Chapter 8 140 Figure 8.2 Proposal of revision of diagnostic criteria for MMN Clinical suspicion of MMN Ultrasound available? Perform ultrasound1 Perform NCS3 Yes No No other diagnosis based on additional laboratory findings2 Start of treatment Definite MMN t+ Perform NCS3 tDefinite, probable or slowing of conduction Inconclusive Definite MMN Possible MMN Definite Definite MMN Probable Slowing of conduction Inconclusive CSF protein < 1 g/L Probable MMN Elevated anti-GM1 antibodies or abnormal MRI4 Possible MMN Possible MMN CSF protein < 1 g/L T+ TT+ Consider alternative diagnosis TThis flow chart summarizes results from recent diagnostic nerve ultrasound and MRI studies on diagnosis of MMN and integrates them in the current diagnostic Utrecht criteria.24 1 Examination of the median nerve in the forearms (> 10 mm2), upper arms (> 13 mm2) and C5 nerve root (> 8 mm2). Abnormal when ≥ 1 measurement site is enlarged. 2 Additional laboratory examination consists of determination of protein in cerebrospinal fluid, serum anti-GM1 antibodies and exclusion of other (metabolic) causes of neuropathy (e.g. diabetes, hypothyroidism, liver or renal insufficiency, vitamin deficiencies). 3 Results of NCS should be interpreted according to the Utrecht electrodiagnostic criteria.24 4 Supportive criteria of MMN can be found in Table 8.1. MRI should be quantitatively assessed. 5 Results of MRI examination should be quantitatively assessed and interpreted using the risk chart in chapter 4, Figure 4.3 Abbreviations: MMN = multifocal motor neuropathy; NCS = nerve conduction studies; CSF = cerebrospinal fluid; MRI = magnetic resonance imaging; T+ = positive result of test; T- = negative result of test; t+ = good treatment response; t- = no treatment response.
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