Monday, October 14, 2019
Transhiatal Approach Essay Example for Free
Transhiatal Approach Essay Abstract: Tethered cord syndrome (TCS) is a stretch-induced functional disorder of the spinal cord, which is directly related to filum fixation. Classic surgical approaches to the filum involve open surgery and include varying amounts of spinal bone removal. In an effort to reduce the morbidity and mortality of these procedures, we explored a less invasive method. We evaluated the ability, safety and feasibility for extradural endoscopic dissection of the filum terminale by performing upward orientated navigation in the sacral spinal canal through the sacral hiatus using a rigid endoscope. Four adult, phenol-formalin embalmed cadavers were used for extradural endoscopic dissection of the filum at the tip of thecal sac. After preparing the anatomical area of sacral hiatus, a rigid endoscope (Storz, of 3.8 mm external diameter with one working channel) was inserted into the sacral spinal canal and the filum was identified and cut easily. In all cases, it was possible to manipulate the rigid endoscope and inspect the full length of the extradural sacral spinal canal, especially at the S1-S2 level. Our results indicate that the tested transhiatal approach for upward orientated extradural endoscopy represents a minimally invasive procedure that provides an appropriate and feasible route to the extradural sacral spinal canal. Furthermore it is an attractive alternative for filum dissection in cases where tethered cord syndrome is not accompanied by any other pathology. Introduction Physicians and scientists have explored the clinical usefulness of spinal endoscopy over six decades. Endoscopic spinal surgery represents a major advance in the treatment of spinal disorders. It involves the use of small incisions that preserve normal tissues while allowing the spinal pathology to be fully treated. This technique carries interesting clinical benefits, and its utility continues to expand as technology advances. Tethered cord syndrome (TCS) is a manifestation of spina bifida occulta and can occur as a complication of surgically closed spina bifida aperta. The mechanical cause of TCS is an inelastic structure anchoring the caudal end of the spinal cord and preventing cephalad movements of the lumbosacral cord. Stretching of the spinal cord occurs in patients either when the spinal column grows faster than the spinal cord or when the spinal cord undergoes forcible flexion and extension. Symptomatic TCS can occur in adults as well as in children, manifesting with various clinical symptoms (Dachling, 1982; Kaplan, 1980; Klekamp et al. 1994), such as pain, neurological deficits, and bowel and bladder dysfunction. Further studies have shown that early surgical correction in adults is recommended because of the high risk for irreversible neurological deficits (Bermans et al. 2001). In recent years, further research efforts of scientists have ranged from full-fledged neurosurgery to minimally invasive approaches and have involved the use of flexible and rigid endoscopes for diagnosis and treatment of certain pathological entities (Heavner et al. 1991; Sabreski Kitahata, 1995 1996; Warnke et al. 2001, I, II; Warnke et al. 2003). Encouraging results from the performance of co-axial downward orientated thecaloscopic procedures, with flexible steerable endoscopes in the lumbar subarachnoid space in living humans (Warnke et al. 2003), prompted us to study further thecaloscopic procedures for filum terminale dissection by using a rigid endoscope. This procedure usually offers a better optical view of the studied anatomic structures. The aim of the present anatomic study was not only to determine if the tip of thecal sac could be clearly visualized. Based on the fact that epidural endoscopy through sacral hiatus was proved to be safe and possible (Sabreski Kitahata, 1995 1996; Sabreski Gerens, 1998), it also sought to explore the possibility of using a rigid endoscope to untether prefixed filum terminale. Materials and Methods For this study, four adult phenol-formalin embalmed male cadavers from the Anatomy Department of the Medical School of the University of Athens were dissected using microsurgical and endoscopic techniques. Neurosurgical technique Fig.2Insertion-of-the-rig Fig.1Sacral-Hiatus Cadavers were placed in the prone position. A midline skin incision was centered over the sacral hiatus [fig. 1]. After anatomical preparation, the rigid endoscope [fig.2] was inserted through the sacral hiatus and directed into the sacral spinal canal cephalad. It was angled in that manner in order that it would face the tip of thecal sac. The filum, which was holding thecal sac, was identified and dissected [fig.3]. The rigid endoscope used was a Storz with a 3.8mm external diameter and one working channel. For the documentation, a video-tape (Fuji VHS) was used and digital photographs were taken using a Fuji AS-205.  