Tethered Cord Syndrome

Original Editor - Steve Shelmov, Cliff Taylor, Salvatore Timboli, Fadi Salama, Marco De Palma, Evan Thomas and Redisha Jakinbanjar as part of the Queen's University Neuromotor Function Project
Top Contributors - Salvatore Trimboli, Cliff Taylor, Fadi Salama, Steve Shelmov, Kim Jackson, Marco De Palma, Redisha Jakibanjar, Nikhil Benhur Abburi and Evan Thomas

Introduction

Tethered Cord Syndrome (TCS) is a broad term that encompasses both congenital (primary) and acquired (secondary) pathologies that anchor, elongate and tension the spinal cord The spinal cord fixation produces mechanical stretch, distortion, and ischemia with daily activities, growth, and development This prevents the spinal cord from freely moving, which then increases stress with flexion and extension movements of the spine. Abnormalities are due to problems with secondary neurulation and are closely related to spina bifida occulta, tumours, lipomas and infections. Ischemic injury from the traction of the conus directly correlates with the degree of oxidative metabolism and degree of neurological compromise. In addition to ischemic injury, traction of the conus by the filum may also mechanically alter the neuronal membranes, resulting in altered electrical activity

Depending on the age and underlying cause of the tethered cord, various signs and symptoms can manifest, including; lower extremity and saddle pain, motor and sensory deficits, urinary dysfunction, orthopaedic anomalies and cutaneous signs.

Generally, surgical interventions are primarily used for the management of TCS.

Etiology 

As previously mentioned, TCS is divided into 2 classifications, which are primary (congenital) and secondary (acquired).

Primary Tethered Cord Syndrome

When focusing on primary TCS, the simplest mechanism by which the caudal spinal cord succumbs to tethering is due to a thickened filum terminale. Normally, the filum terminale is a viscoelastic structure that facilitates the ascension of the conus medullaris during neural development. During secondary neurulation, improper canalization of the neural tube allows for precursor cells (most commonly preadipose cells) to proliferate and differentiate, leading to a thickened ‘fatty’ filum terminale . This thickening prevents the ascension of the conus medullaris, resulting in an abnormally elongated spinal cord. An abnormally thickened filum terminale was classified by Hoffman and colleagues in the 1970s as being greater than 2 millimetres in diameter.

Lipomas, or adipose cell aggregations, around the caudal aspect of the spinal cord have also been linked to TCS. Lipomas associated with TCS are normally subpial in location, whereas subdural lipomas are a lot less associated with this condition. The presence of a lipoma can affect both the filum terminale as well as the conus medullaris, essentially leading to an elongated spinal cord and if large enough, may elicit spinal compression as well.

Spinal Dysraphisms, which are any disorders that result in malformations of the spinal cord, has also been linked to TCS. Spina bifida occulta, split cord malformations such as diastematomyelia and diplomyelia, and neurenteric cysts, have shown to be connected to TCS through improper secondary neurulation.

Secondary Tethered Cord Syndrome

Secondary or acquired tethered cord syndrome can be due to a variety of sources that elicit the fibrotic thickening of the filum terminale, such as infection, fibrotic scarring and the presence of a tumour . Another potential source of secondary TCS could be due to fibrotic thickening following spinal surgery, however, it is said that these individuals most likely possessed abnormal tethering prior to the surgery.

Pathophysiology

The aforementioned mechanisms exert their effect on the spinal cord in a few different manners. Yamada et al. demonstrated that after constant or intermittent traction to the spinal cord, oxidative metabolism was decreased overall. It was proposed that this was likely due to the overall ischemic effect of spinal traction, which subsequently leads to neural cells becoming hypoxic  . Other proposed mechanisms suggest that the disruption of ion channels is also associated with neuronal membrane traction, ultimately contributing to the decreased capacity for oxidative metabolism . Collectively, these mechanisms directly elicit neuronal dysfunction through progressive damage on the caudal spinal cord and can worsen over time. The outcomes of these neural dysfunctions are discussed in the clinical presentation.  

Clinical Presentation

When comparing adult and pediatric populations with tethered cord syndrome, it was found that pediatric populations have a higher proportion of sphincteric problems whereas adult populations more commonly exhibit significant pain.

