Marieke van Rosmalen

Chapter 8 130 and treatment options of MMN and MND differ considerably. Patients with MMN have a normal life expectancy while median survival time in patients with MND, in particular ALS, is 3-5 years. 11 Furthermore, MMN responds to treatment with immunoglobulins while there are no symptomatic or curative treatment options for MND. 12 It is important to note that treatment options between MMN and CIDP differ. MMN does not respond to treatment with corticosteroids or plasmapheresis and symptoms may even deteriorate following the start of corticosteroids. Differentiation between MMN and (the atypical variants of) CIDP is therefore also important. An early start of treatment with immunoglobulins in MMN slows progression of symptoms although treatment cannot always prevent the development of permanent axonal damage. 12,13 Unlike CIDP, a lot is unknown on the other factors that influence disease progression and prognosis in MMN. Therefore, we performed a combined cross-sectional and longitudinal study in chapter 2 to explore the natural history of patients with MMN and to define predictive factors for disease progression and prognosis. This study confirms that, in the large majority of patients, MMN is a progressive disorder, despite the fact that 87% of the patients were treated with immunoglobulins. This finding corroborates with findings in earlier smaller studies on natural history in patients with MMN (n = 11 – 46). 13–15 We found that predictors of a progressive disease course (i.e. a larger decrease of the Medical Research Council (MRC) sum score over time) were (1) the absence of at least one reflex at baseline and (2) more weakness (i.e. a lower MRC sum score) at baseline. We also found that more severe weakness was influenced by a longer disease duration before treatment and the presence of serum anti-GM1 antibodies, which is similar to findings of previous studies. 16–18 These findings indicate that it is crucial to reduce the time to diagnosis and start treatment as early as possible in order to prevent more severe weakness and disease progression. Improvement of the diagnostic value of the currently available diagnostic tools, such as MRI, could help to reduce the time to diagnosis. Diagnosis The next part of this thesis focuses on diagnosis of CIDP and MMN. Several sets of different diagnostic consensus criteria have been developed for CIDP and MMN, which underlines the difficulty of diagnosing these chronic inflammatory neuropathies. The diagnostic criteria for CIDP and MMN consist of a combination of a characteristic clinical presentation and specific features on nerve conduction studies (NCS). The criteria of the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/ PNS) seem to be the most accurate and widely used set of criteria for CIDP. 19 This was established by a study that compared 15 diagnostic criteria sets for CIDP. They found that the criteria of the EFNS/ PNS had the highest sensitivity (73%) and specificity (91%). 20 Another study exclusively focused on comparison of three sets of electrodiagnostic criteria for CIDP and also found highest sensitivity (81%) and specificity (79-96%) for the EFNS/PNS criteria. 21 Therefore, we based our evaluation