Aims: To characterise the natural history of vestibular, trigeminal and lower cranial nerve schwannomas (VS, TS, LCNS) in patients with Neurofibromatosis type 2 (NF2). To understand how pathogenic variants (PVs) of the NF2 gene affect tumour burden and growth rate.
Method: Retrospective analysis of a UK NF2 centre database and imaging. VS, TS and LCNS location and size were measured in accordance with a standardised protocol. PVs were categorised in accordance with the UK NF2 Genetic Severity Score (GSS).
Results: 153 patients (age 5-82) had 458 schwannomas, of which 362 were previously untreated comprising: 204 VS, 93 TS, and 65 LCNS (IX, X, XI). 322 schwannomas had sequential imaging allowing growth rate analysis with a mean follow-up of 45 months.
VS were universally present, and bilateral in 146/153 cases. 65% of tumours grew >2mm during the study period at mean rate 2.0mm/year. Significant association was found between increasing GSS and growth rate. TS occurred in 66/153 patients (bilateral in 27/153); 31% of tumours showed growth (mean 1.8mm/yr). Significant increase in tumour prevalence was noted with increasing GSS. LCNS were found in 47/153 patients (bilateral in 19/153); 27% of tumours showed growth (mean 1.9mm/yr). The trend for increased prevalence with increasing GSS did not reach significance.
Conclusion: We found that VS growth rate was significantly influenced by GSS and they were much more likely to grow than TS and LCNS. TS prevalence also correlated with increasing GSS.