Marieke van Rosmalen

General discussion 141 8 Pathophysiology The second part of this thesis focuses on the feasibility of advanced qualitative and quantitative MRI to study pathophysiology of CIDP and MMN. Qualitative MRI of the intraspinal roots Until now, the majority of studies on nerve imaging in chronic inflammatory neuropathies focused on the peripheral nerves and the brachial or lumbosacral plexus. 25,32,52 Previous studies showed thickening in both CIDP and MMN that suggest that (inflammatory) abnormalities) are sometimes more widespread than results fromNCS seem to indicate. 10,19,25,26,32 Thickening of the peripheral nerves and brachial plexus did not correlate with phenotype or clinical characteristics. 45 Recently developed advancedMRI techniques allow assessment of the morphology of the intraspinal roots (i.e. motor ventral roots and sensory dorsal roots) and provide a new opportunity to assess the most proximal nerve roots and to correlate morphological with functional changes. 53 In chapter 5 we performed a hypothesis generating study to explore whether the cervical intraspinal nerve roots were affected in CIDP and MMN by measuring intraspinal nerve root size. This study showed that the morphology of the intraspinal nerve roots change in CIDP and MMN and that the ventral or dorsal root location of these changes corresponds with the nature of neurological deficits. The heterogeneity of the clinical presentation of CIDP as earlier described is reflected in the abnormalities of the intraspinal roots as well. The pattern of the thickening of the intraspinal nerve reflects the various clinical phenotypes of CIDP. Dorsal intraspinal roots (i.e. sensory roots) were thicker in patients with a pure sensory or ataxic phenotype (i.e. pure sensory CIDP) compared to patients with a sensorimotor CIDP ( p = 0.001) and patients with MND ( p = 0.006). Patients with pure motor CIDP had thicker ventral intraspinal roots (i.e. motor roots) compared to patients with a sensorimotor phenotype ( p = 0.018). MMN has a more homogenous presentation and we found that only the ventral roots were thicker inMMN compared to patients withMND ( p = 0.002) and patients with CIDPwith a sensorimotor phenotype ( p = 0.018). These findings for the first time show that anatomical abnormalities correspond with clinical deficits in chronic inflammatory neuropathies. Previous MRI studies of the intraspinal roots have been performed in patients with Guillain-Barré syndrome (n = 24) and showed enhancement in the spinal roots after infusion with gadolinium with a preferential involvement of the ventral spinal roots in patients with puremotor Guillain-Barré syndrome. This study also showed enhancement of the ventral and dorsal spinal roots in patients with a sensorimotor phenotype. Our study extends these results to chronic inflammatory neuropathies in a large sample of patients. 54–58 MRI of the intraspinal nerve roots allows us to truly study the most proximal parts of the peripheral nervous system.Although NCS techniques can be used to gather information regarding the most proximal parts of the peripheral nerve roots by using F-waves, this technique does not localize the exact site of injury. Furthermore, previous NCS studies did not show a clear relation between nerve function and nerve morphology. 59–61