Case Review. Cystic meningioma

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1 Case Review Cystic meningioma Mamdouh Abdel-Razek, Yousef Al-Awadi, Ali Abo Al-Hassan Abstract: Cystic meningiomas are uncommon tumours. Computed tomography scan and conventional magnetic resonance imaging may not differentiate these lesions from other tumours that are more frequently associated with cystic or necrotic changes; like gliomas or metastases. We are reporting 2 cases of cystic meningiomas in which the diagnosis was not suspected preoperatively because of short clinical history and rapid neurological deterioration. In addition; the cystic appearance of the tumours on imaging studies further confused accurate diagnosis. Although some authors believe that haemorrhage is rare in cases of meningioma, one of our cases was associated with haemorrhage and was proven to be a WHO Grade II meningioma. Because total resection is usually the goal in meningioma surgery, the help of a neuropathologist is important to establish the diagnosis during surgery. (p ) Key words: Meningioma, cystic meningioma and cystic tumours Introduction Meningiomas are usually benign lesions that account for 13-18% of brain tumours. 7,26 They are generally diagnosed preoperatively based on their imaging features. They appear as extra-axial tumours attached to the dura with marked enhancement after intravenous contrast injection. They are most commonly found in the cerebral convexity and parasagittal region. 5,35 Appearance on cerebral angiography is characterized by meningeal vascularization and capillary blush in the venous phase. They are usually solid tumours and are easily recognized during surgery. 1,8,13,17,19,33 However, the diagnosis can be difficult when meningioma is associated with a cystic component, as it can be confused with glial tumours that demonstrate necrotic or cystic changes. 10,21,23,25 Also, they can be confused with other tumours like haemangioblastoma (10,18,25) and neuroblastoma (10,18). Several authors believe that establishing the diagnosis of cystic meningioma based on imaging studies alone can be challenging. 1,2,8,13,17,23,25,29,33 Considering the fact that meningioma is likely a surgically curable condition, frozen sections taken during surgery are crucial in deciding the extent of resection by differentiating meningiomas from Department of Neurosurgery Ibn Sina Hospital Kuwait Correspondence: Dr. Mamdouh Abdel-Razek Ibn Sina Hospital PO Box 5768 Salmiya, Kuwait marazek@yahoo.com other lesions. 38 Case presentations Case 1 This is a seventy-year-old female patient, who is known diabetic and hypertensive. She is also a known case of congestive heart failure and right bundle branch block associated with paroxysmal atrial fibrillation. She was admitted to the medical department because of rapid atrial fibrillation and shortness of breath. The family pointed out that the patient suffered from episodes of confusion for 2 months prior to this admission. On examination, she was confused, opening her eyes to calls and localizing painful stimuli. She had right sided weakness with bilateral extensor plantar response. Computed tomography (CT) scan and magnetic resonance imaging (MRI) of the brain revealed an enhancing left frontal cystic mass lesion surrounded by extensive oedema and marked midline shift. Magnetic resonance angiography showed displacement of the left anterior cerebral artery but did not demonstrate abnormal vascularity within the lesion. Based on imaging studies the lesion was provisionally diagnosed as a highly malignant neoplasm (Fig. 1). The patient underwent an urgent craniotomy for resection of the tumour. The tumour and its cystic component were visible on the surface of the brain and were attached but easily separated from the dura. Nevertheless, we decided to excise that part of the dura. The tumour itself was pale greyish in colour and firm in consistency. The cystic part that contained xanthochromic fluid was dissected from the surrounding brain without difficulty, and excised completely together with the tumour. The frozen section was suggestive of a benign lesion. The paraffin sections showed features of meningioma that 104

2 contained many hyalinized blood vessels with no cellular atypia or mitosis (WHO Grade I). The cyst wall contained isolated clusters of meningothelial cells. The patient had a smooth postoperative course. A few days following the surgery, she regained full consciousness and her dysphasia and motor weakness recovered completely. Eventually she was transferred back to the medical ward for further management of her cardiac problem. focal pleomorphism. It was diagnosed as meningioma (WHO Grade II). Figure 1 - Case 1: Post contrast axial and coronal MRI showing an enhancing cortical lesion with a large cystic component. Radiologist suspected highly malignant tumour. Case 2 This is a forty-six-year-old female patient with past medical history significant for hypertension and bronchial asthma. She complained of non-specific headache for one year. That headache acutely worsened one week prior to her admission to the hospital and was associated with nausea and weakness of the right side of