Tethering of the spinal cord is an insidious cause of worsening incontinence that requires urgent medical assessment and possibly surgical intervention to prevent any further deterioration. Clinicians monitoring young people and adults with spina bifida need to maintain a high degree of suspicion to ensure the early detection of tethered cord syndrome to help promote and maintain independent living.

Key issues for clinicians

• Clinicians need to consider spinal cord tethering as a possible cause of change in continence patterns.
• Any suspicion of spinal cord tethering should be referred to a specialist centre for urgent assessment.
• Earlier surgical intervention in clinically demonstrated spinal cord tethering is more likely to result in an improved long term outcome.

Tethered cord syndrome - an insidious condition
Tethering or stretching of the spinal cord in young people and adults results from fixation of the spinal cord to inelastic structures. Spinal cord tethering is a major source of morbidity in spina bifida and clinicians need to be familiar with its presentation and maintain a high degree of suspicion when monitoring patients with spina bifida.
In the past, spinal cord tethering was thought of as mainly a condition affecting only children, especially during growth spurts, but the condition can occur in people with spina bifida at any age.
Spinal cord tethering is a particularly insidious complication of spina bifida that can have a major adverse impact on independence through its effect on mobility and continence.
Many causes but consistent presentation
The fixation of the spinal cord in spinal tethering is due to fibrous or lipomatous tissue. In spina bifida this can be due to a myelomeningocoele, lipomyelomeningocoele, scar tissue, a fibroadenomatous filum terminale or many other conditions.

Clinical presentation of tethered cord syndrome
Symptoms and signs
Tethered cord syndrome typically causes a progressive loss of function at or below the level of the spinal cord defect, with or without lower lumbar pain.

Tethering may occur in young adults at times of growth spurts, when lengthening of the spinal column can increase spinal cord tension, but it can occur at any adult age.

Key diagnostic issue - progressive loss and change
The key diagnostic issue in spinal cord tethering in young people and adults with spina bifida is a progressive deterioration in neurological function at or below the level of the defect. This includes urinary and faecal incontinence.

Neurological deficits in spina bifida are usually not progressive. Any change in signs requires immediate specialist assessment. Spinal cord tethering can also occur in adults with no known past history of spina bifida.
Patchy distribution of clinical findings of tethered cord syndrome
The pattern of clinical findings of spinal cord tethering often fails to follow strict dermatomal patterns like those due to compression of one or two nerve roots or a particular level of spinal cord injury. Weakness, pain and other signs of spinal cord tethering may have a patchy distribution below the level of the lesion, rather than a strict neurotomal pattern.
Pain in spinal cord tethering
Regardless of the cause, the characteristics of the associated pain are often suggestive of spinal tethering (Table 3).
While other causes of back pain, such as disc herniation, need to be excluded, clinicians still need to organise urgent neurosurgical referral and assessment to ensure that spinal cord tethering is not missed.
Other common findings in tethered cord syndrome
As highlighted above, the findings need to be considered in the context of any pre-existing neurological abnormalities, but clinicians should have a low threshold for specialist referral when there are any changes in
pre-existing clinical findings (Table 4).

Management
Diagnostic imaging
Magnetic resonance imaging
Magnetic resonance imaging (MRI) is the best currently available technique for viewing the spinal cord. Most people with spina bifida will have some MRI findings suggestive of spinal tethering, but the decision to treat is based upon a combination of MRI and clinical findings. Ideally, a baseline MRI should be taken on all young people and adults with spina bifida to compare any changes with subsequent imaging, should symptoms of tethering arise (Figure 5).
Typical MRI findings in spinal cord tethering
Typical MRI findings in spinal cord tethering include:

• thick filum terminale (>2 mm in diameter)
• presence of structures such as fibrolipomatous filum terminale
• obliteration of subarachnoid space suggesting caudal spinal cord or nerve root adhesion
• changes in the structure of the spina bifida lesion such as dermoid, epidermoid cyst, myelomeningocoele, lipomyelomeningocoele or other problem
• elongation of spinal cord
• posterior displacement of conus medullaris with the filum pressing against the thecal lining at or near L5, or when compared with previous films.

Surgical intervention
Indications for detethering the cord
Once the diagnosis of spinal cord tethering is made, the decision for surgical intervention is based on clinical evidence. Treatment is especially indicated in the presence of new or worsening symptoms.
In studies of adults, when performed by experienced neurosurgeons, spinal cord tethering has been demonstrated to be a well tolerated, effective intervention.
Ultimately, the neurosurgeon can only confirm the presence of spinal tethering at operation. The surgery performed depends upon the intraoperative findings.
Effect of surgical intervention on spinal cord tethering
Timely surgical intervention of tethered cord syndrome can arrest, and in some cases improve neurological signs. The more long standing the neurological signs, the less the chance of resolution of symptoms and signs.
Pain improves in many people and is usually relieved within three months of the detethering, but improvements in neurological signs can take many more months.
Patients need constant monitoring after the operation to assess recovery and help to adjust to any lifestyle changes.