▁injury ▁on ▁the ▁opposite ▁hem is phere ▁of ▁the ▁brain . ▁K ern oh an ' s ▁not ch ▁is ▁an ▁i ps il ater al ▁condition , ▁in ▁that ▁a ▁left - s ided ▁primary ▁les ion ▁( in ▁which ▁K ern oh an ' s ▁not ch ▁would ▁be ▁on ▁the ▁right ▁side ) ▁ev okes ▁motor ▁imp air ment ▁in ▁the ▁left ▁side ▁of ▁the ▁body ▁and ▁a ▁right - s ided ▁primary ▁injury ▁ev okes ▁motor ▁imp air ment ▁in ▁the ▁right ▁side ▁of ▁the ▁body . ▁The ▁serious ness ▁of ▁K ern oh an ' s ▁not ch ▁var ies ▁depending ▁on ▁the ▁primary ▁problem ▁causing ▁it , ▁which ▁may ▁range ▁from ▁ben ign ▁brain ▁tum ors ▁to ▁advanced ▁sub d ural ▁h emat oma . ▁ ▁Mechan ism ▁K ern oh an ' s ▁not ch ▁phenomen on ▁is ▁a ▁result ▁of ▁the ▁compression ▁of ▁the ▁c ere br al ▁ped un cle , ▁which ▁is ▁part ▁of ▁the ▁mes ence phal on , ▁against ▁the ▁tent or ium ▁c ere b elli ▁due ▁to ▁tr anst ent orial ▁h erni ation . ▁This ▁produces ▁i ps il ater al ▁hem ip ares is ▁or ▁hem i ple gia ▁ ▁The ▁sk ull ▁is ▁an ▁in com press ible ▁closed ▁space ▁with ▁a ▁limited ▁volume ▁( Mon ro - K ell ie ▁Do ctrine ). ▁When ▁there ▁is ▁increased ▁c ran ial ▁pressure ▁in ▁the ▁brain , ▁a ▁shift ▁in ▁the ▁brain ▁forms ▁towards ▁the ▁only ▁opening