Distinct Imaging Features of Peripheral Nerve Sheath Tumours in <i>NF2</i> ‐Related Schwannomatosis: A Case Report

Signs of a mononeuropathy are a frequent manifestation of <i>NF2</i>-related schwannomatosis in childhood. The here presented nerve imaging characteristics, however, did not correspond to classic schwannomas. The fusiform, long-extended, multifascicular enlargement with mixed hyper- and hypoechogenic components on ultrasound, as well as markedly T2-hyperintense and T1-isointense appearance with diffuse gadolinium enhancement on MRI, is consistent with perineurioma. These mesenchymal nerve tumours have rarely been described in <i>NF2</i>-related schwannomatosis. This association is further supported by the present case and highlights the necessity for additional peripheral nerve imaging studies in NF2-related schwannomatosis, including the application of high-resolution ultrasound.