Tethered spinal cord syndrome
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|Tethered spinal cord syndrome|
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Tethered cord syndrome (TCS) or occult spinal dysraphism sequence refers to a group of neurological disorders that relate to malformations of the spinal cord. Various forms include tight filum terminale, lipomeningomyelocele, split cord malformations (diastematomyelia), dermal sinus tracts, and dermoids. All forms involve the pulling of the spinal cord at the base of the spinal canal, literally a tethered cord. The spinal cord normally hangs loose in the canal, free to move up and down with growth, and with bending and stretching. A tethered cord, however, is held taut at the end or at some point in the spinal canal. In children, a tethered cord can force the spinal cord to stretch as they grow. In adults the spinal cord stretches in the course of normal activity, usually leading to progressive spinal cord damage if untreated. TCS is often associated with the closure of a spina bifida. It can be congenital, such as in tight filum terminale, or the result of injury later in life.
Signs and symptoms
In children, symptoms may include:
- Lesions, hairy patches, dimples, or fatty tumours on the lower back
- Foot and spinal deformities
- Weakness in the legs
- Change in or abnormal gait including awkwardness while running or wearing the tips or side of one shoe
- Low back pain
- Urinary irregularities (incontinence or retention)
Tethered spinal cord syndrome may go undiagnosed until adulthood, when sensory, motor, bowel, and bladder control issues emerge. This delayed presentation of symptoms relates to the degree of strain on the spinal cord over time.
Tethering may also develop after spinal cord injury. 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 or feeling, or the onset of pain or autonomic nervous system symptoms.
In adults, onset of symptoms typically include:
- Severe pain (in the lower back and radiating into the legs, groin, and perineum)
- Bilateral muscle weakness and numbness
- Loss of feeling and movement in lower extremities
- Urinary irregularities (incontinence or retention)
- Bowel control issues
Neurological symptoms can include a mixed picture of upper and lower motor neuron findings, such as amyotrophy, hyperreflexia, and pathologic plantar response, occurring in the same limb. Profound sensory changes, such as loss of pain, temperature, and proprioceptive sensations, are common. Last, progressive symptoms of a neuropathic bladder are noted on over 70% of adult patients, versus only 20% to 30% of children. These symptoms include urinary frequency and urgency, feeling of incomplete voiding, poor voluntary control, and urge and stress incontinence. Chronic recurrent infections are common and occasionally lead to nephrolithiasis (kidney stones), renal failure, or renal transplantation. Female patients also give a history of ineffective labor and postpartum rectal prolapse, presumably due to an atonic pelvic floor.
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For children younger than eight weeks of age (and possibly in utero), a tethered cord may be observed using ultrasonography. Ultrasonography may still be useful through age 5 in limited circumstances. 
A tethered cord is often diagnosed as a "low conus." The conus medullaris (or lower termination of the spinal cord) normally terminates at or above the L1-2 disk space (where L1 is the first, or topmost lumbar vertebra). After about 3 months of age, a conus below the L1-2 disk space may indicate a tethered cord and termination below L3-4 is unmistakably tethered. "Cord tethering is often assumed when the conus is below the normal L2-3 level.
TCS, however, is a clinical diagnosis that should be based on "neurological and musculoskeletal signs and symptoms. Imaging features are in general obtained to support rather than make the diagnosis." Clinical evaluation may include a simple rectal examination and may also include invasive or non-invasive urological examination. "Bladder dysfunction occurs in ~40% of patients affected by tethered cord syndrome. ... [I]t may be the earliest sign of the syndrome." 
Because neurological deficits are generally irreversible, early surgery is recommended when symptoms begin to worsen. In children, early surgery is recommended to prevent further neurological deterioration, including but not limited to chronic urinary incontinence.
In adults, surgery to detether (free) the spinal cord can reduce the size and further development of cysts in the cord and may restore some function or alleviate other symptoms. Although detethering is the common surgical approach to TCS, another surgical option for adults is a spine-shortening vertebral osteotomy. A vertebral osteotomy aims to indirectly relieve the excess tension on the spinal cord by removing a portion of the spine, shortening it. This procedure offers a unique benefit in that the spinal cord remains fixated to the spine, preventing retethering and spinal cord injury as possible surgical complications. However, its complexity and limited “track record” presently keeps vertebral osteotomies reserved as an option for patients who have failed in preventing retethering after detethering procedure(s).
Other treatment is symptomatic and supportive. Medications such as NSAIDs, opiates, synthetic opiates, COX-2 inhibitors, and off-label applications of tricyclic antidepressants combined with anti-seizure compounds have yet to prove they are of value in treatment of this affliction's pain manifestations. There is anecdotal evidence that TENS units may benefit some patients.
