Malignant brain tumors, such as metastatic brain tumors, glioblastomas, and melanoma sometimes lead to intracranial hemorrhage8. However, spontaneous hemorrhage as an initial presentation for meningiomas, even though reported, is less frequent, although they are usually vascular tumors4. The rarity of this condition not only makes determining causative factors of the hemorrhage challenging, but also makes the mechanisms of spontaneous hemorrhage harder to understand4,9,10. Fortunately, some sporadic cases of spontaneous hemorrhage in meningiomas have been reported and many clinical features of such a condition have been characterized.
Although CT is the reference standard for the detection of hemorrhage, this condition of meningiomas with intracranial hemorrhage is not always easy to distinguish on CT, and multi-model radiological examinations are needed4. Brain CT and MRI usually displayed well-defined, dense, contoured extra-axial masses displacing the adjacent brain along with acute or subacute hemorrhage. The site of the hematoma was generally not typical for hypertensive intracerebral bleeding. On MRI with gadolinium enhancement, the mass with a dural base showed moderate to strong enhancement except for the portion representing hemorrhage. These patients could gain good outcomes when they are managed appropriately with early diagnosis and correct treatment2,4. The majority of these cases require surgical intervention because observation and other treatments do not alleviate mass effect and risk of repeated hemorrhage2,11. Previous reports had provided some information on the signal intensity on MRI and indicated hyperintensity on T2-weighted MRI as a risk factor of meningioma bleeding10,12; however, this finding was just found more frequently in the patients with type I and type III bleeding in this study. While the implication of this hyperintensity has not been fully established, some cases with intratumoral hemorrhage may be attributed to the tumors’ soft consistency12–14.
Increased bleeding tendency was found to be associated with two age groups (< 30 years and > 70 years), convexity and intraventricular locations, and fibrous meningiomas2; however, the most frequent localizations were the convexity and parasagittal areas in this study, and their pathological outcomes of these tumors in this study followed the histopathological distribution of meningiomas in general1. Although the patients with type II and type III bleeding had significant PTBE comparing with control group and PTBE might be an indicator for the certain bleeding types, PTBE could be just as a result of the tumor hemorrhage. The exact mechanism of the hemorrhage from meningiomas is not fully understood; however, several pathological mechanisms have been hypothesized to explain this rare condition2,4,9−12. The proposed mechanisms could include rupture from weakened blood vessels, endothelial proliferation and subsequent vascular occlusion, direct vascular invasion by tumor cells, accumulation of bioactive substances in tumor, concomitant vascular malformation or aneurysm, stretching and rupture of subdural bridging veins, tumor growth-induced venous compression associated with peritumoral edema, and infarction owing to rapid growth of the tumor. In addition, two distinct types of blood vessels involving differentiated and undifferentiated vessels were determined in our prior study; undifferentiated blood vessels contribute to a fragile state of tumor vasculature that can be disrupted by a precipitating event, thus leading to spontaneous hemorrhage4.
The above proposed mechanisms were mainly based on reported cases. Among these cases, they were most frequently present according to the site of hemorrhage such as subarachnoid hemorrhage, intracerebral hematoma, intratumoral hemorrhage, or subdural hematoma5,6,9−12. Unfortunately, this description cannot reflect the relationship between meningioma and hemorrhage; moreover, it contributes little to guiding clinical diagnosis and treatment. Correlating prior reports of such cases with our cases, a new bleeding classification of meningiomas was proposed on the basis of the anatomical relationship between meningioma and hematoma. We summarized this special hemorrhage from meningioma into three bleeding patterns: purely intratumoral hemorrhage, purely extratumoral hemorrhage, and combined intratumoral and extratumoral hemorrhage. In addition, intratumoral hemorrhage may penetrate the tumor and result in extratumoral hemorrhage; as a result, the type of combined hemorrhage usually came from the intratumoral bleeding that extended into the surrounding intracranial spaces.
Apart from showing the direct relationship between meningioma and hemorrhage, this new bleeding classification is easier to understand the possible mechanism of meningioma hemorrhage. For example, stretching and rupture of subdural bridging veins may explain the purely extratumoral hemorrhage involving subdural hematoma and subarachnoid hemorrhage. Rupture from weakened or undifferentiated blood vessels is usually associated with purely intratumoral hemorrhage. The extratumoral hemorrhage should be secondary to intratumoral bleeding in the third type of hemorrhage. Infarction and necrosis owing to rapid growth of the tumor could explain the third type of hemorrhage. Traumatic head injury is unlikely to be a causative factor in cases with purely intratumoral hemorrhage. In syncytial meningiomas, the bleeding is probably related to the presence of intratumoral vasoactive substances released, such as histamine, which could induce vasodilatation and result in the purely intratumoral hemorrhage. In addition, cerebral edema and venous obstruction can cause infarction and then usually induce the purely extratumoral hemorrhage.
Emergency or early one-stage total removal of the hemorrhagic meningioma and hematoma is the main treatment of choice2–4,10−12. The risks of meningioma hemorrhage usually vary with the amount of bleeding, the location of bleeding, the size of tumor, or the location of tumor. There was no difference of the therapeutic method for different bleeding patterns; however, this bleeding classification system could offer some implications for the treatment strategy. According to the review of prior cases reported in the literature and such cases in this study4–6,9−12,14−16, the symptoms in most patients with the first bleeding type are usually mild and their clinical statuses are generally stable, and early or selective surgery could be performed following adequate preoperative evaluations; the symptoms in patients with the second bleeding type are sometimes mild and may be sometimes moderate to severe, so emergency or early surgery should be chosen according to the patients’ clinical status; almost all patients with the third bleeding type have moderate to severe symptoms, and these patients usually need emergency surgery after necessary examinations. Recognizing these facts and consequent treatment changes may result in improvement of patients’ outcomes.
Although the data are preliminary, the study highlights the new bleeding classification of meningiomas based on the anatomical relationship between meningioma and hematoma. Moreover, sharing our opinion and typical radiographic images may help improve awareness of this special condition. Future research will focus on the issue of collecting more cases to explore the finding in this study.