Summary Of The Characteristics Of Various Spinal Infections

Spinal discitis accounts for 2% to 7% of all musculoskeletal infections caused by bacteria, fungi, and, more rarely, by parasites. About half of all cases of spinal infections are located in the lumbar spine, slightly more than one-third in the thoracic spine, and the remainder in the cervical spine.

Purulent Infection

Purulent spinal discitis (PS) is usually caused by a hematogenously disseminated infection, with Staphylococcus aureus being the most common pathogen, most often involving the lumbar spine, and x-rays lacking specificity and sensitivity in the early stages of the disease. Enhanced MRI is the method of choice for the early diagnosis of spinal infections; MRI demonstrates bone marrow edema and enhancement of the vertebral bodies, intervertebral discs, epidural space, and/or surrounding soft tissues with or without abscess formation located primarily near the vertebral endplates.

Note: (a) Lateral lumbar spine radiograph showing L4 -L3 disc height loss and destruction of the upper endplate of L4 (arrow). 

(b) Mild posterior slip at L3. destruction of the L3 - L4 disc with erosive changes to the adjacent endplates (arrows). 

(c) Magnetic resonance (MR) image showing erosive changes of the vertebral endplates and abnormal signal of the adjacent vertebral bone marrow (arrow). The prevertebral soft tissues are markedly edematous and have inflammatory changes. 

(d) Sagittal t1 after intravenous contrast injection shows enhanced signal in the bone marrow (asterisk), enhanced signal in the epidural space and prevertebral soft tissue. Note the indentation of the central canal (arrow).

Spinal Tuberculosis

Tuberculosis of the spine (TS), the most common non-purulent granulomatous spinal infection caused by Gram-positive Mycobacterium tuberculosis, and the imaging features that differentiate TS from PS are shown in the table below:

Late radiographs show bone destruction, decreased disc height and soft tissue abscesses with or without calcification of the surrounding soft tissue.

On MRI, the typical t1 low-signal intensity and high-signal intensity of fluid-sensitive sequences involves the anterior vertebral body and may extend through the subligamentous pathway to other vertebrae, generally without involving the disc.

Notes: 65-year-old male with (a) axial and (b) lumbar abscesses (asterisks) with septal and wall enhancement (white arrows).L3 to S1 vertebral body enhancement. Collapsed intervertebral disc with no significant enhancement. Dural sac compression (white arrow). (c) ct reconstruction image of L3 to S1 vertebral body destruction.

Brucella Infection

Brucellosis is a worldwide endemic zoonosis caused by a gram-negative bacillus. It often involves the lumbar spine, especially L4.

The disease begins in the anterior portion of the vertebral body of the intervertebral disc and may damage small joints. Paravertebral abscesses occur less frequently and are smaller in size than TS. The vertebral anatomy remains intact.

Note: Brucella lumborum infection, radiographs show sclerosis of the lumbar vertebrae, forward slippage of the lumbar vertebrae, irregular step-like destruction at the anterior margin of the vertebral body, and formation of bony cribriforms at the anterior margin of the vertebral body.

Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory autoimmune disease that primarily affects the spine and can lead to severe chronic pain from spinal fusion.

Another complication in patients with AS is the development of limited disc disease, and on imaging, AL can be distinguished from inflammatory spondylitis by focal defects in one or two adjacent vertebrae, narrowing of the disc space, and areas of reactive sclerosis surrounding the osteolytic defects.

Note: Patient with ankylosing spondylitis, 44-year-old male with chronic lower back pain and limited range of motion. Sagittal ct of (a) thoracic and (b) lumbar spine bone windows show diffuse ligamentous syndesmosis along the anterior longitudinal ligament (arrows). There is also ossification and fusion of the lumbar interspinous ligaments (arrows shown). (c) Coronal image at the lumbar spine level shows fusion of the posterior elements and articular synovial joints (arrows).

Osteomyelitis Syndrome

The acronym SAPHO refers to a combination of musculoskeletal and cutaneous manifestations (synovitis, acne, pustulosis, osteomalacia, and osteomyelitis), with the anterior thoracic wall (including sternoclavicular joints, costothoracic joints, and sternoacetabular elbow joints) being the most commonly involved, followed by the lumbar and cervical spine.The most common manifestations on x-ray radiographs are vertebral body osteolysis with or without collapse, as well as osteomalacia and paraspinal ossification.MRI is the most sensitive imaging MRI is the most sensitive imaging modality, and its main manifestations include widespread or focal vertebral signal changes on fluid-sensitive sequences with cortical erosion and irregularities at the intervertebral junctions of the intervertebral discs or anterior endplates, and soft tissue edema.

