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Navigation and MRI During Surgery: Spine Advances
Perspectives Commentary on: Intraoperative Magnetic Resonance Imaging and Neuronavigation for Transoral Approaches to Upper Cervical Pathology by Dhaliwal et al. pp. 164-169.
Volker K. H. Sonntag, M.D. Vice Chairman Emeritus, Division of Neurological Surgery Barrow Neurological Institute St. Joseph’s Hospital and Medical Center
Navigation and MRI During Surgery: Spine Advances Volker K. H. Sonntag
T
he transoral approach to the craniovertebral junction (CVJ) provides versatile and direct access to extradural midline pathology. In the past, the transoral approach has also been used to access intradural pathology, but it has mostly been abandoned for this indication because of the high risks of patients developing cerebrospinal fluid leakage, meningitis, and fistulas. Intradural pathologies are mainly approached via a posterolateral or anterolateral approach. The transoral approach allows decompression from the level of the ventral medulla to the upper cervical spinal cord. In most circumstances, the transoral approach permits access from the inferior third of the clivus to the C3 vertebra. Exposure is constrained by patients’ ability to open their mouths and by the soft tissue boundaries of the nasopharynx, oral pharynx, mandible, and skull base. The usual transoral access to the CVJ is through the uncomplicated route that involves retraction of the soft palate and the tongue without incising other soft tissue. If extended exposure is required, the transoral approach can proceed via a transmaxillary, transpalatal, transfacial, or transmandibular exposure. Although such extensions of the transoral exposures offer access, they also increase the morbidity associated with this surgical procedure. The first reported transoral operative procedures were used to drain retropharyngeal abscesses. In 1950, the transoral approach was introduced to access the upper cervical spine and lower clival region for decompression and fusion procedures for the treatment of basilar invagination, tumors, tuberculomas, and traumatic lesions. These early sporadic attempts at transoral surgery were restricted by poor visualization of the operative side, limited exposures, and high risks of complication. Infection, cerebrospinal fluid leakage, and neurologic injury were among the major complications.
Key words 䡲 Craniovertebral junction 䡲 Image guidance 䡲 Intraoperative MRI 䡲 Neuronavigation 䡲 Transoral approach 䡲 Transoral exposure 䡲 Transoral surgery
76
Abbreviations and Acronyms CVJ: Craniovertebral junction MRI: Magnetic resonance imaging
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Over the last several decades, use of the transoral approach has increased significantly with satisfactory results. Improvements in diagnostic techniques, including localization of pathology by computed tomography and magnetic resonance imaging (MRI), have facilitated precise operative planning and enhanced mobilization of extradural compressive pathology. Microneurosurgical operative techniques, intraoperative electrophysiologic monitoring, improved microsurgical instrumentation, and refinement of techniques have substantially improved outcomes. With these advances, the transoral approach of the lower clivus and upper cervical spine has become a safe and effective neurosurgical procedure. As advocated by Menezes et al. (2), if anterior compression at the CVJ is secondary to cranial settling, skeletal traction should be attempted first. If this procedure is successful, anterior decompression via the transoral route is unwarranted, and posterior fusion should be performed with the patient in the reduced position. The most common neurologic symptoms associated with anterior compression of the CVJ, in decreasing order, are neck pain, incoordination, dysesthesia, clumsiness, seizures, numbness, arm and leg weakness, voice change, urinary incontinence, difficulty swallowing, apnea, and diplopia. Associated neurologic signs include decreased neck motion, myelopathy, nasal voice, upper extremity atrophy, decreased rectal tone, decreased gag reflex, atrophy of the lower extremities, uncoordinated swallowing, and bilateral palsy of the sixth cranial nerve (1). The transoral approach usually violates the transverse ligament. Consequently, posterior fusion is mandatory in these cases. Depending on the exact location of the anterior pathology, axial-atlantal fusion may be adequate. Alternatively, the fusion
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona, USA To whom correspondence should be addressed: Volker K. H. Sonntag, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2012) 78, 1/2:76-77. DOI: 10.1016/j.wneu.2011.10.025
WORLD NEUROSURGERY, DOI:10.1016/j.wneu.2011.10.025
PERSPECTIVES
