Background on the Spinal Cord
We find the spinal cord freely floating in the spinal canal encased by the spinal column, a roughly cylindrical column of individual vertebral bones designed to protect the descending cord from damage.
The spinal cord itself is made up of bundles of nerves that communicate with the brain and the rest of our body- within a network we call the central nervous system (CNS). Messages travel in opposite directions in the CNS – up to our brain to process sensation and position and down our spinal cord to act on what we have processed. A simple example would be something like moving our legs to get ourselves out of the way of oncoming danger.
From structure to function, tethered cords can have a marked impact.
So what’s a tethered cord?
Sometimes, the foetus in a mother’s womb develops an abnormal spinal cord that does not freely move – it is fixed or ‘tethered’ to the spinal canal, usually in the lower area of the spine.
As the child bends, stretches or grows the spinal cord will stretch like a rubber band under unnatural tension. Such a process can both acutely and chronically damage the child’s developing nerves as well as the cord itself.
Such damage invariably cause a variety of symptoms associated with the lower body.
These can markedly affect mobility and various bodily functions such as urination and defecation.
What causes a tethered cord?
We mostly find tethered cord with either myelomeningocele or lipomyelomeningocele.
These are both congenital (present from birth) spinal dysraphisms. Put simply, dysraphisms are fusion defects of the bones and/or developing tissues around the spinal cord. As you can read in our spinal dysraphisms article (link), these essentially lead to either the cord or the tissue-covered cord being squeezed into the outside world. These are the closed or open dysraphisms respectively.
For reference then, due to not being covered by skin or other tissues, myelomeningoceles are an example of an open dysraphism whilst lipomyelomeningoceles, being covered by fat, are closed.
Ultimately, whatever the pathology, the cord can attach to these growths and, as both develop, can become symptomatic as the pulling or tethering effect increases.
Other types of spinal dysraphisms like dermal sinus tract (essentially an abnormal connecting tunnel between the skin and the spinal cord) or diastematomyelia (where the spinal cord is congenitally split lengthwise down the middle) are also associated with tethering.
If a lipoma, or a fatty mass, tethers to the filum terminale (we’ll need a drawing), a fibrous band that stabilises the end of the spinal cord by attaching to the coccyx (your tailbone), or if the filum itself thickens pathologically, these are other common causes of tethered cord.
Acquired causes include infection as well as the scar tissue left behind after a traumatic cord injury or surgical intervention.
What are the symptoms?
- Presence of a skin ‘marker’ over the affected area- a tuft of hair, dimple or lump
- Lower back pain
- Scoliosis or abnormal curvature of the spine
- Lower limb numbness or loss of feeling
- Loss of bladder or bowel control
- Frequent urinary tract infections
- Inability to fully empty bladder
- Tremors in the leg muscles
- Uneven appearance between one leg and the other
- Deformities associated with the feet and toes – some patients are forced to walk on their toes as a result
How do we make a diagnosis?
So a clinician will make a diagnosis from the neurological and non-neurological symptoms a patient presents with.
They would also carry out an MRI or CT scan for imaging of the tethered cord.
A urological workup could also inform diagnosis.
In some cases, a tethered cord will not be diagnosed until later in childhood or even adulthood.
This is because the spinal column is both growing and experiencing wear and tear as one grows into an adult. As such, tethered cord can be progressive with symptoms emerging as the nerve roots and spinal cord are stretched with growth.
What does treatment look like?
We mainly treat tethered cord with surgery. In children, this can be effective in reversing or preventing both neurological and non-neurological symptoms.
Surgery usually involves a laminectomy – as a piece of vertebral bone is removed to access the tethered cord – gently moving it away from the scar tissue or fat it attaches to. There may also be splitting of the filum terminale by the surgeon. Both have the effect of releasing the spinal cord to move freely.
Not all children will need surgery if there are few symptoms, though it is an unfortunate fact that the more complex one’s lesion is, the less chance there will be for surgery to offer a definitive cure for the patient’s symptoms.
Moreover, some patients may experience a re-tethering of the cord as the child grows.
We offer surgery for some adults with symptoms.
Yet not all adult patient undergo surgery if their condition is well managed, especially patients that may have a thickened filum but have no symptoms.
Physiotherapy can be beneficial for both surgical and non-surgical patients as it helps with both spine mobility and managing lower limb symptoms.
Brainbook Editorial Officer