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ARNOLD-CHIARI MALFORMATION TYPE 1 AND OCCULT TETHERED CORD

The presence of the occult tethered cord is an element of possible comorbidities in Chiari I malformation very controversial, but not about whether or not there is, but where to draw the line in the diagnosis and in the indication for surgery and the technique used to run it.
 
The team of neurosurgical The Chiari Institute in New York said that you can not give a certain percentage of the presence of the occult tethered cord associated with Chiari I malformation, but probably 5% in the general population.
 
Things are complicated by the fact that there is a subpopulation of Chiari with tethered cord and there is another subgroup in which the occult tethered cord is the cause herniation of the tonsils but patients have the size of the posterior fossa and foramen magnum normal, and then, in this case, is not a Chiari malformation I.
 
In this regard, the colleagues of The Chiari Institute of New York conducted a study published in a medical journal: "Association of Chiari malformation type I and tethered cord syndrome: preliminary results of sectioning filum terminal. Surg. Neurol 2009; 72 (1): 20-25 "
The data in this study were: the tethered cord syndrome was present in 14% (408 cases) of patients with Chiari I malformation and in 63% (182 cases) of the patients with low lying cerebellar tonsils (LLCT: tonsillar herniation between 1 and 4 mm).
In 318 patients undergoing intradural section of the filum terminale there were no differences in the size of the posterior fossa than in healthy controls.
The symptoms, after the resection of the filum terminale were improved or disappeared in 69 children (93%) and 203 adults (83%), unchanged in 5 children (7%) and in 39 adults (16%), worsened in 2 adults (1%) in a period of follow-up between 6 and 27 months (mean 16.1 months). MRI 1 to 18 months after surgery (average 5.7 months) found a migration of cranial medullary cone (average 5.1 mm), and a rise of the cerebellar tonsils (mean 3.8 mm).
The conclusions of this scientific work have been: the association between Chiari I malformation and occult tethered cord is a clinical entity in its own right and is the progression of the association low lying cerebellar tonsils and occult tethered cord. It differs from Chiari I for the presence of a large foramen magnum and the absence of a small posterior fossa. This preliminary experience section of the filum terminale intradural, in this subgroup of patients with Chiari I, may result in a rise of moderate degrees of protrusion of the cerebellar tonsils and is an appropriate treatment.
 
At this point you need to identify the differences of vision and therefore treatment of the The Chiari Institute of New York and the Institut Chiari de Barcelona.
At The Chiari Institute of New York, unlike the Institut Chiari de Barcelona, ​​you do not recognize the tethered cord as the cause of all Chiari malformations, as the cause of all syringomyelie, as a cofactor in all tonsillar herniation. At The Chiari Institute of New York it does not state that the resection of the filum terminale care Chiari I.
 
On the basis of the pathogenetic theory anchor the spinal cord Dr. Royo of the Institut Chiari de Barcelona's in all the above mentioned pathologies, but also in some types of scoliosis, surgical treatment of the section of the filum terminale.
 
The interpretation of the pathogenesis and treatment of Chiari I malformation, but also scoliosis, Dr. Royo of Barcelona has no other evidence at the level of literature or other specialist centers worldwide.
 
Ultimately the approach to the occult tethered cord from colleagues neurosurgeons at The Chiari Institute in New York is much narrower than that proposed by Dr. Royo of the Institut Chiari de Barcelona.
 
The vast majority of neurosurgeons world believes that the section of the filum should not be used as a routine intervention in Chiari I.
 
In Italy, the Italian Society of Neurosurgery, about the indication section of the filum terminalis in treating Chiari I, at its meeting on 12 May 2012, held as follows:
1. There is, in literature and in the experience of the present, no relationship between the Chiari I Syndrome and the presence of spinal fixed;
2. The section of the filum terminal should be paid to cases where there is a radiological evidence or clinical symptoms characteristic of this anomaly (bladder disorders, back pain, weakness in the legs, etc ...);
3. Section extradural filum terminal is not, on the basis of anatomical evaluation, an alternative to the intradural. In literature, there are to date, enough data proving the validity of this method (a single work that shows few cases of Chiari I).
 
The Chiari I malformation can be represented as a box with no one product, but with different products inside. Suspecting that there is the presence of comorbid disease tethered cord in patients with Chiari malformation The main problem is to decide when to the indication for surgical section of the filum terminalis. This question does not have an answer yet. You should still avoid in cases where there is a clear indication for surgical decompression of the posterior fossa.
 
The section of the filum terminalis is reasonable to maintain it in many patients with clinical symptoms and signs of spinal cord anchorage, with symptoms then present at the lumbar spine and lower limbs. The symptoms of the hidden tethered cord are numerous, no one specific, and partly overlap with those of Chiari malformation (see figure).
 
Specifically intervention section of the filum terminalis surgical techniques are two:
 
- Extradural resection of the filum, or rather the section of the filum extradural extension, given by Dr. Royo, under local anesthesia. The first and last scientific paper published by Dr. Royo of this technique dates back to 2005 "Result of the section of the filum terminalis in 20 patients with syringomyelia, scoliosis and Chiari malformation. Acta Neurosurgery (2005; 147: 515-523)" where Dr. Royo describes his first 20 cases operated in 10 years, from April 1993 to July 2003, the series was 11 operated patients (from '93 to '99) under general anesthesia with the section of the filum intradural and 9 patients ( from '99 to '03) with the section of the filum extradural under local anesthesia.
 
- Section of the filum terminalis intradural under general anesthesia. Classic neurosurgical intervention with laminectomy, dural opening and section of the filum. This technique, normally done in all neurochirurgie the world, is the favorite at The Chiari Institute in New York and used the whole world, where there have been reports in which patients already undergoing resection extradural were then subjected to the next intervention intradural section with improvement in the neuroradiology. These few cases do not allow to be able espirmere clinical judgments on the outcome of the two techniques divsere surgical resection of the filum, there are clinical studies which have compared the two techniques.

11/14/2016 08:07 am
Vanni VERONESI MD