Schmorl nodes are mostly found as an incidental finding in the plain radiography, CT scan and MRI scan of the spine. Schmorl nodes are characterized as intraosseous vertebral lesion. Schmorl nodes are also known as intraosseous disc herniation and vertebral endplate irregularities. The Schmorl nodes are disc materials which herniates through the areas that are weak in the adjacent vertebral end plates to the vertebral body. Sometimes especially in the young patient, the physiological consequence of the vascular canal regression near the end of the growth vertebral may contribute to the area of weakness. In other case scenario, it is caused by weakness of the subchondral bone or weakened endplate. Pathological weakness of the bone such as in the lumbar or thoracic spine (rarely in the cervical spine) may lead to herniation and Schmorl nodes.
In term of epidemiology, there is no gender predilection and it affects 10 % of the general population. It presents at all ages (from children to older people).
The metabolic bone disease sufferer is predispose to the herniation of the intraosseous disc secondary to bony matrix defective of the vertebral bodies and decrease bone density.
The degenerative nature or the rupture of the disc endplate acutely as well as the extrusion of the nucleus pulposus provided sufficient force to penetrate the superior and inferior portion of the vertebral body. Any form of acute trauma may lead to penetration injury describe above especially in patient with normal disc and vertebrae. Patient who suffers from degenerative condition may predispose to penetration effect slowly over time.
Schmorl nodes are associated with degenerative disc disease, neoplastic disorder, osteoporosis, trauma, and Scheuermann kyphosis. Scheuermann kyphosis occurs because of decrease growth of the anterior portion of the endplates in more than three adjacent vertebral bodies. Other form of metabolic disorder may also associated with Schmorl nodes.
Patient with Schmorl nodes may remain asymptomatic or complain of pain secondary to Schmorl node. Symptoms that present is associated with insufficiency or degenerative changes of the particular disc. The pain will be radiated laterally around the trunk. It is not radiated distally down to the extremities.
The physical exam may reveal a sign of kyphosis. It is important to estimate the degree of kyphosis. It is important to estimate the degree of kyphosis. Deep palpation of the spine as well as the percussion of the spine may or may not elicit any tenderness. Neurological examination is performed to rule out other conditions as Schmorl node is not causing any neurological deficit.
The test required to diagnose Schmorl node may include conventional radiography, MRI and bone scan. Conventional radiography may reveal the indentation of the vertebral body. There will also be a degree of sclerosis surrounding the radio nuclei of the vertebral body. Displaced nucleus may lead to various degree of disc thinning which is detected on the conventional radiography. Benign appearing lesion may also be detected on the MRI (another form of imaging which is more sensitive than plain radiography). In acute setting of acute intraosseous, there will be a high signal of T2 weighted images and low signal on T1 - weighted images on the MRI. The patient tends to be symptomatic. Asymptomatic patient present with old and asymptomatic lesion which on MRI detected as high signal on T1 weighted image and low signal T2 weighted image. MRI is also useful to rule out any malignant disease. The next form of imaging is bone scanning which is useful to differentiate acute and older lesion.
The differential diagnosis may include bone carcinoma such as metastasis carcinoma to the bone, osteoid osteoma, aneurysmal bone cyst , multiple myeloma, and lymphoma.
The treatment is mostly symptomatic. Rest and NSAIDS are the main form of treatment in acute intraosseous herniation until the patient is stable enough. Bracing is required in the comfort of the patient. A physical therapist is useful especially in the cause of persistent backache. The physical therapy may involve strengthening of the extensor and endurance as well as flexibility training. Schmorl nodes are not required any surgical removal.
The complication may include the degenerative joint disease of the facet joint because of the loss of substantial disc space. The patient may require serial radiography if the cause is unclear and the pain continue up to 8 weeks. (Just to make sure that the lesions do not change in character and do not grow.) The prognosis of Schmorl nodes is good.
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