Idiopathic Lenticulostriate Artery Pseudoaneurysm Protruding into the Lateral Ventricle: A Case Report
A 28-year-old man presented with sudden onset of severe headache without any definite history of trauma. He was previously diagnosed with bipolar disorder and had been taking lithium for 3 years. Computed tomography (CT) scans revealed isolated IVH in the right lateral ventricle. An enhanced small round lesion (4.5 mm in diameter) was found on the medial surface of the right caudate nucleus by contrast CT (). The patient underwent external ventricular drainage (EVD) for the IVH. The following day, digital subtraction angiography (DSA) was performed and revealed an aneurysm arising from the distal part of the medial LSA (). Using 3-dimensional reconstruction images, the aneurysm was measured to be 7.5×4.5 mm. There was no evidence of MMD or AVM. The patient recovered without any newly developed neurological deficits and a follow-up CT scan showed complete resolution of the IVH.\nFollowing removal of the EVD catheter, the size of the aneurysm slightly decreased (4.0×2.3 mm). A short-term follow-up of the aneurysm was recommended, to which the patient agreed. However, DSA performed a month later revealed a slightly enlarged aneurysm (4.2×3.2 mm). Moreover, the shape of aneurysm was changed. Considering the risk of rebleeding, we recommended surgical treatment. Endovascular obliteration of the aneurysm was deemed impossible due to the small caliber of the LSA. Instead, the aneurysm was clipped via the interhemispheric transcallosal approach with assistance of a neuro-navigation system. The aneurysm was found in the right lateral ventricle, attached to the caudate nucleus (). To prevent injury to the caudate nucleus, we decided to clip the neck of the aneurysmal sac rather than undertake a complete resection. This was particularly important since the patient did not present any neurological deficits prior to surgery. A protruding pulsating sac partially enveloped by a hematoma was observed, and 2 aneurysm clips were successfully applied to the most proximal part of the sac (). The patient recovered well.\nDSA performed 4 days later revealed a considerable residual aneurysm sac beside the clips (). Given the risk of rebleeding, a second operation was planned for complete resection of the aneurysm. After revised craniotomy and careful dissection of the caudate nucleus, the aneurysm sac and clips were completely removed (). DSA after revised craniotomy showed no evidence of aneurysm (). Short- and long-term memory tests were performed, and memory impairment was not observed. Fortunately, the patient recovered without any neurological sequelae.\nHistopathological examination was conducted on the resected aneurysm. Hematoxylin-eosin staining revealed partially organized thrombi surrounded by a collagen wall. Examination of the vascular wall structure by elastin staining failed to show an elastin layer around the hematoma. The aneurysm was subsequently diagnosed as a pseudoaneurysm (). Since there was no evidence or history of recent head trauma, this case was regarded as idiopathic LSA pseudoaneurysm causing IVH.