Imaging of acute subarachnoid hemorrhage with a fluid-attenuated inversion recovery sequence in an animal model: comparison with non-contrast-enhanced CT.

BACKGROUND AND PURPOSE: Fluid-attenuated inversion recovery (FLAIR) MR imaging sequences have been previously described in the evaluation of acute subarachnoid hemorrhage (SAH) in human subjects and have demonstrated good sensitivity. The purpose of this study was to evaluate a FLAIR sequence in an animal model of SAH and to compare the results with those obtained with non-contrast-enhanced CT. METHODS: SAH was experimentally induced in 18 New Zealand rabbits by injecting autologous arterial blood into the subarachnoid space of the foramen magnum. Nine animals had high-volume (1-2 mL) injections, and nine animals had low-volume (0.2-0.5 mL) injections. Four control animals were injected with 0.5 mL of saline. The animals were imaged with a FLAIR sequence and standard CT 2-5 hours after injection. Gross pathologic evaluation of seven of the animals was performed. Four blinded readers independently evaluated the CT and FLAIR images for SAH and graded the probability of SAH on a scale of 1 to 5 (1 = no hemorrhage, 5 = definite hemorrhage). RESULTS: Overall, the sensitivity of FLAIR was 89%, and the sensitivity of CT was 39% (P <.01). In animals with a high volume of SAH, the sensitivity of FLAIR was 100%, and the sensitivity of CT was 56%. In animals with a low volume of SAH, the sensitivity of FLAIR was 78%, and the sensitivity of CT was 22%. The specificity of FLAIR in animals without SAH was 100%, and the specificity of CT was 100%. The average reader score for FLAIR was 3.8, and that for CT was 2.2 (P <.001). Reader scores for FLAIR were higher than those for CT in 94% (P <.01) of animals with SAH and in 25% of animals without SAH (P >.05). Seven animals underwent gross pathologic examination, and all had blood in the subarachnoid space around the brain stem. CONCLUSION: FLAIR was more sensitive than CT in the evaluation of acute SAH in this model, especially when a high volume of SAH was present. This study provides a model for further experimentation with MR imaging in the evaluation of SAH. These findings are consistent with those of current clinical literature, which show FLAIR to be an accurate MR sequence in the diagnosis of SAH.

Imaging of head trauma in infancy and childhood.

Neurologic trauma is one of the most common and challenging problems encountered in the pediatric emergency setting. Early and accurate diagnosis is essential to minimize morbidity and mortality. The primary goal of the neuroimager in the acute setting is to provide rapid diagnosis, to monitor the development of complications, and to aid in the determination of prognosis. Unique features of the immature brain and skull influence the patterns and types of injuries observed. It is incumbent on the radiologist to understand these features as an aid to diagnosis. Further, the radiologist must be aware of the pathophysiology and appearance of nonaccidental trauma to ensure recognition of this devastating problem. Lastly, the radiologic tools available, their appropriate use, and their limitations should be understood by the entire trauma team to provide cost-effective and timely care. This article summarizes the pathophysiology and current imaging of neurotrauma in the pediatric population, including trauma, nonaccidental trauma, accidental anoxic injury, and birth injury.

Bilateral type 1 proatlantal arteries with absence of vertebral arteries.

The persistent proatlantal artery is a well-described communication between the carotid and vertebrobasilar system. However, persistence of bilateral proatlantal arteries is exceptionally rare. Although usually noted as an incidental finding, the presence of a proatlantal artery, particularly when bilateral, may result in unusual symptoms or may have implications for therapy. We report a case of bilateral proatlantal arteries, describe their embryology, and consider potential clinical implications of this finding.

Needle diameter in outpatient myelography: rates of adverse effects and current practice trends.

Telephone calls were made to 1251 consecutive patients one day following outpatient myelography. Data were available on 518 patients punctured with 22-gauge (g) (large-diameter) and 465 with 25-g (small-diameter) spinal needles. We surveyed 48 academic and private practice groups regarding needle diameter use in myelography; data were obtained from 34 private practice and 14 academic radiology departments. Patients reported adverse effects including mild and severe headache, back pain and nausea. The percentage of total adverse effects was significantly greater in the 22-g than in the 25-g needle group. The percentage of patients with headache was higher in the 22-g than in the 25-g group, but this difference was not statistically significant. Only 19% of private practice groups and 17% of academic centers use 25-g needles; the remainder use 20-g or 22-g needles.

Sinus histiocytosis (Rosai-Dorfman disease) of the suprasellar region: MR imaging findings--a case report.

Sinus histiocytosis with massive lymphadenopathy (SHML) is an uncommon disorder that typically manifests as systemic symptoms and lymphadenopathy. Extranodal, intracranial disease is uncommon. The authors report on a 15-year-old adolescent girl who had a suprasellar mass at magnetic resonance imaging. Biopsy results demonstrated lymphophagocytosis consistent with a diagnosis of SHML. The clinical, radiologic, and histologic aspects of the disease are discussed.

