**5.2 Surgical exposure**

The skin incision should always be larger than the bone opening, considering the possible need to enlarge the craniotomy. A wide enough craniotomy must be performed for an ideal surgical exposure. Brain relaxation increases visibility and motility, while also diminishing the risk of damaging the brain and vessels. This is vital for certain aneurysms, especially of the skull base (internal carotid artery (ICA), anterior communicating artery (AcoA), basilar apex, etc.) or when attempting to clip mirror aneurysms during the same opening. There are a few methods to achieve brain relaxation, such as hyperventilation, cerebrospinal fluid (CSF) drainage (realized via lumbar drainage or ventriculostomy), intracisternal drainage (the most effective form of intraoperative brain relaxation in our experience, performed by opening the basal cisternae and the Sylvian valley), or with intravenous diuretics (mannitol or furosemide).
