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Syringomyelia and Tethered Spinal Cord

Subsequent to a traumatic SCI, the overarching goal is preservation of residual neurological function and, to the extent possible, reacquisition of previous function. One longer-term pathological process that can interfere with this a spectrum of changes termed spinal cord tethering and post-traumatic syringomyelia.

Over the long term, some scar tissue associates with the injured spinal cord and causes pathological adhesion or tethering to the surrounding dura. This can result in undue traction being placed on the segment of spinal cord cranial to the injury, resulting in new, but delayed, progression of neurological deficit. Similarly, the injured cord can acquire localized atrophy and myelomalacia, resulting in intramedullary cystic cavitation, with the cyst filling with cerebrospinal fluid. If this fluid compartment, or syrinx, develops mass effect, then this can similarly present with delayed worsening of neurological deficit. Both of these processes can have a devastating impact on function depending on the level of injury-for example, an individual with a high thoracic injury can be at risk of losing their upper extremity function if a symptomatic tethered cord or syrinx develops. Because of the significance of this pathology, surgical treatment and/or preventative options have been considered.

 

Table 17. Syringomyelia and Tethered Spinal Cord

Author Year

Country
Research Design
Score
Sample Size

MethodsOutcomes
Bonfield et al., (2010)

USA

Systematic Review

AMSTAR=6

N=22 studies

Objective: To determine the indications for surgical intervention and optimal surgical intervention technique for post-traumatic syringomyelia (PTS).

Methods: Comprehensive literature search of English articles of all individuals with traumatic syrinx, excluding case reports.

Databases: MEDLINE, EMBASE, Cochrane, Web of Science.

Evidence: Levels of evidence were assigned using GRADE criteria (very low, low, moderate, or high). Clinical recommendations were made using a modified Delphi approach (weak or strong).

 

1.     Strength of evidence was very low (n=16) to low (n=6).

2.     Overall recommendations were weak.

3.     The incidence of PTS was 0.5-4.5% and was twice as common in complete versus incomplete injury.

4.     Surgical intervention for PTS was effective at arresting or improving motor deterioration, but not sensory dysfunction or pain syndromes.

5.     Spinal cord untethering with expansile duraplasty was the preferred surgical technique.

6.     Direct surgical decompression beyond realignment/stabilization of a thoracic complete SCI to reduce the risk of future PTS was not supported.

7.     Surgical intervention for incidental, asymptomatic syrinx was not supported.

Falci et al. (2009)

USA

Case Series

N=362

Population: Mean age: 40.5 yr; Level of injury: C1-C6=163, C6-T1=83, T1-S5=116; Severity of injury: AIS A=232, AIS B=36, AIS C=41, AIS D=51, AIS E=2; Mean time since injury: 10.7 yr.

Intervention: Participants who received cord untethering, expansion duraplasty, and cyst shunting for progressive myelopathy were retrospectively analyzed. Outcomes were assessed at pre-op, post-op, and follow-up.

Outcome Measures: American Spinal Injury Association (ASIA) scores; Clinical status; Complications.

1.     At post-op, participants showed significant increases in ASIA light touch score (n=308; +1.39, p=0.029) and pinprick score (n=307; +1.41, p=0.029), and a non-significant decrease in ASIA motor score (n=263; -0.32, p=0.059).

2.     At 1 yr follow-up, participants showed non-significant changes in ASIA motor score (n=100; -.128, p=0.102), light touch score (n=110; +0.74, n=0.437), and pinprick score (n=109; +0.58, p=0.633).

3.     At last follow-up, participants showed a significant decrease in ASIA motor score (n=134; -1.16, p=0.015) and non-significant changes in light touch score (n=157; -0.76, p=0.391) and pinprick score (n=157; +0.1, p=0.996).

4.     Participants reported decreases in neuropathic pain (n=99; 47%), spasticity (n=53; 60%), and hyperhidrosis (n=38; 77%).

5.     Participants reported arrest of progressive loss of both motor and sensory function (n=204; 89%), of motor function (n=152; 93%), and of sensory function (n=128; n=97%).

6.     Complications were CSF leak/collection (3.8%), DVT/PE (2.35%), wound infection (0.48%), bacterial meningitis (0.48%), myocardial infarction (0.24%), and death (0.48%).

