Tethered cord syndrome

Tethered cord syndrome is a neurological disorder caused by tissue attachments that limit the movement of the spinal cord within the spinal column. It can be congenital or acquired and appear in childhood or adulthood. It is considered progressive.

It causes spinal cord hypoperfusion, electrophysical changes and metabolic changes, including impaired glucose metabolism.

There are a range of conditions associated with tethered cord. The most dramatic is spina bifida, where the spinal cord does not complete it's development and is visible on the outside of the body. In a frank tethered cord, the cord is not visible on the outside of the body, but has not fully developed and is anchored to the structures inside the spinal column. Think of a tongue tie, where instead of having a free tongue, there is a thick web that attaches the tongue to the base of the mouth. This is similar to what a tethered cord is like. In some cases, the base of the spinal cord, the conus, is much lower than it should be, and this is how neurosurgeons typically diagnose tethered cord. However, the cord can still be tethered without the conus being below the level of the first lumbar vertebrae - this is referred to as an occult or hidden tethered cord, or a tight filum.

Onset
Some researchers, noting that less severe spinal cord traction may remain asymptomatic in childhood, hypothesize that the age of symptom onset is related to the amount of cord stretch. Factors in adult onset tethered cord syndrome include: transient stretching of the spine, mechanical constriction/narrowing of the spinal canal, and spinal trauma, all in the presence of an already tightly tethered conus medullaris, such as might occur during natural childbirth or in an automobile accident.

Symptoms

 * Leg pain
 * Leg weakness
 * Leg numbness
 * Lower back pain
 * Numbness under soles of feet
 * Rectal pain
 * Urinary urgency or incontinence
 * Urinary retention
 * Bowel dysfunction
 * Constipation
 * Pulling sensation (on brain or upper spine, from below)
 * Scoliosis
 * Foot/ankle deformities
 * Scoliosis
 * Decreased sensation
 * Asymmetry in neurological deficits
 * hyperreflexia/clonus

Signs and symptoms in Children

 * Lesion on the lower back
 * Fatty tumor or deep dimple on the lower back
 * Skin discoloration on the lower back
 * Hairy patch on the lower back
 * Back pain, worsened by activity and relieved with rest
 * Leg pain, especially in the back of legs
 * Leg numbness or tingling
 * Changes in leg strength
 * Deterioration in gait
 * Progressive or repeated muscle contractions
 * Leg deformities
 * Spine tenderness
 * Scoliosis (curvature of the spine)
 * Bowel and bladder problems
 * Difficulty running

Additional symptoms reported by EDS patients with tethered cord

 * Vice like feeling around ribs
 * Difficulty breathing or taking a deep breath
 * Difficulty yawning
 * Head feeling heavy
 * Pressure in the back of the head
 * Band like feeling around the forehead
 * Vision changes such as tunnel vision
 * Difficulty focusing eyes

Imaging
If a tethered cord is suspected, one or more tests may be necessary to confirm the diagnosis. The most common is a lumbar MRI, but a myleogram, CT scan, or ultrasound may also aid in diagnosis

Occult tethered cord syndrome
Occult tethered cord syndrome describes patients with the signs and symptoms of tethered cord syndrome but who have normal neuroimaging. These cases are often diagnosed via a urodynamics study, which can reveal neurogenic bladder.

Treatment
There is no standard technique in the surgical treatment of TCS. Generally, the lamina is removed, anywhere from L2 to S1, a durotomy is made, and electrical stimulation is used to confirm the absence of any nerve roots which may be associated with the filum. Finally, a microsurgical resection of the filum terminale (usually a 10 mm segment for pathology) is performed. The filum tends to be taut, and to briskly retract upon sectioning. However, findings are variable, and there is no evidence to suggest that the intraoperative findings predict or correlate with the surgical outcome and severity of the TCS. In some cases, it may be necessary to perform a lumbar stabilization across the motion segment in which the filum was sectioned. The resected filum should be sent for histopathological evaluation.

Metabolism
Tethered cord, a form of mechanical neural strain, is associated with impaired glucose metabolism in spinal cord tissue, changes in the reduction/oxidation ratio of cytochrome oxidase. and reduced ATP production. Energy loss due to neural membrane stretching contributes to leakage of sodium, potassium and calcium.

A study of energy cost of walking in adolescents with tethered cord, as measured by oxygen uptake, found that “energy cost per metre during walking at preferred speed and physical strain were higher than in peers without disability.”

Blood flow
People with tethered cord syndrome have reduced blood flow to the spinal cord.

“Traction on the caudal cord results in decreased blood flow causing metabolic derangements that culminate in motor, sensory, and urinary neurological deficits. The untethering operation restores blood flow and reverses the clinical picture in most symptomatic cases.”

In a study of five children undergoing surgery for tethered cord syndrome group, spinal cord blood flow prior to untethering was a mean of 12.6 ml/min per 100 g of tissue. It increased in all cases after release to a mean of 29.4 ml/min per 100 g of tissue.

Co-morbidities

 * Ehlers-Danlos syndrome
 * Craniocervical instability

Learn more

 * “Tethered Cord Syndrome,” Journal of Neurosurgery, 2009.