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It is possible the presence of the tethered cord and the occult tethered cord in patients with the Chiari I malformation but it is not simple, nor is it always certain, where to put the limit between the symptoms of the two pathologies, in the diagnosis, in the indication to the treatment and in the technique with which to perform it.
The neurosurgical team of The Chiari Institute in New York said that a certain percentage of the presence of the occult tethered cord associated with the Chiari I malformation cannot be given, but it is probably 5% in the population.
Colleagues from The Chiari Institute in New York conducted a study published in a medical scientific 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 concluded in this study were: the tethered cord syndrome was present:
- in 14% (408 cases) of patients with Chiari I malformation (herniation of cerebellar tosillas of 5 or more millimeters);
- in 63% (182 cases) of patients with low lying cerebellar tonsils (LLCT: tonsillary herniation between 1 and 4 millimeters).
Symptoms, after resection of the intradural filum terminale, improved or disappeared in 69 children (93%) and 203 adults (83%), unchanged in 5 children (7%) and 39 adults (16%), worsened in 2 adults (1%) in a follow-up period between 6 and 27 months (average 16.1 months).
Magnetic resonance imaging 1 to 18 months after surgery (average 5.7 months) found a cranial migration of the medullary cone (average 5.1 mm), and an ascent of the cerebellar tonsils (average 3.8 mm).
The conclusions of this scientific work were: the association between Chiari I malformation and occult tethered cord is a clinical entity in its own right and represents the progression of the association of low lying cerebellar tonsils and occult tethered cord. It differs from Chiari I by the presence of a large foramen magnum and the absence of a small posterior cranial fossa. From this preliminary experience, the section of the intradural filum terminale, in this subgroup of patients with Chiari I, can lead to an ascent of moderate degrees of protrusion of the cerebellar tonsils and represents an appropriate treatment. At this point it is necessary to identify the differences in vision and therefore of treatment between The Chiari Institute in New York which is the center that has the world's largest case series of patients undergoing surgical treatment for Chiari syndrome, and the Institut Chiari de Barcelona.
At The Chiari Institute in New York, unlike the Institut Chiari de Barcelona, the section of the filum terminal is NOT recognized as the surgical treatment of Chiari malformation type I, idiopathic syringomyelias, idiopathic scoliosis, platibasia, basic impression, brain stem kinking.
The Institut Chiari de Barcelona's interpretation of the pathogenesis of all the aforementioned pathologies is not supported by findings at the level of international scientific literature or in other specialized centers in the world.
In 2013 Dr. Royo of the Institut Chiari de Barcelona chose to register the surgical technique of section of the filum terminale extradural within the brand "Filum System ®" (It is the first time that I know it happens) which is a method that should include protocols for the treatment of "Pathology of the Filum" and more exceptionally than certain affected cases of the hypothesized "Neuro-Cranio-Vertebral Syndrome" not congenital, the existence of these pathologies are hypothesized by Barcelona but there is no other scientific evidence in this regard.
Who wants to pursue the protection patent, which means obtaining a patent on something that is kept secret, renunciation of publication and therefore com and researcher does not exist, in the sense that he cannot claim to be recognized by the scientific community for having made known his work, the result obtained and the method adopted.
In short, one cannot claim the scientific substantiation of one's work if one does not submit to peer judgment. Patent protection and scientific substantiation are placed on different levels.
However, it is a free choice that of Dr. Royo to economically exploit his patent for the treatment of various pathologies hypothesized by him in the self-referential pathologies he coined, such as the "Neuro-Cranio-Vertebral Syndrome" and the "Pathology of the filum" between which the Chiari 1 malformation, with respect to the collective interest of sharing knowledge.
In Italy the Italian Society of Neurosurgery, regarding the indication to the section of the filum terminal in the treatment of Chiari I Syndrome, in the meeting of 12 May 2012, expressed itself as follows:
1. There is, in literature and in the experience of those present, no relationship between Chiari I Syndrome and the presence of the tethered cord;
2. The section of the filum terminale should be reserved for cases in which there is radiological evidence or clinical symptoms characteristic of this anomaly (bladder disorders, low back pain, hyposthenia in the lower limbs, etc ...);
3. The extradural section of the filum terminal does not constitute, on the basis of anatomical assessments, an alternative to the intradural section. In the literature, to date, there are not sufficient data attesting the validity of this method (a single work that reports a few cases of Chiari I).
I belive that the Chiari I malformation can be represented as a box not with a single product, but with several products inside. In the suspicion that there is the presence of the comorbidity of the pathology of the tethered cord in patients with Chiari I malformation, the main problem is deciding when to indicate the section surgery of the filum terminale and with which technique. There is still no definitive answer to this question based on studies with large cases. However, the section of the filum terminale should be avoided in cases where there is a clear indication for surgical treatment of decompression of the posterior cranial fossa for Chiari malformation. The symptoms of tethered cord are numerous, none specific, and in part may overlap with those of the Chiari malformation. The section of the filum terminale is reasonable to carry out in patients with symptoms and clinical signs of tethered cord, with symptoms therefore present at the lumbar level, in the lower limbs and / or with altered control of the urinary and faecal sphincters.
Specifically for the section surgery of the filum terminale, there are two surgical techniques:
- Filum terminale externum sectioning (local anesthesia):
a) With sacrectomy (partial removal of sacral bone tissue) proposed by Dr. the Institut Chiari de Barcelona, whose first and only scientific work published by Dr. Royo on this technique dates back to 2005 "Result of the section of the filum terminalis in 20 patients with syringomyelia, scoliosis and Chiari malformation. Acta Neurosurgica (2005; 147: 515-523)" where they were described 20 cases operated in 10 years, from April 1993 to July 2003, the cases were 11 patients operated (from '93 to '99) under general anesthesia with section of the intradural terminal filum and 9 patients (from '99 to '03) with an extradural section of the filum ending with partial removal of the sacrum, under local anesthesia. The case series of the 20 patients consisted of 8 patients with scoliosis, 5 syringomyelia 2 Chiari malformation and 5 with the combination of the three listed pathologies.
b) Without removal of bone tissue in accordance with minimal incision microsurgery (MISS) technique published by us in the scientific journal "Operative Neurosurgery" in 2018 in describing a case report. This technique has been used by us since 2010 and the case study currently includes (april 2020) about 200 patients.
- Filum terminale internum sectioning (general anesthesia): classic neurosurgical surgery with laminectomy, removal of the posterior bone portion of the vertebrae, opening of the meninges and section of filum terminale internum.
Further studies are needed to make clinical judgments on the outcome between the two different surgical techniques of resection of the filum terminale.
LAST UPDATE 13th APRIL
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