MRI Detection of Blood after Perimesencephalic Subarachnoid Hemorrhage (P5.001)

OBJECTIVE: We sought to determine MRI sensitivity for hemorrhage following perimesencephalic subarachnoid hemorrhage (SAH). BACKGROUND: Prior studies have shown that the sensitivity of MRI detection of residual hemorrhage following aneurysmal SAH is > 70% after 3 months [Imaizumi, Stroke 2003]. Perimesencephalic SAH is a subset of SAH associated with hemorrhage confined to the pre-truncal and suprasellar cisterns and is generally associated with a benign prognosis. DESIGN/METHODS: We reviewed consecutive perimesencephalic SAH patients who were hospitalized at our institution from January 1, 2008 to January 1, 2012 who received an MRI brain within 6 months. Perimesencephalic SAH was defined as CT confirmed SAH confined to the cisterns surrounding the brainstem and suprasellar cistern with a diagnostic conventional cerebral angiogram negative for aneurysm. We categorized MRI brains as acute (within 1 week of symptom onset) and subacute-chronic (> 1 week). MRI brains were reviewed by study authors for presence of SAH on sagittal T1, FLAIR, and GRE sequences. RESULTS: Among 29 patients with perimesencephalic SAH, 18 patients had a total of 23 MRI brain studies completed. Mean age was 49.9 years (range 31 to 70) and the majority (61%) were female. Median time from symptom onset to MRI brain was 4 days (range 1 to 183 days). Median length of stay was 7 days (range 4 to 14 days). Among the 15 MRI brain studies that were completed acutely (within 1 week), SAH was visible on 14 of the MRI studies (93%). SAH was detectable on none of the 8 MRI brain studies done in the subacute-chronic period (greater than 1 week after ictus). CONCLUSIONS: In contrast to aneurysmal SAH, the ability of MRI to detect residual hemorrhage after 1 week may be severely limited in perimesencephalic SAH. Clinicians should be aware of the differing time to hemorrhage resolution on MRI of perimesencephalic SAH compared to aneurysmal SAH. Disclosure: Dr. Samuels has nothing to disclose. Dr. Conners has nothing to disclose. Dr. Cutting has received personal compensation for activities with F1000. Dr. Lee has nothing to disclose.