Clinical and radiological aspects of cerebellopontine neurinoma presenting with recurrent spontaneous bleedings.

BACKGROUND: Neurinomas are benign, usually encapsulated, tumors growing in peripheral nerve sheath with a high incidence in the cerebellopontine angle. CASE DESCRIPTION: We report a case of vestibular neurinoma (VN) with a "biphasic" pattern of intratumoral hemorrhage presenting with cephalalgia along with progressive ipsilateral mild impairment of both VII and VIII cranial nerves. A thorough preoperative magnetic resonance imaging study better characterized the patchy pattern of the round shaped lesion, resulting in three different intensity signals, due to the peculiar characteristics of the tumoral mass and the recurrent bleedings, respectively. Postoperatively, histological examination confirmed the diagnosis of neurinoma.
CONCLUSION: Hemorrhagic VN are rare tumors; from the first case described in 1974 only 43 more have been reported in the literature so far. Noteworthy, "biphasic" bleedings are even rarer. From an accurate review of the literature we collected and thus emphasized the radiological and clinical features of this rare entity. Eventually, we suggest that the early surgical removal of clots and tumor is essential to provide the best chance of neurological improvement.

INTRODUCTION

Neurinomas are benign, usually encapsulated, tumors growing in peripheral nerve sheath with high incidence in the cerebellopontine angle (CPA). As most of benign tumors, their presence is suspected by the onset of neurological signs in a slow-growing fashion caused by vascular or nervous conflicts.[2620] Spontaneous intracranial hemorrhage occurs in 3.9% of all brain tumors,[27] especially in aggressive ones, such as metastatic tumors or malignant gliomas. Apart from high-vascularized tumors, as choroid plexus papillomas and pituitary adenomas, spontaneous intracranial hemorrhage associated with a benign lesion is an even more uncommon condition.

CASE REPORT

We report a case of vestibular neurinoma (VN) associated with a radiological “biphasic” pattern of intratumoral hemorrhage (ITH). A 65-year-old woman came to our attention complaining of sudden headache and progressive oral rhyme deviation. Neurological examination showed mild ipsilateral VII cranial nerve palsy and hearing loss. A computed tomography (CT) scan showed a 3 cm hyperdense mass occupying the CPA cistern with compression on adjacent cerebellar parenchyma [Figure 1]. No obstructive hydrocephalus was evident on imaging. A thorough preoperative magnetic resonance imaging (MRI) study better characterized the patchy pattern of the round shaped lesion, resulting in three different intensity signals. In T1-weighted images the roughly ovular mass appeared formed by an isointense inner core surrounded by a hypointense ring [Figure 2a], the latter compatible with hemosiderin signal. This hypointense ring was even more evident in T2-weighted images [Figure 2b], which highlighted also a clear hyperintense signal in an adjacent area expression of a recent bleeding (thick arrow). Cerebral angiography ruled out the presence of arteriovenous malformations (AVMs) or pathologic vasculatures.

Figure 1

CT scans reveal an hyperintense lesion occupying the CPA cistern with compression of adjacent parenchima

Figure 2

(a) T1 WI shows an isointense part (light arrow) surronded by an hypointense part. (b) T2 WI shows a more evident hypointense ring and the presence of a hyperintense area surronding the lesion (thick arrows)

The patient underwent surgical removal of the lesion performed by a suboccipital approach. Macroscopically, the tumor appeared as a soft, grayish mass surrounded by multiple clots. Histological examination confirmed diagnosis of VN type Antoni A. The patient's neurological status improved gradually with mild persistence of VII and VIII cranial nerve deficits.

DISCUSSION

Hemorrhagic CPA mass lesions have been rarely reported in literature,[3] and to the best of current knowledge neurinomas represent the rarest ones. The first case of hemorrhagic VN was reported by McCoyd et al.[18] in 1974, and only 43 more cases have been reported in the literature so far. Clinical presentation of neurinomas with hemorrhagic findings has been sporadically described also in other locations such as trigeminal,[24] accessory,[4] and hypoglossal nerves,[221] or even in cervical junction[8] and in the spinal cord.[23]

At time of presentation, patients are on average aged in their fifties (range from 15 to 71 years) with a slight male predominance (M/F: 1/3). The most frequently reported clinical symptoms are: Headache (27%), hearing disturbance (25.8%), cerebellar symptoms (16.9%), nausea, and vomiting (13.5%) [Figure 3]. The mean maximum diameter demonstrated by CT or MRI scans is 3.3 cm (range from 1 to 5.8 cm). Lesion diameter is calculated using the equivalent tumor diameter formula[22] [Figure 4]. This data could confirm an increased bleeding tendency in lesion bigger than 3 cm, as described in previous reports[715] (For an accurate analysis of the cases described to date in literature, we report the main clinical and histopahological features of hemorrhagic VN in Table 1).

