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Tethered Cord Syndrome

Tethered Cord Syndromes

If the spinal cord of a child is firmly attached to any of the surrounding, rigid tissues, it will be stretched as the patient grows. This results in neurological damage and a variety of symptoms referred to as tethered cord syndrome.


Presentation

Pain and neurological deficits are the most common symptoms of TCS. Most patients claim lower back pain, but many also report leg pain or sciatica. With regards to neurological symptoms, motor deficits of toes and legs are frequently observed. Patients may merely note an increasing weakness and after prolonged periods of time, muscular atrophy may be recognized. Additionally, urologic and anorectal symptoms may be triggered by spinal cord damage. While some patients present with incontinence, urinary retention or the inability to pass stool may be seen in others [10] [11]. Severity of pain and neurological symptoms often increases upon movements of the lower spine. Flexion, extension, rotation and participation in sport activities may all augment mechanical stress of the spinal cord.

Orthopedic symptoms like foot, leg and spinal deformities, particularly scoliosis and lordosis, may be developed concurrently. Less frequently, orthopedic complaints precede notable neurological deficits and predominate the initial clinical picture.

Symptoms generally exacerbate over time. However, disease progress is usually much slower in adult patients. If increasing motor weakness is the only symptom in a particular case of TCS, patients often delay medical examination and thus miss the chance for early treatment.

Perineal Pain
  • CONCLUSION: Perineal pain or hypersensitivity can be an important symptom of spinal cord tethering. Spinal cord detethering may result in a good outcome and relief of perineal pain or hypersensitivity.[ncbi.nlm.nih.gov]
Polydipsia
  • Thus, spinal lesions have to be considered in patients with polyuria and polydipsia.[ncbi.nlm.nih.gov]
Calf Hypertrophy
  • We present a case with calf hypertrophy, likely produced by partial denervation and continuous neuromuscular irritability, which was caused by a tethered spinal cord that was demonstrated by MRI.[ncbi.nlm.nih.gov]
  • Segmental muscle enlargement (calf hypertrophy), an unusual finding, is the result of partial denervation and continuous neuromuscular irritability, which is caused by tethered cord. [17] Conclusions Surgery for tethered cord is safe and effective in[jdrntruhs.org]
Spine Pain
  • Subscribe Help Subscribe Register Login Articles & Issues Current Issue Previous Issues CME Collections General Neurosurgery Infection (Cranial & Spine) Pain and Functional Pediatric Peripheral Nerve Radiosurgery Spine: Cervical Surgical Techniques Trauma[journals.lww.com]
Hyperactivity
  • The characteristic findings in anorectal motility studies conducted in patients with TCS were a hyperactive rectum, diminished rectal saline-retention ability, and diminished maximal flow in saline evacuation.[ncbi.nlm.nih.gov]

Workup

Diagnosis of TCS is based on general and neurological examination as well as diagnostic imaging.

Thorough motor system examination and urodynamic tests are recommended for each patient suspicious for TCS.

Myelography is the method of choice to assess the position of the spinal cord's medullary cone. Even though an elongated spinal cord and a low conus medullaris is detected in most TCS patients, it has been proposed that this syndrome may also be diagnosed in patients with a spinal cord of normal length. Magnetic resonance myelography is a very sensitive technique, but computed tomography scans are usually more suitable to identify areas of adhesion. This information is of great importance for subsequent surgical interventions to untether the spinal cord. Furthermore, computed tomography allows for recognition of osseous anomalies of the vertebral spine. Since a considerable share of TCS patients was born with spina bifida, such developmental defects are not uncommon.

TCS patients need to undergo regular follow-ups. Progression of neurological deficits, exacerbating orthopedic symptoms and caudal displacement of the conus medullaris indicate (renewed) tethering and should prompt adequate treatment.

Treatment

The tethered spinal cord has to be untethered, i.e., adhesions between nervous tissue and surrounding connective tissue have to be broken. Different techniques are available to reduce traction on the spinal cord, e.g., removal of scar tissue in an open-surgery approach, endoscopic untethering, section of filum terminale and vertebral osteotomy to shorten the spine.

Although previously existing neurological symptoms may improve after surgical intervention, patients often suffer from residual neurological deficits. They may exacerbate once more if spinal cord and filum terminale re-adhere to each other. Therefore, regular follow-ups are recommended. They allow for an early detection of renewed tethering, an observation that indicates the need for repeated surgery.

Prognosis

If the spinal cord is not untethered, neurological symptoms exacerbate over time. Surgery significantly improves the outcome, but multiple interventions may be necessary because of relapses. Neurological deficits existing previous to surgical treatment may be irreversible, though.

Etiology

Whereas TCS may be caused by firm attachment of the spinal cord to any rigid tissue covering it in the lower spine, it's generally the filum terminale that retains the conus medullaris within the lumbar and sacral spinal canal.

