[Direct trans-sylvian approach to the ventrolateral pons in surgical management of large cystic cavernous malformations of the brain stem in children].

OBJECTIVES

In the study surgical indications are reviewed and the effect of the applied surgical technique on long-term treatment outcome in children with large cystic brainstem cavernous malformations is evaluated.

METHOD

Clinical data of 5 patients treated surgically for large cystic cavernous malformations of the pons in the years 1995-2001 were retrospectively evaluated. In all the cases the transsylvian approach to the ventrolateral pons with splitting of the crus cerebri was used to reach cavernoma within the cystic cavity. The long-term follow up (mean 4.9 years) included a complete neurological examination and annual MRI studies.

RESULTS

At least one hemorrhagic episode was diagnosed in all the cases, while bleeding to the pons, with clinical course mimicking that of stroke, was noted twice in 3 patients. All the episodes confirmed by MRI imaging appeared to be intralesional. The malformations ranged in size from 30 to 50 mm (mean 36.9 mm). Their most characteristic MRI features were not only the localization in the pontine structure exclusively i.e. within the natural anatomical barriers separating the pons from the midbrain and medulla, but also the growth pattern corresponding to that of brainstem benign gliomas. The patients' mean preoperative KPS score was 60 (30 to 90). Cavernous hemangiomas were totally removed in 3 out of 5 cases. One patient with partially removed lesion presented after a year recurrent hemorrhage and new neurological deficits that required a second stage surgery. In all but one case transient complications included some new cranial nerve, motor and sensory deficits that influenced the patients' immediate postoperative KPS assessment, with the mean score of 48. In a follow-up assessment at 1.5 to 7 years, a significant amelioration of both their neurological status and quality of life was found, with KPS scores from 70 to 90 (mean score 80). Annual MRI examinations showed extensive hemosiderin deposits within the pontine tissue in 3 cases of totally removed cavernous hemangiomas and this image was stable during the follow-up period.

CONCLUSIONS

The findings suggest that resection of large pontine cavernomas in children is indicated in cases of symptomatic hemorrhage with lesions approaching the pial surface, or surrounded by a small margin of normal tissue. Recurrent hemorrhages are intralesional (i.e. limited to pontine structures by the natural anatomical barriers), resulting in a "cyst-like" growth of malformations mimicking that of focal neoplasms and in compression of the brain stem tissue rather than in a direct hemorrhagic insult.