Photopic negative response (PhNR) in the diagnosis and monitoring of raised intracranial pressure in children: a prospective cross-sectional and longitudinal protocol

Marmoy, Oliver Rajesh, Hodson-Tole, Emma ORCID: https://orcid.org/0000-0003-1200-1724 and Thompson, Dorothy Ann (2021) Photopic negative response (PhNR) in the diagnosis and monitoring of raised intracranial pressure in children: a prospective cross-sectional and longitudinal protocol. BMJ Open, 11 (7). e047299. ISSN 2044-6055

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Abstract

Introduction Raised intracranial pressure (rICP) can be a consequence of a variety of neurological disorders. A significant complication of rICP is visual impairment, due to retinal ganglion cell (RGC) dysfunction. In children, subjective measurements to monitor this, such as visual field examination, are challenging. Therefore, objective measurements offer promising alternatives for monitoring these effects. The photopic negative response (PhNR) is a component of the flash electroretinogram produced by RGCs; the cells directly affected in rICP-related vision loss. This project aims to assess the clinical feasibility and diagnostic efficacy of the PhNR in detecting and monitoring paediatric rICP. Methods and analysis Section 1 is a cross-sectional study; group 1 young persons with disorders associated with rICP and a comparator group 2 of age-matched children without rICP. Both groups will undergo a PhNR recording alongside a series of structural and functional ophthalmic investigations, with the rICP group also having measurement of intracranial pressure. Section 2 is a longitudinal study of the relationship between the PhNR and directly recorded intracranial pressure measurements, through repeated measures. PhNR amplitudes and peak times will be assessed against optical coherence tomography parameters, mean deviation of visual fields, other electrophysiology and ICP measurement through regression analyses. Group differences between PhNR measurements in the rICP and control groups will be performed to determine clinically relevant cut-off values and calculation of diagnostic accuracy. Longitudinal analysis will assess PhNR amplitude against ICP measurements through regression analysis. Feasibility and efficacy will be measured through acceptability, practicality and sensitivity outcomes. Ethics and dissemination Favourable opinion from a research ethics committee has been received and the study approved by Manchester Metropolitan University, the Health Research Authority and the Great Ormond Street Institute of Child Health (GOS-ICH) Research and Development office. This project is being undertaken as a doctoral award (ORM) with findings written for academic thesis submission, peer-reviewed journal and conference publications.