Pattern evoked cortical potentials and compressive lesions along the visual pathways.

It is stressed that not only demyelinating diseases, but also compressive lesions along the anterior visual pathways, may cause severely disturbed or clearly delayed occipital potentials to pattern reversal stimulation. Only tumors exerting real pressure on optic nerve fibres cause these relatively marked disturbances of the pattern responses. Such tumors are tumors of the optic nerve itself, those along the optic canal, at the base of the anterior fossa or around the chiasm, and not tumors of the orbit or those situated beyond the chiasm.