A 57-year-old man with epidural calcified disk sequestration in the cervical spine, which was discovered after trauma, is reported. Differentiation between cervical disk herniation and other disease entities on magnetic resonance imaging (MRI) was difficult. The confirmation of the presence of extradural calcification by computed tomography (CT) was helpful in the diagnosis of this disease

Ashizawa Kazuto

Eto Masao

Hayashi Kuniaki

Okimoto Tomoaki

Uetani Masataka

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Acta Med. Nagasaki 44 : 58-60Epidural Calcified Sequestration of Cervical Intervertebral DiskKazuto ASHIZAWA 1), Masataka UETANI 1), Tomoaki OKIMOTO 1), Kuniaki HAYASHI 1), Masao ETO 2)1) Department of Radiology, Nagasaki University School of Medicine 2) Department of Orthopedic Surgery, Nagasaki University School of Medicine A 57-year-old man with epidural calcified disk sequestra-tion in the cervical spine, which was discovered after trauma, is reported. Differentiation between cervical disk herniation and other disease entities on magnetic resonance imaging (MRI) was difficult. The confirmation of the presence of extradural calcification by computed tomography (CT) was helpful in the diagnosis of this disease.Key Words: cervical disk herniation, sequestrated disk,           calcified disk, epidural mass, CT, MRICase report  A 57-year-old man was transferred to an emergency hospital due to trauma to the head and neck. He dem-onstrated quadriparesis on admission; and this was fol-lowed by right hemiparesis during one week of conser-vative treatment. He had had a traffic accident with neck trauma 14 years before. At that time, radiography of the cervical spine showed no definite abnormality.  One month later, he was admitted to our hospital for further examination and treatment. Cervical spine radi-ography revealed spondylosis most marked at C5-6 with disk space narrowing and spur formation, and no evi-dence of calcification at the intervertebral disks or spi-nal canal (Fig. 1). MRI demonstrated a large extradural mass compressing the spinal cord at the C4-C5 level (Fig. 2A,B). The mass had slightly high intensity on both T 1 and T2 weighted images. There was a low intensity rim at the periphery of the mass on axial T 1 weighted images (Fig. 2C). Although MRI showed disk degenera-tion at C5-6, continuity of the extradural mass withAddress Correspondence: Kazuto Ashizawa, M.D. Department of Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan TEL: +81-954-849-7355 FAX: +81-954-849-7357 E-mail: ashi@net.nagasaki-u.ac.jpFigure 1 Calcification is not evident in the spinal canal or disk spaces on lateral plain radiography.that disk was not observed. Spinal cord injury was not detected on MRI. CT performed after MRI showed ring-like calcification corresponding to the low intensity rim of the mass on MRI (Fig. 3).  To decompress the spinal cord, removal of interverte-bral disk materials at C3-C4 and C4-C5 and subtotal re-moval of the C4 vertebral body were performed. Rupture of the posterior longitudinal ligament was not observed where the mass compressed the spinal cord. Incision of the ligament revealed an anterior epidural mass which had the macroscopic appearance of herniated disk material. The lesion was completely removed and an autogenous bone graft was performed to restore the anatomy.  Histological examination of the mass revealed fragments of fibrocartilage with hyaline degeneration and calcifi-cation (Fig. 4). The patient improved but demonstratedmild residual motor and sensory deficits several months after surgery.Figure 2C Axial MRI at the C3-C4 level shows a low inten-sity rim (arrowhead) at the periphery of the mass.Figure 3 Ring-like calcification at the mass is clearly dem-onstrated on axial CT at the C4 level.Figure 2A, B Sagittal MRI demonstrates a slightly high intensity extradural mass at the level of C4 and C5 on both Tl-weighted (500/30) and T2-weighted (2000/80) images. Figure 4 Photomicrograph of the mass shows fibrocartilage with hyaline degeneration and calcification.Discussion  Disk herniation in the cervical spine is not infre-quent, although less common than in the lumber spine. Herniated disk fragments can migrate freely in the epidural space with or without rupture of the posterior longitudinal ligament [1,2]. Disk sequestrations migrat-ing to the lateral aspect of the spinal canal produce symptoms of nerve root compression. In rare cases, disk fragments migrating to the anterior or posterior surface of the spinal canal may cause myelopathy [1]. In the present case, it was thought that a free disk fragment migrated superiorly away from the disk of origin, although rupture of the posterior longitudinal ligament at the C5-C6 level was not confirmed during the operation. The presence of calcification seemed to represent that the sequestrated disk existed many years before discovery.  