Figure 3

List of the main symptoms related to an acute onset of hemorrhagic VN reported in literature

Figure 4

The above formula indicates the equivalent diameter consisting in the cubic root extrapolation of the doubled volume calculated from the lesion major diameters

Table 1

Clinical symptomatology and neuroradiological signs before the acute onset more frequently reported in literature

Hemorrhagic VN presents with two basic kind of bleeding: Intratumoral and subarachnoid ones. The first form accounting for the 86.4% of cases (38 out of 44) consists in a hemorrhage inside the substance of the tumor itself.[1691017] The mechanism in not fully understood but some histological reports describe focal sinusoidal dilatation and hyaline thickening of the walls that could facilitate spontaneous thrombosis, subsequent necrosis, and hemorrhage.[2712] A summary of tumor hemorrhage mechanisms is shown in Table 2. The second kind of bleeding consists in subarachnoid hemorrhage (SAH) reported in 50% of hemorrhagic VN (22 out of 44); thus only in 36.4% of cases the two forms were found concomitantly.

Table 2

Histopathological mechanisms of tumor hemorrhage

Generally speaking, neurinomas present a characteristic MRI signal pattern consisting in a slight hypointensity or isointensity on T1-weighted image and an increased signal in T2-weighted images. Whenever an intratumoral bleeding occurs, a decreased signal can be noted in correspondence of the center of the acute hematoma, due to the T2 shortening effects of deoxyhemoglobin. In subacute hematomas instead a peripheral hyperintensity extending inward is evident in both T1-weighted and T2-weighted images, explained by a T1 shortening effects of proton electron dipole–dipole secondary to methemoglobin interactions. Finally, in chronic hemorrhages a peripheral hypointensity in noted, and hemosiderin laden macrophages are considered responsible of this pattern.[41625] In our case, the presence of a peripheral hyperintensity mixed with a patchy hypointense core reflecting an acute bleeding in the context of a previous one. To this regard, Sprickler et al.[25] suggest that MRI without gadolinium enhancement could be more sensitive to hemorrhage due to the interference of hemoglobin degradation products (methemoglobin and deoxyhemoglobin).

Among the cases described in the literature, most of them showed at the time of histological examination a mixed Antoni A/B pattern (18 out of 24, 75%), whereas only a few exhibited Antoni A pattern, suggesting that the mixed type are the most at risk of bleeding. A recent paper on a cohort of 67 VN patients[10] found a correlation between immunoistochemical inflammation marker (CD68) and microvessel density suggesting that the intensity of inflammatory reaction could facilitate neovascularization and, in turn, tumoral growth and hemorrhagic tendency.

The case herein described shows a radiologically evident biphasic hemorrhage that could confirm the hypothesis of recurrent bleedings along tumoral growth. Subsequent hemorrhages within the tumor mass seem to be quite rare and only four cases are reported in literature.[9131417] Kim et al.[13] described a case of sudden occurrence of headache, nausea, and vomiting in a patient with a hemorrhagic neurinoma previously diagnosed with CT scan; following this clinical exacerbation the patient underwent a second CT showing an enlargement of the intratumoral hemorrhage. Kurata et al.[14] described a progressive hearing loss with episodes of headache; a CT scan, performed 1 year after the onset of symptoms, showed a multi-cystic neurinoma filled with a xanthochromic fluid. Collignon et al.[9] reported a patient presenting with recurrent intraventricular hemorrhage and associated SAH, despite a negative cerebral angiography, in which an intracranial schwannoma was found responsible of those subsequent bleedings.

In our case the second bleeding coincided with a sudden cephalalgia in a clinical history of progressive mild impairment of both VII and VIII cranial nerves. From a review of the literature, headache results as a predominant symptoms (27%, as shown in Table 3) considerably higher when compared with nonhemorrhagic ones if we rule out the cases with increased intracranial pressure (ICP). The sudden onset in a picture of mild symptoms could indeed indicate an acute tumor bleeding as suggested by other authors.[9131417]

Table 3

Summary of hemorrhagic vestibular neurinomas reported in literature

In contrast, since a subtle clinical presentation is often the only finding in patients with hemorrhagic VN,[15111921] even the minimal sign of neurologic impairment should alert clinicians about possible hemorrhagic events in patients harboring a VN (Table 3 shows the most common signs and symptoms reported).

Hemorrhagic VN surely represent a very rare entity. The literature review herein presented highlighted the following risk factors for tumoral bleeding: large size, mixed Antoni type, and secondary vascular changes, like increased/dilated vessels and vascular architecture resembling telangectasia.

The present case and the few similar ones described in literature suggest that subsequent bleedings of VN are associated with a higher morbidity rate. A radiological evidence of hemorrhagic neurinoma should therefore prompt a rapid surgical intervention, even in case of mild presenting symptoms, since only early removal of clots and tumor may provide the best chances of neurological improvement.