[A Case of Segmental Dysgenesis at the Terminal Portion(C1)of the Internal Carotid Artery with an Anomalous Collateral Vessel Containing Plexiform(Twig-like)Networks as a Possible Cause of Intracerebral Hemorrhage].

A 65-year-old woman was transferred to our hospital because of loss of consciousness along with a right hemiplegia due to an intracerebral hematoma(ICH)that extended from the left temporal lobe to the lateral part of the basal ganglia. CT angiograms(CTA)and 3D-rotational angiograms showed an absence of the distal C1 segment of the left internal carotid artery(ICA), and an anomalous collateral vessel arising from the proximal end of the left A2 with plexiform(twig-like)arterial networks, supplying antegrade blood flow to the left middle cerebral artery territory. The caliber of the left carotid arterial system decreased from the origin to the terminal end. The source images of CTA revealed that the plexiform arteries were very close to the ICH, suggesting that the vessels might have caused the bleeding. Because a hypoplastic left carotid canal was observed, the segmental dysgenesis of the C1 portion of the left ICA seemed to have occurred during the early embryonic period. T2-weighted DRIVE images of MRI demonstrated the presence of a cord-like rudimentary structure corresponding to the distal C1 and proximal M1 portions. The patient was managed conservatively and was transferred to another hospital for subsequent rehabilitation. Segmental dysgenesis of the C1 portion is extremely rare. To our knowledge, only a single report has been published. The present findings suggest that 1)an anomalous collateral vessel corresponding to Heubner's artery evolved with residual primitive plexiform(twig-like)arterial networks and 2)this anomalous structure has not been proposed as a type of collateral systems for ICA dysgenesis.