An infundibulum of thalamoperforator arteries: Importance of angiographic images for appropriate diagnosis

BACKGROUND: The identification of infundibula on noninvasive imaging modalities may be challenging. Because these lesions have generally been viewed as nonpathological, distinguishing them from small or micro-aneurysms is important. CASE DESCRIPTION: A 39-year-old male was diagnosed with recurrence of typical orgasmic headache. An outpoutching arising from the distal part of the right P1 at the take-off of thalamoperforator arteries was visualized on noninvasive investigations. The patient was referred to neurosurgery for surgical management of a right P1 aneurysm. Its unusual location and morphology led to be suspicious of an infundibular dilatation. Catheter angiography with 2D projections and 3D rotational reconstruction revealed an infundibulum at the common origin of two thalamoperforators, giving rise to a double-peaked shape, mimicking a true aneurysm, rather than the more characteristic conical shape of an infundibulum. CONCLUSION: Although noninvasive modalities may identify typical infundibula, the catheter angiogram with 2D projections was critical to establishing the diagnosis. The 3D rotational reconstruction enabled a straightforward understanding of the 3D vascular anatomy. This pyramidal variant of infundibular dilatation should be included in the differential diagnosis of a wide-based nonsaccular arterial contour deformities located in an area of multiple perforators.