Two Cases of Dorsal Epidural Migration of Lumbar Disk Fragments

Abstract

Herniated disk fragments are known to migrate in many directions within the spinal canal, but dorsal migration has been rarely reported. This report presents 2 cases of migration of the lumbar disk into the dorsal epidural space. A 65-year-old man complained of sciatica and numbness from the posterior surface of the bilateral thighs. Magnetic resonance imaging (MRI) showed a narrow spinal canal at L3-4. The mass was posterolateral in the epidural space at the L4 level. It was iso-hypointense on T1-weighted images and iso-hyperintense on T2-weigted images. A decompressive lumbar hemilaminectomy was performed. Surgery revealed the mass to be surrounded by a membranous thickened mass of the epidural venous plexus and was dorsal to the dural sac. The mass proved to be a migrated lumbar disk fragment. The patient made a good recovery after surgery. A 73-year-old man complained of lumbar pain and right leg pain in the L5 area. MRI showed a lumbar disk hernia at L4-5. The mass was posterolateral in the epidural space at L5. It was iso-hypointense on T1-weighted images and iso-hyperintense on T2-weigted images. Surgery revealed that the mass was surrounded by a fibrous membrane with epidural venous plexus and was dorsal to the dural sac. It was determined to be a migrated lumbar disk fragment. The patient made a good recovery after surgery. The preoperative diagnosis of a migrated lumbar disk hernia is difficult to make based only on the findings of nonenhanced MRI images, and thus it must be considered in the preoperative differential diagnosis.H erniated disk fragments can migrate in many directions within the spinal canal, but posterior epidural disk fragment migration has been rarely reported. The preoperative differential diagnosis of this condition is difficult. Moreover, the mechanism of posterior epidural disk fragment migration is unclear. This report describes 2 cases of posterior epidural disk fragment migration. CASE PRESENTATION Case 1A 65-year-old man complained of bilateral leg numbness and intermittent claudication. He had undergone cervical laminoplasty (C3-4) 1 year ago. His history showed lumbar canal stenosis at L4-5. His quadriparesis had improved gradually after cervical laminoplasty. The patient noted sciatica and numbness from the posterior surface of his bilateral thighs. Moreover, he had intermittent claudication and acute lumbago. He was given medication, but the symptoms did not improve sufficiently. A neurological examination found left toe and right leg weakness, and intermittent claudication. The pain thereafter gradually became worse when walking and with standing up retro-flexion. There were no bladder or bowel symptoms. Lumbar spine magnetic resonance imaging (MRI) revealed a mass in the dorsal epidural space at L3-4. The lesion was iso-hypointense on T1-weighted images, and iso-hyperintense on T2-weigted images (Fig. 1). MRI myelography revealed narrow canal stenosis and the mass was posterior to the dural sac. A left L3-4 hemilaminectomy was performed. The ligamentum flavum contained t...