伤神 is a separable verb-object compound (离合词). It has two main senses: (1) 'to be mentally draining, to take a toll on one's energy'—used for tasks or situations that require intense concentration or worry; (2) 'to be sad, to be disheartened'—used for emotional distress. When you split it, common patterns are 伤+了+amount+神 (e.g., 伤了不少神 'took quite a lot of mental energy') or 伤+结果补语+神 (e.g., 伤透了神 'completely wore out mentally'). The object 神 cannot take a measure word on its own.