Experiences with the Telovelar Approach to Fourth Ventricular Tumors in Children

Abstract

Background: Fourth ventricular tumors are amongst the most common tumors in the pediatric population. Traditionally, these tumors are approached through the cerebellar vermis, but the telovelar approach is now becoming widespread. Posterior fossa syndrome/cerebellar mutism is a complication of surgery for fourth ventricular tumors whose precise cause remains elusive, but may be related to the surgical approach or injury to adjacent cerebellar structures. We present a small series of fourth ventricular tumors and our initial experience in using the telovelar approach for this surgery. Methods: Twenty patients with fourth ventricular tumors were operated on using the microsurgical telovelar approach, sparing the cerebellar vermis. Data were collected prospectively for all patients with respect to the degree of resection achieved, complications and the incidence of posterior fossa syndrome. Results: A complete resection was achieved on postoperative MRI in 70% of the patients. Residual disease <1.5 cm³ remained in 15% and a further 15% had subtotal resection with >1.5 cm³ of residual disease. Thirty percent had evidence of posterior fossa syndrome in the postoperative period, of which 84% had resolved at the last follow-up. Thirty percent of the patients developed symptomatic hydrocephalus requiring shunting. There were no new neurological deficits and no procedure-related deaths. Conclusion: The telovelar approach provides excellent access to tumors of the fourth ventricle with sparing of the vermis in children. The high incidence of cerebellar mutism in our patients confirms that this phenomenon is unlikely to be related to vermian injury and further study is recommended.

Microsurgical management of pediatric ependymomas of the fourth ventricle via the trans-cerebellomedullary fissure approach: A review of 26 cases

“…The traditional approach for removing ependymomas of the fourth ventricle is incision of the cerebellar vermis, which, however, is often associated with a higher incidence of cerebellar mutism or posterior fossa syndrome, along with chronic neurocognitive sequelae, compared with the trans-CMF appr oach (13,(18)(19)(20)(21)24,25,(41)(42)(43). The trans-CMF approach to the fourth ventricle, which does not cause significant injury to the neural tissue, was first proposed by Matsushima et al (36), and is currently widely accepted (8,13,14,(18)(19)(20)(22)(23)(24)(25)(26)(29)(30)(31)(32)36,43).…”

“…The trans-CMF approach to the fourth ventricle, which does not cause significant injury to the neural tissue, was first proposed by Matsushima et al (36), and is currently widely accepted (8,13,14,(18)(19)(20)(22)(23)(24)(25)(26)(29)(30)(31)(32)36,43). As a natural cleft between the cerebellum and medulla oblongata, the CMF provides sufficient exposure of the fourth ventricle without causing neurological deficits, following incisions in the tela choroidea and inferior medullary velum (14,23,27).…”

“…Ependymomas of the fourth ventricle are usually approached with a posterior median craniotomy/craniectomy, followed by splitting of the vermis; however, this trans-vermian approach could easily injure the vermis, cerebellar dentate and globose nuclei, which may result in tremor, ataxia, atonia and cerebellar mutism, thereby affecting the prognosis (13,14,(18)(19)(20)(21)(22)(23)(24)(25). The establishment of the novel trans-cerebellomedullary fissure (CMF) approach, which provides sufficient access to the fourth ventricle without sacrificing the inferior vermis, has been associated with favorable outcomes (13,14,(18)(19)(20)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32).…”

“…The establishment of the novel trans-cerebellomedullary fissure (CMF) approach, which provides sufficient access to the fourth ventricle without sacrificing the inferior vermis, has been associated with favorable outcomes (13,14,(18)(19)(20)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32). The trans-CMF approach is gaining popularity among the available surgical approaches that are used for the complete removal of fourth ventricular tumors excessively extending laterally into the cerebellomedullary cistern ( children, ependymomas of the fourth ventricle usually originate from the ependymal layer and are well-circumscribed (1,2).…”

“…in the 12 patients with supratentorial ventricular enlargement, 3 patients with hydrocephalus received frontal ventriculostomy 2 or 3 days prior to tumor removal, and the other 9 patients underwent occipital ventriculostomy intraoperatively, prior to dural incision. As previously described (13,14,(18)(19)(20)23,30), all patients were operated on in the prone position with the head flexed at the craniocervical junction. A vertical midline incision was performed, followed by a suboccipital craniotomy/craniectomy, with a bone window of ~5.0x4.0 cm.…”