Some remarks on the mode of spread of primary benign brain-stem tumours based on description of three cases.

On the basis of long-standing own experiences and the literature, the author subdivides the tumours mentioned in the title into two types. Type A (occurring most frequently): Developing in the transversal plane and the longitudinal axis; typical clinical signs on cerebral nerves, long pathways and cerebellar pathways. Choked papilla and signs of cerebral compression develop late or not at all. Surgical removal is impossible. Type B: Tumour growth in the 4th ventricle and subarachnoid space without infiltration of deeper brain-stem structures. Signs of cerebral compression in the early phase. Signs of transversal damage of the brain stem are slight and disappear after decompression. Partial removal and subsequent irradiation lead to a far-reaching freedom from symptoms and a socially useful survival over many years. So these tumours should be operated on with subsequent irradiation.