Residual fatigue in Guillain-Barré syndrome is related to axonal loss

Objective: To determine the occurrence of residual loss of peripheral nerve axons by motor unit number estimation (MUNE) and conventional nerve conduction studies (NCS) in patients with and without severe fatigue. Methods: Thirty-nine patients at a median of 8 years (range 1–23 years) after diagnosis of Guillain-Barre syndrome were neurologically examined and divided in 2 subgroups based on the presence of severe fatigue (defined as a fatigue severity score ≥5). All patients were investigated with standard NCS and MUNE. Normal values for MUNE were collected in 14 healthy controls. Results: MUNE of the thenar muscles was lower in the 15 patients with severe fatigue (median 125, interquartile range 65–141) compared with the 24 patients without severe fatigue (median 258, interquartile range 120–345) ( p = 0.002). In the healthy controls, MUNE was 358 (245–416). Severe fatigue was also related to lower sensory nerve action potential amplitude of the median ( p = 0.01) and ulnar nerve ( p = 0.03). The 2 subgroups did not differ regarding neurologic deficits, disability, and the remaining conventional motor NCS. Conclusion: This study demonstrates that severe fatigue after Guillain-Barre syndrome is related to more pronounced axonal loss, represented by lower MUNEs and lower sensory nerve action potentials.