Presentation, management, and outcomes of anterior inferior cerebellar artery dissecting and fusiform aneurysms: a systematic review and institutional case series.
Bektas D, Hagan M, et al. • Neurosurgical review • 2026
Management of AICA dissecting and fusiform aneurysms is highly individualized, with endovascular approaches frequently used but associated with notable periprocedural ischemic risk, while overall 81.4% of patients with available follow-up achieved good functional outcomes.
Key Findings
Results
Subarachnoid hemorrhage was the predominant presenting symptom in the systematic review cohort of AICA dissecting and fusiform aneurysms.
38 of 49 patients (77.6%) in the systematic review cohort presented with subarachnoid hemorrhage.
49 patients were identified from 36 studies in the systematic review, supplemented by 6 institutional cases.
Compressive cranial neuropathies, particularly involving the vestibulocochlear system, were common in patients with unruptured aneurysms.
Diagnosis often required digital subtraction angiography after initial non-invasive imaging was insufficient.
Results
Endovascular treatment, most commonly parent artery occlusion, was the most frequently employed management strategy.
Endovascular treatment was used in 61.2% (n=30/49) of cases in the systematic review cohort.
Parent artery occlusion was the most common endovascular technique reported.
Bypass surgery was reported selectively for proximal aneurysms with inadequate collateral flow.
Decompression or trapping was pursued as an alternative surgical approach based on aneurysm morphology or clinical context.
Conservative management was typically reserved for select patients with poor-grade SAH, high procedural risk, or patient refusal of intervention.
Results
Ischemic complications occurred in nearly one-quarter of patients treated with endovascular methods, particularly in proximal lesions.
Ischemic complications occurred in 23.3% (n=7/30) of endovascularly treated patients.
Ischemic complications were especially associated with proximal (A1-A2 segment) lesions.
The perforator-rich nature of proximal AICA segments was identified as a notable concern for periprocedural ischemic risk.
The study combined data from 36 published studies and one institutional series to characterize these complications.
Results
The majority of patients with available follow-up achieved good functional outcomes.
81.4% (n=35/43) of patients with available follow-up achieved good functional outcomes.
Follow-up data were not available for all 55 total patients (49 systematic review + 6 institutional).
Outcomes, complications, and radiological evolution were analyzed descriptively due to the rarity and heterogeneity of the lesions.
The study included a total of 55 patients (49 from systematic review and 6 from institutional case series).
Background
AICA dissecting and fusiform aneurysms are rare lesions that are poorly characterized and often require advanced imaging for diagnosis.
Only 49 patients across 36 published studies were identifiable through systematic review, underscoring rarity.
The study was conducted according to PRISMA guidelines.
Initial non-invasive imaging was frequently insufficient, necessitating digital subtraction angiography for diagnosis.
Individual patient-level data were extracted to allow descriptive synthesis given the rarity of cases.
Discussion
Management of AICA dissecting and fusiform aneurysms is highly individualized based on aneurysm location, morphology, collateral circulation, and clinical context.
Proximal (A1-A2) aneurysms with inadequate collateral flow were selectively treated with bypass surgery.
Conservative management was reserved for highly selected high-risk or anatomically inaccessible cases.
Endovascular, surgical, and conservative strategies were all represented in the cohort.
The descriptive and individualized nature of management reflects the absence of standardized treatment protocols for these rare lesions.
What This Means
This research synthesizes all available published cases of a rare type of brain artery abnormality called dissecting or fusiform aneurysms of the anterior inferior cerebellar artery (AICA), a vessel that supplies a critical part of the brainstem and cerebellum. By combining data from 36 published studies with cases from a single institution, the researchers identified 55 patients total. Most patients (about 78%) came to medical attention because the aneurysm had ruptured and caused a type of bleeding in the brain called subarachnoid hemorrhage. Among patients whose aneurysms had not ruptured, hearing and balance problems were common symptoms, reflecting the AICA's role in supplying the inner ear and related nerves.
Treatment approaches varied considerably based on where the aneurysm was located and the patient's overall condition. The most common treatment was an endovascular (catheter-based) procedure to block the affected artery, used in about 61% of cases. However, this approach carried a significant risk of stroke-like complications — occurring in about 23% of those treated this way — especially when the aneurysm was located in the more proximal (upstream) portions of the artery, which supply many small but critical branches. In selected cases where blocking the artery might cause too much damage, surgeons performed bypass grafting to reroute blood flow. Some high-risk patients were managed conservatively without intervention. Despite the severity of these lesions, about 81% of patients with recorded follow-up achieved good functional outcomes.
This research suggests that there is no single best treatment for AICA dissecting and fusiform aneurysms, and that management must be tailored to each patient's specific anatomy, clinical condition, and risk factors. The findings highlight the importance of advanced imaging such as catheter-based angiography for accurate diagnosis, and they draw attention to the substantial risk of brain ischemia (loss of blood supply) when blocking the AICA, particularly in its proximal segments. Given the rarity of these lesions, pooled analyses like this one are essential for guiding clinical decision-making in the absence of large controlled trials.
Bektas D, Hagan M, Graepel S, Lanzino G, Keser Z. (2026). Presentation, management, and outcomes of anterior inferior cerebellar artery dissecting and fusiform aneurysms: a systematic review and institutional case series.. Neurosurgical review. https://doi.org/10.1007/s10143-026-04479-4