Presentation
History withheld. No prior ischemia or hemorrhage.
Patient Data
Short discontinuity of right M1 segment.
Instead, there are several small vessels focally replacing the M1 segment giving a "rete mirabile like" like or twig-like appearance.
No pathology of the distal ICA and (not shown) no signs of pathological leptomeningeal or transdural anastomoses elsewhere (questioning the potential differential diagnosis of Moyamoya-Syndrome).
Young age, no risk factors and no further angiographic signs elsewhere questioning the presence of a unifocal acquired steno-occlusive lesion.
Case Discussion
The literature holds a series of cases called "twig-like MCA" or "rete mirabile anomaly of MCA". In several cases found in the literature, a hemorrhage led to finding the vessel anomaly. The incidence is likely to be << 0,5% but very much unclear at the moment remembering there are no clear criteria separating this from other vascular pathology of the region like in Moyamoya Syndromes.
There are plausible theories a twig-like MCA is a form of MCA aplasia with "rete mirabile" style reconstitution, noting the MCA embryologically is formed by the fusion of twigs from the ICA explaining other similar and more frequent MCA anomalies like MCA fenestration, and noting the distal ICA is unaffected. However, there is no proper evidence to definitely rule out that this might be an acquired condition or a special form of Moyamoya in an least some of these cases.
Further investigation into angiographic features to distinguish this from moyamoya syndromes and the clinical significance of those findings (regarding the outcome, risks of hemorrhage and ischemia) is needed.
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