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TETHERED SPINAL CORD

Tethered Spinal Cord Syndrome is a neurological disorder caused by tissue attachments that limit the movement of the Spinal Cord within the Spinal Column. The course of the disorder is progressive once symptoms are first experienced.

The term "Tethered Spinal Cord" refers to any condition in which the Spinal Cord is attached to an immovable structure. Normally the bottom of the Spinal Cord (called the Conus Medullaris) floats freely within a pool of Cerebrospinal Fluid. There are, however, several pathologic conditions that cause this tethering. This often leads to abnormal stretching of the Spinal Cord and its nerve roots as the patient grows and with movement.

ETIOLOGY

The causes of Tethered Spinal Cord are generally regarded to be errors in the normal development of the fetus. Many of these errors occur even before a woman knows that she is pregnant. Folate (Folic Acid) supplements for women in child bearing years can reduce the rate of some problems (such as open Spina Bifida) but many causes of Tethered Spinal Cord are not affected by Folic Acid.

SYMPTOMS

Over time the "Tethering" can lead to the characteristic symptoms of Tethered Spinal Cord, which are:
  • Muscle weakness
  • Sensory loss
  • Change in bowel or bladder control
  • Orthopedic deformity.
The primary "causes" of Tethered Spinal Cords include conditions such as:
  • Dermal Sinus Tract
  • Diastematomyelia (split Spinal Cord)
  • Lipoma
  • Tumor
  • Myelomeningocele ("Spina Bifida")
  • "tight" Filum Terminale
  • Past trauma
  • Previous surgery on the Spine particularly for Myelomeningocoele repair

DIAGNOSIS

In children, symptoms may include observable surface lesions such as hairy patches, dimples, or fatty tumors (Lipomas) on the lower back; foot and spinal deformities; weakness in the legs; low back pain; scoliosis; and incontinence.

Tethered Spinal Cord Syndrome may go undiagnosed until adulthood, when sensory and motor problems and loss of bowel and bladder control emerge. This delayed presentation of symptoms relates to the degree of strain placed on the Spinal Cord over time. Tethered Spinal Cord Syndrome is closely linked to Spina Bifida and seems to occur as a result of improper growth of the neural tube during fetal development.

Tethering may also develop after Spinal Cord injury and scar tissue can block the flow of fluids around the Spinal Cord. Fluid pressure may cause cysts to form in the Spinal Cord (a condition called Syringomyelia.) This can lead to additional loss of movement, feeling or the onset of pain or autonomic symptoms.

Neuroimaging

Spina Bifida may never cause any symptoms. In cases that eventually become symptomatic (as the Tethered Spinal Cord Syndrome) the onset of symptoms may not become apparent until adolescence or later (including adulthood). In these instances, CT and/or MRI Scans are helpful in establishing the diagnosis. Occasionally Myelography and post-myelographic CT scans are used to more definitively identify the critical anatomical details of the anomaly (See Figure 1).

Figure 1: Post-myelographic CT Scan of Spina Bifida

This Lumbar Vertebra's Spinous Process is "BIFID" (meaning "split in two") indicated by the Double-headed Arrow. In this case the Spinal Cord is split into 2 separate segments (Vertical Arrows).The "Cords" are situated towards the Posterior aspect of the Spinal Canal. The next lower CT Scan images demonstrate the "Tethering" of the Cord by a Lipoma in the Filum Terminale. (See Figures 2-4)

This represents a case that was not identified until later life when as an adult the patient developed urinary incontinence.

Figure 2: Post-myelographic CT Scan at the Sacral Level. Tethered Spinal Cord & Filum Terminale Lipoma

The precise point of tethering of the Spinal Cord, at the bottom of the Spinal Canal, is indicated by the "dark" spot within the Spinal Canal (Arrow). The point of tethering is identified by "indenting" of the "dye" (white material) that was injected to mix with the CSF.

Note: Same patient as Figure 1, 3 & 4.


TREATMENT

Surgery

In children, early surgery is recommended in an effort to prevent further neurological deterioration.

In adults, surgery to release the Tethered Spinal Cord and/or reduce the size of Spinal Cord Cysts may abort the inevitable progression of the symptoms, may restore some function or alleviate other symptoms and stop further development of cysts within the Spinal Cord. If direct surgical relief of the cause of the tethering is not advisable, Spinal Nerve Roots may be cut to relieve pain.

Figure 3: Operative Photo. Tethered Spinal Cord (Filum Terminale) & Lipoma.

A lumbar & Sacral Laminectomy has been performed. The Dura Mater has been opened to expose the Lipoma (which has been cut in two.) Note that the Spinal Nerve Roots (Vertical Arrows) lie beside the Lipoma and extend through the Dura to leave the Spinal Canal at their normal levels.

Figure 4: Operative Photo. Tethered Cord & Lipoma (Same case as Figure 3).

This is a lower power magnification view to demonstrate the distal Spinal (S1 & S2) Nerve Roots (Vertical Arrows). The Lipoma of the Filum Terminale and its attachment to the Dura Mater has been removed (Curved Arrow).

Note: Compare to Figure 3 where the Lipoma is cut in two but left in place for the moment.


ADDITIONAL INFORMATION

http://www.neurosurgerytoday.org/what/patient_e/tethered.asp



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This page last edited on 2/19
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Author, Martin L. Lazar, MD, FACS
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