Figure 1
Subarachnoid haemorrhage (SAH)
Clinical History
The patient was admitted with severe headache and progressive loss of consciousness. A CT of the head at admission revealed a severe diffuse subarachnoid haemorrhage.
Imaging Findings
The patient presented with sudden onset of severe headache, drowsiness and progressive loss of consciousness. After being admitted to the hospital the patient was slightly comatose (Hunt and Hess score III.). A computed tomography (CT) of the head obtained at admission revealed a severe diffuse subarachnoid haemorrhage (SAH) with localized clot in the perimesencephalic cistern on the right side (Fig. 1a) and secondary normal pressure hydrocephalus. Four-vessel digital subtraction angiography (DSA) with multiple views did not demonstrate a cerebral aneurysm. The week after, control CT of the head demonstrated less blood in the subarachnoid spaces and cisterns, but clot in the perimesencephalic cistern persisted (Fig. 1b). Spiral CT angiography (CTA) performed in the same session revealed an aneurysm arising from the basilar artery (Fig. 2). Control DSA performed two hours after CTA also revealed basilar artery aneurysm which was not visible on the initial DSA (Fig. 3). The patient was operated via right pterional surgical approach. During surgery, the aneurysm which measured 8 mm was identified as the source of bleeding and was completely clipped. Postoperatively, the patient regained full capabilities and has returned to work.
Discussion
Spontaneus subarachnoid haemorrhage (SAH) according to the etiology and diagnostic findings could be divided into two groups: perimesencephalic and aneurysmatic.
Perimesencephalic SAH occurs due to leakage from the small veins and capillaries. In such cases no underlying cause of SAH is identified despite a complete angiographical investigation.
Also in 15- 20 % of the cases of the nonperimesencephalic aneurysmatic SAH-s, aneurysms are not detected on initial angiographic images. After the rupture, the aneurysm may thrombose or even be destructed as well as become angiographically occult due to vasospasm or compression from the haematoma.
In our case the aneurysm was not visible on initial angiography and was proved by repeated angiography. The clot visible on CT images in the location of the aneurysm shows that it probably thrombosed which was the reason for non visibility on initial angiography. Another possibility is that an initial small ruptured dissecting aneurysm of the basilar artery occured which enlarged after a few days.
Some authors presume that SAH pattern on CT could indicate when it is possible to detect the aneurysm by means of repeated angiography. In case of a perimesencephalic pattern of SAH and with a four vessel catheterization there is no need for repeated angiography. Angiography must be repeated in all other cases of nonperimesencephalic SAH. CTA could be the method of choice, if intensive SAH site on CT and suspected aneurysm coincide like in our case.
Perimesencephalic SAH occurs due to leakage from the small veins and capillaries. In such cases no underlying cause of SAH is identified despite a complete angiographical investigation.
Also in 15- 20 % of the cases of the nonperimesencephalic aneurysmatic SAH-s, aneurysms are not detected on initial angiographic images. After the rupture, the aneurysm may thrombose or even be destructed as well as become angiographically occult due to vasospasm or compression from the haematoma.
In our case the aneurysm was not visible on initial angiography and was proved by repeated angiography. The clot visible on CT images in the location of the aneurysm shows that it probably thrombosed which was the reason for non visibility on initial angiography. Another possibility is that an initial small ruptured dissecting aneurysm of the basilar artery occured which enlarged after a few days.
Some authors presume that SAH pattern on CT could indicate when it is possible to detect the aneurysm by means of repeated angiography. In case of a perimesencephalic pattern of SAH and with a four vessel catheterization there is no need for repeated angiography. Angiography must be repeated in all other cases of nonperimesencephalic SAH. CTA could be the method of choice, if intensive SAH site on CT and suspected aneurysm coincide like in our case.
Differential Diagnosis List
Ruptured cerebral aneurysm non visible on inital angiography
Final Diagnosis
Ruptured cerebral aneurysm non visible on inital angiography
References
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Case information
| URL: | https://www.eurorad.org/case/1849 |
| DOI: | 10.1594/EURORAD/CASE.1849 |
| ISSN: | 1563-4086 |
Figure 2
Basilar artery aneurysm
CT angiography VRT reconstruction, anterior view, revealed an aneurysm arising from the basilar artery.
Subarachnoid haemorrhage (SAH)
Basilar artery aneurysm
CT angiography VRT reconstruction, anterior view, revealed an aneurysm arising from the basilar artery.