Falci et al.

(1999) USA

Case Series

N=59

Population: Mean age: 38 yr; Gender: males=49, females=10; Level of injury: C1-C6=24, C6-T1=20, T1-S5=15; Severity of injury: AIS A=53, AIS B=1, AIS C=3, AIS D=2; Mean time since injury: 12 yr.

Intervention: Participants who received cord untethering and/or cyst shunting for progressive myelopathy were retrospectively analyzed at 1 yr post-op.

Outcome Measures: American Spinal Injury Association (ASIA) scores; Clinical status; Complications.

1.     Participants showed non-significant increases in ASIA scores when compared to pre-op (p>0.05): light touch (+0.67), pinprick (+1.3), and motor (+0.41).

2.     Participants without previous surgery (n=34) showed increases in ASIA scores when compared to pre-op: pinprick (+3.88, p<0.05), light touch (+2.38, p>.05), and motor (+1.47, p>0.05).

3.     Participants with previous surgery (n=25) showed non-significant decreases in ASIA scores when compared to pre-op (p>0.05): light touch (-0.7), pinprick (-0.8), and motor (-0.5).

4.     Participants showed recovery of lost functional activity (64.3%), substantial improvement in spasticity (62.5%), substantial improvement in neurogenic pain (55.6%), prevention of further neurologic deterioration (95.8%), and improvement in hyperhidrosis (100%).

5.     Complications were CSF leak/collection (8.4%), wound infection (1.7%), cyst recurrence (1.7%), and meningitis (1.7%).

Discussion

The largest case series is that of Falci et al. (2009a) who published both early and late follow-up results. They describe 362 individuals surgically treated for tethered cord and/or syringomyelia. Each had delayed neurological decline after traumatic cord injury, attributable to tethering and/or syrinx, and demonstrated statistically significant declines in AIS scores during the first year of assessment. After surgical detethering (and in 20% of individuals, syrinx shunting), AIS scores remained statistically stable over a variable follow-up period from 2 to 12 years. This suggests that in individuals with delayed deterioration, surgical intervention is capable of arresting neurological decline, but not necessarily restoring neurological function. The same individuals responded via questionnaires that their perceptions of spasticity, hyperhidrosis and neuropathic pain had improved post-operatively, but there was no comparator group.

A systematic review of post-traumatic syringomyelia management (Bonfield, Levi, Arnold, & Okonkwo, 2010b) found that the incidence of this process is 1-4% among spinal cord injured individuals, and is twice as prevalent in complete, compared to incomplete, injuries. Despite post-traumatic syrinx being more prevalent in individuals with residual kyphosis at the level of injury, their review of low and very low quality retrospective studies found no evidence to prophylactically decompress the injured segment during the index surgical treatment; that is, they advised to not change surgical strategy in hopes of syrinx prevention.

With regard to surgical indications for syrinx, the systematic review by Bonfield et al. (2010b) summarized retrospective studies and prospective cohort studies. The authors concluded that surgery was only recommended for progressive motor deterioration, and that progressive pain syndromes, sensory disturbance or other non-motor progression was not recommended. Bonfield et al. (2010a) also addressed different methods of syrinx decompression. These range from spinal cord transection, to cerebrospinal fluid shunting to either the subarachnoid or pleural space, pseudomeningocoele creation, to expansile duraplasty. In general, after review of the mostly retrospective literature, there is no clearly superior technique, although a consensus pointed towards cord detethering and expansile duraplasty.

Conclusion

There is level 3 evidence (from one prospective cohort; (Falci et al., 2009b) that cord detethering with or without syrinx decompression can arrest neurological decline in individuals with delayed progressive myelopathy following SCI.

There is level 4 evidence (from studies from one systematic review; (Bonfield et al., 2010a) that prophylactic measures for cord tethering and/or syrinx should not be taken, other than what is required to achieve primary spinal realignment / stabilization during the index surgery.

  • Post-traumatic tethered cord and syringomyelia has an estimated incidence of 1-4%. Low quality evidence suggests that prophylactic decompression should not be performed, but that patients with progressive motor decline attributable to tethering or syrinx can have an arrest of their decline with surgical management.