Tethered Cord Syndrome-Role of Early Surgery.

PURPOSE: 1. To evaluate the clinical course and effects of surgery on preexisting neurodeficits. 2. To address the issue of timing of intervention. MATERIALS: A prospective study at department of pediatric surgery, Bangalore Medical College and Research Institute and other hospitals from 2013 to 2017.
RESULTS: There were 44 patients. Over 3/4 presented with a cutaneous marker while 9 had deficits and no markers. The commonest marker was a swelling on the back. 1/3 of infants had neurological sequelae while almost all midline older children presented with bowel/bladder/gait disturbances. All underwent detethering. Post-operative complications were minor and self-limiting. None of the children had associated Chiari malformation and 2 had a syrinx which at last follow up has been static and shown no clinical signs. Recovery was mostly seen in infants and only in one older child.
CONCLUSION: Most of the patients with lipomeningomyelocele have early onset deficits and is recommended to operate at diagnosis. Children presenting with only deficits need to be evaluated for tethered cord syndrome but generally show poor or no recovery of deficits. Early prophylactic detethering is safe, feasible and advisable.

INTRODUCTION

Tethered cord syndrome (TCS) refers to a group of neurological (functional) disorders that result from chronic traction to spinal cord as a consequence of it being “tethered” or held by various structures. This is also a component of “occult spinal dysraphism” which refers to a group of malformations that are believed to result from the incomplete fusion of the dorsal midline structures during early embryogenesis.[1] They include lipomeningomyelocoele (lipoMMC), split cord malformation, neurenteric cyst, fatty filum terminale, dermal sinus, etc.[2] They may be associated with cutaneous changes over the back like the focal hairy patch, lipoma, hemangioma, scoliosis, etc. Such markers lead to early diagnosis.[1] In the absence of any cutaneous markers, the onset of leg pain, motor or sensory deficits should prompt the clinician to evaluate for tethered cord.

A taut (short fibrous) or a thick (fat infiltrated) filum is inelastic and causes excessive traction on the conus during spinal movements. Similarly, the cord suffers repeated mechanical shocks if its movement is restricted by fixity to a dorsal (e.g., lumbosacral lipoma) or ventral lesion (e.g., bony spur). These injuries initially cause ischemia and metabolic changes that impair neural transmission resulting in neuronal dysfunction. Studies demonstrate that such metabolic changes are reversible. Eventually, tethering of the cord can produce irreversible neuronal damage that is seen histologically.[3] This evidence prompted some surgeons to recommend early untethering. However, controversies regarding management of asymptomatic and incidentally detected tethered cord still exist.

This study was taken up to prospectively evaluate the presentation of tethered cord in infants and children, their treatment course and effects of surgery on preexisting neurodeficits and address the controversial issue of timing of intervention based on our data and review of the literature.

MATERIALS AND METHODS

This was a prospective descriptive study planned for a 5-year period from January 2013 to December 2017. Approval of the institutional ethical board was obtained.

All patients who presented with cutaneous markers of TCS or neurological deficits (bowel bladder dysfunction or lower limb sensorimotor deficits) and diagnosed to have a tethered cord on magnetic resonance imaging (MRI) were included in the study. All those who had neurological deficits but no tethered cord on evaluation were excluded. All those with classical meningomyelocoele (spina bifida aperta) were also excluded. The study included 44 patients with tethered cord. The clinical signs and symptoms, radiological findings, surgical details, and outcomes were recorded.

