ROLE OF ISCHEMIA IN THE GENESIS OF EDEMA SURROUNDING MENINGIOMAS ASSESSED USING MAGNETIC-RESONANCE-IMAGING AND SPECTROSCOPY

Oedema surrounding meningiomas is well known, but its pathogenesis rem ains obscure. Perfusion and metabolism in this peritumoural parenchyma were studied preoperatively in eight patients using magnetic resonanc e imaging, dynamic perfusion scanning and proton spectroscopy. Relativ e cerebral blood volumes (CBV) and metabolite ratios were calculated f or the tumour and peritumoural brain. All meningiomas showed gadoliniu m enhancement, high choline (Ch), low creatine (Cr) and low N-acetyl a spartate (NAA) [Ch: (Ch + Cr) 0.67, SD 0.13, NAA: (Ch + Cr) 0.18, SD 0 .15]. Lactate was present in four rumours [lactate: (Ch + Cr) 0.32, SD 0.27]. Extremely low gadolinium passage and low CBV were seen in the 2 cm peritumoural region, with elevated lactate [lactate: (Ch + Cr) 0. 26, SD 0.18]. Four centimetres from tumour margin the CBV was still re duced (65, SD 20% with less lactate [lactate: (Ch + Cr) 0.12, SD 0.01] . Relative CBV is reduced around meningiomas and is associated with la ctate, suggesting that oligaemia and altered metabolism may be part of the pathology in peritumoural oedema. Such changes may be important i n determining functional recovery after surgery.