Encroachment

Depiction of a herniated disc
Depiction of a herniated disc. Medical Art Inc/E+/Getty Images

What is Encroachment?

Encroachment refers to the process by which spinal spaces, such as the foramina or the spinal canal, become occupied by a piece of tissue that does not belong in that space.

The spinal canal and the intervertebral foramina contain nervous tissue - the spinal cord in the spinal canal, and spinal nerve roots in the foramina.  When the abnormal tissue, whether it's a bone spur, a thickened ligament, some  migrated disc material or even a synovial cyst, takes over some of the space, it will likely move in (so to speak,) on the nerves that are normally located there.

 The contact between the tissue and the nerve will likely irritate the nerve root and may cause pain and/or other symptoms in your back and/or down one extremity.

What Causes Encroachment?

Encroachment is most often caused by degenerative changes in the spine.  It is associated with central canal stenosis (i.e., spinal stenosis that affects the spinal canal, which is the hollowed out central tube running the length of the vertebral column.)

It is also associated with neuroforaminal stenosis, which is spinal stenosis that affects the intervertebral foramina.  Interbertebral foramina are the holes on either side that, like the canal, run most of the length of the spinal column.  Nerves that branch from the spinal cord into spinal nerve roots and then finally into nerves pass through the foramina as they exit the spine.

Decompression Surgery for Cervical Stenosis may be Recommended to You - But Should You Say Yes?

Some spine specialists encourage their patients with encroachment to agree to a preventative decompression surgery.

 (Decompression surgery is a commonly performed back procedure that removes part of the vertebra in order to make room for the nerve material to pass unimpeded through its respective space.)  

What these surgeons are likely trying to tell you - and many truly believe this - is that even with minor trauma, your risk for spinal cord injury is higher because of the encroachment.

Spinal cord injury is a very serious injury that can result in death or paralysis.  It's usually caused by trauma or impact.

A 2015 study by Chang, et. al. published in the October issue of the journal Neurosurgery looked into this issue because, the authors say, patients who have cervical stenosis but who either experience mild symptoms or none at all commonly have the decompression surgery recommended to them - again, supposedly to reduce or eliminate the risk of paralysis after a traumatic event.  

The researchers examined 55 cervical stenosis patients with an exam and an x-ray.  The patients were also surveyed with questions such as:

  • Has a physician recommended neck surgery to you?
  • Has a physician ever indicated that you would become paralyzed after a traumatic event?
  • During the follow up period for this study, did you experience a traumatic event?

The researchers found that 18% of the (prospective cohort of) patients did experience a traumatic event during the study's follow up period, but none injured their spinal cord.

 They conclude that the "occurrence of SCI in this patient population after minor trauma is likely smaller than many physicians surmise."

The researchers recommend more prospective studies on this important topic.

Related: What is Facet Joint Hypertrophy?

Sources:

Chang, V. Ellingson, B.M., Salamon, N., Holly, L.T. The Risk of Acute Spinal Cord Injury After Minor Trauma in Patients With Preexisting Cervical Stenosis. Neurosurgery. 2015 Oct.

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