The filum terminale is a filament of connective tissue that physiologically extends from the upper sacral region along conus medullaris and cauda equina to the second coccygeal vertebra. Because its cranial part is covered by arachnoid and dura mater, it is also referred to as filum terminale internum. Its caudal part fuses with the dura mater and is therefore designated filum terminale externum. Thus, it bridges conus medullaris and coccyx, serves as an anchor that impedes excess cranial movement of the spinal cord. Due to its distensibility, this structure does not impede normal development of vertebral spine and spinal cord.

Fibrotic thickening and loss of elasticity of the filum terminale is observed in many TCS patients. This is rarely an isolated finding, though, and most children suffering from TCS have previously been diagnosed with other developmental defects. Spina bifida aperta, for instance, is associated with protrusion of spinal meninges and possibly nervous tissue through a gap in the vertebral spine. This gap is frequently located in the lumbar spine and even though the initial lesion may be treated surgically, adhesion processes and reactive fibrosis of the filum terminale may cause secondary TCS. Many children treated for myelomeningocele need to undergo several surgeries to release new adhesions [4]. Of note, spina bifida-induced TCS may also occur in patients born with spina bifida occulta [5] [6]. Because spina bifida occulta is generally not associated with spinal cord damage and neurological symptoms, it is often not diagnosed until diagnostic imaging is carried out for any other reason, possibly due to symptoms related with TCS.

Any pathological condition leading to formation of scar tissue within the lower part of the spinal canal, e.g., tumors other than spina bifida-associated lipoma, infection, trauma or spinal cord surgery, may cause the medullary cone to adhere to adjacent tissues and thus trigger TCS if the patient is still growing.

Epidemiology

Epidemiological data regarding TCS are scarce because for a long time, the condition has not been considered a distinct pathological entity. Presumably, it is still underdiagnosed. Because of the strong correlation between spina bifida and TCS - about one out of four spina bifida patients develops TCS [4] - estimates may currently be based on incidence rates of the former. Spina bifida incidence ranges between 35 and 50 per 100,000 live births, with significant differences between regions of mandatory and voluntary folic acid fortification [7]. One might even speculate TCS incidence to follow this trend.

According to current knowledge, patients pertaining to all races and both genders may present with TCS. Due to the pathogenetic mechanism of growth-induced stretching of the spinal cord, most TCS patients are children. However, symptoms may also be observed for the first time in adulthood. In general, disease progress is less severe in adult patients because they don't grow anymore.

Sex distribution
Age distribution

Pathophysiology

TCS results from firm attachment of the medullary cone to the sacrococcygeal part of the spinal canal and subsequent excessive stretching of the spinal cord during growth. TCS-associated symptoms may, however, also be triggered by disturbances of neurogenesis or impairment of neuronal function due to compression and/or ischemia. The latter constitute separate entities and underlying pathophysiological events may differ from those observed in TCS.

Here, stretching of the spinal cord has been shown to cause malfunction of neuronal metabolism. Moderate distension of cellular membranes, i.e., of membranes surrounding the whole cell as well as those supporting cell organelles, interferes with ion channel and receptor function. This acutely affects the mitochondrial respiratory chain; oxidative metabolism is severely altered [8]. This ischemia-like effect may be further aggravated by true reduction of blood supply due to distension and lesion of vascular structures. In contrast, severe stretching of the spinal cord leads to simple mechanical disruption of cellular structures.

Of note, the spinal cord tries to compensate for increased pulling forces by augmenting its growth rate if tethered to an inelastic filum terminale. Thus, spinal cord elongation may be seen in TCS patients. Their conus medullaris is located more caudal than in healthy peers because it's pulled downwards and because it does grow faster. The position of the medullary cone relative to the vertebral spine may be used to evaluate whether neurological symptoms result from TCS, compression or ischemia, although this is not an exclusion criterion for TCS [9].

Because traction exerted by the filum terminale, which functions as an inelastic anchor, is strongest during growth, disease progress is generally more severe in children than in adults. Pediatric patients may rapidly develop severe neurological deficits that do, however, draw the physician's attention towards a possible spinal cord issue. Less severe symptoms observed in adults often delay medical attention and diagnosis of TCS.

Prevention

Some TCS cases are associated with spina bifida. It has been shown that incidence of spina bifida can be significantly decreased by supplementation of folic acid before and during pregnancy. Individual demands may be calculated after respective analysis of blood samples.

No specific measures can be recommended to prevent TCS resulting from other developmental defects.

Summary

Tethered cord syndrome (TCS) is one of many forms of dysraphism, i.e., it constitutes a developmental defect of the spinal cord. TCS is sometimes also referred to as occult dysraphism because symptoms are not necessarily present at birth. In fact, TCS may rather be considered a consequence of different developmental disturbances that reduce spinal cord mobility within the osseous spinal canal. Any pathologic condition that leads to firm attachment of the spinal cord to any of its surrounding tissues may cause TCS, a syndrome that results from excessive stretching of nervous tissue while the patient is growing.

