1. 极端令人头疼的：nerve-racking 伤脑筋的 | nerve-wracking 极端令人头疼的 | nerved 有勇气的

2. 极端令人头疼的, 非常伤脑筋的：leash: 控制, 约束 | nerve-wracking: 极端令人头疼的, 非常伤脑筋的 | repetitive: 重复的

3. 非常伤脑筋的：nerve-wracking: 非常伤脑筋的 | do away with: 废除 | stereotype: 陈腔滥调;老套

4. 让人伤脑筋的：settle into 适应 | nerve-wracking 让人伤脑筋的 | prospect前景

adj

1. extremely irritating to the nerves

    e.g. nerve-racking noise
           the stressful days before a war
           a trying day at the office

    Synonym: nerve-rackingstressfultrying