Intratumoral hemorrhage after remote subtotal microsurgical resection and gamma knife radiosurgery for vestibular schwannoma.

Our report describes the occurrence of intratumoral hemorrhage in a vestibular schwannoma, which was treated with microsurgical resection thirteen years and gamma knife surgery (GKS) more than two years prior to the event. Although rare, it is apparent that bleeding into a vestibular schwannoma remains a possibility, even after the tumor has responded favorably to GKS. Long-term followup of patients with vestibular schwannoma who have been treated with GKS is advisable to assess treatment response and to detect adverse events (e.g. hemorrhage) suspected on clinical grounds.

Tissue iron deposition in untransfused beta-thalassemic mice.

Homozygous beta-thalassemic mice show many of the features seen in human beta-thalassemia, such as decreased hemoglobin, hematocrit, and red blood cell count as well as increased reticulocyte count. They also exhibit splenomegaly and a decrease in osmotic fragility of red cells. beta-thalassemic mice were examined for spontaneous iron overload at ages ranging from 20 to 595 days. Accumulation of iron was shown to occur in the spleen, liver, and kidneys but not in the heart. Sections of spleen, liver, kidney, and heart were stained for iron and subjectively scored. Image analysis microscopy was used to examine sections of spleen and liver. Nonheme iron in the four tissues was quantitated using the bathophenanthroline sulfonate colorimetric assay. An increase in tissue iron occurred primarily in the spleen, even before weaning, despite the low iron content of milk. Iron accumulation in the absence of blood transfusion is of interest because iron overload is the major cause of death in human beta-thalassemia.

Focal enhancement of cranial nerve V after radiosurgery with the Leksell gamma knife: experience in 15 patients with medically refractory trigeminal neuralgia.

BACKGROUND AND PURPOSE: Gamma knife radiosurgery is an alternative for the treatment of medically refractory trigeminal neuralgia. Few reports of posttreatment MR imaging appearance of cranial nerve V exist. Our purpose was to define MR imaging characteristics in cranial nerve V after gamma knife radiosurgery. METHODS: We retrospectively reviewed MR images of 15 patients who underwent gamma knife radiosurgery for trigeminal neuralgia. Radiation doses were 35-45 Gy at the 50% isodose line. Thin-section T2-weighted images and contrast-enhanced and nonenhanced T1-weighted images were obtained the day of radiosurgery and within the next 5 mo. Images were scored for enhancement and hyperintensity on T2-weighted images. Time to follow-up imaging and radiation dose were recorded. RESULTS: Mean time to follow-up imaging was 61 +/- 29 d. Posttreatment T2-weighted images showed stable signal intensity in all cases, with radiosurgical target site enhancement in 10. All five patients whose images did not show treatment-related enhancement received radiation doses of 35 Gy. The data suggested a correlation between enhancement with radiation dose (P =.06). No correlation of enhancement with treatment response or time to follow-up existed (P >.05). CONCLUSION: The trigeminal nerve often enhances at the target site after radiosurgery. Lack of trigeminal nerve enhancement occurred only with lower doses (35 Gy at 50%). MR imaging may be useful to confirm the presence and location of the treatment site after gamma knife radiosurgery for trigeminal neuralgia.

Helical CT angiography: dynamic cerebrovascular imaging in children.

BACKGROUND AND PURPOSE: The purpose of this study was to assess the feasibility of helical CT cerebrovascular imaging (CTCVI) in children and to make initial comparisons with MR angiography and digital subtraction angiography (DSA). METHODS: Twenty-six patients, ages 3 days to 17 years, were examined with CTCVI. Patients were scanned with 1-mm collimation and 2:1 pitch 30 seconds after the initiation of a hand injection of 2 mL/kg nonionic contrast material (320 mg/dL iodine) with a maximum dose that did not exceed 80 mL (minimum volume, 5 mL in a 2.5-kg infant). Reconstructions were done using maximum intensity projection and integral rendering algorithms. Four patients had CTCVI, MR angiography, and DSA (42 vessels studied) and nine patients had CTCVI and DSA (136 vessels studied). Scores of 1 (not present) to 3 (present in continuity to the first bifurcation) were assigned independently by two radiologists to 32 vessels in each correlated case for each available technique. RESULTS: There were no technical failures. CTCVI depicted 18 thrombosed dural sinuses, three vascular malformations, one intracranial aneurysm, and four tumors. Ninety-five percent of the vessels seen with DSA were also seen with CTCVI. CTCVI identified all vessels seen on MR angiography. CONCLUSION: Helical CTCVI is an effective technique for assessing the intracranial circulation in children. In this initial comparison, CTCVI showed more vascular detail than MR angiography, and had fewer technical limitations.