The vertebral spine is growing faster than the spinal cord. Thus, the caudal end of the spinal cord, the conus medullaris, is slowly pulled cranially until reaching its final position in the upper lumbar spine (between lumbar vertebrae L1 and L2). Spinal nerves, however, don't change their position relative to the spinal cord and emerge between the same vertebrae in children and adults. If the conus medullaris cannot move upwards because of permanent adhesion to adjacent, inelastic connective tissue, the spinal cord is increasingly stretched while the patient grows. Since this process does neither start nor end at birth, symptoms may be present at birth or develop later in childhood, possibly even in adulthood [1] [2]. It is not advisable to use the terms congenital and acquired to distinguish between these "types" of TCS. They should rather be considered more or less severe forms of the disease that result from developmental defects in almost any case. Truly acquired TCS would imply postnatal attachment of the spinal cord to adjacent tissue, something that might happen due to post-infectious adhesion or tumor growth, but this only occurs rarely.

Symptoms aggravate with time and growth unless appropriate treatment is provided. Therapy consists in untethering the spinal cord, i.e., releasing its firm attachment to connective tissue in the lower spine. Neurologic damage can be limited when TCS is diagnosed and treated early and TCS-associated symptoms often improve soon after operation. However, functional impairment due to neuronal death may be irreversible [3].

Patient Information

The spinal cord passes through the osseous spinal canal formed by the vertebral spine. Between two vertebrae, respectively, spinal nerves emerge from the spinal cord and innervate any kind of peripheral tissue.

In the unborn child, the lower tip of the spinal cord - it is called medullary cone - is located very close to the lower end of the vertebral spine, the sacral region. As the child develops, however, the vertebral spine grows faster than the spinal cord. Because the spinal cord's upper tip is connected to the brain, it's lower end has to move upwards. Consequently, the final position of the medullary cone is much closer to the thoracal part of the vertebral spine. In order to avoid excess upward movement, the medullary cone is anchored to the sacrococcygeal part of the vertebral spine by a flexible filament of connective tissue. The name of that filament is filum terminale.

If the filum terminale loses its flexibility, it turns into an inelastic ligament that pulls the spinal cord downwards, against the forces exerted by the growing vertebral spine. This results in distension of the spinal cord and damage to its neurons. The entirety of symptoms that may be associated with that condition is referred to as tethered cord syndrome.

Typical symptoms are:

Symptoms usually exacerbate over time. Early diagnosis and treatment are of utmost importance to avoid irreversible lesions of the spinal cord. Treatment mainly consists in untethering the spinal cord, i.e., in loosening the connection between the spinal cord and the filum terminale. Because tissues may adhere again, many patients suffering from tethered cord syndrome require more than one surgical intervention.

References

Article

  1. Mishra SS, Panigrahi S, Dhir MK, Parida DK. Tethered cord syndrome in adolescents: Report of two cases and review of literature. J Pediatr Neurosci. 2013; 8(1):55-58.
  2. Aufschnaiter K, Fellner F, Wurm G. Surgery in adult onset tethered cord syndrome (ATCS): review of literature on occasion of an exceptional case. Neurosurg Rev. 2008; 31(4):371-383; discussion 384.
  3. Fukui J, Ohotsuka K, Asagai Y. Improved symptoms and lifestyle more than 20 years after untethering surgery for primary tethered cord syndrome. Neurourol Urodyn. 2011; 30(7):1333-1337.
  4. Bowman RM, Mohan A, Ito J, Seibly JM, McLone DG. Tethered cord release: a long-term study in 114 patients. J Neurosurg Pediatr. 2009; 3(3):181-187.
  5. Berbrayer D. Tethered cord syndrome complicating spina bifida occulta. A case report. Am J Phys Med Rehabil. 1991; 70(4):213-214.
  6. Rajpal S, Tubbs RS, George T, et al. Tethered cord due to spina bifida occulta presenting in adulthood: a tricenter review of 61 patients. J Neurosurg Spine. 2007; 6(3):210-215.
  7. Atta CA, Fiest KM, Frolkis AD, et al. Global Birth Prevalence of Spina Bifida by Folic Acid Fortification Status: A Systematic Review and Meta-Analysis. Am J Public Health. 2016; 106(1):e24-34.
  8. Yamada S, Won DJ, Yamada SM. Pathophysiology of tethered cord syndrome: correlation with symptomatology. Neurosurg Focus. 2004; 16(2):E6.
  9. Tubbs RS, Oakes WJ. Can the conus medullaris in normal position be tethered? Neurol Res. 2004; 26(7):727-731.
  10. Tareen B, Memo M, Cerone J, Bologna R, Flora R. Tethered cord syndrome in a 24-year-old woman presenting with urinary retention. Int Urogynecol J Pelvic Floor Dysfunct. 2007; 18(6):679-681; discussion 681.
  11. Granada C, Loveless M, Justice T, et al. Tethered Cord Syndrome in the Pediatric-Adolescent Gynecologic Patient. J Pediatr Adolesc Gynecol. 2015; 28(5):309-312.

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Last updated: 2019-07-11 20:53