Background:

The term sural sparing (SS) consists of the early finding in the nerve conduction studies (NCS) of patients with Guillain-Barré syndrome (GBS) of the preservation or normality of the sural nerve with abnormality in sensory nerves of thoracic limbs. Its pathophysiology lies in the greater vulnerability to demyelinating sensory damage in distal segments of the hand than proximally in the calf. The SS is highly specific of acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and is occasionally found in acute motor/sensory axonal neuropathy (AMAN/AMSAN).

Objective:

We aim to describe the prevalence of SS among the forms of GBS in patients hospitalized in our institute.

Materials and methods:

We reviewed 61 cases of confirmed GBS (19 demyelinating, 25 axonal, and 17 unclassified forms) corresponding to the 1999-2017 period. Exclusion criteria were as follows: NCS report not available or performed 21 days after the onset of symptoms, chemotherapy in the past 2 years, and/or previous polyneuropathy. SS was defined as the preserved amplitude in sensory action potentials (SAPs) of the sural nerve with abnormal findings in median and/or ulnar nerve SAPs.

Results:

Thirty patients (21 men, mean 45.5 ± 21.2 years) met the selection criteria, distributed in 12 AIDP, 3 Miller-Fisher syndromes, 9 AMAN, and 6 AMSAN. The NCS was performed 9.1 ± 6.0 days from debut. There were no significant differences in demographic variables or in the amplitude of SAPs between demyelinating and axonal forms. Two patients with AIDP presented SS (16.7%), which was not observed in any other form of GBS.

Conclusion:

We conclude that, despite the high specificity of SS for AIDP, its low prevalence and the high prevalence of axonal forms in Mexican population suggest that SS is not a suitable electrophysiological screening parameter for differentiating forms of GBS.

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