Treatment may be needed in adults who, while previously asymptomatic, begin to experience pain, lower back degeneration, scoliosis, neck and upper back problems and bladder control issues. Surgery on adults with minimal symptoms is somewhat controversial. For example, a website from the Columbia University Department of Neurosurgery says, "For the child that has reached adult height with minimal if any symptoms, some neurosurgeons would advocate careful observation only." However, surgery for those who have worsening symptoms is less controversial. If the only abnormality is a thickened, shortened filum, then a limited lumbosacral laminectomy with division of the filum may be sufficient to relieve the symptoms.
This syndrome was first noticed in the late 19th century. While information has been available for years, little widespread blind research has been done. More research has been called for, and doctors have conducted many studies with good results. There is a low morbidity rate, and no complications have been documented other than those typical of any type of back surgery. The association of this condition with others has been noticed, and needs further research to understand such relationships. TCS is causally linked to Chiari malformation and any affirmative diagnosis of TCS must be followed by screening for Chiari's several degrees. TCS may also be related to Ehlers-Danlos syndrome, or Klippel-Feil syndrome, which should also be screened for upon a positive TCS diagnosis. Spinal compression and the resulting relief is a known issue with this disorder. Like with the early-onset form, this disease form is linked to the Arnold-Chiari malformation, in which the brain is pulled or lowers into the top of the spine.
The disorder progresses with age, but the aforementioned treatments can help prevent or sometimes relieve symptoms. With treatment, individuals with tethered spinal cord syndrome have a normal life expectancy. However, most neurological and motor impairments are irreversible.
Occult tight filum terminale
In this variation, the filum terminale (which joins the cord to the backbone) thickens or hardens and causes downward pressure on the spinal cord. This can actually cause scoliosis as well as most of the other symptoms of the more typical tethered cord. This syndrome was first noticed and documented in the late 19th century.
- Tethered Spinal Cord, Columbia University Department of Neurosurgery
- Sanford Schneider (2009). "Neurological Assessment of Tethered Spinal Cord". In Yamada, Shokei. Tethered Cord Syndrome in Children and Adults (Rev. ed.). Thieme Medical Publishers, Inc. 44. ISBN 978-1-60406-241-0.
- Nelson, Jr., Marvin D. (2010). "Ultrasonic Evaluation of Tethered Cord Syndrome". In Yamada, Shokei. Tethered Cord Syndrome in Children and Adults (Rev. ed.). Thieme Medical Publishers, Inc. p. 72. ISBN 978-1-60406-241-0.
After the patient reaches 5 years of age, it becomes increasingly difficult to image the thoracic spinal cord to adequately evaluate pulsations.
- Nelson, Jr., Stephen L. (6 October 2013). "Clinical Summary: Tethered Spinal Cord". Medlink.
- Hinshaw Jr., David B. (2010). "Imaging of Tethered Spinal Cord". In Yamada, Shokei. Tethered Cord Syndrome in Children and Adults (Rev. ed.). Thieme Medical Publishers, Inc. p. 51. ISBN 978-1-60406-241-0.
In the mid- and late 1980s, magnetic resonance imaging (MRI) developed to a degree that allowed visualization of the spinal anatomy without the use of x-radiation or subarachnoid injection of contrast agents. It has emerged as the most useful noninvasive modality, providing excellent detail of anatomy and characterization of soft tissue anomalies. ... MRI has become the primary imaging modality for tethered cords and has both facilitated earlier diagnosis and tailored treatment of these disorders.
- Khoury, Antoine E. (2010). "Clinical Experience in Urological Involvement with Tethered Cord Syndrome". In Yamada, Shokei. Tethered Cord Syndrome in Children and Adults (Rev. ed.). Thieme Medical Publishers, Inc. p. 90. ISBN 978-1-60406-241-0.
The diagnosis of TCS is primarily based on neurological and musculoskeletal signs and symptoms. Imaging features are in general obtained to supportrather than make the diagnosis. MRI has revolutionized the noninvasive evaluation of spinal cord lesions. The major obstacle to obtaining an MRI in children is the need for sedation or general anesthesia. Patients with tethered cord have displacement of the conus and elongation of the cord, with a sometimes thickened or fatty density in the filum.
- Kitchens DM, Herndon CD, Joseph DB (2007). "Pediatric urodynamics: basic concepts for the neurosurgeon". Neurosurg Focus. 23 (2): E8. doi:10.3171/FOC-07/08/E8. PMID 17961012.
- Hadley, H. Roger (2010). "Lower Urinary Tract Dysfunction in Tethered Cord Syndrome". In Yamada, Shokei. Tethered Cord Syndrome in Children and Adults (Rev. ed.). Thieme Medical Publishers, Inc. p. 77. ISBN 978-1-60406-241-0.
Urodynamic testing has emerged as the quintessential evaluation to explicitly identify, document, and quantify the effects of neurological dysfunction on the urinary system.
- Hadley, H. Roger (2010). "Lower Urinary Tract Dysfunction in Tethered Cord Syndrome". In Yamada, Shokei. Tethered Cord Syndrome in Children and Adults (Rev. ed.). Thieme Medical Publishers, Inc. p. 47. ISBN 978-1-60406-241-0.
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