Spinal cord tethering can occur from many causes. When the discussion is focused on Chiari I (CM-I) or syringomyelia, most people are referring to tethering caused by a tight filum terminale. The filum is a fibrous band extending from the end of the spinal cord to its attachment inside the sacrum (tailbone).
I have previously posted on the development of the filum terminale and on a retrospective study in 20 patients with filum section for Chiari, syringomyelia, or scoliosis. Preliminary results of a large retrospective study on section of the filum terminale were recently presented at the ASAP meeting. A comment on that post asked for my thoughts on the tethered cord in CM-I.
My thoughts pertain to three scenarios: persons with syringomyelia without CM-I, persons with CM-I, and persons with recurrent symptoms following a posterior fossa decompression for CM-I
Tight Filum Terminale in Syringomyelia without Chiari
In idiopathic syringomyelia, the cause of the syrinx is unknown. There is no evidence of Chiari I, Chiari 0, tumor, or trauma. The classic treatment of idiopathic syringomyelia causing intractable symptoms has been placement of a stent or shunt in the syrinx. Unfortunately, a stent or shunt may fail or cause scarring around the spinal cord.
In order to avoid shunt or stent placement, I have been offering the option of sectioning of the filum terminale in persons with intractable symptoms from idiopathic syringomyelia. This is done through minimally invasive surgery in the mid-lumbar spine. I avoid the lower levels of the spine (L4 and L5) since this is where most adults develop spinal degenerative changes.
Early results from sectioning the filum range from minimal to marked improvement. Whether this means that some of the cavities do not represent true syringomyelia but instead are persistent central canals is unknown. Only a prospective trial, which we are planning, will be allow us to determine the role of filum section in idiopathic syringomyelia.
Tight Filum Terminale and the Chiari I Malformation
Posterior fossa decompression (PFD) for persons with Chiari I malformation is a proven treatment for many patients suffering from CM-I. Diane Mueller and I reported the results of the only prospective trial published using a verified outcome measure (the Sickness Impact Profile). We tested 112 patients before and one year after PFD and found that quality of life was significantly improved in 84% of patients following decompression surgery.
The reported experience in the literature for section of the filum terminale as the primary treatment for CM-I is minimal. Very minimal. The study from Barcelona included only 4 patients with CM-I.
Although a retrospective study was presented at the recent ASAP meeting, full assessment of this work will only be possible after its publication in the medical literature.
Since posterior fossa decompression is effective for many and surgical risks can be kept low with a regimented surgical approach, PFD is our treatment of choice for CM-I. Section of the filum terminale as a primary treatment would only be considered in cases with mild herniation and after careful discussion with the patient.
Persistent or Recurrent Symptoms Following Posterior Fossa Decompression
Persistent or recurrent of symptoms following PFD is a difficult situation. In our study of 112 patients, the quality of life did not significantly improve in 16%. Although follow-up conversations with some of our patients revealed other factors were involved (loss of a loved one, major back surgery) in the year following surgery, it is apparent that some persons can undergo a technically satisfactory procedure and yet continue to have symptoms. If additional evaluation does not reveal the cause of the recurrence, the option of section of the filum is carefully discussed with the patient.
As noted above, we are currently planning a study on the role of section of the filum terminale in these conditions. This will be a prospective study requiring approval by the Institutional Review Board and written consent from those candidates who wish to participate.
John J. Oró, MD
Spinal cord tethering can occur from many causes. When the discussion is focused on Chiari I (CM-I) or syringomyelia, most people are referring to tethering caused by a tight filum terminale. The filum is a fibrous band extending from the end of the spinal cord to its attachment inside the sacrum (tailbone).
I have previously posted on the development of the filum terminale and on a retrospective study in 20 patients with filum section for Chiari, syringomyelia, or scoliosis. Preliminary results of a large retrospective study on section of the filum terminale were recently presented at the ASAP meeting. A comment on that post asked for my thoughts on the tethered cord in CM-I.
My thoughts pertain to three scenarios: persons with syringomyelia without CM-I, persons with CM-I, and persons with recurrent symptoms following a posterior fossa decompression for CM-I
Tight Filum Terminale in Syringomyelia without Chiari
In idiopathic syringomyelia, the cause of the syrinx is unknown. There is no evidence of Chiari I, Chiari 0, tumor, or trauma. The classic treatment of idiopathic syringomyelia causing intractable symptoms has been placement of a stent or shunt in the syrinx. Unfortunately, a stent or shunt may fail or cause scarring around the spinal cord.
In order to avoid shunt or stent placement, I have been offering the option of sectioning of the filum terminale in persons with intractable symptoms from idiopathic syringomyelia. This is done through minimally invasive surgery in the mid-lumbar spine. I avoid the lower levels of the spine (L4 and L5) since this is where most adults develop spinal degenerative changes.
Early results from sectioning the filum range from minimal to marked improvement. Whether this means that some of the cavities do not represent true syringomyelia but instead are persistent central canals is unknown. Only a prospective trial, which we are planning, will be allow us to determine the role of filum section in idiopathic syringomyelia.
Tight Filum Terminale and the Chiari I Malformation
Posterior fossa decompression (PFD) for persons with Chiari I malformation is a proven treatment for many patients suffering from CM-I. Diane Mueller and I reported the results of the only prospective trial published using a verified outcome measure (the Sickness Impact Profile). We tested 112 patients before and one year after PFD and found that quality of life was significantly improved in 84% of patients following decompression surgery.
The reported experience in the literature for section of the filum terminale as the primary treatment for CM-I is minimal. Very minimal. The study from Barcelona included only 4 patients with CM-I.
Although a retrospective study was presented at the recent ASAP meeting, full assessment of this work will only be possible after its publication in the medical literature.
Since posterior fossa decompression is effective for many and surgical risks can be kept low with a regimented surgical approach, PFD is our treatment of choice for CM-I. Section of the filum terminale as a primary treatment would only be considered in cases with mild herniation and after careful discussion with the patient.
Persistent or Recurrent Symptoms Following Posterior Fossa Decompression
Persistent or recurrent of symptoms following PFD is a difficult situation. In our study of 112 patients, the quality of life did not significantly improve in 16%. Although follow-up conversations with some of our patients revealed other factors were involved (loss of a loved one, major back surgery) in the year following surgery, it is apparent that some persons can undergo a technically satisfactory procedure and yet continue to have symptoms. If additional evaluation does not reveal the cause of the recurrence, the option of section of the filum is carefully discussed with the patient.
As noted above, we are currently planning a study on the role of section of the filum terminale in these conditions. This will be a prospective study requiring approval by the Institutional Review Board and written consent from those candidates who wish to participate.
John J. Oró, MD