Ventral Cervicomedullary Junction Research Articles

Neurenteric cysts at foramen magnum in children: presentation, imaging characteristics, and surgical management-case series and literature review.

Neurenteric cysts (NEC) are rare benign tumors of the central nervous system. Even more rare are the NEC at the ventral foramen magnum in children that are misdiagnosed. They cause distortion of the vertebrobasilar vascular system and cervicomedullary neural structures and are adherent to the latter. The inferior portion lies ventral to the upper most dentate ligament. This has implications in the surgical approach for complete excision. We reviewed our series of five children with ventral foramen magnum NEC in the MRI era and analyzed presentation, radiological findings and surgical management. A literature review is also presented. There were two females and five males. Headache and neurological deficit was present in all five; one child presented with recurrent meningitis. The NEC was present ventral to the cervicomedullary junction in all cases. The posterolateral transcondylar approach was used for complete excision with no recurrences. Neurenteric cysts at the ventral foramen magnum can be confused with other cystic lesions. Headaches are the most common presentation. The posterolateral transcondylar approach to the ventral cervicomedullary junction provides the most reliable avenue for entire resection.

Endoscopic Transnasal Odontoidectomy.

Transoral microscopic odontoidectomy followed by posterior fixation has been accepted as a standard procedure to treat nonreducible basilar invagination during the half past century. In recent years, the development of endoscopic techniques has raised challenges regarding the traditional treatment algorithm. The endoscopic transnasal odontoidectomy is a feasible and effective method in the treatment of irreducible ventral cervicomedullary junction compression, which has several advantages over the transoral approach. The endoscopic odontoidectomy includes transnasal, transoral, and transcervical approaches. The 3 different approaches for endoscopic odontoidectomy present complementary advantages and limitations. The necessity of posterior fixation after odontoidectomy should be considered in every single case on the basis of the peculiar anatomic and clinical conditions.

Solitary sclerosis

To present a case series of patients with progressive myelopathy in the setting of a solitary demyelinating lesion. We describe 7 patients evaluated over a 6-year period. All had progressive motor impairment attributable to an MRI lesion compatible with a demyelinating plaque in the brainstem or upper cervical spinal cord. At the time of evaluation, none met the International Panel imaging criteria for dissemination in space, and none described clinical symptoms consistent with relapses affecting other portions of the CNS. Lesions identified were in the ventral cervicomedullary junction in 4 patients, the ventral spinal cord in 2 patients, and the pons in 1 patient. Median age at onset was 43 years (range 33-51 years). Median follow-up interval was 3 years (range 2-27 years). Six patients reached an Expanded Disability Status Scale (EDSS) score of 6.0 or worse. Median time to EDSS score of 6.0 was 7.5 years (range 1.5-26 years). Four had CSF findings characteristic of multiple sclerosis (MS). None had CSF, imaging, or serologic evidence of an alternative etiology of progressive myelopathy. In 3 patients, serial MRI scans of the brain and spinal cord demonstrated no accumulation of lesions. Postmortem examination of a fourth patient demonstrated an isolated pontine demyelinating lesion. Solitary demyelinating lesions may produce a progressive myelopathy similar to primary progressive MS. Demyelinating disease should be in the differential diagnosis of progressive myelopathy despite absence of dissemination in space.

Craniovertebral junction abnormalities with hindbrain herniation and syringomyelia: regression of syringomyelia after removal of ventral craniovertebral junction compression

