The "filling defect" sign helps localise the site of intracranial aneurysm rupture on an unenhanced CT

Transcription

1 The "filling defect" sign helps localise the site of intracranial aneurysm rupture on an unenhanced CT Poster No.: C-3380 Congress: ECR 2010 Type: Topic: Authors: Keywords: DOI: Educational Exhibit Neuro M. Subesinghe 1, R. Patel 1, M. E. Porte 2 ; 1 Leeds/UK, 2 York/UK Filling defect sign, Subarachnoid Haemorrhage, Computed Tomography /ecr2010/C-3380 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 14

2 Learning objectives To illustrate a rarely quoted and often overlooked radiological sign on unenhanced computed tomography (CT) of the head that is useful in identifying the site of a ruptured intracranial aneurysm in subarachnoid haemorrhage. Images for this section: Page 2 of 14

3 Fig. 1: Unenhanced CT scan of the head showing extensive subarachnoid haemmorhage and intraventricular haemorrhage with a "filling defect" with associated peripheral calcification in the midline which corresponds to an aneurysm at the basilar artery tip. Page 3 of 14

4 Background The incidence of subarachnoid haemorrhage (SAH) in the UK is about 10 per 100,000 per year. It is a life-threatening condition with a poor prognosis (50% mortality). The vast majority of cases are secondary to rupture of an intracranial aneurysm. Risk factors for SAH include hypertension, smoking, heavy alochol intake, a family history of SAH and inherited conditions such as adult polycystic kidney disease. Prompt diagnosis and endovascular or surgical intervention can improve outcome considerably. Diagnosis is reliant upon detecting blood within the subarachnoid space either by unenhanced CT in the first instance or secondarily by lumbar puncture when the CT findings are within normal limits (5% of cases). The role of CT in the acute setting is invaluable not only in demonstrating subarachnoid blood but also in identifying complications such as infarct and hydrocephalus. In addition, unenhanced CT is useful in predicting the site of rupture based upon the presence of parenchymal haematoma and the pattern of distribution of blood. The "filling defect" (1) or "aneurysm contour" (2) sign is an additional finding of proven accuracy in predicting the site of rupture. It is of particular usefulness in circumstances when multiple intracranial aneurysms are present when identifying the lesion repsonsible for bleeding is paramount prior to proceeding to endovascular or surgical treatment. Images for this section: Page 4 of 14

5 Fig. 1: Unenhanced CT scan of the head showing acute blood with the interpeduncular, quadrigeminal and ambient cisterns and interhemispheric and sylvian fissures in keeping with extensive subarachnoid haemorrhage. Page 5 of 14

6 Imaging findings OR Procedure details Classical features of SAH on unenhanced CT include: High attenuation material (haemorrhage) within the subarachnoid space +/- ventricular system Typical pattern of haemorrhage, e.g. sylvian fissure - middle cerebral artery, anterior interhemispheric fissure - anterior communicating artery aneurysm. Hydrocephalus Parenchymal haematoma The "filling defect" or "aneurysm contour" sign is visible as low attenuation within the aneurysm itself in relation to surrounding high attenuation subarachnoid blood which acts as a natural contrast agent. The low attenuation is likely to represent unclotted blood within the aneurysm surrounded by acute clotted blood within the subarachnoid space following rupture (2). Noguchi et al (1) reported an incidence of 30% for the "filling defect" sign with the ability to appreciate this sign based upon the size of the aneurysm and the amount of surrounding subarachnoid blood present. They suggest however that this sign should be used in conjunction with other findings to localise the aneurysm. Tryfonidis et al (2) reported an incidence of 48% in their study sample. They stated that the "aneurysm contour sign" was the most important feature associated with correct localisation and in cases of multiple intracranial aneurysms, the location of the ruptured aneurysm was identifed in all instances using the "aneurysm contour" sign solely or in combination with other features of SAH. Importantly, false-positives do occur and are generally associated wtih partial voluming of the adjacent cerebral parenchyma and/or ectasia or tortuosity of nearby cerebral vessels. Despite this, in both studies there were no instances when a ruptured aneurysm was missed or wrongly localised. Page 6 of 14

7 Images for this section: Fig. 1: Unenhanced CT scan of the head showing subarachnoid haemorrhage predominantly within the suprasellar cistern, interhemispheric and left sylvian fissure with a "filling defect" at the site of bifurcation of the left middle cerebral artery within the sylvian fissure. Page 7 of 14

8 Fig. 2: Corresponding CT angiogram confirming the presence of an aneurysm at the bifurcation of the left middle cerebral artery correlating with the "filling defect" seen on the unenhanced study (Fig. 1). Page 8 of 14

9 Fig. 3: Unenhanced CT scan of the head showing a predominantly left temporal haematoma and a "filling defect" at the site of bifurcation of the left middle cerebral artery within the sylvian fissure. Page 9 of 14

10 Fig. 4: Corresponding CT angiogram confirming the presence of an aneurysm at the bifurcation of the left middle cerebral artery correlating with the "filling defect" seen on the unenhanced study (Fig. 3). Page 10 of 14

11 Fig. 5: Unenhanced CT scan of the head showing acute hydrocephalus, subarachnoid haemorrhage within the interhemispheric fissure, a predominantly left temporal haematoma and a "filling defect" at the site of bifurcation of the left middle cerebral artery within the sylvian fissure. Page 11 of 14

12 Fig. 6: Corresponding CT angiogram confirming the presence of an aneurysm at the bifurcation of the left middle cerebral artery correlating with the "filling defect" seen on the unenhanced study (Fig. 5). Page 12 of 14

13 Conclusion CT angiography (CTA) and intra-arterial angiography remain the investigations of choice for aneurysm location in subarachnoid haemorrhage. However, the "filling defect" or "aneurysm contour" sign on unenhanced CT is an important finding to be aware of that is reliable in identifying the site of rupture on unenhanced CT either as a sole feature or in conjunction with other features of SAH. Its use is of special importance in instances where CTA may not be readily available in the acute setting and the aetiology and site of the subarachnoid haemorrhage may be unclear particularly in the presence of multiple intracranial aneurysms. Personal Information M. Subesinghe, R. Patel - Radiology Academy, B Floor, Clarendon Wing, Leeds General Infirmary, Great George St, Leeds, LS1 3EX, U.K M. E. Porte - Department of Radiology, York Hospital, Wigginton Road, York YO31 8HE, U.K References 1. Noguchi K, Ogawa T, Fujita H, Inugami A, Okudera T, Uemura K and Seto H. Filling defect sign in CT diagnosis of ruptured aneurysm. Neuroradiol 1997; 39: Page 13 of 14

14 2. Tryfonidis M, Evans AL, Coley SC, Hodgson TL, Connolly DJA, Romanowski CAJ and Patel UJ. The value of radio-anatomical features on non-contrast CT scans in localising the source in aneurysmal subarachnoid haemorrhage. Clin Anat 2007; 20: Page 14 of 14