1 Department of Neurosurgery, Université Libre de Bruxelles, Erasme Hospital, Brussels, Belgium; Department of Neurology, Saint-Joseph Hospital, Saint-Vith, Belgium; and Department of Neuropathology, Université Catholique de Louvain, Saint-Luc Hospital, Brussels, Belgium
✓ Angiolipomas (ALs) are hamartomas composed of abnormally differentiated vessels and mature adipose tissue. Although they are most commonly found in peripheral tissues, ALs sometimes grow in the spinal epidural space. Intracranial ALs (ICALs) are rare: only seven cases have been reported in the literature. The authors describe the case of a 70-year-old woman who presented with ocular symptoms from a clinically and radiologically progressing parasellar ICAL. The radiological as well as the microsurgical findings are illustrated and compared with the seven previously published cases. The most frequent location of ALs is the skull base, especially the parasellar region. Other ICALs were diagnosed as components of cerebral arteriovenous malformations and were not symptomatic by themselves. Neuroradiological studies of ICALs usually demonstrate the characteristics of both adipose and vascular tissues. However, a review of the literature shows that the diagnosis had not been suspected preoperatively in any of the cases. Operative descriptions emphasize that most neurosurgeons were caught off guard by the profuse bleeding and the unusual relationship of this unexpected lesion to the cavernous sinus, so that removal was rarely complete. The authors conclude that preoperative diagnosis of ICALs is achievable based on magnetic resonance analysis, which should help optimize the microsurgical management of these lesions.
Angiolipomas (ALs) are hamartomas composed of abnormally differentiated vessels and adipose tissue.1,2,5 They represent a distinct clinical and pathological entity, are usually considered to be a variant of lipomas, and are commonly found in the skin, muscle, bone, kidney, or the oral cavity.1,2,4,5 Angiolipomas may grow in the spinal epidural space where their appearance on computerized tomography (CT) and magnetic resonance (MR) imaging exhibits the characteristics of both adipose and vascular tissues.6,7,12,16,17 When these benign lesions grow and become symptomatic, complete surgical removal is necessary and sufficient to be curative.3,8,9,11,16 These lesions rarely occur in the intracranial compartment; only seven other cases of intracranial ALs (ICALs) have been reported.4,10,13–15,18 In this study, we describe the case of a 70-year-old woman who presented with a growing parasellar ICAL revealed by clinical and radiological studies. The presentation on CT and MR imaging as well as the microsurgical findings are compared with those of the seven other cases reported.
This 70-year-old woman was born with a planotuberous deep-red cutaneous hemangioma of the right upper eyelid. Other medical history was uneventful.
In 1991, the patient complained of progressive heaviness of the right eyelid. She later developed a right ptosis and diplopia. Neurological examination at another hospital revealed an incomplete extrinsic right third cranial nerve palsy. Funduscopic examination was normal, whereas MR imaging showed a 2-cm well-circumscribed right parasellar lesion (Fig. 1). The lesion was isointense compared with the brain tissue on T1-weighted images, whereas T2-weighted images as well as the gadolinium-enhanced T1-weighted sequences showed a strongly hyperintense, homogeneous lesion. It seemed to fill the right cavernous sinus (CS) and to extend intrasellarly, and MR imaging showed enhancement of the dura along the superior petrosal sinus, indicating a meningioma. Conservative treatment was proposed, considering the “high surgical risk” of the lesion.
In December 1994, the patient experienced a complete right ptosis with a fixed dilated pupil and ophthalmoplegia. At ophthalmological examination in our hospital, a temporal hemianopsia was diagnosed and funduscopic examination showed a right atrophic papilla. An unenhanced CT scan showed a homogeneous hyperdense mass lesion. The T1- and T2-weighted MR images revealed the same characteristics as previously described, but both intracavernous and intrasellar extensions had progressed when compared with those seen on images obtained in 1991 (Fig. 2). The purely intracavernous location of this lesion led us to rule out the diagnosis of meningioma; however, an ICAL was not suspected. Selective angiographic examination of the right internal carotid artery (ICA) and external carotid artery demonstrated a displacement of all segments of the ICA due to the tumor's protrusion, and a small tumor blush probably arising from the meningohypophyseal trunk. No other abnormalities were seen.
Operation and Postoperative Course
We decided to remove the tumor via a right pterional approach to stop the evolving left visual deficit. We located the optic nerve and the supraclinoid ICA pushed upward and forward by the dilated CS. The dura of its lateral wall was red, bulging, pulsatile, and easily depressible by external compression but reinflated immediately. Incision of the dura led to profuse bleeding from the red tumor, which was composed of a network of large vascular lakes with thin walls, mixed with clear pink soft tissue. A subtotal resection (approximately 80%) was performed by means of ultrasonic aspiration assisted by constant blood suction. Intracavernous venous hemostasis was achieved with hemostatic agents. The dura was then sutured, and 30 seconds later the dilated CS reinflated. A reduction in size was obtained by dural retraction with bipolar coagulation. The patient's postoperative course was uneventful, with the right ophthalmoplegia remaining and the left visual field improving. The control CT scan showed a 75% reduction of the mass with no complications in the operative field.
