Sural sparing pattern discriminates Guillain-Barré syndrome from its mimics

Abstract

Introduction: Electrodiagnostic features of demyelination are essential for establishing the diagnosis in demyelinating subtypes of Guillain-Barré syndrome (GBS), but they may also occur in disorders that mimic GBS clinically. Information about their frequency in GBS mimics is sparse.

Methods: Evaluation of electrodiagnostic features from 38 patients with suspected GBS in whom the diagnosis was later refuted (GBS mimics). Their diagnostic accuracy was analyzed by comparison with nerve conduction studies (NCS) from 73 confirmed GBS patients.

Results: Disorders that mimicked GBS clinically at the time of hospital admission included other inflammatory, metabolic, toxic, or infectious neuropathies and spinal cord disorders. The sural sparing pattern was the most specific electrodiagnostic feature for demyelinating GBS.

Conclusions: Common electrodiagnostic abnormalities in early demyelinating GBS do not usually exclude other rare differential diagnoses. An exception to this is the sural sparing pattern described here, which strongly supports the diagnosis of demyelinating GBS.

Keywords: GBS; Guillain-Barré syndrome; differential diagnosis; misdiagnosis; nerve conduction studies; peripheral neuropathy.

Figure 1

Serial sensory nerve action potentials (SNAP) recordings from ulnar and sural nerves in two patients with Guillain-Barré syndrome (GBS). Figure 1A: Patient 1 has normal ulnar and sural sensory recordings at day 3 after symptom onset. Serial nerve conduction studies at day 6 and day 14 revealed a developing “sural nerve sparing pattern” with decreased ulnar SNAP but normal sural SNAP. Figure 1B: Patient 2 had already “sural nerve sparing pattern” with inexcitable ulnar sensory nerve fibers on admittance (day 4 after symptom onset). Repeated electrophysiological testing shows decreasing sural nerve SNAP which became abnormal low at day 10 (dotted line = normal levels).