What are Schmorl nodules?

What are Schmorl Nodules?

Schmorl nodules are herniations of the nucleus pulposus (the inner gel-like core of the intervertebral disc) through the cartilaginous and bony endplate into the adjacent vertebral body. 1, 2

Epidemiology and Prevalence

• Schmorl nodules are extremely common, with postmortem studies estimating that greater than 70% of the population has these lesions 1
• They are most commonly found in the thoracolumbar junction and lumbar spine 3
• There is ethnic and gender influence on their prevalence 3
• These lesions are frequently associated with mechanical loading and impact stress, particularly from activities involving repetitive spinal loading such as horseback riding, chariot driving, and heavy lifting 4, 5

Clinical Significance

• The vast majority of Schmorl nodules are asymptomatic and discovered as incidental findings on radiographic imaging 1, 2
• Rarely, Schmorl nodules can cause acute back pain, and even less commonly, radiculopathy from nerve root compression 1, 6
• Lumbar Schmorl nodules are frequently associated with disc degenerative disease and back pain 3
• Symptomatic Schmorl nodules are thought to result from the inflammatory response triggered by herniation of nucleus pulposus into the well-vascularized vertebral body 2

Pathophysiology

• An axial load model appears to have the greatest supporting evidence for the pathogenesis of Schmorl nodules 2
• Strain energy changes in the spine, along with morphological aspects of the vertebra, genetic background, and osteoimmunology may constitute possible contributing factors 3
• The herniation occurs through defects in the vertebral endplate, allowing disc material to penetrate into the vertebral body 1, 2

Diagnostic Imaging Characteristics

• MRI is the imaging modality of choice for diagnosing Schmorl nodules, as it has greater capability to detect edema, neovascularization, and extruded disc material 1
• Acute or symptomatic Schmorl nodules demonstrate surrounding cortical edema and enhancement on MRI 1
• On PET/CT imaging, recent Schmorl nodules in direct contact with the intersomatic disk with an osteosclerotic rim can exhibit uptake and may be confused with malignant lesions 4
• Low-dose CT images can help differentiate Schmorl nodules from malignancy or other pathology 4

Critical Diagnostic Pitfall

• It is crucial not to confuse new Schmorl nodules with bone metastases in patients with malignancy 4
• Do not assume all vertebral uptake on PET/CT represents malignancy in elderly patients, as degenerative changes including Schmorl nodules can cause false-positive findings 4
• Use MRI characteristics and low-dose CT to differentiate Schmorl nodules from malignant lesions 4

Management Approach

• In both asymptomatic and symptomatic cases, the mainstay of treatment for Schmorl nodules is conservative therapy 1
• For painful Schmorl nodules refractory to medical or physical therapy, percutaneous transpedicular injection of polymethylmethacrylate (vertebroplasty) has shown swift and persistent improvement in reducing symptoms 7
• Surgical removal of disc material has been successful in cases of persistent radiculopathy from compression by a tunneling Schmorl node 1
• In rare cases, percutaneous biopsy may allow definitive diagnosis and, surprisingly, result in almost immediate and complete resolution of symptoms 6
• Consider the patient's activity level and occupation when planning treatment, as certain activities involving repetitive spinal loading may exacerbate the condition 4