1. There exists a lateral bony recess of the spinal canal at the level of the fifth lumbar dise. This is fairly deep in some insdividuals.
2. The lateral recess may be narrowed from before backward by degenseration and thinning of the fifth lumbar disc, especially if there is backward displacement of the fifth lumbar body or if there is a hypertrophic rim on its inferior border.
3. The first sacral nserve can become caught in this recess and sciatica may result.
4. Myelography will probably not be helpful in diagnsosing this lesions.
5. Compressions of the first sacral nerve in the lateral recess or of the fifth lumbar nserve in the intervertebral foramen shounld be considered as possibilities in patiensts of about fifty or over with sciatica, especially if roentgenograms show thinning of the fifth lumbar disc.
6. It is useful to conceive of disc surgery in this age group in terms of root exploration rather than simple removal of a herniated disc.