Results With the help of a rigid endoscope, it is possible to visualize directly the tip of thecal sac and to perform a dissection of the filum terminale. A rigid endoscope was inserted into the sacral spinal canal and, with the benefit of the visibility it granted, was advanced cephalad with relative ease. The rigid endoscope provided a large field of view, which enabled the anatomical structures to be seen. The filum can be easily identified in fine detail, as it is the only structure adherent to the tip of thecal sac at the S1-S2 level. This procedure represents a minimally invasive method for direct visualization of the tip of thecal sac and dissection of filum terminale. Discussion Diseases of the spine predispose persons to chronic complaints ranging from mild discomfort to intense pain. Endoscopy of the anatomic structures contained within the spine makes possible thorough examinations for existing pathology and facilitates the application of appropriate methods of therapy (Warnke et al. 2003; Sabreski Kitahata, 1996). Use of neuroendoscopy has become widespread in spinal surgery for conditions ranging from degenerative disease to deformity correction (Heavner et al. 1991; Sabreski Gerens, 1998; Sabreski Kitahata, 1995 1996). The growth in the number of minimally invasive spine surgical procedures being performed has been spurred by both technical advances and by its associated reduction in operative morbidity (1998; 1995; 1996). However, minimally invasive techniques are primarily employed in extradural procedures. Transhiatal extradural filum untethering provides the ability to untether a prefixed filum in a minimally invasive way. When referred to a neurosurgical clinic, adult patients with tethered cord syndrome tend to show significant progressive neurological deficits (Klekamp et al. 1994; Dachling, 1982).  Some authors (van Leeuwen, et al. 2001) have advocated prophylactic surgical treatment for the prevention of progressive neurological symptoms, which is, in this case, related to low morbidity. As an alternative to the risky open surgical treatment procedure, we evaluated the extradural endoscopic procedure for untethering of filum in cadavers. Extradural filum untethering could be indicated in cases of prefixed filum without other accompanying pathology such as meningomyelocele, CSF fistula, or arachnoidal cysts. It could also be performed before a surgical intervention, which generally include dura opening and removal of various amounts of spinal bone. During inspection of the sacral spinal canal with the rigid endoscope, the declination of the sacral spinal canal did not bring difficulties for the upward manipulation of the endoscope. Following the physical inclination of the sacral spinal canal, the filum could be approached and dissected before reaching the lumbosacral angle. In some instances, it was difficult to dissect the filum because of its elasticity. However, the minimally invasive nature of neuroendoscopy provided by this procedure, and by the employment of the rigid endoscope, allows for a larger field of view at the sacral spinal canal through a smaller incision. This access and the ability to perform extradural inspection and filum dissection using this transhiatal approach are comparable with other therapeutic interventions used in neurosurgery, such as the endoscopic epidural placement of catheters in anaesthesiology. Conclusions This method of extradural endoscopic dissection of the filum terminale minimizes surgical trauma and provides excellent visualization of and access to the extradural sacral spinal canal. Furthermore, it enables the filum to be identified and thus provides a minimally invasive alternative to current open surgical procedures indicated for filum untethering. Utilization of this procedure could: (1) facilitate untethering of prefixed filum terminale without opening the dura and (2) minimize patient morbidity thereby presenting an overall attractive alternative to current methods of filum dissection. At present, neuroendoscopy is most widely used in minimally invasive spine surgery, but novel uses continue to emerge in the literature. As technology evolves and more experience is obtained, neuroendoscopy will likely achieve additional roles as a mainstay in spinal surgery. References Heavner JF, Cholkhavatia S, Kizelsheeyn G. (1991). 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