key: cord-0720125-m3jk5ybh authors: Garnés‐Camarena, Oscar; Díaz‐Cano, Gonzalo; Stashuk, Daniel title: Motor unit electrophysiological changes in Guillain‐Barré syndrome in the context of a COVID‐19 infection date: 2021-09-14 journal: Muscle Nerve DOI: 10.1002/mus.27407 sha: 5c7002e7d939fe0cc585e64183abde361991dc52 doc_id: 720125 cord_uid: m3jk5ybh nan A 55-year-old woman was admitted to the hospital with unstable gait followed by four-limb weakness with lower limb predominance. Several days before the onset of neurological symptoms, she developed mild respiratory symptoms, generalized myalgias without fever, and an episode of diarrhea. On initial examination, she demonstrated moderate weakness mainly affecting the lower limbs (she could stand but was unable to walk), decreased proprioception, distal hypoesthesia, and generalized areflexia. A polymerase chain reaction nasal swab test was positive for severe acute respiratory syndrome-coronavirus 2; respiratory support was not required. Blood tests, cerebrospinal fluid analysis, chest X ray, and cranial computed tomography revealed no abnormalities. Due to suspected Guillain-Barré syndrome (GBS), electrodiagnostic studies (EDx) were performed on day 9 after admission, and the patient was treated with intravenous immunoglobulin 0.4 g/kg for 5 days. An initial nerve conduction study (NCS) revealed increased temporal dispersion (158%) and reduced proximal/distal compound muscle action potential (CMAP) size (0.5) in the right median and ulnar nerves with elbow stimulation (normal distal CMAP), reduced tibial conduction velocities bilaterally (29 m/s), and absent tibial and median Initially, low-amplitude and -frequency positive sharp waves and fibrillation potentials were recorded bilaterally from the tibialis anterior and gastrocnemius. Recruitment was reduced in all muscles sampled, with a predominance of large-area and irregularly shaped MUPs recorded from early-recruited MUs (more pronounced in distal lower limb muscles). Initial NFEMG measures showed increased dispersion and segment jitter in nearly all lower limb muscles sampled (Figure 1 ). Subsequent EDx, performed 5 weeks later, showed improved NCS results. Although the criteria for demyelinating polyneuropathy were still met, significant clinical improvement was seen, as the patient was able to walk with minor assistance. In addition, MUP area, NFM dispersion, and segment jitter were all reduced Figure 1 . Figure 2 shows examples of initial and subsequently recorded MUPs and NFMs. In GBS, early recruitment of MUs with large MUPs is a consequence of conduction block affecting small-diameter axons. 5 However, the electrophysiology of MUPs in GBS (ie, quantification of MUP size, temporal dispersion, and stability) is not usually included in the diagnostic protocols for GBS. 6 Our results could be explained by both a transient impair- The authors declare no potential conflicts of interest. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines. Data available on request due to privacy/ethical restrictions The electrodiagnosis of Guillain-Barré syndrome subtypes: where do we stand? Decomposition and quantitative analysis of clinical electromyographic signals Near-fibre electromyography P32-S application of decomposition based quantitative EMG (DQEMG) to focal neuropathies Single Fiber EMG Guillain-Barre syndrome subtype diagnosis: a prospective multicentric European study Patterns of recovery in the Guillain-Barré syndromes