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Spinal MR in Sickle Cell Patients: Range of Pathology and Diagnostic MR Features 2006

General Spine

Fabian J Candocia, MD, Non ASSR Member
Brian C Bowen, MD, PhD, FACR, ASSR Member
Judith D Post, MD, FACR, ASSR Member

Scientific Paper

Purpose

Due to the paucity of literature illustrating the use of spinal magnetic resonance (MR) in patients with sickle cell disease (SCD), we undertook our current investigation. Our purpose was to: (1) identify the range of pathology and spectrum of MR abnormalities in SCD patients with spinal symptomatology and (2) identify the characteristic imaging findings which are able to differentiate the various types of spinal pathology in patients with SCD.

Methods & Materials

A retrospective review of 219 cases of SCD patients having presented to Jackson Memorial Hospital over the last five years was performed in order to identify patients diagnosed with SCD and related spinal abnormalities. Of the 219 patients, 10 had been diagnosed with osteomyelitis, only 3 (1.4%) of which involved the spine. Two additional SCD patients outside of this five year time frame were added to this cohort. All patients had undergone MR imaging. Age range was from 4-54 years, but only one of these was over 20 years old. The diagnosis was established by positive blood or specimen cultures (Salmonella Group C and D); (n= 3), and/or by pre-and post contrast MR findings (n=5) which showed improvement or resolution of findings on follow-up MR scans (n=3) along with clinical and laboratory response to therapy (n=3) including decreasing erythrocyte sedimentation rate, fever abatement and pain resolution. In one case, confirmation was obtained after surgical resection of the epidural abscess. The diagnosis of bone infarct was established by improvement or resolution on serial MR and radionuclide scans. All MR imaging was performed on a 1.5 T scanner pre and post administration of intravenous gadopentetate dimeglumine (Magnevist; Berlex Laboratories, Montville, NJ). T1-weighted SE (TE=14 TR=500 ms), T2-weighted FSE (TE=128 TR=4000), short time inversion recovery (STIR) and post contrast T1-weighted SE sequences were performed in all five cases. Additional sequences, such as pre and post contrast fat saturation T1-weighted SE images (TE=14 TR=564), were obtained in three patients. MR images were evaluated by 3 observers for marrow signal abnormalities and enhancement, epidural soft tissue mass and enhancement, epidural fluid collections and intervertebral disc signal abnormalities and enhancement as well as any spinal cord, cauda equina, and subarachnoid sac abnormalities.

Results

Diagnoses in the five collected cases included diffuse marrow replacement from anemia (n=5), epidural abscess (n=2), epidural phlegmon (n=2), osteomyelitis/discitis (n=3), facet osteomyelitis (n=1) and bone infarct (n=3). Infectious organisms included salmonella (n=3) and streptococcus pneumoniae (n=1). In one case, no organism grew out of culture as the patient was on antibiotics (n=1). Anemia was illustrated by diffuse hypointense signal on T1-weighted sequences throughout the marrow. Epidural abscess was characterized by a soft tissue mass with inhomogeneous signal on T1-weighted images corresponding with high signal on STIR and T2-weighted sequences. Upon contrast administration, a ring enhancing mass was seen on T1-weighted images (Fig 1). In one case an epidural abscess was seen with no concomitant discitis/osteomyelitis which extended throughout the thoracic spinal canal causing cord compression prompting surgical decompression. In a second case the abscess extended over one level and was successfully treated medically as verified on follow-up MR scan. MR characteristics of epidural phlegmon included increased soft tissue mass in the epidural space which was isointense on T1-weighted sequences, hyperintense on STIR and T2-weighted sequences and enhanced homogenously following contrast administration. MR findings of discitis/osteomyelitis included: (1) increased disc signal on STIR and T2-weighted sequences as well as enhancement on T1-weighted images following contrast administration, (2) erosion of the adjacent cortical end plate identified on STIR, T1-weighted and T2-weighted sequences, (3) low signal on T1-weighted images, high signal on STIR and T2-weighted sequences and contrast enhancement of the end plates and vertebral bodies adjacent to the infected disc, and (4) adjacent paraspinal soft tissue enlargement and enhancement (Fig. 2,3). Bone infarcts were seen as areas of isointense signal on T1-weighted sequences and high signal on STIR and T2-weighted images that were usually central in location and lacked adjacent endplate destruction, disc space involvement and significant adjacent soft tissue abnormality. T1-weighted sequences displayed patchy enhancement following contrast administration (Fig 1). Three out of five cases had follow-up MR examinations performed several weeks after the patients' initial admission. In all cases the abnormalities improved or resolved while on treatment with the exception of the diffuse anemia.

Conclusion

MR is critical to the detection and differentiation of the various types of spinal pathology seen in SCD patients. MR allows the clinician to make an appropriate decision regarding surgical or medical treatment given its ability to identify cord compression caused by epidural abscesses as well as to differentiate discitis/osteomyelitis from bone infarcts. MR also aids in the monitoring of medical therapy following initial treatment.

References

1. Martino AM, Winfield JA. Salmonella osteomyelitis with epidural abscess: A case report with review of osteomyelitis in children with sickle cell anemia. Pediatr Neurosurg 1990-91;16:321-325.
2. Chambers JB, Forsythe DA, Bertrand SL, et al. Retrospective review of osteoarticular infection in a pediatric sickle cell age group. J Pediatr Orthop 2000;20(5):682-5.
3. Bonnerot V, Sebag G, Montalembert M, et al. Gadolinium-DOTA enhanced MRI of painful osseous crises in children with sickle cell anemia. Pediatr Radiol 1994;24:92-95.
4. Uman H, Nogah H, Flusser G. The diagnostic role of gadolinium enhanced MRI in distinguishing between acute medullary bone infarct and osteomyelitis. Magnetic Resonance Imaging 2000;18:255-262.
5. Frush DP, Heyneman LE, Ware RE, Bisset GS. MR features of soft-tissue abnormalities due to acute marrow infarction in five children with sickle cell disease. AJR 1999;173:989-993.

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