the body. On examination, she was fully conscious and oriented, with mild facial asymmetry and hemiparesis on the right side. Her brain CT scan and MRI revealed an enhancing left frontal mass lesion associated with haemorrhage and a fluid level in an adjoining cystic component on its posterior part of the tumour. The lesion was surrounded by oedema and caused compression of the left lateral ventricle (Fig. 2). Magnetic resonance angiography showed no abnormal vascularity within the tumour. The patient underwent urgent craniotomy for tumour resection. A brain cannula was introduced into the cyst cavity, and 10 cc of dark blood were aspirated. The haematoma was located immediately behind and in direct contact with the tumour. The haematoma cavity was surrounded by brain tissue. The tumour appeared brownish in colour, granular and firm in consistency with increased vascularity. It was attached to the dura of the frontal convexity. On frozen sections the lesion was diagnosed as a malignant tumour. Paraffin section verified a vascular and markedly haemorrhagic tumour, loose in some areas and compact in others with clusters of meningothelial cells. It showed rare mitosis and Figure 2 - Case 2: Non-enhanced CT scan, contrast enhanced axial and sagittal MRI showing a left frontal enhancing lesion associated with area of haemorrhage that demonstrated a fluid level on CT scan (arrow) Discussion Cystic meningiomas are uncommon tumours. The first report of cystic meningioma was by Penfield in Cushing and Eisenhardt reported 13 patients with cyst formation in a series of 313 intracranial meningiomas accounting for 4.2% of all cases. 7 A similar incidence was also described by other authors. 10,26 Hoessly and Olivecrona encountered 177 cases of cystic tumours in their report of 1313 cases of meningioma. 14 The incidence of cystic meningioma in children is higher than 10% (20,22), and a much higher incidence in the range of 55-65% was reported during the first year of life (16,27). Cystic intraventricular meningiomas were reported sporadically. 6,22 The advent of CT and MRI scans resulted into the diagnosis of cases of cystic meningiomas with increasing frequency. 13,30 Russell, et al and Elster, et al reported an incidence of cystic meningioma of 14 and 15%, respectively. 9,30 There is no consensus regarding the cause of cyst formation in meningioma. Penfield believes that it is due to central degeneration within the tumour. 24 Cushing suggested that VOLUME 13, NO. 1, APRIL

3 the formation of cysts in cases of meningioma is due to xanthochromic fluid forming at the periphery and its coalescence leads to the formation of large cavities. 7 Nauta, et al classified cystic meningiomas into four types based on the site of the cavity, 1) Centrally located intratumoural cysts; 2) peripherally located intratumoural cyst; 3) peritumoural cyst in the adjacent parenchyma, and 4) peritumoural cyst between the tumour and the adjacent parenchyma. 21 The walls of the large eccentric cysts are associated with reactive glia or collagen. Neoplastic cells are rarely found in the distal cyst wall. 6 Careful resection of all cyst wall is mandatory to avoid recurrence of the tumour. 10,19,33 Worthington, et al described five types of cystic meningioma. 36 However, the classification of Nauta, et al is thought to be more useful. 21,39 Rengachary, et al described two types of cysts; rare intratumoural cysts and peritumoural cysts depending on the presence or absence of meningothelial cell lining. 28 The intratumoural cysts occur as a result of degenerative process (10,28,30), ischemic necrosis (10,29) or haemorrhage. 10 In addition, cyst formation could be the result of active secretion by tumour cells. This theory is supported by the fact that the cystic fluid has high protein content, low lactic dehydrogenase and glutamine-oxaloacetic transaminase levels together with the absence of cells and serum-like glucose and electrolyte concentration. 34 Other authors thought that cyst formation could be due to demyelination resulting from white matter oedema and perfusion deficit. 23 Peritumoural cysts are large, usually unilocular and contain xanthochromic fluid with high protein content. They may result from glial proliferation secondary to the presence of meningioma with fluid elaboration by glial cells. 3,28 Peritumoural cyst can also represent the final stage of the intense peritumoural oedema secondary to local hydrodynamic changes, demyelination, or haemorrhage. 29 In a series of 420 cases of meningioma Sato, et al encountered 5 cystic tumours that showed evidence of myxomatous or hydropic degeneration. 31 These findings indicate that cyst formation sometimes is the result of tumour necrosis or breakdown. It was also reported that meningiomas that undergo necrosis are more of meningothelial or angioblastic type. 34 The first case we are reporting here demonstrated the picture of meningothelial variety of meningioma. We believe that this case represents type 2 cystic meningioma based on the classification proposed by Nauta, et al. 21 The presence of meningothelial cells in the cyst wall makes it considered as the intratumoural cyst subtype according to the classification by Rengachary, et al. 28 The association of haemorrhage with meningioma is thought to be rare. 20,30 In their study of 313 cases of meningioma, Cushing and Eisenhardt found no patient with hemorrhagic meningioma. 