Purpose: To elucidate the diagnostic value of 7T ultrahigh-field MRI in differentiating intracranial microvascular lesions indeterminate on 3T MRI, and demonstrate its pivotal role in rectifying clinical management through a case involving a lesion misdiagnosed as an A2-segment "aneurysm" for five years.

Methods: A 50-year-old female with a 2.0-mm "aneurysm" at the right ACA-A2 segment on serial 3T MRI (2020-2025) underwent 7T MRI utilizing: Ultrahigh-resolution time-of-flight MRA (0.4-mm isotropic slices); T1-weighted black-blood vessel wall imaging (VWI, 0.45-mm slice thickness)

Comparative analysis focused on: Morphology (spherical pseudolesion vs. linear vessel); Wall architecture (neck-like sign vs. smooth transition)

Results: 3T misdiagnosis mechanism: Partial volume effect manifested as a 2.0-mm spherical protrusion mimicking an aneurysm . 7T diagnostic evidence: TOF-MRA revealed an angled perforating vessel (diameter: 0.8 mm) ; VWI confirmed smooth wall continuity without focal dilatation at the parent vessel-perforator junction. Clinical impact: Lifelong surveillance was discontinued.

Conclusion: 7T MRI submillimeter resolution resolves 3T MRI's limitation in identifying aneurysm-mimicking pseudolesions of perforators, establishing a noninvasive diagnostic benchmark for microvascular pathologies. This case provides direct evidence for preventing overtreatment and advocates incorporating 7T MRI into standardized algorithms for indeterminate neurovascular lesions.