Internal carotid artery-middle cerebral artery junction small arterial ring: A report of two cases diagnosed by magnetic resonance angiography

Purpose To describe two cases of internal carotid artery (ICA)-middle cerebral artery (MCA) junction small arterial ring diagnosed by magnetic resonance angiography (MRA). Methods A 73-year-old woman and a 92-year-old man underwent cranial magnetic resonance imaging (MRI) and MRA using a 3-Tesla scanner. MRA was performed using a standard 3-dimensional time-of-flight technique. Results Cranial MRA showed a small arterial ring at the junction between the ICA and MCA in both cases on maximum-intensity-projection (MIP) images. After the creation of partial volume rendering (VR) images, the variations were clearly identified. The proximal end of the arterial ring was the ICA, and the distal end was the MCA. Conclusion Using MRA, we diagnosed two cases of a small ICA-MCA junctional ring. This variation may not represent ICA or MCA fenestration or MCA duplicate origin. We used the term “ICA-MCA junctional small arterial ring” to describe this variation. Careful observation of MIP images is important for detecting arterial variations on MRA. The creation of partial VR images is useful for the correct diagnosis of arterial variations.