Complex sentence: These branches divide and innervate the skin and intercostal muscles of an individual segment while innervating also the collateral variables, it is necessary to block a level above and below the desired level while performing intercostal nerve block.
Split into simpler sentences: These branches divide and innervate the skin and intercostal muscles of an individual segment while also innervating the collateral variables. It is necessary to block a level above and below the desired level while performing intercostal nerve block.