Changes in hemorrhage pattern on consecutive non-contrast CT scans in non-aneurysmal subarachnoid hemorrhage patients

Introduction: The diagnosis perimesencephalic subarachnoid hemorrhage (PMSAH) is based on a specific distribution pattern within 72 h after ictus. However solid evidence is lacking for this time window with the potential risk that blood distribution can change over time, with implications for the management of these patients. Research question: To study cisternal and intraventricular blood pattern changes on initial and follow-up non-contrast CT scans (NCCTs) during the first 72 h. Materials and methods: This retrospective study included consecutive PMSAH and non-perimesencephalic (NPSAH) patients in whom at least two NCCTs were performed within the first 72 h. Presence and changes in the distribution of cisternal and intraventricular blood was independently assessed by three observers. Results: 135 patients (62 PMSAH and 73 NPSAH) were included. The distribution of SAH remained unchanged within the first 72-h in 63 (47 %) patients (PMSAH: 38 (61 %), NPSAH: 25 (39 %))(p < 0.01). An increase in SAH distribution from 0 to 6 h was seen in 7/47 PMSAH (15 %) versus 24/47 (51 %) in NPSAH patients (p < 0.01). A decrease in SAH distribution from 0 to 6 h was seen in 6/47 (13 %) PMSAH patients versus 2/47 (4 %) NPSAH patients (p < 0.01). Between 6 and 24 h, a 72 % decrease (10/14) was only seen in NPSAH patients. The diagnosis PMSAH never changed to NPSAH or vice versa due to SAH redistribution. Discussion and conclusion: Within the first 72 h after ictus, redistribution of cisternal and intraventricular blood is seen more often in NPSAH than in PMSAH patients but did not change the specific diagnosis.