Does non-perimesencephalic type non-aneurysmal subarachnoid hemorrhage have a benign prognosis?

Abstract

We reviewed and compared the clinical course and long-term prognosis of patients with non-aneurysmal subarachnoid hemorrhage (SAH) with and without a perimesencephalic pattern of hemorrhage on CT scan. In 876 patients with spontaneous SAH, 52 (5.9%) were diagnosed with non-aneurysmal SAH. Based on their CT scans, the SAH was classified as perimesencephalic non-aneurysmal SAH (PNSH) in 23 patients and non-perimesencephalic (non-PNSH) in 29 patients. The patients in the non-PNSH group were further divided into diffuse type (19 patients) and localized type (10 patients). We performed follow-up three-dimensional-CT angiography (3D-CTA) in all possible patients at least 1 year after the attack. The PNSH group had a lower rate of acute hydrocephalus (8.7%) and angiographic vasospasm (0%) complications than the non-PNSH group (37.9% and 27.6%, respectively). Only one case of rebleeding occurred in the non-PNSH group. No demonstrable source of bleeding was found on follow-up 3D-CTA, which was performed 1 year after the attack. All patients with non-aneurysmal SAH had similarly favorable long-term functional outcomes. Based on our study, patients with non-PNSH have a more complicated clinical course than those with PNSH. However, the long-term prognosis was similarly favorable for both the PNSH and non-PNSH in limited circumstances when they showed normal findings on a series of two-dimensional and 3D angiographic work-ups.

Introduction

Spontaneous subarachnoid hemorrhage (SAH) is mostly caused by rupture of a saccular aneurysm, but conventional angiography fails to reveal an aneurysm in about 15% of patients with spontaneous SAH.[1], [2], [3], [4], [5], [6], [7], [8], [9] In general, specific therapy cannot be offered to these patients and they are therefore treated with conservative therapy alone. The clinical course of spontaneous SAH varies according to location and amount of hemorrhage observed on CT scans.[10], [11] Van Gijn et al. reported a benign subgroup of patients with SAH of unknown origin, called perimesencephalic SAH.¹² Perimesencephalic SAH is characterized by a CT scan pattern of hemorrhage restricted to the perimesencephalic or prepontine cisterns and accounts for 20% to 68% of all patients with angiography-negative SAH.¹³ However, other types of angiography-negative SAH might be susceptible to complications, such as rebleeding, vasospasm, and hydrocephalus.[14], [15] One aim of this study is to compare the clinical course of angiography-negative SAH patients with and without a perimesencephalic pattern of hemorrhage on CT scans.

Repeat angiography is usually performed about 2 weeks after ictus in most centers, and it usually yields negative results. In several published series, patients with angiography-negative SAH have a more favorable prognosis than those with a demonstrable bleeding source.[16], [17] However, these patients could potentially suffer fatal rebleeding and long-term disability, hence their long-term prognosis remains uncertain.¹⁸ Moreover, most previous studies investigating the prognosis of angiography-negative SAH were restricted to evaluating functional grades (modified Rankin scale [mRS] or Activity of Daily Living [ADL] scale).[19], [20]

We aimed to provide evidence of a benign prognosis in these patients. Therefore, all patients diagnosed with angiography-negative SAH were assessed using three-dimensional CT angiography (3D-CTA) during follow-up. The other aim of this study was to evaluate, functionally and radiologically, the prognosis of the patients with angiography-negative SAH.