Extraforaminal disc herniation.

Atypical disc herniation, especially extra foraminal disc herniation (EFDH), is apt to be overlooked, because myelography and peridurography can give false positive and false negative findings. Eleven cases of EFDH were diagnosed since 1975, and all were confirmed by operative treatment. This number is a very small percentage of the total, but if these cases had not been diagnosed correctly, the results of surgery would have been poor. Selective lumbosacral radiculography and nerve root block techniques are very useful in determining the nerve root involved. Discography is an excellent diagnostic technique for finding the relationship between the nerve root and hernia mass. Extra foraminal disc herniation must be kept in mind as a cause of lumbar radiculopathy.