By: 8 October 2024
Tethered Spinal Cord Syndrome (TSCS): Pathophysiology and clinical presentation with a focus on anaesthetic management

Dr. Sher Mohammad and authors discuss Tethered Spinal Cord Syndrome, its causes and pathophysiology

TSCS refers to a group of neurological disorders that relate to malformation of the spinal cord [1]. This is a group of dysraphic conditions in which the conus medullaris is located in an abnormally low position and is fixed there in a relatively immobile state. The disorders include tight filum terminals, lipomeningocele, split spinal cord malformations, dermal sinus tracts and dermoids. Previously, this disorder was termed the filum terminale syndrome.

The term TSCS was coined in 1976 by the Canadian neurosurgeon Harold J Hoffman [2] and colleagues, who described a series of patients with neurologic symptoms associated with low conus and/or thick filum identified on iophenyldate myelography. Since then, the concept of TSCS has expanded beyond the tight filum and now many of the dystrophic conditions that were excluded by Hoffman and colleagues are considered typical aetiologies under the umbrella of TSCS.

 

Normal Spinal Cord

The cord consists of a long bundle of axons and interneurons that connect the sensory and motor neurones within the spinal cord. The spinal cord is connected to the base of the brain and is continuous to the filum terminale at the bottom.

The filum terminale which is composed of glial tissue (supportive structure of nerve cells) and covered by pia mater, is a delicate strand of fibrous tissue, bridging the spinal cord tip and the sacrum. Due to its high viscoelasticity, the filum terminale allows movement of the spinal cord. If abnormal fibrous tissue grows into the filum and replaces glial tissue, the filum loses its elasticity and abnormally fixes (tethers) the spinal cord, and becomes a mechanical cause of tethered cord syndrome. The inelastic filum is commonly thickened in children, but found less frequently in adults.

 

Sagittal Section of Lumbo-sacral vertebral Canal

  1. Spinal Cord ends
  2. Dura mater
  3. Subarachnoid Space
  4. Filum Terminale ends at first coccygeal segment

 

Pathophysiology of TSCS

Normally the spinal cord ascends in the vertebral canal as the spinal column starts to grow faster than the spinal cord at 9th week of gestation. Consequently, the spinal cord is pulled upwards due to the growth difference. Barson’s studies showed that in the 20-week embryo, the conus medullaris terminated at the L4-5 level [3]. By the term, conus had ascended to L3 and by two month of postnatnatal age, the conus reached the adult L1-2 level. Tethering of the conus prevents this normal ascent. Yamada’s studies have conclusively shown that if stretch is placed on the conus medullaris, progressive ischaemia happens, leading inevitably to neurologic sequelae [4].

An elastic, extremely extensible filum allows for the ascension of the less elastic spinal cord. If the filum becomes inelastic in an embryo, then the spinal cord is anchored and ceases to ascend. Compensatory to the stretching force, the lumbosacral cord naturally grows more than seen in normal subjects, and becomes elongated. Associated with the tethered cord syndrome, the elongated cord is often noted in children, but less often in adults.

In most cases, the abnormal tension of the spinal cord increases over time, but disturbing symptoms often develop quickly during a few weeks. Certain activities such as flexion or extension of the lower spinal column can put tension on spinal cord and often worsens TSCS. Participation in physical activities such as strenuous sports and ballet dancing with high kicks can worsen the signs and symptoms. Special physical features such as abnormal curvature of the spine (scoliosis and exaggerated lordosis) are potential for symptomatic acceleration.

 

Causes of TSCS

  • Incidence is not known.
  • Male and female are equally affected.

Since TSCS is a mechanical disorder and develops only when it is abnormally stretched, it cannot be connected to genetic factors, unless the congenital susceptibility of spinal cord to oxidative metabolic impairment is proven.

Secondary causes of TSCS include tumours, infection or development of scar tissue connected to the spinal cord. TSCS may develop as a result of spinal surgery. Trauma to spine results in a band of scar formation attached to the spinal cord and can cause TSCS.

 

Table-1: A list showing the causes of TSCS

 

Signs and Symptoms TSCS in children

If the spinal cord is tethered at the caudal end and is unable to grow as fast as the vertebral column in childhood, the spinal cord is stretched beyond its physiological tolerance. In turn, this causes various metabolic abnormalities in the spinal cord and, ultimately, the various neurological symptoms of this disorder. To remember the signs and symptoms in children, refer to the acronym TANGLED -SPINE -CORD

 

Table-2: Clinical features of TSCS in children

Adult Patients with TSCS

In patients with adult TSCS, the end of spinal cord is restricted inside vertebral canal and results in low location of conus medullaris. The spinal cord and conus medullaris are elongated and blood flow diminishes. The clinical manifestations depend on the degree of traction which differs greatly in adult TSCS. Typical symptoms of adult TSCS are severe pain located in back, perineal region or legs. Neurogenic bladder such as frequent micturition, urgent urination and urgent incontinence are common. In some patients, a subtle onset of motor or sensory changes can be seen. Foot deformities are less common in adults. The clinical features are listed in table-3.

 

Table-3: Clinical features of TSCS in adults, remember 5Bs

Patients with TSCS and Central Neuraxial Anaesthesia

Normally, the conus medullaris ends at the disk space between L1 and L2. But in patients with TSCS, the conus medullaris ends at a lower level, and sometimes at L5-S1. In this case, dural puncture should be avoided because of the possibility of injuring spinal cord, mechanical trauma with the needle or chemical injury due to local anaesthetics. The injury could be transient or persistent.

Theoretically, epidural analgesia seems to be ok but cases have been reported when epidural was used in the labour ward in a patient with undiagnosed TSCS and resulted in failure. Similarly, caudal anaesthesia/analgesia is best avoided.

