Twig-like MCA is a rare anomaly with prevalence of 0.1-1% in literature[1 ], possibly explained by failure fusion of primitive MCA[2 ]. Pathogenesis is not fully understood. Hemorrhage (50%)[3 ], cerebral ischemia ([Figure 1 ]), aneurysm or incidental fidings the clinical presentation. It’s important to know
this entity not to misdiagnose as Moyamoya or steno-occlusive disease[4 ].
Figure 1 A) Axial non contrast Brain CT with hypodensity on the striatocapsular area (arrow);
B) Axial intracranial CT angiography (CTA) image with MCA occlusion (arrow) and anastomotic
vessels (arrowhead) to the distal part of the MCA trunk.
Features of Tw-MCA are reported and presented in our case ([Figures 2 ], [3 ] and [4 ])[2 ].
Figure 2 Four Features of Twig-Like MCA: A) DSA frontal view of early arterial phase of the
left ICA with 1) unilateral proximal M1 occlusion (arrow) and 2) plexiform arterial
network instead of MCA trunk (arrowhead); anomalous artery from left A1 segment (asterisk);
B) Late arterial phase DSA of the left ICA with 3) Perforators from the plexiform
network (arrow) and 4) Cortical branches beyond occluded MCA trunk with anterograde
flow with normal configuration (arrowhead); C) DSA lateral view of early arterial
phase of the left ICA with the plexiform arterial network (arrow); D) DSA lateral
view of early arterial phase of the left ICA with cortical branches beyond occluded
MCA trunk with anterograde flow with normal configuration (arrow).
Figure 3 A) DSA oblique view of early arterial phase of the left ICA; B) DSA oblique view
of late arterial phase of the left ICA; C) DSA oblique view of arterial phase of the
left ICA with leptomeningeal collaterals from the distal left anterior cerebral artery
and distal branches of MCA; D) Diagnostic DSA 3D reconstruction of the left ICA with
the MCA occlusion (white arrow); and an anomalous artery from left A1 segment of the
ACA (arrowhead). Also, the plexiform arterial network instead of MCA trunk is demonstrated
with the normal distal MCA trunk.
Figure 4 A) Diagnostic DSA 3D reconstruction of the left ICA with the plexiform arterial network;
B) Diagnostic DSA 3D reconstruction of the left ICA with the plexiform arterial network
and the normal distal MCA trunk.
Moyamoya has different characteristics from Tw-MCA: progressive bilateral terminal
carotid occlusion with MCA, ACA involvement and extensive lenticulostriate collaterals.