Scalp Nerve Blocks for Post-Craniotomy Pain

Inclusion Criteria:

* adults aged 18 years and over;
* patients scheduled for elective craniotomy under general anaesthesia for one of the following surgeries:

  * resection of a supratentorial brain tumour,
  * clipping of an un-ruptured supratentorial cerebral aneurysm,
  * excision of a supratentorial arterio-venous malformation (AVM),
  * removal of an epileptic focus under general anaesthetic.
* ASA physical status \< IV.

Exclusion Criteria:

* history of significant coronary artery disease (NYHA class III or IV) which would contraindicate the use of epinephrine;
* presence of pain related to the intracranial pathology (e.g. tumour pain) since it could make difficult the discrimination between the tumour pain itself and the surgery related pain;
* current history of alcohol abuse or recreational drug abuse;
* active psychotic disorder;
* history of chronic pain requiring chronic opioids use (patients on opioids for \> 2 weeks);
* known or suspected addiction to narcotic substances;
* presence of any acute distracting pain;
* history of migraines;
* inability to understand or incapacity to use the VAS;
* proven or suspected allergy to local anaesthetics;
* craniotomy incision extending beyond the field of the block;
* predicted need for postoperative ventilation;
* history of scalp paresthesia or scalp scarring that may preclude normal nerve anatomy;
* previous craniotomy or cranial irradiation;
* history of malignant hyperthermia, which would contraindicate the anaesthesia maintenance protocol of this study;
* pregnancy.