Evaluation of the circle of Willis with three-dimensional CT angiography in patients with suspected intracranial aneurysms.

PURPOSE: To determine the usefulness of CT angiography in the setting of suspected acute subarachnoid hemorrhage or intracranial aneurysm. METHODS: We prospectively studied 68 patients suspected of having subarachnoid hemorrhage or an intracranial aneurysm with noncontrast CT of the head followed immediately by contrast-enhanced helical CT of the circle of Willis with three-dimensional reconstruction. Twenty-seven patients with CT findings positive for subarachnoid hemorrhage or intracranial aneurysm were evaluated with digital subtraction angiography or MR angiography within 12 hours of CT angiography. Patients with negative CT/CT angiography findings were followed up with lumbar puncture. RESULTS: CT angiography showed 23 of 24 aneurysms and 2 of 2 arteriovenous malformations (sensitivity, 96%; specificity, 100%). Aneurysm size ranged from 2 to 40 mm (mean, 7.9 mm). Interobserver variability was 10%. In the 23 cases of subarachnoid hemorrhage, cisternal blood did not limit the three-dimensional reconstruction. Two patients with aneurysms on CT angiography had normal noncontrast scans. CONCLUSIONS: CT angiography of the circle of Willis is a useful technique for evaluation of suspected acute subarachnoid hemorrhage and intracranial aneurysm. It provides anatomic display of intracranial aneurysms, allowing for planning of conventional angiography and surgical approach. In selected cases, CT angiography may eliminate the need for preoperative conventional angiography.

Half-fourier acquisition single-shot turbo spin-echo (HASTE) MR: comparison with fast spin-echo MR in diseases of the brain.

PURPOSE: To compare an ultrafast T2-weighted (half-Fourier acquisition single-shot turbo spin-echo [HASTE]) pulse sequence with fast spin-echo T2-weighted sequences in MR imaging of brain lesions. METHODS: Fast spin-echo and HASTE images of 34 consecutive patients over the age of 50 years or with suspected demyelinating disease were reviewed independently by two neuroradiologists for the number of lesions less than 5 mm and greater than or equal to 5 mm, and for lesion conspicuity, gray-white matter differentiation, and extent of periventricular confluent signal abnormality. The reviewers also assessed for the presence of hemosiderin and extent of motion artifacts. RESULTS: Per patient, the mean number of 5-mm or larger lesions detected on fast spin-echo images (1.4) relative to the number detected on HASTE images (0.8) was not statistically significant. For lesions less than 5 mm, fast spin-echo images showed more lesions (7.5) than HASTE images did (2.4). The fast spin-echo images were better at depicting gray-white matter differentiation, conspicuity of lesions, and periventricular signal abnormality. Of four T2 hypointense lesions seen on fast spin-echo images, none was detected on HASTE images. CONCLUSION: Although the HASTE technique might be useful for rapid imaging of the brain, our study shows a diminished sensitivity for the detection of lesions less than 5 mm in diameter and for T2 hypointense lesions.

Integral and shell-MIP display algorithms in MR and CT three-dimensional models of the brain surface.

