Spinal tumors in neurofibromatosis type 2. Is emerging knowledge of genotype predictive of natural history?

OBJECT: The authors conducted a study to examine the incidence, classification, and progression of spinal tumors in patients with neurofibromatosis Type 2 (NF2) treated at a single center, and to examine relationships with the known mutational subtypes of NF2.
METHODS: They performed a retrospective review of clinical records, neuroimaging studies, and genetic data obtained in 61 patients with NF2. Forty-one (67%) of 61 patients harbored one or more spinal tumors. Thirty-four patients had undergone serial spinal magnetic resonance imaging during a mean follow-up period of 52 months (range 10-103 months; median 53 months). In 16 patients there were multiple extramedullary tumors smaller than 5 mm, which did not progress. Fourteen patients harbored at least one extramedullary tumor that was greater than 5 mm; of these, radiological progression was demonstrated or spinal tumor excision was performed during the follow-up period in eight cases (57%). Eleven patients harbored intramedullary cord tumors in addition to small and large extramedullary tumors, three (27%) of which exhibited radiological progression. In cases in which genotypes were known, protein-truncating mutations were significantly more likely to be associated with the presence of spinal tumors than in other types (p = 0.03, Fisher exact test). No associations between clinical behavior of spinal tumors and genotype, however, could be demonstrated.
CONCLUSIONS: Spinal tumors in cases involving NF2 are heterogeneous in type, distribution, and behavior but larger-size tumors are more likely to progress significantly. Intramedullary tumors usually accompany multiple extramedullary tumors. In the authors' experience subtyping of the NF2 mutation has not yet influenced management. Protein-truncating mutations are associated with an increased prevalence of spinal tumors.