While reviewing major pathological conditions, the radiologist must learn to adapt his technique to the indication and look for multifocal lesions. In conditions involving malformation, transdural cord herniation and diastematomyelia may be discovered late. In vascular diseases, a dural arteriovenous fistula with perimedullary venous drainage is the most common vascular malformation and a source of diagnostic error. On discovering a medullary cavity, the radiologist needs to know when to discount focal distensions of the ependymal canal and how to detect tumoral syringomyelia. In the case of a tumour, he should know the characteristics of common tumours such as astrocytomas, ependymomas, haemangioblastomas and cavernomas. In inflammatory diseases, he should know when a brain examination is required. When faced with images appearing to show a tumour, he should consider the possibility of pseudotumours and in particular of granulomatoses.