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OCCULT TETHERED CORD: DIAGNOSTIC DEFINITION

ANATOMICAL CONSIDERATIONS AND PHYSIOPATHOLOGICAL
The spinal cord ends in the shape of a cone (conus medullaris) and is connected to a thin extension called the filum terminale. The filum terminale is considerably thinner than the spinal cord and is not constituted by nervous tissue. The filum terminale has a portion within the meninges (intradural) and an external portion of the meninges (extradural). The extradural part of th filum terminale starts within sacral vertebra and ending in tailbone.
The central nervous system is based on the oxidative metabolism to produce adenosine triphosphate which is the molecule necessary for the production of energy and for the neuronal function and cells.
In the central nervous system (brain and spinal cord), whenever the operation of the oxidative metabolism is compromised the pathophysiological consequences are obvious and often rapidly fatal and are related to the extent and duration of the loss of oxidative metabolism.
 
TETHERED CORD SYNDROME
The tethered cord syndrome is a set of symptoms related to an anatomical variation of the terminal part of the spinal cord that is located most caudal (toward the sacrum) from the normal position represented between the first and the second lumbar vertebra.
The tethered cord syndrome is present in adult and pediatric populations.
The pathogenesis of the bone anchored is due to traction on the lower end of the spinal cord (conus medullaris) by the tense filum terminale and at times of increased thickness.
This traction on the medullary cone leads to reduction of blood flow with decreased oxidative metabolism and may cause clinical symptoms and signs of tethered cord syndrome.
 
OCCULT TETHERED CORD SYNDROME
Khoury and collaborators in 1990 expressed the concept of the occult tethered cord in the absence of changes in the position of the medullary cone. The medullary cone represents the terminal part of the caudal spinal cord, usually is positioned between the first and the second lumbar vertebrae.
The pathophysiology of the occult tethered cord is difficult to understand because the spinal cord ends in the usual position and there are no associated malformations of the spine.
Recent studies, in cases of occult tethered cord have shown a change in the structure of the filum terminale with increasing fibrous component or the presence of adipose tissue. These changes can lead to lowered elasticity of the filum terminale and a consequent traction on the medullary cone to which the filum terminale is connected.
The definition of the syndrome in medicine means a complex of symptoms that may be caused by different causes. The symptoms of this syndrome are not specific and are mainly but not exclusively represented by low back pain, pain and / or abnormal sensations in the legs, urinary dysfunction, stiffness of the spine.
The diagnosis of occult tethered cord syndrome had the opportunity to support with objective medical scans. The Japanese colleagues have published in 2013, on scientific journal, a study with a particular MRI performed in the prone position (patient lying on the bed belly-down). This particular examination provides for the first time the possibility to objectify this pathology and not to rely only on the presence of symptoms that are often non-specific. If the test is positive the filum terminale remains in the back of the spinal canal and does not follow before the radicelle nerve.
For our patients, from 2013, it was then adopted a diagnostic-therapeutic protocol that provides for the collection of medical history, the medical neurosurgical, the execution of the MRI with the patient in the prone position. If the Magnetic Resonance in the prone position is positive for the presence of the occult tethered cord and there is congruous with clinical symptoms and signs, can be evaluated or the traditional surgical treatment under general anesthesia with removal of the back of the vertebrae (laminectomy) opening of the dura mater (meninges), detection and section of the intradural filum terminale or the new surgical treatment of minimally invasive surgical section of the extradural filum terminale by transhiatal approach in local anesthesia.
It notes that the Japanese colleagues have surgically treated patients with classic surgery under general anesthesia with the opening of the meninges and, after detection of the filum terminale between the nerve roots, cutting the filum terminale in the intradural portion.
The minimally invasive technique under local anesthesia by cutting the extradural filum terminale presents less risk than the traditional surgical treatment and less anesthesia risk.
If you make first the minimally invasive technique you can then run the traditional technique but not vice versa.

11/14/2016 08:30 am
Vanni VERONESI MD