 

Other scenarios in which Central Neuraxial anaesthesia is likely to fail with more complications:

  • Ankylosing spondylitis
  • Cystic neuroma
  • Dural ectasia
  • Torlov’s cyst
  • Loeye-Dietz syndrome
  • Ehler Danlos syndrome (resistant to the action of Local anaesthetics)

 

Patients with TSCS and Plexus Blocks

Particularly in adults, plexus blocks and peripheral nerve block are highly desirable as a sole anaesthetic technique or in combination with GA.

 

Anaesthestic Management for Untethering TSCS

Because neurological deficits are generally irreversible, early surgery is recommended when symptoms begin [8].

In adults, surgery to de-tether the spinal cord can reduce the size of further development of cysts in the cord and may restore some function or alleviate other symptoms.

Although detethering is the common approach to TSCS [9], another surgical option is a spine-shortening vertebral osteotomy. This will indirectly relieve the excess tension on the spinal cord [9,10]. However, its complexity and limited “track record” presently keeps the vertebral osteotomies reserved as an option who have failed in preventing retethering after detethering procedure [11].

Spinal cord monitoring for Motor Evoked Potentials (MEPs) and Sensory Evoked Potentials (SEPs). The spinal cord may be at risk if the amplitude of SEPs is reduced to >50% of baseline value. Anaesthetic vapours of 0.5 MAC are generally not compatible with reliable monitoring. TIVA is better but propofol (TIVA) may also depress cortically evoked responses.

If a patient is scheduled for untethering of spinal cord, the patient will need GA in prone position. It is expected to be a relatively long procedure and there is a potential for blood loss, peri-operative hypothermia and necessitates spinal cord monitoring.

 

Remember ABC approach

Table-4: Anaesthetic management of untethering spinal cord

*Safe prone positioning is important, use foam bolsters, one at axillary and the other at iliac crest level.

Avoid pressure on the abdomen as it reduces venous return as well as cardiac output and also IAP is increased.

Mirror is used to facilitate intra-op checking of ETT and face.

Ischaemic optic atrophy has been reported

Brachial plexus injuries and ulnar nerve injuries have been reported

**Opiates are the mainstay of post-op analgesia, multi-model approach using paracetamol is often employed. NSAIDs are avoided because of bleeding concerns. Ketamine 1 mg /kg bolus followed by 1-2 mg kg/24 hour (40-80 µg/ kg/hour).

 

Conclusion

Central neuraxial anaesthesia should be avoided in patient with TSCS as it can result in complex neurological complications. When a patient has mild symptoms such as backache, neurogenic bladder, motor or sensory deficits, then it is important to suspect TSCS. When acute onset of paraesthesia or weakness exists after operation, MRI is recommended to make diagnosis.

 

Conflict of Interest Non-Declared

 

References

  1. “Tethered Spinal Cord”, Columbia University Department of Neurosurgery
  2. The Paediatric Spine 2 by Harold J.Hoffman, pp177-188
  3. A.J.Barson, Department of Pathology, University of Manchester (June 1969)
  4. Wood KR,Colohan AR, Yamada S, Yamada SM, Won DJ. Intrathecal endoscopy to enhance the diagnosis of TSCS. J Neurosurg Spine.2010; 13;477-83
  5. “Tethered Spinal Cord-an overview” Science Direct Topics. Archived from original on 2022-11-28
  6. Emos.Marc Christopher; Rosner, Julie (2022),Neuro-anatomy, Upper motor Nerve signs, StatPearls, Treasure Iseland (FL) ,PMID 31082126
  7. Recurrence of symptoms post-surgery, Chiary Online Support Group.6 August 2013.Retrieved 2017-12-12
  8. Iskandar BJ, Fulmer BB, Hadley MN, Oakes WJ(2001)”Congenital Tethered spinal cord syndrome in adult ”Neurosurgical focus.10(1):1-5.DOI:10.371/foc.2001.10.1.8
  9. ”TSCS “National Institute of Health. Retrieved 2008-08-28
  10. Kokubun,S;Ozawa,H.;Aizawa,T;Ly,N.M;Tanaka,Y(July 2011)”Spine shortening osteotomy for patients with TSCS caused by lipomyelomeningocele ”.Journal of Neurosurgery:spine.15:21-27 doi:10.3171/2011.2.SPINE10114
  11. Miyakoshi,N;Abe,E,;Suzuki,T;Kido,T;,Chiba,M,;Shimada,Y(2009).Spine.34(22):    E823-E825
  12. Adgcombe H, Carter K, Yarrow S. Anaesthesia in prone position ,Br JAnaesthesia,2008,vol.100(page 165-83)
  13. S, Namiki. Continous low dose ketamine infusion improves the analgesic effect of fentanyl PCA after spine surgery, Anaes Analg, 2008, vol.107 (page 1041-4)

 

Authors and Contributors:

  1. Dr. Sher Mohammad, Consultant Anaesthetist (retired) STH NHS FT Sheffield
  2. Dr. Parhaizgar Khan, Prof. Anaesthesia, Pak International Medical College, Peshawar
  3. Dr.Aftab Alam,Asstt.Professor Anaesthesia,Swat Medical College,Saidu Sharif
  4. Dr. Sayed Irfan Ali, Medical Officer Anaesthesia, Saidu Group of Hospitals, Swat
  5. Gul Rukh, Trainee Anaesthetics year-2, Khyber Teaching Hospital, Peshawar
  6. Abdul Hamid, Physician Assisstant Anaesthetist, STH NHS FT Sheffield
  7. Dr. Sibghat Ullah Khan, Women Wellness Hospital, Hamad Medical Corporation,Doha

 

Correspondence Address: smyousafzai@doctors.org.uk