Duraplasty Prevents Retethering In Complex TCS Cases

May 31st, 2009 -- Researchers at Johns Hopkins (Samuels et al.) have found that using duraplasty as part of surgical detethering is effective in preventing retethering in complex cases. They recently published this result on-line in the journal, Child's Nervous System.

Like many studies, the research was done retrospectively, meaning that the scientists reviewed medical records and performed statistical analysis to achieve their results. While considered weaker from a scientific stand-point than prospective studies, which define their hypothesis before any medical intervention and follow a group of patients over a period time, retrospective studies remain a stalwart in Chiari related research.

Tethered Cord Syndrome, where the tissue of the spinal cord is put under abnormal tension due to attaching, or tethering, to something else, is of growing interest to the Chiari community for a couple of reasons. Probably first and foremost is the controversial subject of occult tethered cord and its relationship, if any, to Chiari. Occult tethered cord refers to a condition where the thread-like bottom of the spinal cord, the filum terminale, is less flexible than it should be. This, in turn, pulls down on the cord, and essentially puts it in traction causing lower body problems such as pain, loss of sensation, and loss of bowel and bladder function.

There are two controversial.htmlects to this type of tethered cord as related to Chiari. First is the fact that this type of tethered cord is not always apparent on MRI; thus the word occult. While a fatty or tight filum sometimes can be seen on MRI, surgeons who treat occult tethered cord tend to rely more on patient symptoms in making a diagnosis and recommending a surgical release. [Ed. Note: Most people are aware of the controversy surrounding The Chiari Institute as detailed in the mainstream media and discussed at length on the Chiari message boards. The use of tethered cord surgery at TCI is part of that controversy. Conquer Chiari, as a matter of policy does not endorse, or align with, any doctors or hospitals. This has been our stated position from the beginning and will remain our position. As such, we will take no position in this situation except for reporting on (and funding) any related, scientific research which may help shed light on the potential link between TCS and Chiari.

The second controversial.htmlect is whether TCS can cause a Chiari malformation, meaning that the downward pull on the spine can lead the cerebellar tonsils to herniate. This has been proposed, most notably, by Royo-Salvador, but is not widely accepted. Indeed, there is evidence to support both sides of the argument. Ellenbogen documented, via MRI, a child with a clearly fatty and tight filum, who then developed Chiari over time. Although this is compelling, an MRI alone does not mean that the tight filum actually caused the tonsils to herniate. On the flip side, Tubbs found, through a cadaver study, that tension applied to the bottom of the spinal cord dissipates very quickly as you move up the spine, and thus is unlikely to affect the brain. However, Tubbs also found, in a different study, that an unusually high percentage of people with lipomyelomeningocele also have Chiari.

Regardless of the controversies, there are well established reasons for the Chiari community to be interested in TCS. Namely, that many of the leading causes of TCS have a high co-incident rate with Chiari. Recall that up to a third of spina bifida patients also suffer from Chiari II. It turns out that surgical repair of spina bifida can lead to tethering of the cord after surgery due to scar tissue and adhesions. Similarly, lipomyelomeningocele can lead to spinal cord tethering, and as mentioned above is somehow linked to Chiari. Finally, there is no question that some TCS cases are due to a fatty, tight filum, which as discussed above, may or may not be linked to Chiari.

The Hopkins study reviewed their medical records over a ten year period and identified 110 children who had been operated on for first time untethering of the cord. TCS surgery, like Chiari surgery, varies in the details, and the researchers wanted to know if there were any differences in the outcomes based on whether the patient had received a duraplasty (meaning the dura was expanded with a patch) versus just having the dura sewn shut after the detethering.

The average age of the children was 5.7 years and they were monitored for an average of 42 months after surgery. Monitoring occurred for 30 days post-op to look for signs of surgical complications, plus follow-up visits one month, three months, and then every six months after surgery. The children's clinical status was determined to be improved, unchanged, or worse. Patients who had worsening symptoms and MRI evidence of retethering of the cord, were classified as retethered. In addition, based on established criteria, the researchers grouped the cases as complex TCS or simple TCS.

On average, the children had shown symptoms for 3 months prior to surgery, with the most common being leg weakness and urinary problems (Fig 1). The most common causes of the TCS were post-surgical scarring from spina bifida repair and a fatty filum terminale (Fig 2). In all, the majority of the patients (75) did not receive a duraplasty while 35 did.

In terms of complications and outcomes, the researchers could not find any differences between the duraplasty and no-duraplasty groups in terms of length of hospital stay and post-op complications. Similarly, there were 29 total cases of retethering during the follow-up period, but there was no statistical difference between the duraplasty and no-duraplasty group in this regard (Fig 3).

However, of the 29 retethered cases, 25 of them had what were categorized as complex TCS, which was statistically more significant than the retethering rate for simple TCS cases. Further, however, the researchers found that within the retethered, complex TCS group, those who had undergone duraplasty did not have a higher rate of retethering. In other words, the only sub-group with a comparatively high rate of retethering was the complex TCS patients who had not had duraplasty. Despite the structural limitations of the research, the authors feel this a good indication that duraplasty should be considered when detethering complex cases, although further research is needed to confirm this.

The relationship between TCS and Chiari is likely to remain controversial for quite some time, however, for patients with widely recognized TCS, it appears that duraplasty should be considered as part of the surgical procedure to release the cord.

Figure 1: Common Presenting Symptoms (110 Patients)

Symptom # (%)
Lower limb weakness 58 (53%)
Urinary problems 48 (44%)
Pain 40 (36%)
Trouble walking (Gait) 42 (38%)
Avg. Duration of Symptoms 3 months

Figure 2: Cause of Tethered Cord (110 Patients)

Cause # (%)
Post Myelomen. Repair 35 (32%)
Fatty Filum Terminale 26 (24%)
Lipomyelomeningocele 20 (18%)
Lipoma 18 (16%)
Intra-dural neoplasm 4 (4%)
Post Lipomyelo. Repair 2 (2%)

Figure 3: Cord Retethering (110 Patients)

Duraplasty (35 patients) 12 (41%)
No-Duraplasty (75 patients) 17 (59%)
Total 29 (26%)

Related C&S News Articles:

Two Cases Provide Clues To A Link Between Tethered Cord And Chiari

Possible Biomarkers Found For Tethered Cord

Chiari Linked To Lipomyelomeningocele

New Study Casts Doubt On Tethered Cord Causing Chiari

MRI Documents Acquired Chiari Due To Fatty Filum

Minimal Tethered Cord Shows Abnormal Anatomy