Solving Brown Patches On Conifer Hedges.
With Brown patches on conifers the brown patches will not grow back unless is a yew which is a form of conifer.The only solution is to prune the brown areas out and plant other plants in front of the brown area to mask the bare areas.Suitable plants include Bamboos and Lonicera Piliata which will grow in the shade dry conditions created by the conifer or conifers in the case of a hedge.
Other information on brown patches in conifer hedges.
http://gardenadvice.co.uk/advisor/gardening-tips/browning-in-older-leylandii-conifers/