Acute subarachnoid haemorrhage: detection with magnetic resonance imaging

Comparison of Magnetic Resonance Imaging Sequences With Computed Tomography to Detect Low-Grade Subarachnoid Hemorrhage

OBJECTIVES

To compare computed tomography (CT) with magnetic resonance imaging (MRI) for the presumptive diagnosis and localization of acute and subacute low-grade subarachnoid hemorrhage (SAH).

METHODS

We consecutively enrolled 45 patients clinically suspected of low-grade SAH, comparing them with a control group. We obtained axial nonenhanced CT scans as well as fluid-attenuated inversion recovery (FLAIR) and T2-weighted gradient echo (T2*) MRI sequences at 1.0 T. Two neuroradiologists scrutinized the presence of blood at 26 different regions in the intracranial subarachnoid space (SAS).

RESULTS

Three of 45 patients had normal CT and MRI scans, and SAH was excluded by lumbar puncture. We demonstrated SAH on CT scans in 28 of 42 (66.6%) patients, T2* sequences in 15 of 42 (35.7%) patients, and FLAIR sequences in 42 of 42 (100%) patients. Fluid-attenuated inversion recovery sequences were superior to CT in 16 of the 26 evaluated regions.

CONCLUSIONS

The FLAIR sequence was superior for presumptive diagnosis and localization of acute and subacute low-grade SAH, representing a potential tool in this setting.

Imaging of posterior fossa epidermoid tumors

OBJECTIVE

Epidermoid tumors have similar radiologic characteristics with arachnoid cysts on routine imaging techniques. Since they warrant different therapeutic interventions, it is essential to differentiate the two pathologies and to assess operative results.

PURPOSE

The purpose of this study is to define the MR characteristics of epidermoid tumors in posterior fossa particularly on fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI).

PATIENTS AND METHODS

During a 10-year period, we operated 19 cases with epidermoid tumor of posterior fossa. The localization of the epidermoids was cerebellopontine angle in 16 patients, within the fourth ventricle in 2 patients and pineal region in 1 patient. Neuroimaging included CT in all patients, conventional MR in 14 patients and FLAIR and DWI in the last 6 patients.

RESULTS

In the first 13 cases, diagnosis of epidermoid tumor was difficult on CT and conventional MR. Epidermoids appeared as heterogeneous hyperintense lesions on FLAIR and homogenous hyperintense lesions on DWI in the last 6 patients. While total resection of the tumor was achieved in 17 patients, subtotal resection was performed in 2 patients. Histopathological examinations of the specimens revealed epidermoid tumor in all cases.

CONCLUSION

Advances in neuroradiology provide us advantages for planning the treatment modalities in epidermoid tumors of the posterior fossa. The difficulties in preoperative differential diagnosis and judgment for reoperation in the postoperative course have been decreased particularly via FLAIR and DWI.

Detection of subarachnoid hemorrhage at acute and subacute/chronic stages: comparison of four magnetic resonance imaging pulse sequences and computed tomography

BACKGROUND

Acute subarachnoid hemorrhage (SAH) has traditionally been diagnosed by computed tomography (CT); however, fluid-attenuated inversion recovery (FLAIR) is a magnetic resonance imaging (MRI) modality currently used to detect acute SAH. CT is insensitive in the detection of subacute or chronic SAH. The purpose of this study was to compare 4 MRI pulse sequences and CT in the detection of SAH in acute and subacute-to-chronic stages.

METHODS

From 2001-2003, we collected data for 22 patients (12 men and 10 women, aged 35-80 years) with SAH due to ruptured aneurysm (n = 11), trauma (3), or unknown origin (8). All patients underwent MRI and CT examination, with an interval of less than 12 hours between the 2 procedures. We divided patients into 2 groups according to the time from symptom onset to MRI evaluation: patients with MRI performed < or = 5 days post-ictus had acute-stage illness, whereas patients with MRI performed from day 6-30 post-ictus had a subacute-to-chronic condition. MRI (1.5-T) pulse sequences comprised spin-echo T1-weighted, fast spin-echo T2-weighted, FLAIR, and gradient-echo (GE) T2*-weighted images.