Hindbrain herniation syndrome, or Chiari malformation Type I (CM-I), occurs frequently with craniovertebral junction (CVJ) abnormalities when there is reduction in the posterior fossa volume. Syringomyelia is often present. Posterior fossa dorsal decompression (PFDD) is typically performed but has adverse results when ventral bone abnormality exists. This paper presents the results of a prospective study on CVJ abnormalities in patients with CM-I and syringomyelia. Between 1984 and 2008 (the MR imaging era), 298 patients with CVJ abnormalities and CM-I underwent ventral cervicomedullary decompression. Eighty-four patients had associated syringomyelia (15 with secondary invagination and 69 with primary basilar invagination, os odontoideum, or malunion of fractures). Of these 84 patients with CVJ abnormalities, CM-I, and syringomyelia, 46 had previously undergone PFDD, and 28 had previously undergone PFDD combined with fusion procedures or shunt placements. Of the 84 patients, a cervicothoracic syrinx was observed in 57, thoracic syrinx in 14, and holocord syrinx in 13. Studies included CT, MR imaging, and cine flow studies. All 298 patients who underwent ventral CVJ decompression had irreducible or partially reducible pathology. All 84 with syringomyelia showed brainstem dysfunction, lower cranial nerve symptoms, or myelopathy. Brainstem signs improved in 66 of the 84 patients, myelopathy improved in 58, and syringomyelia regressed in 64. Neurological improvement and syringomyelia resolution can occur using only ventral cervicomedullary junction decompression in patients with basilar invagination and basilar impression. This is likely due to the relief of neural encroachment and reestablishment of CSF pathways.

Efficacy and limitations of intraoperative spinal cord monitoring using nasopharyngeal tube electrodes

Motor evoked potentials are widely used for intraoperative spinal cord monitoring. However, there are problems with anesthetic constraints and high trial-by-trial variability of compound muscle action potential amplitude in muscle motor evoked potential monitoring. It is difficult to determine when to warn the surgeon of an occurrence of spinal cord risk. A method of estimation for motor function in the spinal cord has not been established. To monitor spinal cord function with reliable evoked potentials, including the upper cervical spinal cord and the ventral spinal cord, the authors developed a nasopharyngeal tube electrode that can be placed in front of the upper and ventral cervical spinal cord. The purpose of this study was to investigate the origins and pathways of descending or ascending spinal cord evoked potentials (SCEPs) elicited with this electrode, and the usefulness and limitations of this method. A nasopharyngeal tube electrode was inserted into the nostril. A catheter electrode was placed in the epidural or subarachnoid space at the thoracic spine. Ventral SCEP was recorded from the thoracic spinal cord after transpharyngeal stimulation, and dorsal SCEP was recorded with the nasopharyngeal electrode after thoracic spinal cord stimulation. There was no restriction of anesthetic technique in recording. When the amplitude of either of the SCEPs declined to 80% of the baseline, a warning was provided to the surgeon during the observed operative procedure. At the end of surgery, less than 50% or more than 30% of the baseline amplitude was considered a significant change in both SCEPs. The sensitivity and specificity for both SCEPs to detect neurological deterioration were calculated. The electrode provided noninvasive access to the ventral cervicomedullary junction. The SCEPs showed stable responses. A response change was only observed in situations involving a risky procedure for the spinal cord. Ventral SCEPs showed high sensitivity (73.1%) for identifying patients with new neurological deficits or an exacerbation of preexisting neurological deficits after surgery, but dorsal SCEPs showed lower sensitivity (46.1%) in the total number of cases. Both SCEPs showed high specificities. The sensitivities of ventral SCEP, dorsal SCEP, and either SCEP were 100.0%, 50.0%, and 100.0% for the upper cervical spinal cord, 33.3%, 0%, and 55.6% for the lower cervical spinal cord, and 77.8%, 64.7%, and 88.2% for the thoracic spinal cord. Combined recording of both SCEPs estimated the ventral and dorsal white matter function in the spinal cord. Measuring the SCEPs with the nasopharyngeal electrode can be another useful approach for upper cervical and thoracic spinal cord monitoring. Ventral SCEP was more reliable for monitoring postoperative spinal cord function than dorsal SCEP. Ventral SCEP does not estimate the gray matter and spinal root functions in the lower cervical spinal cord.

Surgical approaches: postoperative care and complications “transoral–transpalatopharyngeal approach to the craniocervical junction”

