Preoperative diffuse leptomeningeal spread in a medulloblastoma: Paraplegia following surgery for posterior fossa and call for newer management protocols.

Management of patients with medulloblastoma presenting with multiple metastasis in subarachnoid space preoperatively is unclear. An 11-year-old boy presented with vermian medulloblastoma with an unusually long segment cervico-dorsal lesion and suprasellar lesion. The child underwent a posterior fossa craniotomy (prone position) and excision of vermian mass. He developed paraplegia in the immediate postoperative period, the possible causes for which are being discussed. Besides, treatment options for patients presenting with disseminated disease preoperatively have been highlighted. Preoperative chemotherapy to downstage such lesions may be tried and such complications could be avoided.

Introduction

Medulloblastoma constitutes 20% of all childhood primary CNS tumors.[1] Metastasis of medulloblastoma can be found in both neuraxis and extraneural locations. Supratentorial metastasis is found in 14.6% of cases, intraspinal mets in 12.5%, and systemic metastasis in 9.7%.[1] The management of patients who present with diffuse leptomeningeal spread preoperatively has not been clearly defined.

Case Report

An 11–year-old boy presented with progressive headache and gait ataxia for 1 year. On examination he was found to have only cerebellar ataxia with no signs suggestive of spinal cord involvement. He was investigated with cranio-spinal contrast MRI, which showed three lesions, one in the region of the vermis and the other in the suprasellar region and long segment cervico-dorsal region [Figures 1, 2a–b and 3a–b]. The lesions were hypointense on T1W, and hyperintense on T2 with heterogenous contrast enhancement. The right ventriculo peritoneal shunt was inserted as the patient had features of raised ICP with hydrocephalus. The CSF workup was normal and negative for malignant cytology. The headache improved to some extent following shunt. However, the ataxia persisted. Three days later he underwent posterior fossa craniectomy and excision of vermian mass. He was operated in prone position with flexion at atlanto-occipital joint, thereby opening up the operative site, taking care not to overflex to avoid blocking the venous drainage or airway. The intraoperative period was uneventful. The patient had paraplegia in the immediate postoperative period. The sensory loss was below first dorsal segment. There was minimal improvement in sensory loss but none in motor power in 1 week. In view of his repeat MRI spine showed no hemorrhage in the spinal lesion or in the tumor bed. The relatives did not give consent for surgery for spinal metastasis. There was minimal improvement in sensory loss but none in motor power in 1 week. In view of his lower cranial nerve palsies he was tracheostomized. Unfortunately he succumbed to trachea-innominate fistula, a week after his surgery.

Figure 1

Mid-sagittal MRI showing fourth ventricular mass and sellar mass

Figure 2

(a) Mid-sagittal MRI of cervico-dorsal showing dorsally placed lesion extending from C3 below. (b) Mid-sagittal MRI of cervico-dorsal showing dorsally placed lesion, expanding the spinal subarachnoid space above and below the lesion

Figure 3

(a) Axial T2 MRI showing mass in dorsal posterior aspect of the cord. (b) Another axial T2 MRI showing mass in dorsal posterior aspect of the cord

Discussion

Drop metastasis from the primary location to anatomically lower sites including whole-spinal cord is known as a potential way for tumors like medulloblastoma to spread and are seen in approximately 40% of patients. The high incidence of involvement of the lumbosacral region shows the effect of gravity on CSF borne metastases. Disseminated plaques and nodules are also more common in the dorsal region, supporting the theory of spread along the CSF pathways as the normal caudal flow of CSF is along the dorsal aspect of the cord. By far the most common presentation is that of the intradural, extramedullary type though intramedullary metastases are also reported.[2] The presence of leptomeningeal metastasis in medulloblastoma is used for clinical staging and is already demonstrated as an independent prognostic factor.[3] “Early drop metastasis” is used to describe the group of patients with positive preoperative or immediate postoperative (less than 1 month) MRI findings. “Late drop metastasis” has been defined by new image evidence of leptomeningeal enhancement found after the primary surgical procedure with at least one negative prior whole-spine MRI examination. Leptomeningeal metastases found at presentation seem not to be a prognostic factor though late drop metastasis reflects the relative resistance of adjuvant therapy and may be viewed as a possible poor prognostic factor in this small patient group.[3]

The uniqueness of this case lies in the fact that the spinal drop metastases were sheetlike extending from the C3 to D8 region. This patient had presented with features of only cerebellar ataxia. Postoperatively he became paraplegic. Postoperative paraplegia following nonspinal surgical procedures is very rare.[4] The causes of postoperative paraplegia following posterior fossa surgery could be the following: intraoperative patient position, overflexion of neck and/or imbalance of the subarachnoid pressure between rostral and caudal thoracic spine, and by removing CSF at the operative site.

Another possibility was that the contamination of CSF with blood after posterior fossa surgery could lead to the development of a symptomatic spinal hematoma being explained by the movement of blood from the tumor bed into the spinal canal under the effect of gravity, during or after the surgery. Meticulous homeostasis and isolation of the surgical area from the spinal space with avoidance of over drainage of CSF have been stressed upon.[5]

The hydrodynamic changes that occur following a shunt placement can be speculated as another cause of paraplegia following surgery for nonspinal lesions.

The current staging stratifies patients harboring these tumors in two groups, a high risk and a low risk group, with the mainstay of treatment being surgery, craniospinal irradiation, and chemotherapy.[1] However, the exact management for patients presenting with disseminated leptomeningeal spread prior to surgery (high risk), like in our case, is not clear.

We would like to discuss two new options regarding the management of medulloblastoma with disseminated metastases. The first option is the administration of neoadjuvant chemotherapy in order to downstage the tumor, followed by surgery and radiotherapy. Ricco et al. reported on three cases of presumed medulloblastomas who were preoperatively treated with chemotherapy consisting of high doses of carboplatin alone. The treatment improved the clinical condition prior to surgery and facilitated tumor removal, resulting in partial regression of tumor. The preoperative single-drug therapy did not affect the histological diagnosis or prevent the presence of an effective degree of tumor sensitivity to the drug and all the three children were disease-free for a mean period of 42 months.[6] Multidrug chemotherapy after a endoscopic/small biopsy has shown to reduce the tumor bulk significantly, downstaging the tumor and making total excision feasible.[7]

Another option would be to operate on the drop metastases, especially those with long segment involvement, in the same sitting. The literature search did not reveal any studies which had dealt with this kind of management. Besides, it may not be feasible in cases with long segment involvement like in our case.

Conclusion

Presently there is no set protocol for the management of disseminated medulloblastomas. The possibility of neoadjuvant chemotherapy and/or single sitting surgical intervention for drop metastases needs to be explored in order to improve the outcome for such lesions.