Surgical management of tumors producing the thalamopeduncular syndrome of childhood

Abstract

Object: Thalamopeduncular tumors arise at the junction of the inferior thalamus and cerebral peduncle and present with a common clinical syndrome of progressive spastic hemiparesis. Pathologically, these lesions are usually juvenile pilocytic astrocytomas and are best treated with resection with the intent to cure. The goals of this study are to define a common clinical syndrome produced by thalamopeduncular tumors and to discuss imaging characteristics as well as surgical adjuncts, intraoperative nuances, and postoperative complications relating to the resection of these neoplasms.

Methods: The authors present a retrospective review of their experience with 10 children presenting between 3 and 15 years of age with a thalamopeduncular syndrome. Formal preoperative MR imaging was obtained in all patients, and diffusion tensor (DT) imaging was performed in 9 patients. Postoperative MR imaging was obtained to evaluate the extent of tumor resection. A prospective analysis of clinical outcomes was then conducted by the senior author.

Results: Pilocytic astrocytoma was the pathological diagnosis in 9 cases, and the other was fibrillary astrocytoma. Seven of 9 pilocytic astrocytomas were completely resected. Radical surgery was avoided in 1 child after DT imaging revealed that the corticospinal tract (CST) coursed through the center of the tumor, consistent with the infiltrative nature of fibrillary astrocytoma as identified by stereotactic biopsy. In 8 patients, tractography served as an important adjunct for designing a surgical approach that spared the CST. In 6 cases the CSTs were pushed anterolaterally, making a transsylvian approach a poor choice, as was evidenced by the first patient in the series, who underwent operation prior to the advent of tractography, and who awoke with a dense contralateral hemiparesis. Thus, subsequent patients with this deviation pattern underwent a transcortical approach via the middle temporal gyrus. One patient exhibited medial deviation of the tracts and another had lateral deviation, facilitating a transtemporal and a transfrontal approach, respectively.

Conclusions: The thalamopeduncular syndrome of progressive spastic hemiparesis presenting in children with or without symptoms of headache should alert the examiner to the possibility of a tumoral involvement of CSTs. Preoperative tractography is a useful adjunct to surgical planning in tumors that displace motor pathways. Gross-total resection of pilocytic astrocytomas usually results in cure, and therefore should be entertained when developing a treatment strategy for thalamopeduncular tumors of childhood.

Fig. 1

Illustrative neuroimaging studies. Eight of 9 tumors in this series demonstrated pilocytic histological features. Some tumors were solid and some included cystic components. All lesions displayed variable contrast enhancement. One tumor was thought to be a glioblastoma based on imaging findings because of the heterogeneous enhancement pattern; however, results of stereotactic biopsy sampling proved it to be pilocytic.

Fig. 2

Large left thalamopeduncular tumor. Axial T2-weighted MR image (A) revealing a hypodense structure passing through the posterior aspect of the lesion. The DT imaging color map (B) and fractional anisotropy map (C) demonstrated that the hypodense structure on T2- weighted imaging was the CST (blue arrows) passing directly through the tumor. The right-hand panels are enlarged views of the areas of interest.

Fig. 3

Left thalamopeduncular pilocytic astrocytoma. A: Composite of 3 axial T1-weighted Gd-enhanced MR images demonstrates that the tumor arises from the lateral aspect of the peduncle underneath the thalamus, pushing the normal thalamus superiorly. The thalamic displacement made a transcallosal approach to the tumor a poor choice, because the surgeon would have violated the normal thalamus to reach the tumor. B: The optic tract, a structure that must be carefully avoided in removing the tumor, is deviated superior and lateral to the tumor. The arrow designates the optic tract. C: An axial DT image of the same tumor shows the CSTs deviated anteriorly and laterally (arrow; CSTs are in blue); this was the most common pattern of CST displacement in this series, noted in 7 of 10 patients. This pattern of tract displacement made a transsylvian approach unattractive; one would have to transect the tracts to reach the tumor. D: The authors chose an approach through the middle temporal gyrus by using frameless stereotactic navigation to approach the tumor just posterior to the CSTs.

Fig. 4

Left thalamopeduncular cystic and solid pilocytic astrocytoma. A: A coronal FLAIR MR image demonstrating that the tumor grows from the thalamopeduncular junction, across the ambient cistern, and through the choroidal fissure of the temporal horn of the lateral ventricle to invade the middle fossa. B: Coronal DT images showing that the CSTs are displaced medial to the tumor. Medial tract displacement made an image-guided approach through the middle temporal gyrus optimal to reach both the superior and inferior extent of the neoplasm. C: A coronal T2-weighted MR image obtained the day after surgery, demonstrating the approach through the temporal lobe and a gross-total resection of the tumor, sparing the CSTs.

Fig. 5

Pilocytic tumor in a 3-year-old child presenting with spastic hemiparesis. A: Axial T2-weighted MR image showing displacement of the thalamus anterior and posterior to the tumor. B: A DT imaging color map. The arrows (tracts in blue) designate the CST. C: A fractional anisotropy map demonstrating that in this case the CSTs (arrows) were draped around the lateral aspect of the tumor, which made a lateral approach unattractive. D and E: Sagittal T1-weighted MR images showing previous biopsy track; note enhancement of the track. F: The authors chose to use the previous biopsy track, a transfrontal corticotomy, to remove the tumor; the patient’s hemiparesis improved postoperatively.

Fig. 6

Left: Thalamopeduncular tumor with cystic component and heterogeneous enhancement. Right: Postoperative sagittal Gd-enhanced MR images reveal the resection cavity and illustrate the multifocal nature of the tumor.