Hyperacute relapse of Lewis-Sumner syndrome during influenza A (H1N1) virus infection

Lewis-Sumner Syndrome (LSS) is considered an asymmetric sensory-motor variant of Chronic Inflammatory Demyelinating Polyneuropathy (CIDP), mostly affecting the limbs distally, with electrophysiological evidence of multifocal motor conduction blocks. Cranial nerve involvement is present in a minority. Various well-known infectious agents, directly or via the host's immune responses, may trigger or exacerbate acute and chronic peripheral neuropathies, which may manifest clinically through a multitude of signs and symptoms.

We present the case of a 57-year-old male with Lewis-Sumner Syndrome, whose clinical course was quite stable over many years. He developed severe hyperacute relapse of his neuropathic disease in the context of active pneumonia due to influenza A (H1N1) virus infection. During this exacerbation, besides the obvious worsening of the previous asymmetric limb involvement, the patient also manifested left peripheral facial palsy and dysphagia that rapidly evolved over minutes, mimicking a stroke. The patient also showed rapid recovery, with marked improvement of the acute neuropathic dysfunction, immediately after initiation of treatment with oseltamivir. Our hypothesis is that the direct modulation of Na + ion channel activity in the host's peripheral nerve cell by H1N1 viral proteins could cause acute and potentially reversible dysfunction in the conduction of nerve action potentials. Direct viral neuritis could also have been the cause. Immunomodulatory agents, namely IVIg, were not administered due to the swift clinical improvement noticed in the following days.

We aim to raise awareness of the possibility of atypical neurological presentations of viral infections, especially relevant in the context of the pandemic the world is now facing.