may need to be extended to the occiput or more caudally into the midcervical spine posteriorly. Dhaliwal et al. described 20 patients who underwent the transoral approach for compressive lesions at the CVJ. The pathologies addressed included seven neoplasms, seven congenital anomalies, and six degenerative disease processes. In 11 patients, the transoral procedure was performed without splitting of the palate or without a mandibulotomy. However, nine patients underwent an additional palatal split. Of those nine patients, five also required a mandibulotomy for appropriate exposure. The authors used intraoperative MRI and neuronavigation to facilitate removal of these lesions, measures that may have increased the precision and accuracy of their surgeries. Images were obtained in the intraoperative MRI suite after the induction of anesthesia and placement of scalp judicial markers, before any incisions were made and before insertion of the retractors, which are incompatible with MRI. After the MRI examinations were completed, the magnet was removed. Registration was performed based on the intraoperative MRI scans. The actual system was verified by correlation with identifying landmarks in the region of interest. The dissection images were performed any time during the course of the procedure by placing sterile drapes over the surgical site. These images were acquired after the surgical team had completed extensive dissection of pathology. Of the 20 patients in whom the surgeons thought they had completely removed the abnormality, intraoperative MRI showed residual lesions in 3 patients, which were subsequently removed. After the transoral approach, a second procedure for posterior stabilization was required in 19 patients. One patient required revision of the posterior construct because of cranial settling 7 months after the initial stabilization. One patient had an incomplete spinal cord injury during the anterior approach for resection
WORLD NEUROSURGERY 78 [1/2]: 76-77, JULY/AUGUST 2012
of an osteochondroma. In retrospect, the original patient neuronavigation was thought to be unreliable, possibly because of movement of the patient or movement of the neuronavigation triangulation device during the case. Other than that one patient, unexpected complications consisted of prolonged dysphagia, respiratory distress, and infection. During follow-up, one patient died of renal failure, and two patients died because of progression of their disease, in both cases, chordoma. Of the patients followed, the neurologic status had improved in 92% at a mean follow-up of 1.8 years. The authors do not claim that the use of neuronavigation with intraoperative MRI makes the operation safer and more likely to be successful. Nonetheless, their use allowed registration of anatomic landmarks to confirm the extent of dissection during the procedure and contributed to intraoperative decision making about the extent of lesion dissection. The increased time and expense associated with using these techniques seem to be justified, especially in the three patients who did not have complete initial resection of the abnormality.
REFERENCES 1. Dickman CA, Spetzler RF, Sonntag VKH, Apostolides PJ: Transoral approach to the craniovertebral junction. In: Dickman CA, Spetzler RF, Sonntag VKH, eds. Surgery of the Craniovertebral Junction. New York: Thieme; 1998. 2. Menezes AH, Van Gilder JC, Graf CJ, McDonnell DE: Craniocervical abnormalities: a comprehensive surgical approach. J Neurosurg 53:444-455, 1980. Citation: World Neurosurg. (2012) 78, 1/2:76-77. DOI: 10.1016/j.wneu.2011.10.025 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2012 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
77
Volker K. H. Sonntag, M.D. Vice Chairman Emeritus, Division of Neurological Surgery Barrow Neurological Institute St. Joseph’s Hospital and Medical Center
Navigation and MRI During Surgery: Spine Advances Volker K. H. Sonntag
T
he transoral approach to the craniovertebral junction (CVJ) provides versatile and direct access to extradural midline pathology. In the past, the transoral approach has also been used to access intradural pathology, but it has mostly been abandoned for this indication because of the high risks of patients developing cerebrospinal fluid leakage, meningitis, and fistulas. Intradural pathologies are mainly approached via a posterolateral or anterolateral approach. The transoral approach allows decompression from the level of the ventral medulla to the upper cervical spinal cord. In most circumstances, the transoral approach permits access from the inferior third of the clivus to the C3 vertebra. Exposure is constrained by patients’ ability to open their mouths and by the soft tissue boundaries of the nasopharynx, oral pharynx, mandible, and skull base. The usual transoral access to the CVJ is through the uncomplicated route that involves retraction of the soft palate and the tongue without incising other soft tissue. If extended exposure is required, the transoral approach can proceed via a transmaxillary, transpalatal, transfacial, or transmandibular exposure. Although such extensions of the transoral exposures offer access, they also increase the morbidity associated with this surgical procedure. The first reported transoral operative procedures were used to drain retropharyngeal abscesses. In 1950, the transoral approach was introduced to access the upper cervical spine and lower clival region for decompression and fusion procedures for the treatment of basilar invagination, tumors, tuberculomas, and traumatic lesions. These early sporadic attempts at transoral surgery were restricted by poor visualization of the operative side, limited exposures, and high risks of complication. Infection, cerebrospinal fluid leakage, and neurologic injury were among the major complications.
