Ruptured aneurysm often presents with SAH and based on the characteristic CT imaging it’s easy to make the diagnosis of aneurysmal SAH (aSAH). However on very rare occasions, ruptured aneurysm could present with isolated ICH and/or IVH without SAH [1, 2, 4–8], which may lead to delayed and incorrect diagnosis and management [9]. Because of their anatomic characteristics, it’s understandable that aneurysms at the peripheral cerebral arteries could cause isolated ICH and/or IVH, but aneurysms at the main trunks of the Willis cycle with such presentation is rather obscure [2, 9]. The cause of this rare entity is multifactorial.
Firstly, delayed CT scan after bleeding ictus might lead to false negative result of SAH. The sensitivity of CT imaging continues to decrease with the development of time in diagnosing SAH [10, 11]. According to Thai et al.’s case series 6 of the 13 ruptured aneurysms without SAH had reported or suspected sentinel events, averaging 6.3 days before admission [1]. Secondly, the mass effect of ICH could compress the brain parenchyma and makes it denser. ICH could also squeeze out and dilute the blood component under the subarachnoid space. The superposition effect of aneurysmal ICH during this process increases the difficulty of diagnosing tiny SAH. Thirdly, dome of an aneurysm buried into the cerebral parenchyma is another cause. The intraoperative findings of one previous case report and our cases had demonstrated and recorded this fact [6]. Our review showed that the average diameter of the aneurysms presented with isolated ICH and/or IVH was 16.21 mm, which is apparently larger than that of the general intracranial aneurysms. And it’s conceivable that larger aneurysms have more chance to be partly buried into the cerebral parenchyma. Furthermore, it’s noteworthy that severe acute or chronic anemia is another cause of false negative result. The hyperintensity appearance on noncontrast head CT is a reflection of electron density, and there is a linear relationship to the hematocrit and hemoglobin concentration [8]. The preliminary statistical analysis of our review showed that 57 % (12/21) of the patients were female, which is in accordance with the sex differences in the incidence of aSAH [12]. This might imply that sex does not play an important role in the incidence of this specific entity.
One of the challenges this entity poses to us is correct and timely diagnosis. According to Park J’s analysis of 62 patients with spontaneous putaminal hemorrhage, 62.5 % of the younger (≤55 years) normotensive patients resulted in angiographic abnormalities (including 1 MCA aneurysm) [5]. So, angiographic modalities should be considered for younger and normotensive patients with spontaneous putaminal hemorrhage. Furthermore, patients presenting with a head CT scan revealing ICH in the temporal lobe with or without frontal, parietal, and/or intraventricular involvement should be considered for the possibility of a ruptured aneurysm, even in the absence of diffuse SAH [1]. However, of the identified 21 patients, definite mention of whether having a history of hypertension or not was only recorded in six patients. Three out of the six (50 %) patients, had a history of hypertension. And 7 of the 21 patients were older than 55 years old. So, patients of isolated ICH and/or IVH with a history of hypertension and older age could not be exempted from ruptured aneurysms. As delayed CT scan after bleeding ictus might lead to false negative result of SAH, patients of isolated ICH and/or IVH who have reported or suspected recent sentinel events should undergone angiographic screening [1]. As average diameter of the aneurysms presented with isolated ICH and/or IVH was apparently larger than that of the general intracranial aneurysms, occupying lesion in the hematoma might be noticed in some cases [4]. Just as our case two illustrated, suspicious occupying lesion in the hematoma warrants further angiographic investigation.
The management of ruptured cerebral aneurysms at the main trunks of the Willis cycle with a presentation of isolated ICH and/or IVH is another challenge both for its urgency in treatment and poorness in prognosis. Perhaps as a result of the mass effect by ICH and/or IVH, most of the reported cases (18/21) underwent urgent surgical clipping of the responsible aneurysms and simultaneous evacuation of the hematoma, except one underwent coiling and the other two died of too rapid deterioration to further management. However, the prognosis was not so encouraging based the now available data. Good recovery was only achieved in ten patients (47.6 %).