Neurofibromas of the spine -- a pathognomonic sign

Neurofibromas growing from spinal nerve roots commonly cause enlargement of the intervertebral foramen. The enlargement is occasionally minimal if the bulk of the tumour is outside the spinal canal, in which case there is widening of the gap between the zygapophyseal joints and transverse processes of adjacent vertebrae seen on anteroposterior projection. This sign is regarded as pathognomonic of neurofibroma.