THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES MRI Diagnosis of Brainstem Cavernous Angiomas Presenting as Tumours

We report experience with 11 patients misdiagnosed for years, on the basis of computed tomography (CT) and angiography, as harbouring brainstem tumours in whom magnetic resonance imaging (MRI) demonstrated cavernous angiomas. Seven had undergone external irradiation, 2 had a ventriculo-peritoneal shunt, 2 developed aseptic femur necrosis following corticosteroid treatment, 1 had undergone a biopsy with a pathological diagnosis of glioma. CT had depicted ill-defined, hyperdense, faintly enhancing lesions. Angiography was normal, or showed an avascular mass or subtle venous pooling. MRI delineated discrete lesions, typical of cavernous angiomas, with a mixed hyperintense, reticulated, central core surrounded by a hypointense rim. Six patients subsequently underwent stereotactic radiosurgery without changes in clinical status or lesion. Although hemorrhagic neoplasms may mimic the clinical course and MRI appearance of cavernous angiomas, MRI is useful in the diagnosis of brainstem cavernous angiomas and should be performed in patients with suspected brainstem tumours. RESUME: Diagnostic par MRI des angiomes caverneux du tronc cerebral se presentant comme des tumeurs. Nous rapportons les cas de 11 patients diagnostiques a tort pendant des annees, sur la base de la tomodensitometrie (CT) et de l'angiographie, comme etant porteurs de tumeurs du tronc cerebral, chez qui l'imagerie par resonance magnetique (MRI) a demontre des angiomes caverneux. Sept avaient subi une irradiation externe, 2 avaient subi un shunt ventriculo-peritoneal, 2 avaient developpe une necrose aseptique du femur suite au traitement par des corticosteroides et 1 avait subi une biopsie dont le diagnostic anatomopathologiques etait celui de gliome. Le CT avait montre des lesions mal definies, hyperdenses, faiblement rehaussees par la substance de contraste. L'angiographie etait normale ou montrait une masse avasculaire ou une accumulation veineuse discrete. La MRI a defini des lesions discretes, typiques d'angiomes caverneux, avec un noyau central hyperintense, reticule, entoure d'une bordure hypo-intense. Six patients ont subi une radiochirurgie stereotaxique par la suite, sans changement dans le statut clinique et sans lesion. Bien que les neoplasies hemorragiques peuvent imiter revolution clinique et l'aspect des angiomes caverneux a la MRI, cette derniere est utile au diagnostic des angiomes caverneux et devrait etre pratiquee chez les patients chez qui on suspecte des tumeurs du tronc cerebral. Can. J. Neurol. Sci. 1992; 19: 376-382 Brainstem cavernous angiomas can mimic pontine hemorrhages, demyelinating disease, or neoplasms. The differentiation of cavernous angiomas from pontine hemorrhage and demyelinating disease is well described, but few reports address the tumour-like presentation of cavernous angiomas. As cavernous angiomas and brainstem tumours are treated differently, it is important to differentiate the two. This can readily be achieved with magnetic resonance imaging (MRI). A series of patients with cavernous angiomas initially misdiagnosed and treated for years as having brainstem neoplasms has not previously been reported. We described a group of 11 such patients found to harbour a probable brainstem cavernous angioma based on the MRI appearance of their lesions and discuss the treatment of patients with cavernous angiomas who were previously treated for brainstem neoplasms. PATIENTS AND METHODS Eleven patients with a brainstem cavernous angioma initially misdiagnosed as glioma (9 cases), glioma or pinealoma (1 case), and glioma, other third ventricle tumour or aneurysm (1 case) were seen over a 38 month period (Table 1). They comprise a subset of over 40 patients with a brainstem cavernous angioma referred to our institution over the past 5 years. All patients had a fluctuating clinical course over the 1 to 23 years following initial diagnosis of brainstem tumour and were referred to our institution after acute exacerbation of symptoms. One patient had undergone a posterior fossa craniectomy and biopsy of his lesion which was interpreted as a low grade glioma at pathological examination. They had previously been treated with whole brain irradiation (7 cases), ventricular shunting (2 cases), and long term corticosteroids (8 cases). The latter treatment had proFrom the Divisions of Neurosurgery (M.C.R, J.-G.V., R.L.), and Neuroradiology (R.d.C.-O.), Montreal Neurological Institute and Hospital, McGill University, Montreal Received October 17, 1991. Accepted in final form March 9, 1992. Reprint requests to: Jean-Guy Villemure, M.D., FRCSC, Division of Neurosurgery, Montreal Neurological Institute and Hospital, 3801 University St., Montreal, Quebec, Canada H3A 2B4 376 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0317167100042013 Downloaded from https://www.cambridge.org/core. IP address: 54.191.40.80, on 30 Jul 2017 at 10:28:55, subject to the Cambridge Core terms of use, available at LE JOURNAL CANADIEN DES SCIENCES NEUROLOGIQUES duced bilateral femoral aseptic necrosis in 2 cases. Follow-up ranged from 18 to 42 months (mean 30 months). Non-contrast computed tomography (CT) depicted an illdefined, hyperdense lesion in all cases. Faint contrast enhancement was identified in 8 of 10 cases and 1 showed marked enhancement (one patient did not have a contrast-infused CT). The cavernous angioma of one patient showed no contrast enhancement on one CT scan, although 6 months later, there was marked enhancement. Angiography (including delayed venous phase and subtraction imaging) showed a mass lesion with adjacent vessel displacement in 3 patients; and venous pooling in another. Three patients had a normal angiogram (Table 2). Magnetic resonance imaging was performed with a 1.5 Tesla scanner (Phillips Gyroscan, The Netherlands) using Tl-weighted (TR = 550 ms, TE = 30 ms), proton density and T2-weighted (TR = 2000-2100 ms, TE = 30, 60-80 ms) spin echo pulse sequences with two excitations. Multiple slice data acquisition was used, acquiring 6-8 mm thick slices with a 256 x 256 matrix. The lesions were delineated distinctly in all cases. The volume of the lesions ranged from 2.6 cm to 35 cm. The lesions and clinical progression of 10 of 11 patients were studied with serial MRI scans. The diagnosis of cavernous angioma was made on the basis of the demonstration of a characteristic, heterogeneous (mainly hyperintense), reticulated, central core surrounded by a prominent hypointense rim, with absence of edema, and of feeding or draining vessels on T2-weighted and proton density images." The cavernous angiomas were localized to the pons and extended to the pontomedullary junction, the posterior third ventricle (thalamus), to the cerebellum, and the cerebral peduncles (Table 2). Six patients were treated by stereotactically focussed radiosurgery. The size of their lesions ranged from 2.6 to 20 cm