near site (within the vascular territory supplying the AVM) or far site (outside the vascular territory supplying the AVM). One patient had a normal baseline and normal augmentation of CBF (group 1). The other patients had a combination of one or more of the other three categories. Ten patients had parenchymal areas that exhibited either a normal or low baseline CBF with decreased augmentation; both conditions were interpreted as decreased vascular reserve (groups 2 and 3). Eleven patients had parenchymal areas that showed a low baseline CBF and normal augmentation with acetazolamide (group 4), interpreted as having a decreased demand for CBF but having a normal vascular reserve. Decreased vascular reserve was found in 27% of the nearsite areas and 17% of the far-site areas. No patients had only far-site abnormal vascular reserve. We believe that compromised vascular reserve can best be evaluated with a challenge study, such as this acetazolamide-challenge Xe/CT study.(ABSTRACT TRUNCATED AT 250 WORDS)

Species typical display behavior following stimulation of the reptilian striatum.

Seventy unanesthetized, unrestrained western fence lizards (Sceloporus occidentalis) were electrically stimulated through implanted electrodes. Behavior elicited included the species typical assertion display, elements of the challenge display and elementary locomotor responses: circling, rolling and curling. The assertion and challenge displays were elicited from telencephalic sites whereas the elementary locomotor effects were elicited from electrodes in the brain stem. Assertion displays were consistently elicited in 25 animals at an average threshold current of 46 microA. Sites showing the lowest threshold and greatest reliability were tightly clustered in the striatum and nucleus accumbens. Challenge behavior was elicited in eleven animals at an average threshold of 58 microA. Seven of the animals with challenge responses had electrodes in a small area anterior and dorsal to nucleus sphericus. The implications of these results are discussed relative to current views of the comparative neuroanatomy of the basal ganglia and relative to the basic functional organization of the vertebrate central nervous system.

Computed tomography and magnetic resonance imaging of the acute abdomen.

CT is a noninvasive investigation that in many instances is more sensitive in elucidating intra-abdominal and retroperitoneal disease than is conventional radiography. With modern scanners, the procedure is rapid and efficient and suitable for the most severely ill and infirm. The scans are easily interpretable, and the anatomic and morphologic depiction of disease is readily understood by those with surgical training. Information regarding the state of the bowel wall, mesentery, and intraperitoneal and retroperitoneal structures is displayed in greater detail than by any other diagnostic imaging modality. The use of intravenous contrast medium is rarely essential. The concentration of iodinated contrast needed for opacification of the bowel is no greater than 2 per cent to 5 per cent and will not complicate bowel surgery, as would standard upper gastrointestinal or barium enema studies. Abscess, free air, calcium, and intraperitoneal fluid are very sensitively detected. CT is extremely useful in aiding surgical decision making in the acute abdomen and is complementary to or has replaced conventional studies.

The effects of angular and rotational deformities of both bones of the forearm. An in vitro study.

UNLABELLED: In intact fresh cadaver specimens, we experimentally studied angular and rotatory deformities at the distal and middle levels of the forearm. The remaining pronation and supination motions were measured. When both bones of the forearm were angulated with a combined deformity (radio-ulnar or dorsovolar, or both) of 10 degrees, a loss of pronation-supination of 12.5 +/- 4.5 per cent occurred in the forearms with a distal-third fracture; in the forearms with a middle-third fracture the average loss was 16.0 +/- 5.7 per cent. Pronation losses were similar for both distal and middle-third deformities. However, supination losses were much less affected (p less than 0.01) in forearms with deformities at the distal-third level while the losses were considered drastic for middle-third deformities. Rotatory deformities produced losses of pronation-supination that were equal to the degree of deformity. CLINICAL RELEVANCE: Study of the artificially created deformities in cadavera indicated that angular and rotatory deformities of the forearm of 10 degrees or less result in minimum limitation of pronation-supination. These degrees of limitation of motion in clinical practice are easily compensated for and are cosmetically acceptable. The fact that the perfect anatomical restoration of fracture alignment that often is obtained with internal fixation does not always result in complete restoration of motion suggests that: (1) this residual impairment of function is due to soft-tissue scarring, and (2) the mild angular and rotatory deformities resulting from nonsurgical treatment of fractures of the forearm may produce limitations of motion of an equally acceptable degree.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of prosthetic stem stiffness and of a calcar collar on stresses in the proximal end of the femur with a cemented femoral component.

UNLABELLED: We used three-dimensional finite-element models of the proximal end of the femur to examine the influence of stem material, stem geometry, and the use of a calcar collar on the stresses in and around implanted total hip-replacement femoral components. Anatomical bone geometries and realistic prosthetic geometries were considered. A slender titanium-alloy stem with a collar allows creation of calcar stresses of approximately 80 per cent of the anticipated normal levels. A similar stem of cobalt-chromium alloy creates calcar stresses of 67 per cent of these normal values. Stem designs without a collar were shown to generate no more than 40 per cent of normal values while larger, stiffer stems were seen to create less than 30 per cent of normal values, with or without a collar. Proximal cement stresses were increased by the use of titanium-alloy stems, but were reduced to low levels by a functioning collar. The highest cement stresses in the system were found near the tip of the stem, where titanium-alloy stems create lower stresses than do corresponding cobalt-chromium-alloy stems. The achievability of calcar loading with a titanium prosthesis was demonstrated in in vitro strain-gauge tests. CLINICAL RELEVANCE: Loosening of the femoral stem and calcar resorption are problems that are seen in many long-term clinical series of total hip prostheses. In order to reduce the incidence of these problems, the goal of the designer of a prosthesis is to reduce cement and cement interface stresses around the femoral stem and to create stress distributions in the bone that will prevent resorption.(ABSTRACT TRUNCATED AT 250 WORDS)