Evaluation of literature finds clinical symptoms to be:

Pain	Perineogluteal region radiating into lower limbs Aggravated by prolonged sitting and forward bending
Motor	Weakness (does not follow myotomal pattern) Hyperreflexia Spasticity (mostly distal lower limb)
Sensory	Saddle area Distal portion of lower limb Lhermitte's Sign (electric shock sensation through spine, legs, arms, trunk)
Urological	Detrusor hyperreflexia Urinary urgency Stress incontinence Insufficient stream Enuresis
Orthopaedic	Club foot Trophic ulcerations of the foot Lower leg atrophy Scoliosis Gait abnormalities
Cutaneous	Cutaneous lipoma Tail Dermal sinus Cutaneous hemangioma Aberrant dimple Gluteal crease deviation

Diagnostic Procedures

• Magnetic Resonance Imaging (MRI) is currently the best available imaging technique to study TCS. Low conus medullaris (below L2-L3), thickened filum (>2mm) and fat in the filum are characteristic of this condition. However, it has been found more recently that TCS symptoms can be observed in patients with a normal L1/L2 conus position.
• Electromyography (EMG) may be used to assess nerve function, particularly in regards to urinary dysfunction.
• X-ray's can be used to identify bony anomalies consistent with spina bifida.
• Ultrasound can be used in early infancy to identify the position of the conus, the existence of lipomas and movement of the spinal cord.
• Physiotherapy Examination can identify signs and symptoms as previously highlighted in the clinical presentation section. This will allow for better insight on the proper diagnosis of TCS.

Epidemiology

Tethered cord syndrome is normally diagnosed only after the onset of signs and symptoms or found incidentally when looking for unrelated problems. Due to this, the true incidence and prevalence in the general population are not known. However, the onset of symptoms seems to appear more commonly in childhood than in adulthood.

Management / Treatment

Surgical Intervention 

In most cases, TCS requires surgical intervention by a process called untethering . The goal, in this case, is to try to restore mobility to the conus medullaris and filum terminale in the caudal spinal column. Results of surgery are strongly correlated to the severity and chronicity of this disorder. Therefore, surgery at a pediatric stage is usually advocated in order for successful management. Studies have shown that patients who have delayed treatment are more likely to present irreversible urological and neurological deficits. Furthermore, 47% of patients who refused surgery experienced worsening of symptoms. Many authors agree that this would likely have been prevented with earlier treatment .

That being said, patients who have TCS but remain symptom-free are not recommended to undergo surgery. A study was conducted where surgical intervention was suggested to treat infants who did not show any signs or symptoms. The goal was to prevent deficits in the future. Following the study, there was no evidence to conclude that surgery was necessary in infants who were asymptomatic. Therefore, it is recommended that surgery be avoided if a patient does not experience any deficits.

Evidence has shown that pain reduction and neurological improvement was seen in 81-89% of adult patients who underwent surgery. In addition, this intervention has been successful in improving urinary tract dysfunction among patients. A study was conducted where individuals who previously complained of urinary tract dysfunctions before surgery showed a reduction in symptoms in 72% of patients within three months of surgery. Therefore, surgical intervention is recommended for those who experience symptoms from this disorder due to the many post-operative benefits. 

Physical Therapy 

Currently, there is a lack of evidence on physical therapy associated with this disorder seeing as the primary mode of treatment is surgical intervention. That being said, below is a list of important ideas that need to be considered:

• As previously mentioned, one of the causes of TCS is spinal lipomas. In this case, symptoms may aggravate in patients who experience rapid weight gain as the lipoma may increase in size. Therefore, if neurological deficits in patients are not severe, weight loss may be a beneficial treatment to be considered before any surgical intervention. This could be achieved through proper dieting and exercise that does not require excessive tension and bending in the spinal cord. 

• It has been noted that individuals with less severe cases of tethered cord syndrome may remain symptom-free in childhood, but neurological deficits may occur later in life due to repeated spine flexion, extension, or trauma that may aggravate symptoms. Therefore, it is imperative that patients receive proper education on posture, gait, and functional movements when participating in recreational and daily activities in order to limit progressive tension on the spinal cord.

• Patients with a walking disorder can be treated with an exercise programme to make walking comfortable and easier.

Differential Diagnosis

There are many spinal disorders that share similar signs and symptoms as tethered cord syndrome (especially in adult=onset TCS). These include any conditions that result in back and leg pain, motor and sensory deficits or incontinence and may include: disc disease, spondylolisthesis, spine diseases, spinal cord disorders, peripheral nerve disease and herniated discs. Yamada and Lonser provide some key characteristics of TCS to help differentiate between some spinal disorders and TCS:

• Motor and Sensory deficits will not follow a normal myotomal/dermatomal pattern.
• Coughing and sneezing will not aggravate the pain.
• Lying supine will not make the pain better.
• Straight leg raising will not aggravate the pain.

Other conditions that could present with similar signs and symptoms include:

• Spinal cord tumours: depending on the location of the tumour, there could be pain, motor and sensory deficits and in rare cases, bladder control could be affected.
• Peripheral Neuropathy: Damage to the peripheral nerves can lead to pain, altered sensation and weakness.
• Myelopathy: This term describes any neurologic deficit related to the spinal cord and includes a wide variety of spinal conditions including spinal cord compression, spondylosis and damage due to inflammation or lack of blood supply.