Note: 62-year-old male with SAPHO syndrome. (a) Sagittal t2-weighted and (b) computed tomography (CT) images show ossification of the anterior longitudinal ligament (black arrows) No significant abnormalities of the disc or paravertebral fluid. The L1 is highly repositioned after an old compression fracture. (c) Axial CT shows ankylosis of the right costovertebral joint (asterisk). (d) Oblique coronal CT reconstruction shows bilateral thoracic ribcage clavicle ankylosis (black asterisks). (e) Bone scan showing radiotracer uptake in both affected joints (white asterisks).

Dialysis-related Spondyloarthropathy

Dialysis-related spondyloarthropathy (DRS) is a pathologic change in patients on long-term hemodialysis. It is most common in the cervical spine and typically presents with narrowing of the intervertebral space, destruction of the endplates, lack of sclerosis, new bone formation, paraspinal infections/abscesses, and strengthening of the space.

Note: Extensive osteoporosis of the lumbar and sacral pelvis. Destruction of the anterosuperior margin of the lumbar 5 vertebrae with sclerotic hyperplasia of the margins (shown by the red arrow). Adjacent scarring hyperplasia. Destruction of the left sacroiliac joint with destruction of the lateral articular surface of the ilium, multiple internal dead bones, and localized scar-like tissue hyperplasia (shown by blue arrows).

Note: Enhanced MR: Lumbar 4/5 disc bulge with vertebral rim osteophytes, hypertrophy of ligamentum flavum, slight narrowing of the spinal canal, and compression of the anterior edge of the dural sac. The lumbar 5 vertebral body is limitedly concave and can be seen as strips of long T1 and T2 WI compression fat high signal, and enhancement is seen after enhancement. Multiple patches of abnormal signal are seen under the endplates of lumbar 5 and sacral 1 and under the sacroiliac joints, with low signal on T1WI and slightly high signal on T2WI, and enhancement is seen on enhancement scans (red arrows). Soft tissue thickening at the anterior margin of the sacral vertebrae was seen, and enhancement was seen on enhanced scan (blue arrow). The bone signals of the ilium, hip, sacrum and femoral head on both sides of the pelvis did not show any obvious abnormality, and the signals of the internal and external pelvic muscles were normal, with clear muscle gaps and normal joint gaps, without signs of widening and narrowing.

Spinal Gout

Spinal gout is characterized by deposits of monocrystalline urate crystals (MUCs) in the spine. Spinal gout mainly affects the lumbar spine. radiographs show nonspecific manifestations and CT better characterizes bone erosion with sclerotic margins. mri manifestations are nonspecific.

Note: CT plain scan shows joint space narrowing and bilateral articular surface destruction. Arthrocentesis is required to confirm the diagnosis.

Neurospondylitis

Neurogenic spondylitis (NS), a destructive progressive arthropathy, occurs after loss of sensation and proprioception. The most common cause is traumatic spinal cord injury, which accounts for 70% of cases. Other causes include diabetes mellitus, spinal cord cavernous disease, and other neurologic disorders such as peroneal muscular dystrophy and Guillain-Barré syndrome. Due to the role of the thoracolumbar and lumbosacral junctions in weight-bearing, they are the most commonly involved sites.

Typical manifestations of NS are bone fragments, intervertebral joint irregularities and inconsistencies leading to vertebral body slippage, multiple endplates and small joint erosions as well as preservation of bone density in sclerosis, and also soft tissue masses.

Note: 58-year-old male with neuropathic spine. (a) Sagittal and (b) coronal computed tomographic reconstructions show multiple lumbar vertebral endplates and articular synovial joint erosions (arrows) with bone fragments. Destruction of the L2-L3 intervertebral disc unit with widening of the intervertebral space (asterisk). (c) Sagittal and (d) axial t2-weighted magnetic resonance sequences confirming widening of the L2-L3 intervertebral space. significant alterations of the affected spinal cord posterior to L2-L3-L4. There is also effusion in the soft tissues posterior and anterior to the spinous processes (asterisks).