Tumors of Posterior Cranial Fossa and Their Surgery

V.A. Khachatryan, A.V. Kim, K.A. Camochernykh

(Polenov Research Neurosurgical Institute, Saint Petersburg)

Some conceptual aspects, concerning neuroectodermal subtentorial tumors, are referred to children’s neurosurgery. It appears, that one of the optimum ways of improving results and developing new surgical approaches is a retrospective analysis of different treatment-and-diagnostic concepts, based on numerous and adequately verified clinical data. Thus, we studied treatment outcomes in 446 children, aged 1-18. All of them had tumors of the posterior cranial fossa and were treated during 1981-2006.

Estimation of a blastomatous process consisted in comparison of clinical, introscopic (CT, MRI, ultrasonography, PET, SPECT), electrophysiologic examinations with intraoperative ultrasonic navigation, biochemical monitoring and morphometry.

Treatment results were assessed by determining dynamics of a blastomatous process before and after operation. Astrocytomas and medulloblastomas were the most spread neoplasms. They were diagnosed in 42% and 31% of cases respectively. Among other tumors one can mention ependimoma, choriopapilloma, dermoid, teratoma, neurinoma, glioblastoma, angioreticuloma, etc.

Total and subtotal resection was achieved in 63% of cases. Partial resection was performed in 24% patients. The rate of mortality in the nearest postoperative period (during a month) was 8.6%. This index in a more remote period (during a year) was 13%.

The analysis of results demonstrated dependence both of an intraoperative state of a patient and treatment outcome (resection extent, mortality, a relapse-free period) on a degree of the stem involvement into a blastomatous growth zone.

As for surgical microanatomy, we suggest, that the rhomboid fossa area should be divided into vitally significant, eloquent and non-eloquent zones. When vitally significant zones of the stem are involved into a blastomatous process, total resection of a tumor, accompanied by persistent disorders of vital functions, is inexpedient. Manipulations, aimed at total resection in involvement of eloquent areas of the stem, result in persistent neurological disturbances; thus, they can be performed only in presence of some additional indications. Striving for total resection of a tumor is justified in all other versions of structural-and-functional organization of a blastomatous process.

Other peculiarities of a blastomatous growth, watched in children (age, disease duration, a tumor volume), have a small effect on an operation course and outcome.

Introduction of this concept into practice at the last stages of our research (2000-2006) led to a reliable increase of operation efficacy and reduction of postoperative mortality and complications.