Abstract and Introduction
Abstract
Objectives To review neurological complications after the influenza A (H1N1) pdm09, highlighting the clinical differences between patients with post-vaccine or viral infection.
Design A search on Medline, Ovid, EMBASE, and PubMed databases using the keywords "neurological complications of Influenza AH1N1" or "post-vaccine Influenza AH1N1."
Setting Only papers written in English, Spanish, German, French, Portuguese, and Italian published from March 2009 to December 2012 were included.
Sample We included 104 articles presenting a total of 1636 patient cases. In addition, two cases of influenza vaccine-related neurological events from our neurological care center, arising during the period of study, were also included.
Main outcome measures Demographic data and clinical diagnosis of neurological complications and outcomes: death, neurological sequelae or recovery after influenza A (H1N1) pdm09 vaccine or infection.
Results The retrieved cases were divided into two groups: the post-vaccination group, with 287 patients, and the viral infection group, with 1349 patients. Most patients in the first group were adults. The main neurological complications were Guillain-Barre syndrome (GBS) or polyneuropathy (125), and seizures (23). All patients survived. Pediatric patients were predominant in the viral infection group. In this group, 60 patients (4.7%) died and 52 (30.1%) developed permanent sequelae. A wide spectrum of neurological complications was observed.
Conclusions Fatal cases and severe, permanent, neurological sequelae were observed in the infection group only. Clinical outcome was more favorable in the post-vaccination group. In this context, the relevance of an accurate neurological evaluation is demonstrated for all suspicious cases, as well as the need of an appropriate long-term clinical and imaging follow-up of infection and post-vaccination events related to influenza A (H1N1) pdm09, to clearly estimate the magnitude of neurological complications leading to permanent disability.
Introduction
In 2009, a new strain of swine-originated influenza A (H1N1) caused the first pandemic of the 21st century. Clinical manifestations of influenza A (H1N1) pdm09 infection ranged from mild symptoms to severe illness and death. Most patients with severe or fatal disease were reported to have underlying medical conditions, including chronic lung disease, diabetes, cardiovascular disease, neurological disease, and pregnancy; nevertheless, some individuals developed neurological complications without having underlying comorbidity. In fact, neurological complications associated with either vaccination or infection events are well described in influenza.
Here, we present a literature review of influenza-related neurological complications related to influenza A (H1N1) pdm09, highlighting the different clinical outcomes between those patients who developed neurological complications after vaccination and viral infection, respectively. Additionally, two vaccine-related neurological complications observed in our own neurological care center in Mexico are reported.