Getting More Out of Follow-up Three-Dimensional Time-of-Flight Magnetic Resonance Angiography in Endovascularly Treated Intracranial Aneurysms

BACKGROUND: We retrospectively re-evaluated follow-up three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) in patients with aneurysms treated with coiling at our Institute. AIMS: To document the type and frequency of postcoiling residue patterns as seen on follow-up MRA and to document their evolution with time where a further follow-up MRA was available. To assess the implications of the location of the aneurysm on residue and recurrence. SUBJECTS AND METHODS: 3D TOF MRA for 104 aneurysms were evaluated for residue size and residue pattern. Mainly, three residue patterns were identified. The aneurysms were allocated to different groups depending on the location. Multiple MRA studies were available in subgroup 1* and subgroup 2* where the residue growth or reduction and pattern change was noted and residue growth rates were calculated. RESULTS: Collectively 54 (51.92%) aneurysms showed occlusion (pattern 1 and 1A), 31 (29.81%) showed neck residue (pattern 2A, 2B and 2C) and 19 (18.27%) showed recurrence (pattern 3A, 3B and 3C, residue size >3 mm) at the last follow-up MRA. Type 2A/3A patterns were more common. In terms of residue and recurrence, the distally located aneurysms (Group 3) appeared to do well. For those showing growing residue/recurrence, the average growth rate was calculated at 0.094 mm/month and 0.15 mm/month, respectively, for subgroup 1* and subgroup 2*, although the difference was not statistically significant. With longer follow-up the persisting and growing residues from both the subgroups, not warranting early re-treatment, showed a low growth rate at approximately 0.05 mm/month. CONCLUSIONS: TOF MRA helps in identifying different residue patterns in coiled aneurysms. Serial follow-up MRA appears useful in showing the pattern and size changes in the residual aneurysm. Although more work is required in this regard, calculation of aneurysm/residue growth rate may be useful in prognostication and in scheduling further follow-up or retreatment. The risk factor related to the location of the aneurysm warrants further study.