Tethered Cord Syndrome (TCS)

Diagnostic criteria

Termination of the conus below the L3 vertebral body

A filum thicker than 2 mm.

Others

In patients with demonstrated low lying conus, the presence of fat within the filum is suggestive of cord tethering.

Mechanism

Normal: The filum terminale is normally viscoelastic in nature, and serves to dampen movements of the spine during flexion and extension, without applying undue traction to the moving spinal cord.


flowchart LR
    A["Spinal cord attached to<br>abnormally inelastic caudal</br>structures (eg. fibrous/fat-<br>infiltrated filum, tumor,<br>meningoceles/myelomeningoceles,<br>scars, septa<br>(as seen in SSCM)"] 
        --> B["Caudal portion of spinal<br>cord stretches between<br>point of tethering and<br>dentate ligaments that fixes<br>the cord proximally"]
    B --> C["Repeated spinal extension/<br/>flexion and/or differential<br>growth between vertebral<br>column and spinal cord"]
    C --> D["Progressive neurological<br>dysfunction"]

Clinical presentation

Finding	%
Cutaneous findings • Hypertrichosis • Sub-Q lipoma (no intraspinal extension) • Miscellaneous (hemangiomatous discoloration, dermal sinus, multiple manifestations)	54 • 22 • 15 • 17
Gait difficulty with LE weakness	93
Visible muscle atrophy, short limb, or ankle deformity	63
Sensory deficit	70
Bladder dysfunction • Bladder dysfunction as only deficit	40 • 4
Pain in back, leg, or foot arches	37
Scoliosis or kyphosisa	29
Posterior spina bifida (lumbar or sacral)	98

Associated features

Hydrocephalus 80%

Chiari malformation (almost all) 20% symptomatic

Vertebral anomalies - kyphoscoliosis

Secondary/skip lesions - up to 20%

Syringomyelia

Orthopaedic problems - spasticity, dislocations, talipes

Urogenital

Comparison of childhood and adult TCS

Children

Aetiology

Myelomeningocele patients

Almost all MM patients have tethered cord

If an MM patient has increasing scoliosis, increasing spasticity, worsening gait (in those previously ambulatory), or deteriorating urodynamics:

Always make sure that there is a working shunt with normal ICP
If painful, should be considered tethered cord until proven otherwise
If painless, should be considered syringomyelia until proven otherwise
May be due to brainstem compression (Symptomatic Chiari II malformation)

Requiring posterior fossa decompression

Spinal Lipomas

Tight filum terminale

A short thick filum (> 2 mm without fat), which impairs the ascent of conus medullaris.

The result is a low-lying tethered cord causing TCS.

No other dysplastic states are present except dermal sinus

Clinical features

Scoliosis in tethered cord

Progressive scoliosis may be seen in conjunction with tethered cord.

Early untethering of the cord may result in improvement of scoliosis;

However, untethering must be done when the scoliosis is mild.

≤ 10° scoliosis were untethered,

68%: Neurologic improvement
32%: stabilized

Scoliosis is severe (≥ 50°) ≈ 16% deteriorated.

Bowel bladder dysfunction

Loss of anal crimpling

Foot deformity: Clawing of foot

Increased lower limb tone

Adults

Aetiology

Iatrogenic

Trauma

Vascular

Infections

Clinical presentation

Asymptomatic - incidental

10% of babies born have closed spinal dysraphism
Adults might consider bladder symptoms as normal

Progressive

Leg or back pain
Motor and sensory symptoms

Finding	Childhood tethered cord	Adult tethered cord
Aetiology	• Myelomeningocele • Spinal Lipomas • Tight filum terminale	• Iatrogenic • Trauma • Vascular • Infections
Clinical features	• Scoliosis in tethered cord • Bowel bladder dysfunction • Loss of anal crimping • Foot deformity: Clawing of foot • Increased lower limb tone	• Asymptomatic - incidental • Progressive ◦ Leg or back pain ◦ Motor and sensory symptoms
Pain	Uncommon; usually in back and legs, not peri-anal nor perineal	Present in 86%, often peri-anal & perineal; diffuse & bilateral; occasionally shock-like
Foot deformities	Common early; usually progressive cavo-varus deformity (club foot)	Not seen
Progressive spinal deformity	Common; usually progressive scoliosis	Uncommon (<5%)
Motor deficits	Common; usually gait abnormalities & regression of gait training	Usually presents as leg weakness
Urological symptoms	Common; usually continuous urinary dribbling, delayed toilet training, recurrent UTIs, enuresis	Common; usually urinary frequency, urgency, sensation of incomplete emptying, stress incontinence, overflow incontinence
Trophic ulcerations	Relatively common in LEs	Rare
Cutaneous stigmata of dysraphism	Present in 80–100% (tuft of hair, dimple, capillary angioma [naevus flammeus])	Present in <50%
Aggravating factors	Growth spurts	Trauma, maneuvers associated with stretching conus, lumbar spondylosis, disc herniation, spinal stenosis

Evaluation

Radiographically

Investigation of choice
Features

Low conus medullaris (below L2)
Thickened filum terminale (normal diameter < 1mm; diameters > 2mm are pathological).

Apparent filum diameter on CT-myelogram may vary with concentration of contrast material.
Difficult to differentiate a tethered cord from a congenitally low lying conus (filum diameter is generally normal in the latter).

