Objective: Non-traumatic subarachnoid hemorrhage [SAH] is mostly caused by a ruptured intracnial aneurysm. A conventional or three dimension [3D] digital subtraction angiography [DSA] is a gold standard radiographic modality to detect intracranial aneurysm. Those SAH patients with negative DSA or 3D-DSA are called angiogram-negative non-traumatic SAH. A natural history and prevalence of this condition in northeastern Thailand are limited.
Materials and Methods: The present study was conducted at Srinagarind Hospital or Khon Kaen University Hospital. The
study period was between January 2014 and June 2016. The inclusion criteria were adults patients (age over 15 years)
diagnosed as non-traumatic SAH; no definite abnormality of intradural vascular structures under baseline 3D-DSA except:
vasospasm; available data on clinical and radiographic follow-up.
Results: During the study period, there were 252 patients diagnosed with SAH who underwent 3D-DSA. Of those, 42
patients (16.6%) had negative results of baseline 3D-DSA. Only 22 patients (52.4%) had available follow-up clinical data.
At 6-month of follow-up, the numbers of patients with a modified Rankin Scale of 0 to 1 was 86.4% (19 patient). In total of 42 patients, 32 patients (76.2%) had the good prognosis. None of the 22 patients had no vascular aneurysm on follow-up MRA or CTA.
Conclusion: Angiogram-negative non-traumatic SAH was found 16.6% in northeast Thailand. Most patients had better
prognosis (76.2%) and had negative results on follow-up radiological studies.

Keywords: Prognosis, Aneurysm, Digital subtraction angiography