Angiographic correlation of CT calcification in the carotid siphon.

BACKGROUND AND PURPOSE: Calcification in the coronary arteries has been correlated with significant vessel stenosis. The predictive value of calcification within the carotid siphon has not been characterized; however, stenosis in the carotid siphon is potentially important in determining management of patients with ipsilateral carotid bifurcation stenosis. The purpose of this study was to determine optimal parameters for assessing carotid siphon calcification on head CT scans and to compare the CT findings with angiographic results. METHODS: We performed a retrospective review of patients referred for diagnostic carotid arteriography. Those patients who also had undergone a head CT study at our institution were selected. The CT scans and angiograms of 64 patients (128 vessels) were reviewed. Carotid siphon calcification on CT scans was characterized on brain and bone windows as mild, moderate, or severe. Comparison was then made with angiographic findings. RESULTS: The sensitivity and specificity of CT for depicting greater than 50% angiographic stenosis in the carotid siphon were 86% and 98%, respectively, for bone windows and 100% and 0%, respectively, for brain windows. The positive predictive value (PPV) for a stenosis of greater than 50% as evidenced by severe calcification was 86% on bone windows and 11% on brain windows. The PPV for mild and moderate calcification on bone windows was 2.5% and 0%, respectively. CONCLUSION: Severe CT calcification in the carotid siphon as characterized on bone windows correlates with a carotid siphon stenosis of greater than 50% as determined angiographically. Therefore, the identification of severe calcification offers a potential noninvasive method for identifying stenosis of the carotid siphon. This information may be essential in determining management and prognosis for patients with carotid bifurcation stenosis.

Patterns of hemorrhage with ruptured posterior inferior cerebellar artery aneurysms: CT findings in 44 cases.

OBJECTIVE: We intended to characterize the CT patterns of hemorrhage associated with ruptured posterior inferior cerebellar artery (PICA) aneurysms. MATERIALS AND METHODS: CT scans of 44 cases of angiographically confirmed ruptured saccular PICA aneurysms (4) aneurysms at the junction of the vertebral artery and the PICA and three distal PICA aneurysms) were retrospectively reviewed. All scans had been obtained within 2 days of the subarachnoid hemorrhage (SAH) (day 0 [less than 24 hr], 35 patients; day 1, eight patients; day 2, one patient). Presence or absence of hemorrhage in specific subarachnoid, intraventricular, and intraparenchymal locations was noted, as were the presence and degree of hydrocephalus. RESULTS: Posterior fossa SAH was present in 95% of cases. Isolated posterior fossa SAH was present in 30% of cases, but in no case was isolated supratentorial SAH present. Supratentorial SAH was present in 70% of cases. SAH involving the sylvian fissure or the interhemispheric region was present in 25% and 23% of cases, respectively. SAH along the convexity was present in 2% of cases. Intraventricular hemorrhage (IVH) with or without associated SAH was seen in 95% of cases, whereas isolated IVH was seen in 5% of cases. Hydrocephalus was present in 95% of cases and was moderate to marked in 70%. Both IVH and hydrocephalus were present in 93% of cases. CONCLUSION: Ruptured PICA aneurysms almost always coexist with hydrocephalus and IVH, as seen in 93% of cases, and almost never coexist with SAH along the convexity. The most common pattern of hemorrhage associated with such aneurysms includes IVH and posterior fossa hemorrhage. Extensive supratentorial SAH, in conjunction with posterior fossa SAH, is a common finding in patients with ruptured PICA aneurysms. SAH isolated to the posterior fossa is present in a sizeable minority of cases.

Optimization of parameters for the detection of cerebral aneurysms: CT angiography of a model.

PURPOSE: To optimize parameters with computed tomographic angiography for the detection of cerebral aneurysms. MATERIALS AND METHODS: Model aneurysms were placed randomly at various branch points and scanned multiple times with spiral technique. The final analysis included 63 branch points and 22 aneurysms. Each spiral scan used a different parameter combination. Collimation ranged from 1.5 to 4.0 mm and pitch ranged from 1:1 to 1.5:1. Images were constructed with shaded surface display (SSD) and maximum intensity projection (MIP) algorithms and were interpreted by three readers for the presence or absence of aneurysm. RESULTS: The receiver operating characteristic (ROC) curve area for 1.5-mm collimation was greater than those of 3- or 4-mm collimation (P < .01 and P < .001, respectively). There was no statistically significant difference in the ROC curve areas between 3- and 4-mm collimation (P = .37). There was no statistically significant decrease in ROC curve area when increasing pitch from 1:1 to 1.5:1 for any value of collimation (P = .96). For all parameter combinations the ROC curve areas for SSD images was greater than that of MIP images (P < .0001). CONCLUSION: For cerebral aneurysm detection, narrow collimation is superior to wider collimation. Mild increases in pitch do not substantially degrade diagnostic accuracy. SSD offers improved diagnostic accuracy over MIP display in this model.