All patients underwent MRI spine and brain (to identify the location of conus, tethering elements [Figure 1] and the presence or absence of hydrocephalus, etc.) and ultrasonography of kidneys and bladder. A micturating cystourethrogram was performed if any abnormal findings were noted on ultrasound imaging. A urodynamic study (UDS) was done in all children older than 4 years and selectively in younger children (those who had dysfunctional voiding symptoms or abnormal uro-radiological findings). Patients with clinical bowel and bladder dysfunction (BBD) were started on enemas/rectal washes and clean intermittent catheterization (CIC) preoperatively. Pediatric orthopedic opinion was taken for those with limb deformity. All patients underwent surgery. Detethering by excision of tethering element (bony spur-Figure 2/ lipoma-Figure 3/ dermal sinus) and division of filum was accomplished with or without a laminectomy. As per the WHO protocol for antibiotics, only one prophylactic dose of intravenous ceftriaxone (100 mg/kg) was given 30 min before incision. A second dose was given if surgery exceeded 3 h. All patients received one intra-operative dose of dexamethasone (0.2 mg/kg) and this was repeated 8th h for 48 h. No drains were used. All patients had a pressure dressing for 48 h. Surgical complications if any were documented. The onset of new symptoms or change of neurological status immediate postsurgery was noted. Monitoring for change in symptoms continued during follow-up. Follow-up ranged from 3 months to 4 years.

Figure 1

Magnetic resonance imaging spine showing bony spur

Figure 2

Operative picture showing bony spur (bold arrow) splitting cord into 2 hemi cords with separate dural sheaths (dashed arrows)

Figure 3

Operative picture showing lipo meningomyelocele (dashed arrow) and filum terminale (bold arrow)

RESULTS

A total of 44 patients were operated for tethered cord from January 2013 to December 2017, of which 28 were male and 16 females. Twenty-six of them were infants (under 1 year of age).

The most common presentation was with a swelling over the back (24). Eleven had other cutaneous markers such as dermal sinus (6), hairy patch (4), and hemangioma (1 patient). Nine other children presented with sequlae of tethered cord (BBD in 4, trophic foot ulcer in 2, one each of pyonephrosis, gait disturbance, and back pain) [Table 1].

Table 1

Clinical profile of patients

Markers (n=35: 79.5%)	Sequelae (n=9; 20.5%)
Back swelling (n=24)	BB disturbance (n=4)
Dermal sinus (n=6)	Trophic ulcer (n=2)
Hairy patch (n=4)	Gait disturbance (n=1)
Hemangioma (n=1)	Pyonephrosis (n=1)
	Back pain (n=1)

The various tethering elements were lipoMMC (24), diastematomyelia (7), fatty or thick filum with low lying conus (9) and dermal sinus (4).

Of the 24 lipoMMC, 16 were under 1 year of age. Five of these infants had deficits before surgery. Two of them presented with BBD and paraparesis and other 2 were found to have bladder dysfunction during evaluation and one had unilateral lower limb weakness. Eight children with lipoMMC were older than 1 year and 3 of these presented with deficits [Table 2].

Table 2

Presentation and outcomes of various types of tethering elements

Lesion	n	Symptoms	Outcome
Lipo MMC	24 (some patients had both deficits)	BBD (n=7)	3/7 improved
		Sensori-motor (n=3)	1/3 improved
		Asymptomatic (n=16)	-
Split cord	7	Asymptomatic (n=7)	-
Thickened filum	9	BBD (n=4)	1/4 improved
		Sensori-motor (n=5)	2/5 improved
		Asymptomatic (n=0)	-
Sinus	4	Asymptomatic (n=4)	-

BBD: Bowel and bladder dysfunction, MMC: Myelomeningocele

Interestingly, 5 of the 7 patients with diastematomyelia were diagnosed antenatally. All 7 had cutaneous markers. One infant had discrepancy in length and diameter of lower limbs which later corresponded to the intra-operative finding of asymmetrical hemicord [Table 2].

Thirty-two of 44 patients required a laminectomy for exposure.

Five lipoMMC patients developed subcutaneous collection after the removal of routine pressure dressing on postoperative day 2. Three required aspirations and repeat pressure dressing. This might have been transient self-limiting CSF leak. One child had febrile convulsions on postoperative day 2. Four asymptomatic patients had immediate postsurgical motor neuropraxia which recovered by 3 months. Three of these were infants with lipoMMC and one diastematomyelia. Patients with neurogenic bowel and bladder were continued postoperatively with CIC and rectal washes. Six patients with limb deformity received treatments such as splints and tendon release as required.

