ep·i·neu·ri·um 
(ĕp′ə-nrē-əm, -nyr-)
(ĕp′ə-nrē-əm, -nyr-)n. pl. ep·i·neu·ri·a (-nrē-ə, -nyr-)
The thick sheath of connective tissue surrounding a nerve trunk.
[New Latin : EPI- + Greek neuron, nerve, tendon; see NEURON.]
ep′i·neuri·al adj.