A Comparative Study Of Different Electrophysiologically Defined Subtypes Of Guillain-barré Syndrome

Objective: Based on the electrophysiological and pathological findings, GBS iscurrently divided into two major subtypes, acute inflammatory demyelinatingpolyneuropathy (AIDP) and acute motor axonal neuropathy (AMAN)(also known asdemyelinating and axonal subtypes). The prevalence of GBS and its subtypes varies indifferent geographical regions. Additionally, it is important to identify these subtypessince each type has different pathogenesis and pattern of prognosis. The aim of thepresent study is to compare whether or not the epidemiological features, clinicalmanifestations and short-term prognosis differ between the demyelinating and axonalsubtypes in Dalian, and to search for any characteristic parameters which can help indistinguishing the two electrophysiological subtypes.Methods: A retrospective review of medical records of149consecutive patientswith GBS admitted into our neurology ward in the First Affiliated Hospital of DalianMedical University between January2002and December2011was performed. Wecollected data on the epidemiological characteristics including gender, age, urban/ruralresidence, seasonal incidence, and preceding events，clinical manifestations includinginitial symptoms, neurological findings during the course, respiratory failure, andcomplications, results of electrophysiological study, and specific treatments includingintravenous immunoglobulin, plasmapheresis, and steroids. The severity of neurologicaldeficits on admission, at nadir, and on the day of discharge from hospital was assessedusing the Medical Research Council (MRC) score. Intervals between symptom onsetand hospitalization or nadir (the maximal severity) were also analyzed to evaluate thepatterns of disease progression. The electrophysiological classification of GBS wascarried out using the electrodiagnostic criteria proposed by Ho and colleagues. Theprimary outcome measures included the duration of hospitalization, in-hospitalmortality rate, and the MRC score at the hospital discharge. Results: Based on the electrophysiological findings,149patients with GBS could beclassified as demyelinating subtype [67(45%)], axonal subtype [47(32%)] andunclassifiable subtype [35(23%)]. Men were more likely to be affected than women in bothdemyelinating and axonal subtypes,and there was no statistically significant difference ingender distribution between the two subtypes（P＞0.05). The mean age did not differsignificantly between the patients with the demyelinating subtype and those with the axonalsubtype（46.1±19.1years VS.45.1±15.6years, P＞0.05). In addition, no significantdifference in age-specific incidence appeared between the two subtypes（χ2=7.784，P=0.348）. Neither the urban/rural nor the seasonal distribution differed significantly for thetwo subtypes. The preceding infections such as upper respiratory tract infection anddiarrhea were equally frequent in both demyelinating and axonal subtypes. The MRCscores obtained on admission, at nadir, and on the day of discharge from hospital were46.8±9.8,43.1±13.5, and52.8±12.0in the patients with the demyelinating subtype, and45.5±11.5,38.5±14.5and48.4±12.5in those with the axonal subtype, respectively. Eachsubtype had significantly lower MRC scores at nadir than that at hospital admission, andhad much higher MRC scores at discharge than that at nadir（P＜0.05, respectively), whilecomparison of the demyelinating and axonal subtypes at each time point showed nostatistically significant differences in the MRC scores（P＞0.05, respectively). The intervalfrom onset to hospital admission was significantly shorter in patients with the axonalcompared with demyelinating subtype（P＜0.05), whereas either the interval from onset tonadir or the duration of hospitalization did not differ significantly between the two subtypes（P＞0.05, respectively). There were no significant differences between the subtypes in thefrequency of the initial symptoms, cranial nerve dysfunction, sensory deficits,hyporeflexia/areflexia, autonomic dysfunction, respiratory failure, and complications. Deathoccurred in only one case with the demyelinating subtype.Conclusions: In this study45%patients had demyelinating subtype of GBS,32%patients had axonal subtype and23%remained unclassified. There were no specificclinical features that can help to distinguish between the demyelinating and axonalsubtypes. Given that patients with demyelinating and axonal subtypes had similarpattern of disease progression and short-term prognosis, electrodiagnostic axonalsubtype of GBS may not always be a sign of more serious illness.