Spondylodiscitis - uncommon etiology

Clinical History

Low Back pain (lumbar) with irradiation into the right ower limb since 4 months and recent worsenning (1 week).

Imaging Findings

A 61 year old male patient presented with lower back pain (lumbar) irradiating to the right lower limb (until the knee), localized tenderness, muscular spasm, and stiffness since 4 months, and with recent worsening (last week). The pain caused mobility limitation. He had no fever or other complaints. Medical examination revealed proximal muscle atrophy in the lower limbs and weakness of lower limbs. No other neurologic deficits were found. Laboratory tests were done. He had normal white blood cell counts (no leukocytosis) and high erythrocyte sedimentation rate (41 mm; 0-25). Rose Bengal test (RB) and Wright sero-agglutination tests were positive. So, serological methods favoured the diagnosis of Brucellosis infection. Microbiological diagnosis (blood culture) was also positive for the bacteria. Neuroimaging examinations (CT and MR) were done and suggested the diagnosis of Granulomatous - Brucellosis Spondylodiscitis (also known as osteomyelitis-discitis). Immobilization and specific antimicrobial treatment was introduced. He had progressive resolution of symptoms, and surgical intervention was not required. (However, in a small proportion of cases, open or endoscopic surgery is warranted). Five months later, MRI was done and showed resolution of infection-related abnormalities.

Discussion

Spondylodiscitis has varying patterns of involvement in the Spine: vertebral body (more frequent), intervertebral disc, posterior osseous elements, epidural space, and paraspinal soft tissues. MRI is the most useful radiologic modality for investigating spondylodiscitis. MRI criteria can differentiate the types of spondylodiscitis: pyogenic, tuberculous (the two most common) and brucellosis.
Brucellosis is a widespread zoonosis of great public health importance and economic in some countries. Although the final diagnosis of spondylodiscitis still relies on biopsy and culture, it is not infrequent to treat patients based solely on MRI findings because of clinical findings are usually non-specific and the high rate of negative cultures (falsely negative in up to 40-65%), depending on the disease stage. The diagnosis of infection is properly and non-invasively made by MRI (high sensitivity and specificity in diagnosing and localizing infection) and proper treatment must be done.
Brucellosis can affect the spine in either a focal or a diffuse pattern. The focal form is localized to the anterior aspect of an endplate, most typically the superior endplate of L4. The diffuse form initially involves an endplate and spreads to involve the entire vertebral body, with subsequent extension into the adjacent body and disk. The more important differential diagnosis of Brucellosis spondylodiscitis is tuberculous infection. They are more commonly in the lower lumbar spine, with intact vertebral body margins despite hyperintense vertebral bodies on T2-weighted images and do not have posterior element involvement, paraspinal abcess and gibbus deformity (as TB). Tuberculous spondilytis has imaging findings more typical of tumours than of pyogenic infection: sparing of the intervertebral disk space (no high signal on T2) because of the lack of proteolytic enzymes in mycobacteria; preferential involvement of the posterior elements and posterior portions of vertebral bodies; involvement of multiple (more than 2) vertebral bodies and large paraspinal soft tissue masses/abscesses. TB infection begins in the anterior-inferior portion of the vertebral body and spread beneath the longitudinal ligaments.
Pyogenic (bacterial) Infections involve the vertebral body with ill-defined hypointense vertebral marrow (T1-weighted images), destruction of vertebral endplate cortex on both sides of the disc; involve intervertebral disc (high signal on T2WI) and are associated with paraspinal and/or epidural infiltrative soft tissue and/or loculated fluid collection.
Other important differential diagnosis are with pathologies in extradural compartment and with abnormal marrow signal: Vertebral fracture with epidural haematoma; pyogenic osteomyelitis; metastases (blastic/ lytic osseous); granulomatous osteomyelitis; multiple myeloma; plasmacytoma; lymphoma; haemangioma.
Spinal DWI will further characterize spondylodiscitis and abscesses of the spine and help in differential diagnosis - benign/malignant fractures.
Although MR has already been established as the most sensitive technique for diagnosing spondylodiscitis, the MR findings may still lag behind the clinical symptoms, which may even include severe back pain. When the diagnosis is uncertain, a follow-up MR in 1 week may be helpful to show the evolution of the early changes.
Radiographic and MR findings may be also very slow or inconsistent in resolution. The efficacy of conservative care may be estimated in individual cases by diminution of symptoms.

Differential Diagnosis List

Final Diagnosis

Brucellosis spondylodiscitis (diffuse pattern)- granulomatous spondylodiscitis

URL:	https://www.eurorad.org/case/7261
DOI:	10.1594/EURORAD/CASE.7261
ISSN:	1563-4086