虽然出血的信号通常十分清楚,但是蛛网膜下腔出血仍然经常未被诊断出来,有时亦难以辨认出来。常可误诊为窦炎、颈纤维织炎和脑膜炎。蛛网膜下腔出血可能表现为突然头痛,或者急剧起病的脑症状,接着发生呕吐。偏头痛第一次发作可能造成鉴别诊断上的困难。这可能就需要神经科医师协助诊断。明确的出血初期往往未能认出。因此,在许多病例常常不能发现出血的预兆。这些前兆性症状可能与实际出血的性质极为相似,往往有小量血液从动脉瘤 Although the signs of bleeding are often clear, subarachnoid hemorrhage is still often undetected and sometimes illegible. Often misdiagnosed as sinusitis, cervical fibrosis and meningitis. Subarachnoid hemorrhage may manifest as a sudden headache, or a sharp onset of brain symptoms followed by vomiting. The first attack of migraine may cause differential diagnosis difficulties. This may require neurologists to help diagnose. Clear early bleeding often failed to recognize. Therefore, in many cases often can not find a sign of bleeding. These precursor symptoms may be very similar to the nature of the actual bleeding, often a small amount of blood from the aneurysm