[A case of DiGeorge syndrome with left internal carotid artery absence probably causing one-and-a-half syndrome]

We experienced a case of DiGeorge syndrome with left internal carotid artery absence probably causing one-and-a-half syndrome. MR angiogram demonstrated the apparent absence of the left internal carotid artery and consequently abnormal blood supply to the left middle cerebral artery, which was derived from the basilar artery via the left posterior communicating artery. The patient alsoshowed both an extremely narrow carotid canal on the left side and a very fine vessel extending to the terminal of the left internal carotid artery. Therefore, we regarded this abnormality as severe hypoplasia of left internal carotid artery and supposed that this hypoplasia had originated in maldevelopment of the third aortic arch based on the coexisting lower bifurcation of the right common carotid artery. Since the lesion of one-and-a-half syndrome is restricted to the pontine tegmentum, we speculated that it had resulted from ischemia of the basilar artery area during the embryonic period associated with the absence of the internal carotid artery. To our knowledge, DiGeorge syndrome has never been reported as a complication of internal carotid artery absence. The patient did not demonstrate either chromosome 22q11.2 deletion or TBX1 gene mutation, which is considered the gene responsible for 22q11.2 deletion syndrome. Therefore, the etiology of DiGeorge syndrome in this case remains unclear.