The patient presented in this case report had a PAM that was misdiagnosed as an arteriovenous malformation. PAM is a rare vascular malformation, which is defined as dilated, overlapping, and tortuous arteries forming a mass of arterial loops with a coil-like appearance in the absenceof arteriovenous shunting[1–3]. PAMs are rare and usually occur in young women. They frequently involve the distal branches of the anterior or posterior cerebral artery[1, 3–5]. Involvement of the distal M3 segment of the middle cerebral artery, as in our patient, is rare.
Previous studies have indicated that PAMs of specific cerebral arteries frequently have certain characteristics. For example, PAMs of the middle and posterior cerebral artery and the posterior communicating artery often have a tight vascular circle with multiple aneurysms and calcification. Those of the distal anterior cerebral artery tend to be moderately curved with less dense coils and often contain calcification. Superior cerebellar and posterior inferior cerebellar artery PAMs often lack substantial dilation and are accompanied by aneurysms.The PAM in our patient involved the distal left middle cerebral artery.
As blood flows through the spiral collection of arteries in a PAM, it slows down and gradually rotates, causing arterial dilation and clot formation. Arterial elongation and angulation can cause stretching and distortion of arterial branch openings, which can result in reduced blood flow to the perfused region and consequent cerebral infarction and atrophy. Our patient had evidence of cerebral infarction in the involved brain area and a small amount of hemorrhage.
Although the cause of PAMs remains unclear, several hypotheses have been proposed. Congenital factors such as an inherited defect or insult during brain development can result in arterial dysplasia. Acquired factors such as somatic mutations occurring later in life, viral infection, chronic healed dissection, and inflammatory, immune-related, and degenerative factors may also play a role[5, 6].
PAMs are often found incidentally. However, our patient was symptomatic with dizziness and convulsions, which may have been caused by left temporoparietal hemosiderin deposition and fiber bundle damage.
PAMs are often misdiagnosed as arterial prolongation or dilation or arteriovenous malformations. Arterial prolongation and dilation are more common in elderly men with a history of hypertension and smoking. Although the involved blood vessels are dilated and curved in patients with arterial prolongation and dilation, vessels of the vertebrobasilar circulation vessels and internal carotid artery are usually affected. PAM vessels are severely curved and overlapped, which leads to a large number of arterial loops . Draining veins are seen in arteriovenous malformations .
Previous studies have demonstrated that PAMs do not usually progress; therefore, conservative treatment of incidental PAMs is recommended . However, those associated with an aneurysm should be closely monitored, as aneurysm treatment may be necessary if imaging progression is observed .