1. Chiari I 
- herniation of cerebellar tonsils below foramen (>5mm is an oft-reported limit, although this is controversial and depends on the age of the patient- 5mm in infant vs giant adult is obviously a different amount of relative herniation)
- milder, occurring primarily in young adults
- symptoms: most commonly occipital/upper cervical headache worse with valsalva. May also have weakness (unilateral grasp, b/l spasticity of lower limbs)
- often associated with syrinx
- rarely may be accompanied with myelomenigocele or hydrocephalus
2. Chiari II 
- herniation of the lower brainstem (medulla, pons, 4th ventricle) below foramen
- more severe, usually presents in infancy or childhood
- often associated with myelomeningocele, tethered cord, hydrocephalus,
- indications for surgery: dysphagia, apnea, drop attacks/syncope, syrinx
3. Surgical management of chiari: 
- posterior fossa decompression
- C1 laminectomy (if you do any lower than that, you worry about instability-- some surgeons will bipolar off the cerebellar tonsils that remain compressed after C1 lami rather than extend the lami to C2 or 3)
- Lyse the constricting bands over the dura at the foramen magnum... some believe these are the true source of compression.
- Dural patch graft
4. Things to mind mindful of in chiari surgery:
- Torcula can be very low in chiari
- Some people have incomplete C1 rings, or have had previous decompression surgery, so you can't assume there is bone posterior.
5. Non contrast HCT
- Hyperintense with no surrounding edema- blood vs calcification. Check the bone window.
6. Tumors that present with calcification: 
- Ganglioglioma (calcified 40% of the time)
- Craniopharyngioma (90% of the time are calcified; midline, near pituitary)
- Meningioma
- Oligodendroglioma (calcified 90% of the time, often extends all the way to pial surface of cortex)
- Astrocytoma (calcified 20% of the time)
- Choroid plexus (25%) and ependymoma (50% calcified)
- Bone tumors (chordoma, chondrosarcoma)
- Pineal tumors can expand endogenous calcifications of pineal gland but are not themselves calcified
7. AVMs
- Spetzler Martin grade 3s: some people further subclassify into "good" 3's and "bad" 3s, depending on whether the nidus is tight or loose. If there is a tight nidus there's a good chance of a complete resection with limited damage to normal brain.
- Indication for embolization: to make surgery easier, or to palliate symptoms (ie. pain) in inoperable cases. Some evidence that embolizing before radiosurgery leads to worse outcomes.
8. Tentorial meningiomas
- Will see tentorial artery (comes early off ICA, goes in straight line back towards tentorium) light up on angio as feeder artery.
- VS hemangioblastoma - will see blush of blood on angio in posterior fossa
9. Spinal tumors:
- Intramedullary: ependymoma, astrocytoma
- Extramedullary intradural: meningioma, schwannoma
- Extradural: mets, bony tumors (chordoma, chondrosarcoma)
10. Cervical stenosis can lead to myelopathy that leads to lower extremity pathology, but rarely will it present with NO upper extremity symptoms (i.e. no hand weakness/clumsiness). In someone with a compressed looking c-spine and exclusively lower extremity myelopathic symptoms, scan the thoracic spine.