In its initial stages, Guillain-Barré syndrome (GBS) is difficult to identify, because diagnostic criteria may not always be fulfilled. With this retrospective study, we wanted to identify the most common electrophysiological abnormalities seen on neurophysiological examination of GBS patients and its variants in the early phases.
We reviewed the clinical records of patients admitted to our Neurology Unit with a confirmed diagnosis of GBS. The study sample was divided in two subgroups according to whether the neurophysiological examination was performed: within 7 days (very early group) or within 7-15 days (early group). H reflex, F waves, and motor and sensory conduction parameters were judged abnormal if they were outside the normal range for at least two nerves. We evaluated neurophysiological findings in Miller-Fisher syndrome (MFS) separately.
The study sample comprised 36 patients. In GBS, the most frequent abnormal neurophysiological parameter was the bilateral absence of the H reflex, followed by F wave abnormalities. Motor conduction parameters were altered in less than 50% of patients, and even less common were sensory nerve action potential reduction and the \"sural-sparing\" pattern. In MFS, H reflex was absent bilaterally in 100% of patients, followed by a predominant peripheral sensory involvement, whereas motor conduction parameters were frequently normal.
Bilateral absence of the H reflex is the most sensitive parameter in early diagnosis of GBS and its variants.

BACKGROUND: A retrospective analysis was performed to document the clinical and electrophysiological features of Guillain-Barré syndrome (GBS) subtypes using different diagnostic criteria.
METHODS: One hundred GBS patients were included. Clinical and laboratory features were analyzed, and patients were classified according to four sets of diagnostic criteria. Electrodiagnostic criteria were also analyzed.
RESULTS: A total of 69 patients met Asbury and Cornblath\'s criteria, 96 met Van der Meché\'s criteria, 99 met Wakerley\'s diagnostic classification and 86 met level 1 or 2 of the Brighton criteria. Rates of GBS subtypes were: 69% classic GBS; 8% Miller-Fisher syndrome; 12% paraparetic GBS; 2% pharyngeal-cervical-brachial GBS; and 9% unclassified. Those for electrodiagnostic subtypes were 52% demyelinating and 9% axonal according to Hadden\'s criteria vs 41% demyelinating and 41% axonal as per Rajabally\'s criteria.
CONCLUSIONS: In this study of case distribution within the GBS spectrum of a retrospective cohort of French patients, the application of new diagnostic criteria enabled accurate diagnoses and classifications of the different subtypes, and also increased the recognition of axonal GBS.