Neuroradiology (2005) 47: 91–96 DOI 10.1007/s00234-004-1290-3 P. Vilela P. Saraiva A Goulão Received: 1 April 2004 Accepted: 12 August 2004 Published online: 21 January 2005 Ó Springer-Verlag 2005 P. Vilela (&) Æ P. Saraiva Æ A Goulão Serviço de Neurorradiologia, Hospital Garcia de Orta, Av. Prof. Torrado Silva. Pragal, 2801-591 Almada, Portugal E-mail: ferrovilela@hotmail.com Tel.: +351-21-2948080 Fax: +351-21-2726860 DIAGNOSTIC NEURORADIOLOGY Intracranial angiolipoma as cause of subarachnoid haemorrhage. Case report and review of the literature Abstract A 33-year-old female with a longstanding history of seizures was admitted to our hospital with subarachnoid haemorrhage (SAH). Computed tomography (CT), magnetic resonance imaging (MRI) and digital subtraction angiography (DSA) depicted a vascular fat-containing lesion overlying a right frontal cortical polymicrogyria. The diagnosis of angiolipoma was established. Conservatory management was undertaken with full recovery. She has been followed for 5 years since, with neither re-bleeding nor morphologic change of the lesion. This is a rare intracranial lesion, with only 11 intracranial angiolipomas published in the literature, and is the first case reported which is associated with SAH caused by this lesion. Keywords Intracranial angiolipoma Æ Angiolipoma Æ Lipoma Æ Subarachnoid haemorrhage Æ Haemorrhage Æ Cortical malformation Introduction Case report Howard and Helwig were the first to establish angiolipoma as a specific entity in 1960 [1]. Angiolipomas are rare and benign mesenchymal tumours composed of mature adipocytes and abnormal vasculature [1–4], capillary, sinusoidal, venous and/or arterial [5]. Their main pathologic characteristics are macroscopic evidence of tumour formation, with or without capsule, and microscopic evidence of mature lipocytes as the major cell population, with angiomatous proliferation inside the mass [3]. Angiolipomas are further divided into non-infiltrating (capsulated) and infiltrating (non-capsulated) types, the former being more common and the latter showing a tendency to recur after surgery [3, 6]. We report the clinical and imaging features of a right frontal lobe angiolipoma responsible for subarachnoid haemorrhage (SAH) and review the literature. A 33-year-old female was admitted to our hospital after experiencing a sudden and severe episode of headache. No precipitating factor was identified. Except for mild neck stiffness, general physical and neurological examinations were unremarkable. The patient had been followed in another institution for several years due to a longstanding history of seizures. She was known to be on oral phenitoyn, but on admission blood levels were below therapeutic range. Personal history was otherwise irrelevant. There was no family history of seizures or other neurological disease. Previous electroencephalograms had shown abnormal electric activity over the right frontal region. On admission, computed tomography (CT) scan showed a thin collection of blood on the right sylvian cistern, establishing the diagnosis of SAH. In addition, two fat-attenuated lesions were seen in the right 92 operculum and right frontopolar surface (Fig. 1). Digital subtraction angiography (DSA) with selective internal and external carotid and vertebral bilateral injections was subsequently performed, excluding other causes of bleeding, namely intracranial aneurysms, arteriovenous malformations (AVM), dural fistulae or dissections. However, DSA revealed the presence of a confined arteriolocapillary blush fed by distal branches of the right orbitofrontal and frontopolar arteries persisting till late venous phase (Fig. 2). No arteriovenous shunting and early draining veins were seen. On the sixth day after admission, a magnetic reso- Fig. 1 a–d Axial noncontrast CT scan: spontaneous blood hyperdensity on the right sylvian cistern and two hypodense lesions in the right operculum and right frontopolar surface nance imaging (MRI) scan was performed, demonstrating an inhomogeneous lesion which was hyperintense on both T1 and T2 (FSE) WI and isointense on fat-suppression technique. The lesion had marked gadolinium enhancement. The diagnosis of angiolipoma was made. Additionally, a frontal lobe cortical development malformation consistent with polymicrogyria underlying the angiolipoma was also depicted (Fig. 3). A conservative approach was proposed. The patient recovered uneventfully and was discharged asymptomatic 2 weeks later. She has been followed up for 5 years 93 Fig. 2 Right internal carotid angiogram. Early (a) and late (b) arterial phases: arteriolocapillary lesion fed by branches of the right orbitofrontal and frontopolar arteries (arrows). Absence of arteriovenous shunting and early draining veins since. During this period she has been clinically stable, with no re-bleeding history. She is seizure-free with single anti-epileptic drug therapy. Follow-up MRI scans have shown no interval changes. Discussion Central nervous system angiolipomas are uncommon lesions that have been increasingly demonstrated both in spine and cranial MRI studies. The majority have been found in the spinal canal, mostly at the thoracic level [6–9]. More than 95% are epidural, and intradural angiolipomas are exceptional, accounting for less than 5% of cases [10]. The aetiology of angiolipomas remains unclear, and the relationship between lipomas, angiolipomas, angiomiolipomas and haemangiomas needs to be further elucidated. Most authors accept that these different lesions may arise from the abnormal development of a primitive pluripotential mesenchymal cell from which adipose tissue, smooth muscle and vascular endothelium develop. Central nervous system lipomas are benign, congenital and malformative lesions, mainly composed of mature adipose cells, resulting from abnormal differentiation of the meninx primitiva, and do not grow over time [11]. Lipomas may contain variable amounts of connective tissue, vascular elements, calcium, glial and neuronal tissues [12]. Classically, angiolipomas have been classified as a distinct pathological entity representing a variant of lipoma [1, 3, 12]. They differ from angiomiolipomas in