A 30-year-old female presented with a history of headaches. Imaging revealed a saccular aneurysm of the distal basilar artery. Specifically, a lobulated lesion was seen in the ventral prepontine cistern, more towards the right side, with hypersignal corroborating subacute blood products. A tortuous vessel was seen entering the bulk of the aneurysm, which showed luminal clots/thrombosis. The aneurysm had mass effect on the right side of the pons. The key findings were of a lobulated, saccular aneurysm of the distal basilar artery with intraluminal clots and mass effect on adjacent structures.

1. SACCULAR ANEURYSM OF BASILAR ARTERY MERCURY IMAGING INSTITUTE SCO 172-173 SEC 9C CHANDIGARH MERCURY IMAGING CENTRE SCO 16-17 SEC 20D CHANDIGARH 30 YR OLD FEMALE WITH H/O HEADACHE

2. SACCULAR ANEURYSM OF BASILAR ARTERY INTRACRANIAL SACCULAR ANEURYSMS Incidence – 1 %to 5 % 90% circle of willis /MCA bifurcation. Age of presentation : 40 to 60years Multiplicity : 15 % to 20% (Female predominance) Symptoms : Usually subarachnoid haemorrhage , Headcahe, seizure,TIA,Infarction)

3. LOBULATED LESION IN THE VENTRAL PREPONTINE CISTERN( MORE TOWARDS RT SIDE). INTERSPREAD HYPERINTENSE SIGNAL COROBORATES WITH SUBACUTE STAGE BLOOD PRODUCTS. MASS EFFECT IS APPRECIATED ON ADJACENT PONS WITH CHRONIC INFARCT IN THE LEFT PARAMEDIAN LOCATION OF THE CENTRAL PONS.

4. Lobulated outline. Intraluminalheterogenousity representing luminal clots / thrombosis in saccular aneurysm of the basilar artery

5. TORTUOUS VESSEL ENTERING THE BULK OF THE ANEURYSM

6. Bloom on GRADIENT SEQUENCE – CHRONIC HAEMORRHAGE PRODUCTS/ LUMINAL CLOT) LAMELLATED INTRALUMINAL CLOTS IN LOBULATED SACCULAR ANEURYSM WITH ASSOCIATED MASS EFFECT ON THE RT SIDE OF PONS.

7. SACCULAR ANEURYSM OF THE DISTAL BASILAR ARTERY

8. SACCULAR ANEURYSM OF THE DISTAL BASILAR ARTERY

9. LESSON LEARNT THROMBOSED ANEURYSMS HAVE MASS EFFECT AS EVIDENT IN THIS CASE.