Marieke van Rosmalen

General discussion 129 8 GENERAL DISCUSSION This thesis focuses on the different clinical and imaging characteristics of chronic inflammatory neuropathies. Diagnostic, pathophysiological and prognostic characteristics are evaluated by clinical and magnetic resonance imaging (MRI) studies in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). This chapter discusses the main findings of this thesis, puts these findings into perspective of the current literature and provides recommendations for clinical practice. Disease hetero- and homogeneity Clinical presentation, treatment options and prognosis differ between patients with CIDP and MMN. CIDP has a very heterogeneous presentation. Typical CIDP (approximately 50-70% of patients with CIDP) is characterized by slowly progressive symmetric proximal and distal weakness and sensory deficits with absent reflexes in the extremities. 1,2 Symptoms are present in all extremities, but are most pronounced in the legs. 2 Variants of CIDP include focal CIDP (< 5% of patients with CIDP), distal CIDP (7-15%), multifocal CIDP (also known as Lewis-Sumner syndrome, MADSAM or MIDN, 4-15%), motor CIDP (4-9%) and sensory CIDP (4-35%). 3–5 Diagnosis of CIDP can be challenging as its atypical variants may be difficult to recognize. This might result in underdiagnosis which is undesirable as CIDP responds to treatment with immunoglobulins, corticosteroids or plasmapheresis. 6 Early treatment can improve muscle strength or sensory symptoms, and prevents progression of symptoms and permanent axonal damage. Immunoglobulins are probably the most effective treatment option (76-82% responsiveness), followed by corticosteroids (59-70% responsiveness) and plasmapheresis (58-67% responsiveness). 7,8 Patients with CIDP can improve using a second treatment option if the first treatment was ineffective, as shown by a multi-center study in treatment-naïve patients with CIDP. 8 Prognosis of CIDP is as heterogeneous as its clinical presentation. Previous longitudinal studies on disease course of CIDP report that approximately 25% of patients with CIDP experience remission after treatment that allows discontinuation of treatment. 7 Partial remission occurs in 60% of patients: in half of these patients treatment can be discontinued, the other half requires maintenance treatment. 7 In approximately 10% of patients symptoms remain severe after five years of treatment. 7,9 Predictors for complete remission are a subacute onset, symmetry of symptoms and absence of muscle atrophy. Nerve conduction abnormalities in the distal segments are predictors for complete remission or good response to initial therapy. 7 MMN has a more homogeneous presentation than CIDP. MMN is usually characterized by slowly progressive, asymmetric weakness without sensory deficits that dominates in the arm but weakness may also be present in the distal leg. 10 Important clinical mimics of MMN are motor neuron disease (MND), such as amyotrophic lateral sclerosis (ALS) or progressive muscular atrophy (PMA), and segmental spinal muscular atrophy. MMN mimics the early stages of these disorders, in particular MND, and differentiation can be challenging. However, differentiation is important as the prognosis