The patient came with prominent frontal horns of the lateral ventricles on either side of the cavum septum pellicudum giving a butterfly appearance. Beneath the butterfly looking area the dilated third ventricle could be seen. Fourth ventricle was normal.
The lower ventricle showed dangling choroid plexus with separation of one corner from the nearest wall of the lateral ventricle by 8.5 mm. (a significant finding)
A cystic oval-shaped area close to the upper abnormal lateral ventricle was seen without any communication with the lateral ventricle. This area appeared to extend to the posterior margin of the cranium as a tubular anechoic space. However, on closer examination the tubular space was seen to be separated from the oval shaped area by a thin wall.
The tubular space was interpreted as the straight sinus which was seen to extend on either side of midline along the occipital region. into the transverse sinuses.
On color application the oval shaped area filled with color with aliasing. Color was seen to extend into the surrounding communicating arteries. The velocity of flow in the adjacent arterial region was high, approx 135 cm/sec.
The possibility of porencephalic cyst was ruled out since there was no communication with the ventricle.
Schizencephaly was not considered since that involves the grey matter of brain and thus extends to periphery.
Arachnoid cyst was strongly considered since the cystic anechoic nature of the mass with mass effect and lack of communication with ventricle favoured it. However once color was applied and the vascular nature of mass was seen the diagnosis of vein of Galen aneurysm with arteriovenous malformation was clear.