Defining Central Nervous System Involvement in Patients with Acquired Demyelinating Peripheral Neuropathies (S25.002)

OBJECTIVE: To explore the presence and distribution of brain structural abnormalities in patients with chronic acquired demyelinating peripheral neuropathies (PNP). BACKGROUND: PNPs include heterogeneous conditions in term of aetiology, clinical presentation, prognosis and treatment. In chronic inflammatory demyelinating polyneuropathy (CIDP) a dysimmune aetiology is presumed, while for the demyelinating neuropathy associated with IgM antibodies against myelin-associated glycoprotein (antiMAG) a causative link with these antibodies has been supposed. DESIGN/METHODS: We recruited 16 antiMAG-PNP and 16 CIDP patients, and 32 healthy controls (HC) age- and gender-matched with the PNP patients. Voxel-wise methods were used to define the regional distribution of damage in the brain gray and white matter. RESULTS: Compared to HC, both groups of patients had increased volume of the right cerebellum. Compared to HC, CIDP patients had significant atrophy of the left middle and inferior temporal gyrus and left inferior frontal gyrus. They also showed a pattern of distributed atrophy and reduced fractional anisotropy involving the bilateral corona radiata, corpus callosum, external capsule, cingulum, left superior longitudinal fasciculum and right internal capsule. Compared to HC, antiMAG-PNP patients had decreased mean diffusivity in the posterior thalamic radiations and left sagittal stratum as well as decreased axial diffusivity (AD) in the bilateral corona radiata, internal capsule, sagittal stratum, corticospinal tracts and thalamic radiation, left corpus callosum, external capsule and fornix. These AD abnormalities were also detected when comparing antiMAG vs CIDP patients. CONCLUSIONS: Distributed abnormalities occur at the level of the CNS of PNP patients. Increased cerebellar volume could be an index of a compensatory mechanism, while white matter alterations in CIDP patients support the occurrence of central myelin involvement. The different behaviours of FA, MD and AD indices in PNP patients may suggests different pathogenetic mechanisms, which may contribute to explain differences in clinical profiles.