Axonal loss at time of diagnosis as biomarker for long‐term disability in chronic inflammatory demyelinating polyneuropathy

INTRODUCTION/AIMS: We hypothesized that early, pretreatment axonal loss would predict long‐term disability, supported by a pilot study of selected patients with chronic inflammatory demyelinating polyneuropathy (CIDP). To further test this hypothesis, we examined a larger consecutive group of CIDP patients. METHODS: Needle electromyography and motor and sensory nerve conduction studies were carried out in 30 CIDP patients at pretreatment and follow‐up 5 to 28 years later. Changes in amplitudes were expressed as axonal Z scores and changes in conduction as demyelination Z scores and correlated with findings of the Inflammatory Rasch‐built Overall Disability Scale (I‐RODS), the Neuropathy Impairment Score (NIS), and isokinetic dynamometry (IKS). RESULTS: At follow‐up, the median I‐RODS score was 73, the NIS was 23, and the IKS was 56%. The median axonal Z score was unchanged at follow‐up. Conversely, the corresponding demyelination Z scores improved. The initial axonal loss was correlated with the clinical outcome and was an independent predictor of outcome by multivariate regression analysis. Axonal loss at follow‐up was also correlated with the clinical outcome. Only the follow‐up demyelination Z score was correlated with the clinical outcomes. Furthermore, the latency until treatment initiation was predictive of all three clinical outcome scores at follow‐up, and of axonal loss and demyelination at follow‐up. DISCUSSION: The present study findings indicate that pretreatment axonal loss at diagnosis in CIDP is predictive of long‐term disability, neurological impairment, and strength. A delay in treatment is associated with more pronounced axonal loss and a worse clinical outcome.