In adults, degenerative calcification of the intervertebral disks is a relatively common finding, especially in the thoracic spine [3,4]. Calcified thoracic intervertebral disks are often associated with continuous calcified disk herniation [5]. Therefore, calcified herniated disk mate-rial in the spinal canal is found in a higher percentage of thoracic than lumber or cervical disks. On the other hand, sequestrated disk herniation with calcification in the cervical spine is rare, although its exact frequency is unknown. In our case, no calcified intervertebral disks were found and the herniated disk fragment was not continuous with the intervertebral disks. These features made the correct diagnosis before surgery difficult. How-ever, disk herniation is a common disorder, and should always be considered in the differential diagnosis even when radiologic findings reveal less common abnormali-ties such as calcification.  A wide variety of lesions are recognized as causes of extradural mass which may occasionally mimic seques-trated disk herniation. On MRI, the differential diagno-sis in our case would include epidural hematoma, ossifi-cation of the posterior longitudinal ligament (OPLL), and extradural tumor. The possibility of an epidural hematoma was the major concern in our case, since the neurological symptoms appeared after trauma. However, the confirmation of calcification within the mass by CT made it unlikely that it was an epidural hematoma. OPLL, seen most commonly in the cervical spine, usu-ally demonstrates homogeneous low signal intensity on both T 1 and T2 weighted images. Occasionally, ossifica-tion with associated marrow formation can demonstratehigh signal intensity within the mass similar to the findings in our case. However, the diagnosis of OPLL is established by plain radiographs or CT as a dense, ossified band posterior to the vertebral bodies and intervertebral disks. MRI is not always sufficient to distinguish disk sequestration from epidural neoplasm, even when Gd-DTPA enhancement is performed.  Generally, MRI in combination with plain radiogra-phy can provide the best information for evaluating cervical spondylosis and herniated disk disease [6-8]. The application of radiography is useful in the assess-ment of the osseous elements of the spine and calcifi-cation. MRI is useful in the detection of disk herniation including sequestrated disk fragments and in evaluat-ing its relationship to the spinal cord. However, calcifi-cation and osseous change of the spine may be difficult to detect with MRI and plain radiographs alone [4]. CT is beneficial in detecting calcification and separating hypertrophic bony change from soft disk herniation [4,9,101. In the present case, CT confirmed that the low intensity rim of the mass on MRI corresponded to calcification and was not hemosiderin associated with hematoma. We, therefore, emphasize that CT has an important role as a supplementary examination tool in the diagnosis of cervical disk herniation to provide in-formation not clearly defined on MRI and plain radiog-raphy.References1) Manabe S, Tateishi A. Epidural migration of extruded cervical disc    and its surgical treatment. Spine 11: 873-878, 1986 2) Schellinger D, Manz HJ, Vidic B, et al. Disk fragment migration.    Radiology 175: 831-836, 1990 3) Blumenkopf B. Thoracic intervertebral disc herniation: diagnostic    value of MRI. Neurosurgery 23: 36-40, 1988 4) Wallace CJ, Fong TC, MacRae EM. Calcified herniations of the tho-   racic disk: role of magnetic resonance imaging and computed    tomography in surgical planning. Can Assoc Radiol J 43: 52-54,   1922 5) Ryan RW, Lally JF, Kozic Z. Asymptomatic calcified herniated tho-   racic disks: CT recognition. AJNR 9: 363-366, 1988 6) Russell EJ. Cervical disk disease. Radiology 177: 313-325, 1990 7) Nakstad PH, Hald JK, Bakke SJ, Skalpe IO, Wiberg J. MRI in cervi-   cal disk herniation. Neuroradiology 31: 382-385, 1991 8) Brown BM, Schwartz RH, Frank E, Blank NK. Preoperative evalua-   tion of cervical radiculopathy and myelopathy by surface-coil MR    imaging. AJNR 9: 859-866, 1988 9) Lester JW, Miller WA, Carter MP, Hemphill JM. MR of childhood    calcified herniated cervical disk with spontaneous resorption. AJNR    10: S48-S50, 1989 10) Jahnke RW, Hart BL. Cervical stenosis, spondylosis, and herniated    disc disease. Radiol. Clin. North. Am. 29: 777-791, 1991

Epidural Calcified Sequestration of Cervical Intervertebral Disk

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Epidural Calcified Sequestration of Cervical Intervertebral Disk

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