Growth dynamics of intramedullary spinal tumors in patients with neurofibromatosis type 2

Volumetric data on the natural growth of intramedullary tumors in patients with neurofibromatosis type 2 (NF2) are rare, but crucial for long-term disease monitoring. Our aim was to evaluate the growth rates and growth patterns of these tumors.

Patient records from the regional neurofibromatosis referral center were evaluated for inclusion in this analysis. Magnetic resonance images of the spine were collected and digitized as necessary. Tumor volumes were determined by volumetric extrapolation after segmentation in datasets (iPlan Net software, BrainLAB, Munich) if the tumors met the following inclusion criteria: sagittal T2-weighted MRI scans had to be available from at least two investigations and tumors had to be visible on at least two slices. All tumors that had undergone previous therapy, such as surgery, radiation or bevacizumab treatment were excluded from this study.

Suitable MR images of the spine were available from 51 patients (20 males, 31 females) with NF2. The median follow-up time per patient was 54 months (range 0-190 months). 23 patients (15 females, 11 males) of the 51 patients with spinal imaging harbored intramedullary tumors. Across this cohort, there was an aggregate of 68 tumors at baseline. Over the course of follow-up, the patients developed 19 additional tumors, resulting in a total of 87 tumors. A final set of 42 tumors from 19 patients met the inclusion criteria and was included in the growth analysis. The median follow-up time per tumor was 44 months (range 9-122 months). 23 of the tumors were located in the cervical spine; 19 of them were located in the thoracic spine. The median tumor size±standard deviation (SD) after 5 years was 136±71.0% compared to baseline. The median time to ≥20% tumor growth was 24 months. Overall, 30 tumors (71.4%) grew, 8 (19.1%) remained stable and 4 (9.52%) decreased in size. The most common growth pattern was saltatory growth.

Intramedullary spinal cord tumors are present in about half of patients with NF2. The majority of these tumors grow over time, albeit slowly. Given the confines of the spinal medulla and the limited scope for functional recovery after symptomatic tumor expansion, NF2 patients should be under continual surveillance in order to rapidly identify intramedullary spinal tumors that may require microsurgical resection.