Angiographically Occult Subarachnoid Hemorrhage: Yield of Repeat Angiography, Influence of Initial CT Bleed Pattern, and Sources of Diagnostic Error in 242 Consecutive Patients

Abstract

Background and purpose: Nearly 20% of patients with spontaneous SAH have no definitive source on initial DSA. The purpose of this study was to investigate the timing and yield of repeat DSA, to clarify the influence of initial CT bleed pattern, and to characterize sources of diagnostic error in this scenario.

Materials and methods: We evaluated the yield of repeat DSA and clinical outcomes stratified by hemorrhage pattern on CT in consecutive patients with nontraumatic SAH with negative initial DSA findings at a referral center. Cases in which the culprit lesion was subsequently diagnosed were classified as physiologically occult (ie, undetectable) on the initial DSA, despite adequate technique and interpretation or misdiagnosed due to operator-dependent error.

Results: Two hundred forty-two of 1163 (20.8%) patients with spontaneous SAH had negative initial DSA findings between 2009 and 2018. The SAH CT pattern was nonperimesencephalic (41%), perimesencephalic (36%), sulcal (18%), and CT-negative (5%). Repeat DSA in 135/242 patients (55.8%) revealed a source in 10 patients (7.4%): 4 saccular aneurysms, 4 atypical aneurysms, and 2 arteriovenous shunts. The overall yield of repeat DSA was 11.3% with nonperimesencephalic and 2.2% for perimesencephalic patterns. The yield of the second and third DSAs with a nonperimesencephalic pattern was 7.7% and 12%, respectively. Physiologically occult lesions accounted for 6/242 (2.5%) and operator-dependent errors accounted for 7/242 (2.9%) of all angiographically occult lesions on the first DSA.

Conclusions: Atypical aneurysms and small arteriovenous shunts are important causes of SAH negative on angiography. Improving DSAs technique can modestly reduce the need for repeat DSA; however, a small fraction of SAH sources remain occult despite adequate technique. These findings support the practice of repeating DSA in patients with a nonperimesencephalic SAH pattern.

FIG 1.

A 78-year-old woman with an example of a physiologically occult aneurysm on the initial DSA on the postbleed day 1. A frontal projection (A) with 3D reconstruction shows no source lesion (B). A second DSA on postbleed day 6 had normal findings. The patient was discharged and re-presented with worsening headache on postbleed day 12. A third DSA on postbleed day 12 (C) demonstrated a submillimeter basilar artery perforator blister aneurysm (curved white arrow) that was clipped.

FIG 2.

A 36-year-old woman admitted with an internal carotid artery blister aneurysm, misdiagnosed due to 2 forms of operator-dependent error. The initial DSA (A) shows a perceptual-type interpretive error in that a laterally projecting blister (white arrow) was not recognized. The blister was more evident on the second DSA (B) and perceived but misinterpreted as vasospasm due to developing vasospasm elsewhere (dashed arrows). Finally, the lesion (yellow arrow) was recognized on the third DSA (C) as vasospasm abated. Intraoperative photographs (D) confirm the rupture site (yellow arrow) secured with clipping.