Lumbar Diskal Cyst Containing Intervertebral Disk Materials

Full article available online at ORTHOSuperSite.com. Search: 20110922-29 The diskal cyst is a relatively new clinical entity and develops clinical symptoms of a unilateral single nerve root lesion. Although many cases of diskal cyst have been reported, the pathogenesis of diskal cyst remains unclear, and several theories regarding the pathogenesis have been proposed. This article presents 2 cases of diskal cyst communicating with an adjacent herniated disk. Magnetic resonance imaging fi ndings showed diskal cysts in the epidural space of the lumbar spine. Surgical resection was performed, and apparent connections between the corresponding disk and cysts were found. Histopathologic examinations of the cyst wall demonstrated cartilaginous tissue including nucleus pulposus and annulus fi brosis. These patient’s symptoms improved remarkably postoperatively, and there was no recurrence of diskal cyst. The hypothesis supported by many authors is hemorrhage from the epidural venous plexus. Diskal cysts arise fi rst from an underlying intervertebral disk injury that causes an annulus fi brosis fi ssure in the posterior intervertebral disk. Hemorrhage from the epidural venous plexus with a rich blood fl ow then occurs in the space between the peridural membrane and vertebral body. However, in our cases, we confi rmed that the diskal cyst could have developed from the resorption process of an intervertebral disk herniation. Only 5 cases of diskal cyst demonstrating the presence of cartilaginous tissue in the cyst have been reported. Our 2 cases are rare and support the hypothesis of resorption of intervertebral disk herniation. Drs Tsuchie and Shimada are from the Department of Orthopedic Surgery, Akita University Graduate School of Medicine, Akita, and Drs Nishi, Tani, and Maekawa are from Ugo Municipal Hospital, Ugo, Japan. Drs Tsuchie, Nishi, Tani, Maekawa, and Shimada have no relevant fi nancial relationships to disclose. Correspondence should be addressed to: Hiroyuki Tsuchie, MD, Department of Orthopedic Surgery, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan (tsuchie@doc.med. akita-u.ac.jp). doi: 10.3928/01477447-20110922-29 Lumbar Diskal Cyst Containing Intervertebral Disk Materials HIROYUKI TSUCHIE, MD; TOMIO NISHI, MD; TAKAYUKI TANI, MD; SHIGETO MAEKAWA, MD; YOICHI SHIMADA, MD Figure: Sagittal T1-weighted lumbar vertebrae MRI with low-signal intensity (A), sagittal T2-weighted lumbar vertebrae MRI with high-signal intensity (B), and axial T2-weighted lumbar vertebrae MRI with high-signal intensity (C) showing a spherical extradural cystic mass behind the L5 vertebral body (arrows). A B