Key words 䡲 Craniovertebral junction 䡲 Image guidance 䡲 Intraoperative MRI 䡲 Neuronavigation 䡲 Transoral approach 䡲 Transoral exposure 䡲 Transoral surgery
76
Abbreviations and Acronyms CVJ: Craniovertebral junction MRI: Magnetic resonance imaging
www.SCIENCEDIRECT.com
Over the last several decades, use of the transoral approach has increased significantly with satisfactory results. Improvements in diagnostic techniques, including localization of pathology by computed tomography and magnetic resonance imaging (MRI), have facilitated precise operative planning and enhanced mobilization of extradural compressive pathology. Microneurosurgical operative techniques, intraoperative electrophysiologic monitoring, improved microsurgical instrumentation, and refinement of techniques have substantially improved outcomes. With these advances, the transoral approach of the lower clivus and upper cervical spine has become a safe and effective neurosurgical procedure. As advocated by Menezes et al. (2), if anterior compression at the CVJ is secondary to cranial settling, skeletal traction should be attempted first. If this procedure is successful, anterior decompression via the transoral route is unwarranted, and posterior fusion should be performed with the patient in the reduced position. The most common neurologic symptoms associated with anterior compression of the CVJ, in decreasing order, are neck pain, incoordination, dysesthesia, clumsiness, seizures, numbness, arm and leg weakness, voice change, urinary incontinence, difficulty swallowing, apnea, and diplopia. Associated neurologic signs include decreased neck motion, myelopathy, nasal voice, upper extremity atrophy, decreased rectal tone, decreased gag reflex, atrophy of the lower extremities, uncoordinated swallowing, and bilateral palsy of the sixth cranial nerve (1). The transoral approach usually violates the transverse ligament. Consequently, posterior fusion is mandatory in these cases. Depending on the exact location of the anterior pathology, axial-atlantal fusion may be adequate. Alternatively, the fusion
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona, USA To whom correspondence should be addressed: Volker K. H. Sonntag, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2012) 78, 1/2:76-77. DOI: 10.1016/j.wneu.2011.10.025
WORLD NEUROSURGERY, DOI:10.1016/j.wneu.2011.10.025
PERSPECTIVES
may need to be extended to the occiput or more caudally into the midcervical spine posteriorly. Dhaliwal et al. described 20 patients who underwent the transoral approach for compressive lesions at the CVJ. The pathologies addressed included seven neoplasms, seven congenital anomalies, and six degenerative disease processes. In 11 patients, the transoral procedure was performed without splitting of the palate or without a mandibulotomy. However, nine patients underwent an additional palatal split. Of those nine patients, five also required a mandibulotomy for appropriate exposure. The authors used intraoperative MRI and neuronavigation to facilitate removal of these lesions, measures that may have increased the precision and accuracy of their surgeries. Images were obtained in the intraoperative MRI suite after the induction of anesthesia and placement of scalp judicial markers, before any incisions were made and before insertion of the retractors, which are incompatible with MRI. After the MRI examinations were completed, the magnet was removed. Registration was performed based on the intraoperative MRI scans. The actual system was verified by correlation with identifying landmarks in the region of interest. The dissection images were performed any time during the course of the procedure by placing sterile drapes over the surgical site. These images were acquired after the surgical team had completed extensive dissection of pathology. Of the 20 patients in whom the surgeons thought they had completely removed the abnormality, intraoperative MRI showed residual lesions in 3 patients, which were subsequently removed. After the transoral approach, a second procedure for posterior stabilization was required in 19 patients. One patient required revision of the posterior construct because of cranial settling 7 months after the initial stabilization. One patient had an incomplete spinal cord injury during the anterior approach for resection
WORLD NEUROSURGERY 78 [1/2]: 76-77, JULY/AUGUST 2012
of an osteochondroma. In retrospect, the original patient neuronavigation was thought to be unreliable, possibly because of movement of the patient or movement of the neuronavigation triangulation device during the case. Other than that one patient, unexpected complications consisted of prolonged dysphagia, respiratory distress, and infection. During follow-up, one patient died of renal failure, and two patients died because of progression of their disease, in both cases, chordoma. Of the patients followed, the neurologic status had improved in 92% at a mean follow-up of 1.8 years. The authors do not claim that the use of neuronavigation with intraoperative MRI makes the operation safer and more likely to be successful. Nonetheless, their use allowed registration of anatomic landmarks to confirm the extent of dissection during the procedure and contributed to intraoperative decision making about the extent of lesion dissection. The increased time and expense associated with using these techniques seem to be justified, especially in the three patients who did not have complete initial resection of the abnormality.
REFERENCES 1. Dickman CA, Spetzler RF, Sonntag VKH, Apostolides PJ: Transoral approach to the craniovertebral junction. In: Dickman CA, Spetzler RF, Sonntag VKH, eds. Surgery of the Craniovertebral Junction. New York: Thieme; 1998. 2. Menezes AH, Van Gilder JC, Graf CJ, McDonnell DE: Craniocervical abnormalities: a comprehensive surgical approach. J Neurosurg 53:444-455, 1980. Citation: World Neurosurg. (2012) 78, 1/2:76-77. DOI: 10.1016/j.wneu.2011.10.025 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2012 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
77