Finger drop sign as a new variant of acute motor axonal neuropathy

We propose the finger drop sign as a new clinical variant of acute motor axonal neuropathy (AMAN) defined by immunological and radiological evidence. We identified eight consecutive patients who had AMAN. All of them developed prominent involvement of the finger extensors. We performed magnetic resonance imaging (MRI) of the extremity muscles and serological assays for antiganglioside antibodies and Campylobacter jejuni. Patients with AMAN showed characteristic and a markedly sustained weakness of the finger extensors with a distinctive pattern of the finger drop sign. Limb MRI revealed unevenly distributed abnormal signals in the muscles mainly innervated by the posterior interosseous nerve. All tested patients showed positivity for immunoglobulin G antibody against ganglioside complex of GM1 and phosphatidic acid. A pathophysiological understanding of this unique syndrome can provide further insight into antiganglioside-antibody-mediated axonal injury in Guillain-Barre syndrome.

Automated summary

The finger drop sign is proposed as a new clinical variant of acute motor axonal neuropathy (AMAN) based on immunological and radiological evidence. This unique syndrome is characterized by sustained weakness of the finger extensors and a distinctive pattern of abnormal signals mainly in muscles innervated by the posterior interosseous nerve on limb MRI. Testing showed positivity for immunoglobulin G antibody against ganglioside complex of GM1 and phosphatidic acid in all patients. Understanding the pathophysiology of this syndrome may provide insights into antiganglioside-antibody-mediated axonal injury in Guillain-Barre syndrome.