1. Before surgery
- Foley if case > 2 hrs
- Anesthesia on the side of the bed facing the face, for access to ET tube
2. Positioning
- Supine (+/- turning of head/neck, +/- shoulder roll) for frontal, temporal, and parietal approaches
- 3/4 prone (lateral oblique or park bench) for posterior parietal, occipital, sub-occipital
- Sitting: some prefer for sub-occipital approach; pros: increased venous/csf drainage. Cons: increased risk of air emboli, muscle fatigue from having to operate with your arms outreached the whole case
3. Incision
- Base should be broad in flap; flaps with narrow base are more likely to go ischemic.
- Try to avoid superior temporalis artery in case patient needs future EC-IC bypass (especially try to avoid cutting through main trunk of parietal STA.. that one's the really good one for this procedure) and try to avoid hacking up the facial nerve at the root (in front of tragus). Basically don't cut right in front of tragus.

4. Skin + Bone Flap elevation 

- Use periosteal rather than bovie to elevate temporalis as the vessels and nerves that supply it run in that fascial attachment layer and electrocautery will destroy it  

- The more burr holes you drill (i.e. the smaller the distance between burr holes) the lower the risk of tearing the dura in between. This is why you put them close together if you're going across a sinus. 

5. Moya moya disease
- Progressive intimal thickening affecting arteries coming off COW
- Usually b/l, can be u/l
- Cause unknown; may be genetic (thought to be AD with variable penetrance). Some have a higher level of thyroid antibodies; may have autoimmune component as well
- Higher incidence in asians, especially Japan
- Death (~5% in children, 10% in adults) is usually from hemorrhage. Deterioration from progressive strokes.
- Adults have more hemorrhage, children more ischemia
- Medical treatment: antiplatelet/anticoagulation, control BP if there is hemorrhage
6. Surgical management of moya moya: 
- EC-IC bypass - STA to MCA (M4) graft. Very difficult in children <2 years 2/2 small diameter of STA
- EDAS - dissect out STA, lay directly on arachoid (or on pia) and wait for smaller blood vessels to come in. Some theorize that its' not so much the direct revascularization process as the pro-angiogenic factors released by extracranial vessels that is of benefit.
7. Posterior fossa Tumors - ependymoma vs medulloblastoma
- both most common posterior fossa tumors in kids - each about 1/4-1/3, but medulloblastomas more common
- can appear very similar on imaging - somewhat heterogenous, T2 bright, enhancing.
- ependymomas tend to arise from floor of 4th, and medulloblastoma from roof ("medulloblast" thought to be granular cell layer precursors, hence cerebellar)
- if it extends through the foramina of lushka or magendie, it's more likely an ependymoma
- medulloblastomas tend to light up hot on dynamic perfusion MR (dsc-t2) since they are higher grade, while ependymomas (and jpa) are colder.
- maybe ependymomas are a little brighter on dwi/adc... They are hypercellular and so tend to restrict
- other possibly helpful tips that may or may not help - ependymomas sometimes are calcified, some say ependymomas conform to the shape of the 4th while medulloblastomas are rounder.
8 Cystic posterior fossa lesions with mural nodule
- Kid - jpa
- Adult - hemangioblastoma. (Also should make you think of von hipple lindau)
- In the above, the capsule usually doesn't enhance but if it does you need to take it surgically (along w mural nodule).
- enhancing capsule should make you expand differential to include higher grade lesions (mets, gbm)
9. Posterior fossa lesions in adults:
- most common tumor: met
- most common primary: hemangioblastoma
10. CPA Tumors
- 7/9 vestibular Schwannoma aka acoustic neuroma
- 1/9 meningioma
- 1/18 epidermoid cyst (diffusion restricts)