BACKGROUND AND PURPOSE: Our purpose was to demonstrate the use of integral and shell maximum intensity projection (shell-MIP) display algorithms in the 3-D CT and MR depiction of cerebral gyral and surface venous anatomy and disorders. These new algorithms are compared against MIP and shaded-surface-display (SSD) algorithms. METHODS: Integral and shell-MIP displays were generated from a specified number of proximal surface voxel layers in a 3-D model. Algorithmic models were compared on nine contrast-enhanced spoiled gradient-recalled acquisition in a steady state (SPGR) MR venograms for brain surface anatomic identification and detail. Seven CT venograms were compared for conspicuity of filling defects. Twelve contrast-enhanced preoperative planning 3-D MR models were rated for neurosurgical utility. RESULTS: A shell-MIP score of 7.00 and an integral score of 6.78 represented the highest mean subjective MR gyral quality (1-10 scale) followed by an SSD score of 3.89 and an MIP score of 1.06. Mean confidence scores for MR central sulcus identification (1-10 scale) were shell-MIP, 7.67; integral, 7.00; SSD, 3.22; and MIP, 1.00. Mean superficial venous quality MR ratings (1-10 scale) were shell-MIP, 8.22; MIP, 7.39; integral, 7.00; and SSD, 3.72. The mean number of cortical veins draining into each side of the superior sagittal sinus on MR was as follows: MIP, 6.19; integral, 6.06; shell-MIP, 5.94; and SSD, 3.81. Mean confidence scores for filling defect identification on CT venograms (1-5 scale) revealed a shell-MIP score of 4.36 and an integral score of 4.29 to be superior to a MIP score of 3.00. In selected cases, 3-D presurgical planning, prior to tumor resection, was clinically useful. CONCLUSION: Integral and shell-MIP are useful 3-D display algorithms for simultaneous display of superficial cerebral veins and gyri on MR images and of thrombosis on CT venograms.

Thick-section reformatting of thinly collimated helical CT for reduction of skull base-related artifacts.

OBJECTIVE: Our purpose was to evaluate thick-section reformatted helical CT of the brain base as a technique for reducing skull base-related artifacts and to compare it with conventional CT. MATERIALS AND METHODS: Twenty-three patients with suspected intracranial abnormalities related to the brain base, as determined either by clinical examination or at the time of imaging, were evaluated with contrast-enhanced conventional CT of the brain (5-mm collimation, 140 kVp, 170 mA, 2-sec rotation time) and reformatted helical CT (1-mm collimation, 1.5 pitch, 120 kVp, 220 mA). Helical sections were reformatted to a thickness of 5 mm by a volume-averaging algorithm using a computer workstation. Three observers retrospectively and blindly reviewed the images and qualitatively scored artifacts at the foramen magnum, middle cranial fossa, anterior cranial fossa, interpetrous region, and internal occipital protuberance. Image graininess and observer confidence were also scored. Paired statistical analyses using score differences in each patient were possible. RESULTS: Reformatted helical CT reduced skull base-related artifacts across all five anatomic regions (p < 0.05). The foramen magnum showed the greatest reduction in artifacts and the anterior cranial fossa the least. Image graininess was increased on reformatted CT compared with conventional CT (p < 0.05), but observer confidence remained higher for reformatted CT (p < 0.05). Total additional scan time was 3.15 +/- 0.38 min with 5.3 +/- 1.2 min required for reformatting. CONCLUSION: Reformatted CT significantly decreases skull base-related artifacts in the brain, improving confidence in evaluation of the brain base and adding an average of only 8.45 +/- 1.6 min of scanning and processing time to each examination.

Cerebral venography: comparison of CT and MR projection venography.

