Role of ischaemia in the genesis of oedema surrounding meningiomas assessed using magnetic resonance imaging and spectroscopy.

Oedema surrounding meningiomas is well known, but its pathogenesis remains obscure. Perfusion and metabolism in this peritumoural parenchyma were studied preoperatively in eight patients using magnetic resonance imaging, dynamic perfusion scanning and proton spectroscopy. Relative cerebral blood volumes (CBV) and metabolite ratios were calculated for the tumour and peritumoural brain. All meningiomas showed gadolinium enhancement, high choline (Ch), low creatine (Cr) and low N-acetyl aspartate (NAA) [Ch: (Ch + Cr) 0.67, SD 0.13, NAA: (Ch + Cr) 0.18, SD 0.15]. Lactate was present in four tumours [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 reduced (65, SD 20% with less lactate [lactate: (Ch + Cr) 0.12, SD 0.01]. Relative CBV is reduced around meningiomas and is associated with lactate, suggesting that oligaemia and altered metabolism may be part of the pathology in peritumoural oedema. Such changes may be important in determining functional recovery after surgery.