RESUMEN
PURPOSE: To examine long-term alterations of the dorsal root ganglia (DRG) and the peripheral nerve in patients with neurofibromatosis type 2 (NF2) by in vivo high-resolution magnetic resonance neurography (MRN) and their correlation to histology. METHODS: In this prospective study the lumbosacral DRG, the right sciatic, tibial, and peroneal nerves were examined in 6 patients diagnosed with NF2 and associated polyneuropathy (PNP) by a standardized MRN protocol at 3â¯T. Volumes of DRG L3-S2 as well as peripheral nerve lesions were assessed and compared to follow-up examinations after 14-100 months. In one patient, imaging findings were further correlated to histology. RESULTS: Follow-up MRN examination showed a non-significant increase of volume for the DRG L3: +0.41% (pâ¯= 0.10), L4: +22.41% (pâ¯= 0.23), L5: +3.38% (pâ¯= 0.09), S1: +10.63% (pâ¯= 0.05) and S2: +1.17% (pâ¯= 0.57). Likewise, peripheral nerve lesions were not significantly increased regarding size (2.18â¯mm2 vs. 2.15â¯mm2, pâ¯= 0.89) and number (9.00 vs. 9.33, pâ¯= 0.36). Histological analyses identified schwannomas as the major correlate of both DRG hyperplasia and peripheral nerve lesions. For peripheral nerve microlesions additionally clusters of onion-bulb formations were identified. CONCLUSION: Peripheral nervous system alterations seem to be constant or show only a minor increase in adult NF2. Thus, symptoms of PNP may not primarily attributed to the initial schwannoma growth but to secondary long-term processes, with symptoms only occurring if a certain threshold is exceeded. Histology identified grouped areas of Schwann cell proliferations as the correlate of DRG hyperplasia, while for peripheral nerve lesions different patterns could be found.