Recent data showed increasing numbers of cases of spontaneous nonaneurysmal subarachnoid hemorrhage.
Spontaneous Subarachnoid Hemorrhage with Negative Angiography can be determined in 14-22 %.
Intracranial arteriovenous malformation (AVM): 45% of cases (AVMs more commonly cause ICH & IVH than SAH)
Certain vasculitides that involve the CNS
Rarely due to tumor
Cerebral artery dissection (may also be posttraumatic)
Rupture of a small superﬁcial artery
Rupture of an infundibulum
Iatrogenic or bleeding dyscrasias:
Dural sinus thrombosis
Spinal AVM: usually cervical or upper thoracic
Pretruncal nonaneurysmal SAH
Rarely reported with some drugs: e.g. cocaine
Sickle cell anemia
The studies show a low complication rate for subarachnoid hemorrhage (SAH) patients with a normal angiography, especially in the perimesencephalic subarachnoid hemorrhage group. The prognosis appears to be less favorable in terms of a more frequent need for external ventricular drainage (EVD), so a more cautious approach is recommended in this subgroup 1).
Between 1999 and 2013, 214 patients suffered from nonaneurysmal subarachnoid hemorrhage (NASAH), 14% of all patients with SAH. Outcome was assessed according to the modified Rankin Scale (mRS) at 6 months. Risk factors were identified based on the outcome.
The number of patients with NASAH increased significantly in the last 15 years of the study period. There was a statistically significant increase in the rate of nonperimesencephalic (NPM)-SAH occurrence and antiplatelet agents use, while the proportion of elderly patients remained stable.
Favorable outcome (mRS 0-2) was achieved in 85% of cases, but patients treated with antiplatelet agents had a significantly higher risk for an unfavorable outcome. Further analysis showed that elderly patients, and especially the subgroup with a Fisher Scale 3 bleeding pattern, had a high risk for an unfavorable outcome, whereas the subgroup of NPM-SAH without a Fisher Grade 3 bleeding pattern had a favorable outcome, similar to perimesencephalic subarachnoid hemorrhage (PM)-SAH.
Over the years, a significant increase in the number of patients with NASAH has been observed. Also, the rate of aCP use has increased significantly. Risk factors for an unfavorable outcome were age > 65 years, Fisher Grade 3 bleeding pattern, and aCP use. Both “PM-SAH” and “NPM-SAH without a Fisher Grade 3 bleeding pattern” had excellent outcomes. Patients with NASAH and a Fisher Grade 3 bleeding pattern had a significantly higher risk for an unfavorable outcome and death. Therefore, for further investigations, NPM-SAH should be stratified into patients with or without a Fisher Grade 3 bleeding pattern. Also, cases of spontaneous SAH should be stratified into NASAH and aneurysmal SAH 2).
From 1999 to 2009, data of 125 patients with non-aneurysmal SAH were prospectively entered into a database. All patients underwent repetitive cerebral angiography. Outcome was assessed according to the modified Rankin Scale (mRS) (mRS 0-2 favorable vs. 3-6 unfavorable). Also, patients were divided in two groups according to the distribution of blood in the CT scan (perimesencephalic and non-perimesencephalic SAH).
106 of the 125 patients were in good WFNS grade (I-III) at admission (85%). Overall, favorable outcome was achieved in 104 of 125 patients (83%). Favorable outcome was associated with younger age (P < 0.001), good admission status (P < 0.0001), and absence of hydrocephalus (P = 0.001).73 of the 125 patients suffered from perimesencephalic SAH, most patients (90%) were in good grade at admission, and 64 achieved favorable outcome.52 of the 125 patients suffered from non-perimesencephalic SAH and 40 were in good grade at admission. Also 40 patients achieved favorable outcome.
Patients suffering from non-aneurysmal SAH have better prognosis compared to aneurysm related SAH and poor admission status was the only independent predictor of unfavorable outcome in the multivariate analysis. Patients with a non-perimesencephalic SAH have an increased risk of a worse neurological outcome. These patients should be monitored attentively 3).