A 51-year-old woman presented to the emergency department with acute weakness, numbness and headache. Her past medical history was non-contributory. A non-contrast head CT scan was performed (Fig. 1) and then the patient returned to the ER. While talking with the attending ER physician, she suddenly passed out and became completely unresponsive. She then returned to the CT suite for a repeat scan (Fig. 2) less than 90 minutes after the initial scan.
Which of the following are in the differential diagnosis regarding this woman’s CT head finding in Figure 1?
b) intracranial aneurysm
c) pituitary tumour
d) primary CNS germ cell tumour
1) a & d
2) b only
3) c & e
4) all of the above
5) none of the above
4) All of the above; (i.e. the differential diagnosis of the suprasellar mass lesion could potentially include meningioma, intracranial aneurysm, pituitary tumour, primary CNS germ cell tumour and craniopharyngioma).
When a mass lesion is identified in the suprasellar CSF space, there is a pneumonic that can be attributed to the collection of potential diagnoses in the differential list. That pneumonic is SATCHMOE, which stands for:
In children, the differential diagnosis of a suprasellar mass differs slightly and includes:
In the case presented, the mass lesion is uniformly hyperdense (white) on the initial scan (Fig.1). In essence, that would rule out a number of considerations or place them much lower on the list of potential diagnoses, such as an arachnoid cyst, which is typically uniformly hypodense, isodense to CSF fluid. An intracranial aneurysm (ICA) might be considered less likely here as well due to the uniform hyperdensity on the presented lesion on these non-contrast scans, as an intracranial aneurysm is usually hypodense or very slightly hyper dense. However, when a giant ICA acutely thromboses, the lesion can be homogeneously hyperdense, as in the case presented. In fact, that exact pathological entity becomes overtly evident as the primary diagnosis in this case when reviewing the follow-up scan (Fig. 2). Figure 2 now shows diffuse hyperdense material in the basal cisternal CSF spaces in keeping with acute subarachnoid hemorrhage, confirming the diagnosis of a ruptured thrombosed giant ICA.
Many ICAs are incidental and unrelated to prior medical conditions or family history; however, there’s a much greater incidence of ICAs in patients with some conditions, such as fibromuscular dysplasia, Ehlers-Danlos syndrome, adult onset polycystic kidney disease, and certain other familial conditions. Ninety percent of ICAs involve the Circle of Willis, and 90% of those arise from the anterior circulation (internal carotid artery and anterior communicating artery). ICAs that develop away from the Circle of Willis are more likely to be trauma-related, mycotic or oncotic in nature. 15-20% of ICAs are multiple. Annual risk of rupture of a known ICA is about 1-2%, greater for larger aneurysms. Treatment options include surgical excision (usually reserved for aneurysms larger than 2.5 cm, and endovascular coils or glue (for those under 2.5 cm).
The imaging modalities of choice for screening and diagnosis of ICAs are magnetic resonance angiography, and CT angiography. The former is preferred, if available, due to increased spatial resolution, multiplanar capability and lack of ionizing radiation.
1. Hacein-Bey L, Provenzale JM. Am J Roentgenol 2011;196:32-44.
2. Takao H, Nojo T. Radiology 2007;244:755-66.
3. Dahnert W. Radiology Review Manual. Lippincott Williams & Wilkins. Philadelphia, 2004.
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