1. Vertebral artery segments: 

2, Dominance: 
- 45% L dominant
- 30% R dominant
- 20% Co-dominant
Not unusual to have one be smaller or to have one terminate into PICA.
Relevant during c-spine surgery: if you hit the vertebral artery, it's bad, if you hit the dominant vertebral artery, it's really, really bad.
3. Vertebral artery dissections: 
- Extradural: manage with BP control, antiplatelets to minimize stroke risk.
- Intradural: risk of SAH; if there is good collateral circulation (Good contralateral vertebral artery, intact COW) consider sacrifice of the vessel, particularly after SAH
4. Vertebral artery dissection imaging:
- CTA: higher resolution
- MRA: lower resolution, allows visualization of brain/ischemia
- Angio: can worsen dissection, don't use
5. Lateral medullary syndrome: occlusion of PICA at ostium, generally vertebral artery dissection or thrombus lodging in vert @ pica junction:
- Loss of pain/temp (contralateral body, ipsilateral face), vestibular system compromise, cerebellar peduncle compromise (cerebellar signs), nucleus ambiguus (9/10) - palate hemiparesis

6. PICA territory ischemia: 

(caudal cerebellar hemisphere)
7. PICA on angio 

8. PICA view (gross anatomy): 

9. More gross anatomy: 

10. TB came from seals... and you thought they were cute and harmless. http://www.economist.com/news/science-and-technology/21613103-tuberculosis-was-first-carried-america-pinnipeds-seals-doom