Scalp Nerve Blocks for Post-Craniotomy Pain

The proposed study is a randomized, placebo-controlled, triple-blinded, parallel-group clinical trial. Patients will be recruited from the neurosurgical population at St. Michael's Hospital. The inclusion criteria are: * Adults aged 18 years and over; * scheduled for one of the following supratentorial craniotomy: 1. resection of a brain tumour 2. clipping of an un-ruptured cerebral aneurysm 3. excision of an artero-venous malformation (AVM), or 4. removal of an epileptic focus * ASA physical status \< IV Intervention group: scalp nerve blocks with 20 ml of bupivacaine 0.5% + epinephrine 1:200,000 (divided among the different injection sites) at the end of surgery and before removal of the endo-tracheal tube. Control group: equal injections with 20 ml of saline + epinephrine 1:200,000 (at same time). In both study arms, post-operative rescue analgesia will be provided with hydromorphone patient-controlled analgesia (PCA). The primary outcome of this study will be the 24h post-operative pain score as assessed by the visual analogue scale (VAS). Important secondary outcomes will be: * the total PCA hydromorphone consumption in the first 24 and 48 post-operative hours; * the incidence of nausea and vomiting in the first 24 and 48 post-operative hours; * time to reach discharge eligibility from the PACU/ICU and hospital length of stay. Patients will be asked to rate their pain using the VAS at 30 min, 1, 2, 4, 8, 12, 18, 24, and 48 h, postoperatively by the research coordinator/bedside nurse. Pain will be also assessed at 5, 30 and 60 days postoperatively with the use of a Numeric Rating Scale (0-10).