The tumor was composed of mature fat cells and numerous congested, thin-walled blood vessels, which appeared to be scattered or closely grouped, displaying a focal angiomatous character (Fig. 3). The pathological features were those of an AL. No fibrous capsule was found in the tumor specimen.
Intracranial ALs have been reported only seven times in the literature.4,10,13–15,18 We have carefully reviewed these cases and they are summarized in Tables 1 and 2. The ICALs seem to have some specific characteristics with respect to their clinical, anatomical, radiological, and microsurgical presentation. Taking into consideration the findings in the present case, we will discuss the characteristics of these rare lesions and try to clarify a course for their optimum management.
Diagnostic presentation of eight patients with ICALs*
Cases 1 through 7 correspond to references 15, 18, 4, 10, 10, 13, and 14, respectively. Case 8 is the one presently reported.
Although spinal ALs are extradural, this tumor of mesenchymal origin was found in various intracranial intradural locations. The majority of ICALs of the skull base were located in the parasellar region, in close relationship with the CS (Cases 1,15 2,18 3,4 7,14 and 8 [present case] in Tables 1 and 2). The similarities among these cases indicate that the parasellar location may be a classic presentation for ICALs. Indeed, the CS is in close contact with the sella turcica and the pharyngeal cavity, where the three primitive layers have intimate contacts. Ectopic mesenchymal tissue could therefore remain included in any layer of the CS, allowing the development of partially intradural ICALs.17 The two ICALs diagnosed as components of hemispheric arteriovenous malformations ([AVMs] Cases 410 and 6;13 see Tables) probably correspond to another entity. These two reports did not describe the role of the AL in producing the clinical symptoms, bringing into question the progressive potential of these lesions. Indeed, some areas of the AVMs may have undergone either lipomatous or angiolipomatous differentiation. Recent immunohistochemical studies indicate a developmental association of all cell types forming vascular walls (for example, endothelium, pericytes, or smooth-muscle cells) and adipose tissue, which arise from a common precursor.4 Hemangiomas and lipomas could therefore represent a spectrum within which ALs and angiomyolipomas are intermediate forms.4 It is also worth noting that two cases of parasellar ICALs (Cases 1 and 8; see Tables) were associated with ipsilateral cephalic vascular lesions, which could correspond to a conjoint abnormality of the mesenchymal precursor.
The growth potential of ALs has been questioned.1,2,5 The review of ICALs, however, confirms their potential. Indeed, all ICALs of the skull base showed a history of progressing symptoms, and a growing lesion was further confirmed by consecutive imaging in two cases, including ours. Therefore, we recommend surgical removal of these lesions when they grow and become symptomatic.
Most ICALs presented as low-density images on CT scans and showed partial enhancement after addition of contrast materials. This is the typical presentation of spinal ALs and corresponds to the characteristics of both adipose and vascular tissues.6,7,9,12,16,17 Magnetic resonance images of ICALs were available in only three cases, and the presentation was also similar to the typical appearance described in spinal ALs.6,7,9,12,16,17 These lesions are typically hyperintense on T1- and T2-weighted MR sequences and enhance strongly after gadolinium administration. However, our patient presented with atypical MR findings, with an isointense signal on T1-weighted images. This radiological presentation has also been reported in some spinal ALs.17 This could be explained by a predominance of stromal or vascular components. Indeed, the MR and CT appearance of ALs can vary according to their variable ratio of adipose to stromal or vascular tissue, ranging from ALs that are predominantly lipomatous to ALs in which dense vascular and stromal elements have replaced most of the fat.12,17 We believe that MR imaging represents a key investigative tool for studying ICALs. It allows a fine analysis of the interface between the AL and the dura, especially in the CS region, which can help in differentiating ALs from pituitary adenomas, meningiomas, or even giant aneurysms. The general lack of experience using MR imaging to study ICALs may explain why the diagnosis was never proposed. It is worth noting that the last six cases of ICALs were reported after 1995, indicating that ICALs could be more common than it appears.8 Careful MR analysis should allow a surgeon to diagnose ICALs preoperatively.
Like spinal ALs, ICALs are often well delineated and even encapsulated, but they may sometimes infiltrate the neighboring nerve tissue.1–5 They usually appear as soft, crumbly, highly vascularized reddish purple tumors. Complete removal should be the goal of surgery to cure the patient. However, in a parasellar location the relationship between the ICAL and the CS is a source of difficulty reported by all neurosurgeons performing microsurgery for these lesions. This is a major feature to assess on the preoperative MR image. Parasellar ICALs grow either partially or totally inside the CS. Therefore, the microsurgical strategy consists of opening the lateral wall of the CS and aspirating this particularly soft tumor, keeping in mind that ALs are known to be predominantly extradural tumors.17 Our case also illustrates that the lesion itself may be an important source of perioperative bleeding, which may preclude its total removal.
We report a rare case of a clinically and radiologically progressing ICAL, illustrated with modern imaging techniques. Preoperative detailed analysis of the MR characteristics of the lesion should allow the practitioner to suspect this diagnosis and to optimize the microsurgical management. The present case and the review of the other seven reported cases refine some preoperative diagnostic criteria, especially when the ICAL presents as a skull base lesion.