OBJECTIVE: The purpose of the study was to show equivalence or superiority of CT venography compared with the existing test of choice--MR venography--in the evaluation of dural sinus thrombosis and in the identification of cerebral veins and dural sinuses. MATERIALS AND METHODS: Twenty-four patients underwent both CT and MR venography of the intracranial venous circulation. Seventeen patients were examined for suspected dural sinus thrombosis. Four patients underwent projection venography to assess tumor invasion of a major dural sinus. The remaining three patients were examined for cavernous sinus thrombosis, arteriovenous malformation, and an elevated jugular bulb. Without knowledge of the patients' case histories, two radiologists evaluated each CT venogram and MR venogram. The radiologists then arrived at a consensus regarding the absence or presence of dural sinus thrombosis. Later, the radiologists conducted a second interpretation with knowledge of the patients' clinical histories during which time MR and CT venograms were compared with regard to the advantages and disadvantages of each imaging technique. In addition, the venograms were assessed for the presence of 12 different venous structure. Projection venograms were displayed using a maximum-intensity-projection (MIP) algorithm, and the individual source images were also evaluated. The CT venograms were also displayed using shell-MIP and integral display algorithms. RESULTS: Using MR venography, the two radiologists diagnosed dural sinus thrombosis in eight of the 17 patients with suspected dural sinus thrombosis. In these eight patients, the diagnosis was also made with CT venography. The diagnosis was confirmed by follow-up CT in four patients and by follow-up MR imaging in two patients. The MIP algorithm did not allow direct visualization of thrombus by either the CT or the MR imaging technique; however, the CT integral display algorithm enabled direct visualization of thrombus on the three-dimensional projection venograms. The systematic comparison of imaging techniques showed that CT venography reliably reveals all cerebral veins and sinuses when they are seen with MR venography. In addition, CT venography more frequently visualizes sinuses or smaller cerebral veins with low flow as compared with MR venography. CONCLUSION: Cerebral CT venography is superior to MR venography in the identification of cerebral veins and dural sinuses and is at least equivalent in the diagnosis of dural sinus thrombosis. CT venography is a viable alternative to MR venography in the examination of patients with suspected dural sinus thrombosis.

Randomized comparison of intra-arterial and intravenous thrombolysis in a canine model of acute basilar artery thrombosis.

We compared the rates of recanalization cerebral infarct and hemorrhage between intra-arterial (i.a.) reteplase and intravenous (i.v.) alteplase thrombolysis in a canine model of basilar artery thrombosis. Thrombosis was induced by injecting a clot in the basilar artery of 13 anesthetized dogs via superselective catheterization. The animals were randomized in a blinded fashion, 2 h after clot injection and verification of arterial occlusion, to receive i.v. alteplase 0.9 mg/kg over 60 min and i.a. placebo, or i.a. reteplase 0.09 units/kg over 20 min, equivalent to one-half the alteplase dose, and i.v. placebo. Recanalization was studied for 6 h after treatment with serial angiography; the images were later graded in a blinded fashion. Blinded interpretation of postmortem MRI was performed to assess the presence of brain infarcts and/or hemorrhage. At 3 h after initiation of treatment, partial or complete recanalization was observed in one of six dogs in the i.v. alteplase group and in five of seven in the i.a. reteplase group (P = 0.08). At 6 h, no significant difference in partial or complete recanalization was observed between the groups (two of six vs. five of seven; P = 0.20). Postmortem MRI revealed infarcts in four of six animals treated with i.v. alteplase and three of seven treated with i.a. reteplase (P = 0.4). Intracerebral hemorrhage was more common in the i.v. alteplase group (four of six vs. none of seven; P = 0.02). This study thus suggests that i.a. thrombolysis affords a recanalization rate similar to that of i.v. thrombolysis, but with a lower rate of intracerebral hemorrhage.

Cerebral CT venography.

PURPOSE: To produce cerebral venograms with thin-section helical computed tomography (CT) and to assess their diagnostic utility. MATERIALS AND METHODS: Thirty-six CT venograms were obtained in 33 patients after intravenous administration of iodinated contrast material. Eighteen patients had suspected dural sinus thrombosis. Twelve patients had tumor adjacent to a major venous structure. Three patients underwent CT venography during CT angiography. RESULTS: Superior sagittal, transverse, and straight sinuses were identified on every CT venogram. Other veins were seen with high frequency. Dural sinus thrombosis was diagnosed in seven patients, with magnetic resonance (MR) venographic correlation in five patients. CT venograms were easier to interpret and had fewer artifacts than MR venograms. Relationships of tumor to adjacent cerebral venous structures were well shown on CT venograms. CONCLUSION: CT venography yields detailed images of the intracranial venous circulation with consistently high quality. It is a rapid, useful method for diagnosis of dural sinus thrombosis and for preoperative mapping of venous structures in patients with neoplasm.