Diagnosis of Central Canal Stenosis

A diagnosis of symptomatic spinal stenosis includes findings from clinical examination and medical imaging results. A medical professional typically conducts a physical examination and reviews the patient’s medical history. Medical imaging tests help confirm the location of the stenosis and rule out other possibilities causing stenosis-like symptoms, such as peripheral vascular disease.

It is important to note that even though stenosis may be seen on imaging tests, patients may not always experience symptoms. Almost 30% of people above the age of 55 years have some form of spinal stenosis seen on medical images that do not cause any problems.¹Ammendolia C. Degenerative lumbar spinal stenosis and its imposters: three case studies. J Can Chiropr Assoc. 2014;58(3):312–319.

Clinical findings are usually assessed in a physical examination and the findings are correlated with the patient’s medical history.

Physical Examination and Review of Medical History

The first step in diagnosing spinal stenosis includes a physical examination and review of medical history.

• Physical examination. The doctor observes and palpates the affected body part (neck, arms, back, and/or legs) to check for pain and/or local tenderness. The doctor may also check for muscle weakness and/or decreased muscle reflexes.
• Medical history. A medical history includes an in-depth review of the patient’s symptoms, such as:
  • Positions or activities that make the symptoms better or worse
  • Duration of the symptoms
  • If the symptoms started gradually or after an injury
  • What treatments have been tried

A medical history will also include a review of conditions that may be in the patient’s family, such as arthritis.

If stenosis is suspected based on clinical findings, medical imaging tests may be requested in an attempt to confirm the diagnosis.

Medical Imaging Tests for Central Canal Stenosis

The first line medical imaging technique used to assess the location and severity of stenosis of the spine is a magnetic resonance imaging (MRI) test. If the MRI is inconclusive or not possible, a computed tomography (CT) scan may be done.²Kanno, H., Endo, T., Ozawa, H., Koizumi, Y., Morozumi, N., Itoi, E., & Ishii, Y. (2012). Axial Loading During Magnetic Resonance Imaging in Patients With Lumbar Spinal Canal Stenosis. Spine, 37(16), E985–E992. https://doi.org/10.1097/brs.0b013e31821038f2

MRI for central canal stenosis

An MRI of the spine shows detailed images of soft tissues, length of the spinal canal, the cross-sectional area of the central canal, and any other changes in the surrounding structures. However, standard MRI’s may have some limitations in detecting the severity of certain types of stenosis, such as lumbar stenosis.

In order to accurately visualize the extent of lumbar stenosis on an MRI, the spine is subjected to a load, which is hung behind the patient. With the help of pulleys and a loading plate (placed under the patient’s feet), compressive forces are transmitted to the feet, which load the knee joint. This process creates a load on the spine. An MRI is then taken in this position. This technique is called axial loaded MRI and provides accurate results of the severity of stenosis. The loads used differ based on the patient's body weight.

CT scan, CT myelogram, and multi-detector CT for central canal stenosis

A CT scan is useful in analyzing tissues such as calcified discs, which may not be clearly visible on an MRI. Apart from conventional CT, a CT myelogram, which, includes injecting a contrast dye into the fluid bathing the spinal cord and then performing a CT scan for better visualization of spinal stenosis may also be performed. A multi-detector CT, which includes a rotating device to capture images of the spine, may be useful in identifying soft tissues, herniated discs, and ossification of ligaments with good detail.³Cowley, P. (2016). Neuroimaging of Spinal Canal Stenosis. Magnetic Resonance Imaging Clinics of North America, 24(3), 523–539. https://doi.org/10.1016/j.mric.2016.04.009^,4Eun, S. S., Lee, H.-Y., Lee, S.-H., Kim, K. H., & Liu, W. C. (2012). MRI versus CT for the diagnosis of lumbar spinal stenosis. Journal of Neuroradiology, 39(2), 104–109. https://doi.org/10.1016/j.neurad.2011.02.008

While MRIs are considered the first-line diagnostic aid in detecting central canal stenosis, the use of CT scans have also gained popularity in the recent years for diagnosing central stenosis.

Other diagnostic tests for central canal stenosis

Other tests may include an electromyogram or nerve conduction velocity test, which measures the speed with which the nervous system sends and receives signals that communicate sensations, such as touch, pain, and vibration. In case of stenosis, these signals usually travel at a slower speed. An electromyogram also measures the irritability of the muscles and if there is a loss in nerve supply to the muscle.

Nonsurgical treatments are usually tried first while treating central canal stenosis. If neurological deficits are present and worsening, such as numbness or weakness, surgery may be indicated.