Overall, 8 infants and 8 older children had preoperative neurological deficits or bladder dysfunction diagnosed during evaluation. Four infants (3 lipoMMC and one tight filum) and 1 older girl (low lying conus with fatty filum) demonstrated functional recovery. Of these 4 infants, one had selective recovery of the limb weakness. The two infants who were asymptomatic but demonstrated bladder changes on imaging, showed normal bladder empting with nil postvoid residue and normal detrusor thickness postoperatively. The older girl with bladder dysfunction demonstrated complete resolution of vesicoureteric reflux and normalization of voiding pattern [Table 3]. The follow-up urodynamics also showed normalization of high detrusor pressures. However 1½ years later, she had an episode of acute retention of urine and was re-initiated to CIC. She is awaiting an MRI to look for re-tethering. One older girl presented with back pain which resolved, postdetethering.

Table 3

Age-wise outcome of neurological deficits postde-tethering

Problems at presentation	Age	Postde-tethering outcome of deficits
BBD	<1 year (n=4)	Recovered (n=2)
		Persistent (n=2)
	>1 year (n=7)	Recovered (n=2)
		Persistent (n=5)
Sensori-Motor	<1 year (n=3)	Recovered (n=1)
		Persistent (n=2)
	>1 year (n=5)	Recovered (n=2)
		Persistent (n=3)

BBD: Bowel and bladder dysfunction

None of our patients had associated Chiari malformation. Two had a syrinx which at last follow-up was asymptomatic.

DISCUSSION

We observed that cutaneous findings are common in occult spinal dysraphism and must prompt further evaluation. Guggisberg et al.[4] studied the diagnostic value of midline cutaneous lesions in the lumbosacral region for closed spinal dysraphism. They recommended MRI evaluation if patients had markers such as a lipoma, tail, dermal sinus, atypical dimple, deviation of the gluteal crease, hamartoma, hemangioma, and port-wine stain. They concluded that hypertrichosis and pigmentary nevus in the absence of other signs and symptoms were unlikely to be associated with cord tethering. In contradiction, all children with hypertrichosis were associated with cord tethering in our series. The subgroup of patients having a low lying conus or a fatty or thickened filum as a tethering element were picked on MRI which demonstrated conus ending way below the normal L1–L2 junction or had fat signals in the filum causing a thickened filum which was defined as more than 2 mm in diameter.[5]

Before an MRI, an ultrasound of spine was done in all our neonates who were diagnosed antenatally and those with cutaneous markers. This is limited to infants as the spinal acoustic window closes by 3–6 months. Ultrasound can detect the position of the conus, the presence of any fat, and decreased spinal cord motion, any of which might indicate tethering.[2]

In children with no obvious markers, various neurological signs should prompt evaluation of the spine. These vary from decreased spontaneous leg movements in infants to abnormal gait, trophic ulcers (as seen in one of our patients), orthopedic deformities, or urological dysfunction in older children.[6]

UDS was done selectively in our patients. Subtle urological symptoms go undetected in infants and the role of UDS in them is limited. San Woon Kim et al.[7] made an attempt to validate the Meyrat UD scoring system and provide a comprehensive evaluation of the course of urological function after detethering surgery. They concluded that UD scores at 6 months postdetethering may be an important predictor of long-term urological outcome. However, Yener et al.[8] found that the best outcome with detethering were in those patients without urinary symptoms but having urodynamic changes. In their patients who presented with urinary symptoms, there was no correlation between improvement in symptoms and urodynamic findings. Frainey et al.[9] while stating that pre or postdetethering UDS did not predict continence status, concluded that the role of UDS in picking up re-tethering required further clarification. In our study, all older children with bowel and bladder symptoms had changes in UDS. Of the 13 children who underwent UDS in our series, 9 were beyond 4 years of age. Five of these had normal bladder function on UDS. We feel UDS has a greater role as a tool in urological management rather than in prognostication. However, UDS in all older children with tethered cord might help in the early detection of bladder dysfunction while clinically asymptomatic. Given the difficulty of doing and interpreting UDS in infants, it might be reserved for those infants with BBD.