7 Hoessly and Olivecrona reported a series of 280 cases of meningioma but there was no mention of a case of hemorrhagic meningioma. 14 In a CT study of 131 cases of untreated meningiomas, there were 3 patients with evidence of haemorrhage in the tumour. 30 However, CT scan may not accurately diagnose haematoma especially in the subacute and chronic stages. In a report of 4 cases of haemorrhagic meningiomas, Modesti, et al indicated that 3 of them were of meningothelial and one was of the angioblastic type. 20 They also reported that in their review of the literature there were 9 cases of haemorrhagic meningiomas and all of them were meningothelial type. Detailed histological studies of 5 of those cases showed constant association of haemorrhage with the presence of small and large thin walled endothelial channels. Helle and Conley reported one case of haemorrhage associated with meningioma. 12 In their review of the literature, they found 43 patients of haemorrhagic meningiomas and that is most frequently associated with the meningothelial and angioblastic meningiomas. Haemorrhages can be intratumoural, subarachnoid, or, rarely, subdural. In a series of 15 patients with cystic meningiomas, there were 3 cases of haemorrhagic meningiomas, first was of the angiomatous, the second was malignant, and the third was meningothelial types. Haemorrhages occurred in 2 patients with type 1, and in one patient with type 2 cystic meningiomas. Tumoural haemorrhages may be the mechanisms for the formation of type 1 or 2 cystic meningiomas. Haemorrhages are not encountered in type 3 cystic meningiomas. 39 The second case we reported here corresponds to type 4 according to the classification suggested by Nauta, et al. 21 It showed haemorrhage on imaging studies and that was also confirmed during surgery. The tumour was a meningothelial meningioma that showed some malignant changes. Of note here is the risk of haemorrhage in cases of large necrotic or cystic meningioma and that was reported when embolization was contemplated. This haemorrhage is probably due to increased intraluminal pressure proximal to the site of microparticulate occlusion of the vessels. 37 The differentiation between cystic meningiomas and other tumours of the brain; like gliomas and metastatic tumours is difficult and is commonly made after pathological examination. 13,22,33,4,11 Cerebral angiography is thought to help differentiate meningioma from other cystic lesions as it shows the meningeal supply for the tumour from the external carotid artery in cases of meningioma. 22 Zee, et al found that MRI had an accuracy of 80% in the diagnosis of cystic meningioma as compared with CT scan that rendered a diagnostic accuracy of only 50%. 39 The most frequent site of occurrence of cystic meningioma is the cerebral convexity followed by the parasagittal region. 10,17,33 Contrast enhanced MRI can distinguish between cyst walls that is infiltrated by tumour cells (type 2) from the cyst walls that is composed only of gliotic tissue (type 3). 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4 2 cystic meningioma should be removed totally along with the cyst wall to prevent recurrence. 39 The resection and careful pathological evaluation of the walls of any cyst are mandatory to avoid recurrence. 2,15 Senbokuya, et al reported a case of a cystic meningothelial meningioma that was diagnosed as an atypical meningioma. The cyst wall was difficult to remove from the surrounding brain and on histological examination it was infiltrated by tumour cells. The patient had to receive radiotherapy after surgery. This report underscores the importance of resection of the wall of the cyst whenever feasible to minimize the chances of recurrence. 32 In addition to the uncertainty of the diagnosis of cystic meningiomas based on imaging studies, the clinical presentation may also add to the diagnostic dilemma as in the 2 cases we reported here. They had rapid deterioration in their clinical condition and did not follow the usual slowly progressive course typical of meningioma. That also added to the implausibility of a preoperative diagnosis of meningioma. Conclusions Preoperative differentiation of cystic meningioma from other lesion in the brain is difficult to ascertain based on imaging studies. The difficulty can be confounded by an atypical presentation like the cases we reported here. This differentiation however, is crucial for surgical decision making. While subtotal resection or even biopsy can be appropriate in some malignant tumours, total resection is the goal in the case of meningioma for best results. Meningioma should be considered in the differential diagnosis of intracranial tumours even with the presence of cystic changes. Although correct diagnosis may not be accurately ascertained with frozen section in all cases, we believe that it will help to establish the diagnosis in many cases. 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