The ventral approach to the craniocervical border has been described for decompression of irreducible extradural pathology. The procedures utilized encompass the transoropharyngeal and median mandibulotomy with glossotomy and the transpalatal procedures. This study was aimed to review the utility of the transoral-transpalatopharyngeal approach. Seven hundred thirty-three patients underwent transpalatopharyngeal approach for decompression of the brain stem and cervicomedullary junction. Of these, 280 were children below the age of 16 years. The main indication was irreducible ventral pathology compressing the brain stem and cervicomedullary junction. Two hundred two children had irreducible basilar invagination, 28 had proatlas segmentation abnormalities, os odontoideum with a dystopic os odontoideum in 30, and spinal tumors in seven (chordoma, fibrous dysplasia, osteoblastoma). Seven patients with Down's syndrome and irreducible bony compression of the ventral cervicomedullary junction were seen. There were six other miscellaneous diagnoses. All children required craniocervical stabilization which was carried out under the same anesthetic as the transoral procedure. The procedure entailed fiber-optic intubation. The patient was placed in cervical traction prior to the anterior procedure. The soft palate was split only in individuals with a short clivus with a high riding clivus-odontoid articulation. Craniocervical stabilization was performed in the prone position under the same anesthetic. There was one retropharyngeal infection postoperatively. No cesium fluoride leaks were encountered. Velopalatine incompetence was seen in five children who already had preoperative brain stem dysfunction. Neurological recovery was the rule. Patients who had preoperative syringohydromyelia had resolution of the syrinx on postoperative magnetic resonance imaging. The author's technique is described. Since 1977, the procedure has been performed in 732 patients (280 children) and has evolved into a safe and direct approach to the ventral cervicomedullary junction with minimal morbidity and mortality.

Spinal Neurenteric Cysts in the Magnetic Resonance Imaging Era

Neurenteric cysts are derived from displaced entodermal tissue. They are infrequently found in the ventral spinal canal with varying degrees of success in their removal. Experience with 10 such individuals is critically analyzed to aid in the diagnosis and management. Ten patients, ages 4 through 55 years, with neurenteric cysts were encountered in the last 20 years. This series included three females and seven males; seven children and three adults. The follow-up periods ranged from 3 to 18 years. Three cysts were located at the ventral cervicomedullary junction, five in the midventral cervical spine, and one thoracic and one lumbosacral. The symptoms reflected the location. Six of the 10 patients had associated bony abnormalities such as bifid clivus, hemivertebrae, segmentation failures at the site of the lesion, and blocked vertebra. The patient with the thoracic spinal lesion (age, 55 yr) had symptoms from early childhood. A diplomyelia at the site of the lesion was seen in one individual and tethered spinal cord in the same adult and in a young child. Two patients had undergone laminectomy for aspiration and partial resection before referral to our institution at the time of recurrence. Cervicomedullary junction lesions were approached via the far lateral transcondylar approach; two of the cervical intramedullary lesions were resected via a ventral corpectomy with radical resection and interbody fusion. The goal in each case was complete resection to avoid recurrences. Spinal neurenteric cysts are ventrally located, usually intradural and extramedullary, but may insinuate into the spinal cord. They are isointense on T1 images and hyperintense on T2-weighted images on magnetic resonance imaging without true enhancement. These lesions may be associated with block and hemivertebrae with a predisposition to the craniocervical region. Partial resections have led to recurrence and arachnoiditis.

Frameless Stereotactic Guidance

The application of a video-interactive frameless stereotactic guidance system for the treatment of ventral cervicomedullary junction compression is described in a patient with basilar invagination, odontoid dysgenesis, and a Chiari malformation who had irreducible impingement on the ventral brainstem by a partially fused mass of bone made up of the malformed odontoid peg, the inferior clivus, and dorsally protruding osteophytes at the odontoid-clival junction. This technology permitted instantaneous feedback of the surgeon's orientation in all planes, facilitating extensive removal of the dens and clival tip to achieve adequate ventral brainstem decompression. In view of the distortion of the craniovertebral anatomy produced by the patient's anomalies, the ability to visualize three dimensionally the location of the vertebral arteries also added an element of safety to the lateral bone removal. Similarly, the ability to localize the rostral limit of the clivus that needed to be resected and the caudal extent of C2 that needed to be removed to achieve an adequate decompression helped ensure that the extent of bone removal was appropriately tailored to the patient's anatomy. The authors believe this technique represents a significant advance over standard radiographic intraoperative localization techniques during transoral approaches to the ventral cervicomedullary junction for patients in whom the odontoid is fixed in position in relation to the clivus. This is based on the speed with which localization can be obtained, the accuracy of the information provided, the ability to obtain localization in multiple planes simultaneously, and the lack of radiation exposure during the procedure.