At The Monitor Timothy Mick, DC, DACBR, FICC Center for Diagnostic Imaging

1. At The Monitor Timothy Mick, DC, DACBR, FICCCenter for Diagnostic Imaging

2. Case 7 54 year old male with low back pain for 6 weeks. X-rays at the time of presentation were interpreted as negative for pathology. There was lack of anticipated response to chiropractic care. No fever, malaise or other abnormality to suggest systemic disease were present. Referral for MRI was prompted by the failure of anticipated response to conservative chiropractic care.

6. Key Imaging Findings MRI demonstrates marked focal disc space narrowing at L3-4, with bright T2 signal remaining within the disc. This speaks against degenerative disc changes, which typically show diminished disc T2 signal, reflecting disc dessication. There is extensive vertebral marrow signal abnormality with decreased T1 (left sagittal image) and increased T2 signal (right sagittal image), extending from the discovertebral margins. The cortical margins of the L3-4 endplates are disrupted/indistinct, with evidence of erosion, most evident in the superior endplate of L4. There is abnormal soft tissue with bright T2 signal surrounding the discovertebral junction of L3-4 and extending caudally along the medial margin of the left psoas. The psoas muscle lies immediately adjacent to the discovertebral margins, with the normal muscle demonstrating uniformly low signal, in contrast to the abnormal bright signal focus at the medial margin of the left psoas.

7. Discussion The MRI findings are typical of disc space infection, with paraspinal soft tissue abscess extending along the left psoas muscle. Clinical-imaging correlation suggests the possibility of atypical or granulomatous infection, versus the more common pyogenic infection (most often due to staphylococcus), accounting for about 90% of spinal infections. The clinical course here reflects that of many spinal infections. The low back pain may not be readily distinguished from mechanical low back pain. The severity of pain is variable, but tends to be moderate to severe. Initial plain films are often negative or, at most, demonstrate only some focal disc space narrowing and, perhaps, subtly indistinct cortical margins or small erosions. There is a “radiographic latent period” of as much as three weeks before any abnormal x-ray findings are present. In contrast, the “latent period” for extremity infections is typically about 7-10 days. Confounding clinical findings are also common in spinal infections. Systemic symptoms, including fever, malaise and altered laboratory tests (e.g. white cell count and sedimentation rate) are often absent, as are focal signs & symptoms such as local warmth, erythema and swelling. These are more reliable findings in extremity infections.

8. Discussion Causes of disc space infection include: Surgery or other invasive spine procedure (MC cause) Immunocompromised patient (Including corticosteroid treatment) Infection of another organ system, with hematogenous spread (e.g. the genitourinary tract) Intravenous drug abuse

9. Discussion Primary “discitis” may occur in children, in whom the disc has a direct vascular supply. In adults, disc space infections usually begin as osteomeyelitis, in the vertebral body marrow immediately adjacent to the endplates. In both populations, an inciting organism may or may not be identified. Intravenous antibiotic therapy is typically used, whether or not a specific microorganism is isolated. Childhood “discitis” is probably more often classified as “idiopathic,” but may follow a viral infection, as in the upper respiratory tract. Focal intradiscal calcification may be seen with childhood “discitis.” Disc space infection in adults does not usually produce disc calcification, although paravertebral calcification may be seen with granulomatous infections such as tuberculosis, histoplasmosis and coccidioidomycosis.

10. Discussion Disc space infection should be considered when there is ongoing (especially increasing) neck or back pain, with conservative care. The clinical concern increases when there is an underlying predisposing condition, although many cases of disc space infection occur without a clear underlying cause. As stated previously, clinical findings are variable and often unreliable. However, correlation for clinical and laboratory findings of infection is appropriate, along with consideration of referral for MRI.

11. Thank You!

12. Center for Diagnostic Imaging (CDI) brings you the most comprehensive chiropractic diagnostic and therapeutic imaging services in Minnesota, including x-ray, Open Upright MRI, High-field, Shortbore MRI (1.5T and 3T), and Diagnostic Injections and Pain Management procedures, among other services at CDI's outpatient imaging centers in the Twin Cities. Working together, our goal is to ensure your patients receive the right exam, at the right time, with accurate results.  For more information or for a list of the CDI facilities in Minnesota go to our website at www.cdi-rad.com