None of our patients had associated Chiari malformation. Although the association of Chiari malformation is common with meningomyelocoele, children with lipoMMC rarely have associated hydrocephalus, Chiari malformations, or other brain anomalies.[10] Only 6%–7% of split cord malformations have associated Chiari malformations.[11] In a study by Valentini et al.,[12] they found that tethered spinal cord was associated with Chiari malformations in <6% of patients.

We did not use intraoperative neurophysiological monitoring. A combination of motor and sensory-evoked potentials, electromyography, and anal manometry can aid in the differentiation of nerve roots from other structures during surgery.[5]

CSF leak and wound infections are commonly reported complications. Thuy and Chaseling[13] reported a CSF leak in 8% and all except one required return to theater for re-exploration and closure or CSF diversion. We had transient CSF leak in 12%, which were self-limiting and none required re-exploration. Interestingly, these were all in children with lipoMMC who generally have dysplastic dura which precludes a good watertight closure.

One-third of our patients with lipoMMC had deficits at presentation. We noted that children older than 3 years were more likely to present with established neurological deficits without significant improvement of these deficits post-tethered cord release. We also observed that patients with lipoMMCs could manifest neurodeficits as early as 2 months of age. One of the 2 infants with multiple deficits showed recovery of limb weakness but no change in BBD. Out of 5 infants with deficits, 3 had reversal postdetethering while none of the 3 older children showed any improvement. Byrne et al.[14] did a retrospective analysis of 100 infants who underwent resection of spinal lipomas and untethering procedure. It revealed that symptoms were present preoperatively in 33. Thirteen of the 33 symptomatic children (39%) showed improvement in motor or urologic function with the operation. Most of the improvements were minor, but 4 (12%) of these symptomatic infants became asymptomatic postoperatively. They concluded that an operation performed during the 1st year of life with the goal of untethering the spinal cord and debulking the spinal lipoma was safe and effective and recommended.

Another theory states that there is a possibility that spinal lipomas increase in size and mass effect as patient gains weight[5] or with patient growth.

There is no consensus regarding the timing of surgery or the role of detethering in those who have no bladder or other neurological dysfunction. Proponents of early surgery believe it reduces the risk of neurological deterioration. In their study with long follow-up Rendeli et al.[15] showed that the best outcomes with respect to bladder capacity were in children who were operated before 1 year of age. A 20-year outcome study by Pang[16] on 315 patients with lipoMMC concluded that the ideal patient with the best outcome is an asymptomatic child <2 years without previous surgery. Although numbers are small to do a statistical analysis, our study points toward the benefit of early surgery in reversing neurodeficits. Based on long-term studies of others and our own series, we believe there is a role for prophylactic detethering following diagnosis of tethered cord rather than waiting for neurological symptoms, especially in lipoMMCs.

CONCLUSION

All infants with antenatally detected occult spinal dysraphism and those presenting with markers should undergo postnatal definitive evaluation of the spine by an MRI including screening for Chiari malformation. Children with symptoms of BBD and sensory-motor deficits of the lower limbs would need a thorough evaluation, which would include an MRI spine for definitive diagnosis, uro-radiological evaluation and muscle charting. Patients with lipomeningomyelocele can have early-onset deficits and respond best when operated at diagnosis. Older children presenting with deficits generally show poor or no recovery of deficits postdetethering.

Detethering in infants is safe, feasible, and advisable for preventing deficits and maximizing recovery.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.