RESULTS

In the acute-stage group, SAH was seen as an area of high signal intensity compared with surrounding cerebrospinal fluid in 36.4% of cases on T1-weighted images, and in 100% on FLAIR images; low signal intensities were seen in 18.2% of cases on T2-weighted images, and in 90.9% on GE T2*-weighted images. High-attenuated SAH was seen on CT in 90.9% of cases. FLAIR (p = 0.008), GE T2*-weighted images (p = 0.012) and CT images (p = 0.012) were all statistically significant indicators of acute SAH. In the subacute/chronic-stage group, SAH was detected on T1-weighted images (36.4% of cases), FLAIR (33.3%), T2-weighted images (9.1%), GE T2*-weighted images (100%), and CT (45.5%). GE T2*-weighted images were significantly superior (p = 0.001) to other MRI pulse sequences and CT as indicators of subacute-to-chronic SAH.

CONCLUSION

FLAIR and GE T2* MRI pulse sequences, and CT scans, are all statistically significant indicators of acute SAH. GE T2*-weighted images are statistically significant indicators of subacute-to-chronic SAH, whereas other MRI pulse sequences, and CT scans, are not.

New magnetic resonance imaging and computed tomography techniques for imaging of acute stroke

With continued advances in acute stroke therapy, the ability to accurately assess the physiologic status of ischemic brain tissue and related vascular lesions has become increasingly important. In this review, evidence regarding the use of new magnetic resonance imaging and computed tomography techniques to guide thrombolytic therapy, diagnose stroke subtype, and detect acute hemorrhage are discussed in order to provide a clearer picture of the status of these neuroimaging techniques in the assessment of acute ischemic stroke patients.

Imaging of haemorrhagic stroke

Computed tomography (CT) is the reference standard for the imaging of acute non-traumatic intracranial haemorrhage. The sensitivity with which CT detects haemorrhage falls with time and lumber puncture remains mandatory for the exclusion of subarachnoid haemorrhage (SAH). Magnetic resonance (MR) imaging is, however, superior to CT in the subacute and chronic stages after haemorrhage. MR in addition offers pathophysiological information that can help with assessment of both the aetiology of and complications arising from both SAH and intra-parenchymal haemorrhage.

MR imaging of intracranial epidermoid tumors: specific diagnosis with Turbo-FLAIR pulse sequence

The purpose of this study is to present the imaging findings with particular reference to the FLAIR magnetic resonance (MR) pulse sequence, of four patients with epidermoid cysts. In all cases CT showed hypodense lesions with stippled peripheral calcifications and no enhancement. The MR showed low signal intensity lesions in T1-weighted images, high signal intensity in T2-weighted lesions, no or minor enhancement after gadolinium administration and characteristic heterogeneous appearance in FLAIR images. Including the FLAIR sequence in MR imaging, a specific diagnosis can be suggested.

Detection of subarachnoid haemorrhage with magnetic resonance imaging

OBJECTIVES

To measure the sensitivity and specificity of five MRI sequences to subarachnoid haemorrhage.

METHODS

Forty one patients presenting with histories suspicious of subarachnoid haemorrhage (SAH) were investigated with MRI using T1 weighted, T2 weighted, single shot fast spin echo (express), fluid attenuation inversion recovery (FLAIR), and gradient echo T2* sequences, and also by CT. Lumbar puncture was performed in cases where CT was negative for SAH. Cases were divided into acute (scanned within 4 days of the haemorrhage) and subacute (scanned after 4 days) groups.

RESULTS

The gradient echo T2* was the most sensitive sequence, with sensitivities of 94% in the acute phase and 100% in the subacute phase. Next most sensitive was FLAIR with values of 81% and 87% for the acute and subacute phases respectively. Other sequences were considerably less sensitive.

CONCLUSIONS

MRI can be used to detect subacute and acute subarachnoid haemorrhage and has significant advantages over CT in the detection of subacute subarachnoid haemorrhage. The most sensitive sequence was the gradient echo T2*.

Hyperacute perimesencephalic subarachnoid hemorrhage: demonstration of blood extravasation with MRI

Perimesencephalic subarachnoid hemorrhage (SAH) is a benign subtype of SAH without known vascular pathology. We report a case of current subarachnoid bleeding in the vicinity of the basilar artery. The patient was on anticoagulation medication and had sustained a head injury 2 days earlier. The bleeding was documented by contrast agent extravasation in MRI. Because of the isointensity of hyperacute blood to CSF in conventional T2 sequences, FLAIR images are mandatory for diagnosis in the hyperacute state.