With solid haemangioblastomas, however, you ‘develop the plane’ between the tumour and the brain, creating a narrow crevice a few millimetres wide by gently holding the brain away from the surface of the tumour. You coagulate and divide the many blood vessels that cross from the brain to the tumour’s surface, trying not to damage the brain in the process. All this is done with a microscope under relatively high magnification – although the blood vessels are tiny, they can bleed prodigiously.
