简介：Postauricalinjectionoftherapeuticswasrecentlyappliedinclinicalpracticetotreatinnereardiseasesbasedonsupposedexistenceofadirectchannelfromthepostauricalareatotheinnerear.Doubtingontheassociatedreportsandaimingtoprovideevidenceontheinnerearuptakemechanism,thepresentstudytrackedthedynamicdistributionofgadolinium-tetra-azacyclo-dodecane-tetra-aceticacid(Gd-DOTA)inratinnerearsafterpostauricalinjectionusingMRI.Atargetedtympanicmedialwalldeliverywasutilizedascontrol.Theresultsshowedthat,attheearlytimepointsafterpostauricalinjection,Gd-DOTAdistributedmainlyintissuessurroundingthebulla,temporalboneandskullandneckspace.Intheinnerear,therewasgradualuptakeofGd-DOTAonboththeipsilateralandcontralateralsideswithequalsignalintensities.Therewasnosignofdirectchannelcarryingtheagentfromthepostauricalareatotheinnerear.TargetedtympanicmedialwalldeliveryinducedsignificantlygreateruptakeofGd-DOTAintheinnerearthandidpostauricalinjection.At30minpost-administration,targetedtympanicmedialwalldeliveryyielded4.6-foldshighersignalintensitythandidpostauricalinjection.ThetotaldoseofGd-DOTAdeliveredbythetargetedtympanicmedialwallapproachwasonly0.1%ofthatdeliveredbypostauricalinjection.Inconclusion,postauricalinjectionisasystemicadministration,whichissimilartohypodermicinjection,ratherthanafocaldeliverymethod.Bycontraries,targetedtympanicmedialwalldeliveryinducesfastandabundantuptakeofGd-DOTAintheipsilateralinnerearwithoutsignificantdistributioninunwantedareas.