view of the fact that they lack the smooth muscle cells component [13]. Some authors consider angiolipomas as an intermediate stage between lipoma and haemangioma, with invasive angiolipomas representing a preliminary stage leading to haemangioma, given the fact that vascular components of both entities are similar on pathological studies [9, 13–15]. Moreover, the presence of dividing capillary endothelial cells in angiolipomas [13] suggests a common root with haemangiomas, and the association of this broad spectrum of lesions with cortical development malformations and cephalic vascular malformations favours a malformative aetiology. Angiolipomas have a female predominance, most being diagnosed during the fifth decade [6, 9, 10]. Spinal angiolipomas usually present with back pain and symptoms related with progressive spinal cord compression [9, 10, 16–18]. Infiltrative lesions may be responsible for vertebral fracture [19]. Hypercortisolism and obesity have been implicated in the pathogenesis and growth of the angiolipomas [9, 17, 20–22], and worsening of symptoms has also been reported with weight gain and during pregnancy, especially during the third trimester [6, 9, 10]. Nowadays, angiolipomas can be diagnosed with a high degree of certainty based on the imaging features. On CT they are, for the most part, inhomogeneous hypodense lesions with slighter higher density than normal fat and variable contrast enhancement [6, 7]. Due to their fat content, angiolipomas are predominantly hyperintense on noncontrast T1 weighted MR images (T1WI) [7]. However, they are generally inhomogeneous, with slightly hypointense signal relative to normal fat and with focal areas of hypointense signal [6, 7]. Fat-suppression techniques are particularly helpful to confirm the lipomatous nature of the lesion and to demonstrate the enhancement of the lesion [6, 7]. The contrast enhancement and the hypervascularity on angiograms differentiate angiolipomas from other lesions with fat-signal, such as dermoids and lipomas, that do not show contrast enhancement and are avascular lesions on angiography. Provenzale et al. correlated the radiological and histological characteristics of 94 Fig. 3 MRI performed on the sixth day after admission. a, b Coronal T1WI (3D SPGR): hyperintense inhomogenous lesion, slightly hypointense relative to epicranial fat, is coating the external and internal surfaces of the right basal frontal lobe. There is a focal area of frontal cortical thickening underlying the angiolipoma with irregular cortical-subcortical junction suggestive of polymicrogyria. c, d Axial noncontrast T1WI (Spin Echo); e, f Axial T1WI with fat saturation technique (Spin Echo); g, h Axial contrast-enhanced T1WI with fat saturation technique (Spin Echo): nonhomogenous diffuse signal loss of the lipomatous component with the T1WI fat saturation technique and a markedly diffuse enhancement of the mass 95 spinal angiolipomas, stating that hypointense foci on noncontrast T1WI would be expected in those with high vascularity and that vascular content would determine the degree of gadolinium enhancement [7]. Nonetheless, angiolipomas do not exhibit vascular flow voids within the lesion [7]. To our knowledge, only 11 intracranial angiolipomas have been published in the literature [13, 14, 23–30]. However, previously-reported lipomas with hypervascularity [31, 32] may, in fact, also correspond to angiolipomas. Intracranial angiolipomas have a female predominance, and commonly present with seizures and/ or progressive neurological deficits due to mass effect [13, 14, 23–25, 27–30]. Only one case has been reported with an intracranial bleeding, namely a thalamic haematoma, caused by the angiolipoma [26]. They occur more often in the sellar and parasellar regions, and as opposed to spinal angiolipomas they are generally intradural. Our case shares the imaging features of those previously reported. Cortical development malformations are known to be associated with intracranial lipomas and angiolipomas, being identified in half of cerebral-surface lipomas, specially in those associated with epilepsy [31, 32], and in one of the angiolipomas [29] reported. Angiographic patterns of angiolipomas are variable, even in the presence of vascular components demonstrated on pathologic specimens. In our case, the angiogram confirmed the presence of the vascular component of the lesion, showing an arteriolocapillary blush fed by branches of right anterior cerebral artery. Six of the intracranial angiolipomas were evaluated with cerebral angiography [13, 14, 23, 25, 26, 30]. In three cases there was an avascular mass [13, 14, 23] and in the other three [25, 26, 30] the cerebral angiography clearly showed abnormal arteries supplying the lesion. The angiographic pattern of angiolipomas may be deceptive and mimic pial AVM, but they lack arteriovenous shunting or early draining veins. The vascular component of the mass is a potential source of haemorrhage, and vascular complications have been reported on rare occasions in spinal angiolipomas, including acute and subacute clinical neurological deterioration due to haemorrhage [17] and venous infarcts due to venous thrombosis [18, 20, 33]. In our case, the close topographic relationship between the angiolipoma and the subarachnoid blood, and the exclusion of other potential bleeding lesions, led us to assume the rupture of the vascular component of the angiolipoma as the cause of SAH. To the best of our knowledge this has not been published before. A conservative approach, with both clinical and MRI monitoring, was chosen based on the uncertainty of the natural history of angiolipomas and the morbidity associated with surgery of cortical lipomas [34, 35]. Surgery was kept in reserve, in case of growth of the lesion and/or the appearance of disabling, uncontrolled symptoms. Furthermore, we agree with authors who suggest that associated cortical malformations are responsible for the seizures’ clinical picture, and that eradication of lipoma will not cure the epilepsy [34, 35]. Finally, in our patient epilepsy was controlled with proper medical therapy. 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