Background data: The intraradicular penetration of a disc fragment was first reported in 1984 and is much less frequent than the intradural disc herniation. Both types of disc herniation are predominantly found in lumbar spine and rarely in the thoracic and cervical spine. The pathogenesis of lumbar intradural disc herniation is most likely related to dense adhesions between the ventral dura mater and the posterior longitudinal ligament. The adhesions can apparently result either from repeated minor trauma or from prior surgery.Purpose: In this report, the authors presented the first case of extraforaminal intraradicular disc herniation, which was at first misdiagnosed as a schwannoma, and suggested a new classification for the intradural disc herniations.Study design: Case report.Methods: Clinical and radiological examination of a case of extraforaminal intraradicular disc herniation is presented.Results: In our case the MRI had shown an extraforaminal lesion at the region of L3. As the possibility of extraforaminal intraradicular disc herniation is very remote,
the diagnosis of schwannoma was made. However, the diagnosis was then proved by histopathology to be intraradicular disc herniation. Because of this new category of intraradicular disc herniation, we modified the classification of intradural disc herniation into type A: intradural disc herniation (IDH); type B: Intraforaminal intraradicular disc herniation (IIDH); and type C: Extraforaminal intraradicular disc herniation (EIDH).Conclusions: When the diagnosis is suspected of an extraforaminal nerve root tumor,we should not forget the possibility of intraradicular disc herniation and the removed
material should be sent to the histopathological examination to confirm the diagnosis. (2012ESJ001)