Erb's and Klumpke's brachial palsies

Erb's - Upper trunk ( C5, C6 ) {See the picture mnemonic above -  imagine the '6' to resemble 'b' of erbs ; 's' resembles '5' }
Klumpke's - Lower Trunk ( C7, C8, T1 )
Remember 'E' comes before 'K' in alphabetical order, so Erb's is upper and Klumpke's lower trunk.
Now Klumpke's start with C7. Note that K-L-U-M-P-K-E is 7 letters.