Diagnostic and prognostic value of nerve ultrasound in peripheral nerve disease

Abstract

Diagnosing peripheral nerve disease and predicting disease course can be challenging. Nerve conduction studies (NCS) have been the hallmark in diagnosing nerve disease, but these are often inconclusive and require electric shocks to determine nerve function, which may be burdensome. Nerve ultrasound is a new technique which is cheap, well tolerated, and allows investigation of anatomy of multiple nerves in short time. Several aspects of diagnostic and prognostic value of nerve ultrasound were investigated in this thesis. In chapter 2 currently available literature on nerve ultrasound in polyneuropathy was evaluated. In chapter 3 interobserver variability of nerve ultrasound was investigated. In a multicenter study we found that there were no large systematic differences between investigators, and that performance of nerve ultrasound in different hospitals or on different sonographic devices had no significant influence on results. These findings support that ultrasound is a reliable technique that can be applied reliably in daily clinical practice. In chapter 4 and 5 diagnostic value of nerve ultrasound in chronic inflammatory polyneuropathies was investigated. We investigated patients suspected of chronic inflammatory polyneuropathy in a monocenter and multicenter cohort. The studies showed that a short nerve ultrasound protocol can reliably detect chronic inflammatory neuropathy. Moreover, it allows identification of up to 25% additonal patients with a treatment-reponsive neuropathy compared to conventional NCS. In chapter 6 we investigated prognostic value of nerve ultrasound in chronic inflammatory neuropathies. We investigated 237 patients with axonal and demyelinating polyneuropathy in a multicenter cohort study . We found that development of complaints and sonographic abnormalities varied greatly among patients. In contrast to its diagnostic value, prognostic value of nerve ultrasound in these neuropathies thus seems limited. In chapter 7 and 8 we investigated applications of nerve ultrasound in neurofibromatosis type 1 (NF1), a hereditary disorder associated with nerve tumors. These nerve tumors are benign, but are at risk of malignant transformation. We found a wide range of sonographic abnormalities. Nerve ultrasound could, thus, help to identify patients with higher risk of malignancy. However, our studies also show that nerve ultrasound is currently unable to reliably detect tumor growth. Therefore, a reliable screening strategy for detection of malignant nerve tumors in NF1 will have to be developed. In chapter 9 we describe sonographic abnormalities in neurofibromatosis type 2 (NF2). This disorder is mainly associated with vestibular schwannomas, which are localized near the central nervous system, but in our study we also find frequent involvement of peripheral nerves. In conclusion, nerve ultrasound is a reproducible technique that may yield very useful diagnostic information, especially in case of chronic inflammatory neuropathies. It not only allows detection of patients that would otherwise only be detected by burdensome diagnostic tests, but even improves detection of treatment-responsive patients. Nerve ultrasound is currently less useful as a prognostic or screening tool. Nonetheless, nerve ultrasound is a very useful tool that should be added to standard work-up of patients with peripheral nerve disorders.