Fat within the filum

Other abnormalities like dermal sinus tracts or spinal dysraphism.

CISS sequence: improves delineation of the tethering structures and correlate well with intraoperative findings.

Dynamic MRI Techniques

Positional and dynamic MRI sequences measure cord movement and angulation

Aoun 2019: Anteroposterior conus movement >10% canal width on prone imaging suggests less likelihood of tethering

Urodynamic testing can detect preclinical urologic dysfunction in children with CSD.

Conservative management

Watchful monitoring

Indication

Asymptomatic
Mildly symptomatic

Monitor for neurologic, genitourinary or gastrointestinal symptoms,

Via Urodynamics test

Surgical treatment

Indication for surgery

Children/adults

New onset neurological symptom
Progression of neurologic symptoms
Spinal instability
Pain relief

Neonates

Early neurosurgical intervention is warranted for severe neonatal symptoms such as bowel obstruction.
Spinal cord is internally exposed

To decrease the risk of infection and meningitis,

Not indication

Severely disabled patients with static deficits related to CSD are unlikely to benefit from surgery.

Controversial

Radiographic demonstration of a tethered cord in asymptomatic patients
Abnormal findings on urodynamic studies in a patient with CSD.

Argument for surgery

Even infants and children who are asymptomatic or mildly symptomatic may go on to develop progressive and irreversible neurologic deficits.

Argument not for surgery

There is high variability in the natural history of CSD

Pre-op evaluation

Preoperative cystometrogram is strongly recommended, especially if the patient seems continent

Postoperative changes in bladder function are not uncommon, possibly due to stretching of the lower fibers of the cauda equina.

MRI T1 and T2 axial

Check where on axial the tethered cord is the most obvious on T1 axial

Technique

Prone

X-rays to localize level with two needles that are placed at the pedicle above and below the level of interest

Local used

Midline incision made

Bilateral stripping.

Find Spinous and interlaminar space

Using Mitchell's trimer to dissect the soft tissue away from the cranial and caudal lamina

Use USS to check for filum

Can be hypo or hyper echoic

Get the flavum off under the lamina

Try to make this easier by lifting the spinous process up to tent the flavum
Cut the flavum so that it can be hitched laterally

Use Kerrison to widen the interlamina/spinous space to expose the theca and fat

Use bipolar and scissors to buzz and remove the fat away from theca.

Place two small patties lateral to the theca so to stop bleeding and also the elevate the theca off the vertebral body

Flow seal the theca and use micropattie to push the flowseal under the lamina cranial and caudally

Use USS to check for filum

Can be hypo or hyper echoic

When it is dry under microscope use a diamond knife to open dura.

Small opening of 7mm or so required only
Optional

Forming a large intradural compartment, with duraplasty to reduced risk of developing arachnoid adhesions
If the only abnormality is a thickened, shortened filum, then a limited lumbosacral laminectomy may suffice, with division of the filum once identified. If a lipoma is found, it may be removed with the filum if it separates easily from neural tissues.

Hitch stich dura one on each side

Suck CSF out

Examine Intradural contents and look for filum that is thickened

Distinguishing features of the filum terminale intraoperatively

Filum has squiggly vessel on surface of filum.
Filum whiter appearance than the nerve roots
Filum has ligamentous-like strands can be seen running through it.
Filum is not stimulate-able on EMG

NB: intra-op electrical stimulation and recording of anal sphincter EMG are more definitive.

Use a blue plastic material to place under the filum.

Removal of any anatomic structure that is acting to tether the spinal cord, and may include

Transection of the filum

Check the filum for any large cyst or nerve attachment
Free nerve from area where planned transection of filum would be

No need to free nerve completely from the filum
Pick up the filum and look under and on the sides of it
Check for visible vessels

Resection of transitional lipoma
Lysis of adhesions
Excision of dermal sinus tracts

Buzz al visible superficial vessels

Buzz the filum as much as possible

Ask assistant to hold the filum at its cranial end so that it would not disappear after being cut

Use microscissor to cut the filum layer by layer and buzz after every cut

Buzz the end of the filum

Check for any bleeding

Close theca

Close flavum

Close fascia

Close skin

Post op

Remain under close monitoring because of the risk of future worsening due to

Spinal cord retethering OR
Progression of a preexisting syrinx.

Symptoms to monitor

Urologic symptoms

Earliest indication of retethering
Via Urodynamics test

Progression of preexisting scoliosis and pain.

Outcome

Usually impossible to permanently untether a cord
However, in a growing MM child, it may be that after 2–4 untethering, the child will be finished growing and tethering may cease to be a problem
Cases that are untethered early in childhood may recur later, especially during the adolescent growth spurt.

Incidence of post-op CSF leak: 15%.

Adult form

Surgical release

Good for pain relief.
Poor for return of bladder function.

Surgical outcomes

Wound probs 10-20%
Surgical deterioration 1-2%
Symptom free 5yrs 53%
Reoperation in 20%
20% will deteriorate still
16% late onset neurological deterioration
Re-tethering
Re-operation

Personal impressions

More complicated in adults
More complex consultations
Tissues more difficult to dissect
Previous surgeries adding to scarring
Cord tethered therefore, stretched, for longer so more 'fragile'
More comorbidities