We report a preterm newborn who presented extensive cerebral vein thrombosis on MRI but no abnormal neurological signs. The baby underwent MRI as germinal-matrix intraventricular haemorrhage was revealed by a routine ultrasound brain scan performed on day 16; earlier ultrasound scans (day 2, 7, 12) were all normal. Cerebral vein thrombosis was diagnosed at the first MRI scan together with abnormal restriction in diffusion weighted imaging in the frontal white matter parenchyma. Bilateral microcavitations with a linear pattern of distribution reflecting the distribution of medullary veins developed a week later in the same white matter areas where abnormal diffusion weighted imaging was formerly noted. The baby was later found to be heterozygous for factor V Leiden.