The incidence of neurological complications of varicella-zoster virus infection in hospitalised children in a population with low vaccination coverage

Introduction
Varicella is an infectious disease with potentially severe and not uncommon complications. Aim of the study was to assess the occurrence of neurological complications of varicella-zoster virus among hospitalised children and to analyse the specific clinical picture and outcome.

Material and methods
This retrospective study reviewed the medical records and collected post-hospitalisation interviews of children admitted to the hospital for varicella complications between January 2009 and December 2018. None of the patients was vaccinated. Patients were divided into two groups: neurological and non-neurological complications. Statistical analysis of the data was performed, and the results were compared with published data.

Results
Of the 484 patients admitted to the hospital with chickenpox, 71 (14.7%) met the study assumption of neurological complications. The median age of subjects in the study group was 4.3 years old (2 months to 16 years). The leading causes for hospitalisation in the study group were: cerebellar ataxia (39.4%), convulsions (26.8%), meningitis and encephalitis (14.1% each). An association between age and type of neurological complication was found. Rates of hospitalisation decreased with age, and the highest was found in children in the first six years of life. No laboratory parameter was found to be a prognostic factor for the development of neurological consequences. The majority of patients showed no comorbidity and hence were not considered as potentially at risk of a severe course of illness. The clinical outcome at one-year follow-up was favourable in most patients (64 of 71, 91.5%). One child died (1.4%).

Conclusions
The potential severity of neurological complications and sequelae of chickenpox in unvaccinated children is significant. Even though neurological complications of chickenpox may not result in long-term effects, they significantly prolong hospitalisation.