1. STIR sequence: 

- T1, but looks like T2

- Suppresses signal from fat, but highlights fluid

- Allows you to differentiate true edema from fat (i.e. suppresses marrow fat signal in spine vertebral body, allows detection of edema in bone that may reflect osteomyelitis). 

- Also allows easy detection of ligamentous injury in the spine

- In the brain, STIR highlights the contrast between grey and white, and can show hippocampal edema which may indicate epilepsy

2. Most common structural causes of epilepsy, from {radiologyassistant.nl} - 

3. FLAIR sequence

- T1, but looks like T2

- Suppresses CSF, detects edema. 

- Useful in the evaluation of tumors and MS plaques 

4. 100% supplemental O2 causes artifactual hyperintensity on FLAIR imaging! 

Normal volunteer breathing room air: 

 Same volunteer breathing 100% O2:

{image source}

Note increased hyperintense signal in quadrigeminal/ambient cisterns, suprasellar cistern, cerebral sulci, sylvian fissures, etc. 

- The paper in AJNR (linked above under image source) found that the artifact went away at 50% oxygenation, and was unaffected by the type of anesthesia. 

5. Schizencephaly: 

- Cleft between ventricle and cortical surface, often lined with polymicrogyria. 

6. Interpreting blood on MRI- helpful hints: 

- Intracellular stuff= dark on T2, extracellular stuff= bright on T2

- Methemoglobin = bright on T1 

Age	Contents	T1	T2
Hyperacute	Intracellular oxyHb	Isointense	Isointense to bright
Acute  (hrs-days)	Intracellular deoxyHb	Isointense	Dark
Early subactue (days-weeks)	Intracellular metHb	Bright	Dark
Late subacute	Extracellular metHb	Bright	Bright
Remote/Chronic	Ferritin Hemosiderin	Dark	Dark

7. Tumor hemorrhage: 

- 14% of mets and <5% of primary tumors are hemorrhagic 

- Often heterogenous and complex in appearance 

- Mets that bleed: chorio, thyroid, renal cell, melanoma, breast, lung

- Often have hypointense T2 rim 

8. Venous bleeds: 

- can look like tumor bleeds (heterogenous) 

- temporal/thalamic 

- can be at grey-white border

9. Arterial bleeds: 

- Follow single vessel arterial distribution

- Often on the convexity  

10. Other bleeds: 

- Amyloid: peripheral, parietoccipital, does not affect basal ganglia, generally age>75 (younger than 75- think of another etiology) 

- Contusion: bone-dural interface

- DAI: punctate, dorsal upper brainstem, corpus callosum 

1. Dynamic CT with diamox challenge: 
- Diamox (acetazolamide) causes vasodilation of cerebral arterioles for some unknown reason
- In cases of stroke, the arterioles in that distribution are already dilated, so the administration of diamox will cause a steal phenomenon and decrease perfusion to that area.

- Images from {this paper} by Eastwood et al in AJNR. 

- See the low perfusion in L MCA before diamox, and even less perfusion in L MCA after diamox (small arrowhead pointing to relatively decreased perfusion to L basal ganglia) 

2. Risk of air embolus with craniotomy-- higher risk with surgery where the surgical field is >5 cm above the R atria (i.e. sitting craniotomy) 

- Dural veins have no valves, and thus air is more likely to travel to lungs

- Dural veins are less collapsible 

- When the field is above the heart, there is a greater likelihood of air being "sucked into" the venous system 

3. Flying after craniotomy: 

- Postop pneumocephalus can hypothetically turn into tension pneumocephalus with the decreasing ambient air pressures associated with higher altitudes, however this study of 21 patients with posttraumatic/postoperative pneumocephaus who had to be airlifted found.... "The volumes of pneumocephalus ranged from 0.6 to 42.7 ml, with mean volume of 9.3 ml and median volume of 4.2 ml. No patient sustained a temporary or permanent neurologic decline as a result of air transportation. Three patients with continuous monitoring of intracranial pressure (ICP) were not observed to have any sustained pressure elevations during flight" 

4. X-stop vs decompressive surgery: no difference in outcomes or complications, higher rate of re-operation in x-stop, according to this meta-analysis of 5 prospective trials. 

5. Roof of 4th ventricle: superior cerebellar peduncle and anterior medullary velum. 

6. Review of cisterns: sagittal 

Chiasmatic = suprasellar 

Cerebellomedullary = cisterna magna

cistern of great vein = quadrigeminal 

7. Review of cisterns: axial 

What is labelled here as "crural" I learned by the name of "perimesencephalic"; I've heard that same space referred to as part of the ambient. I've even heard the quadrigeminal cistern referred to as part of the ambient, and I've heard the term perimesencephalic refer to all of the above labeled.
8. Relationship of lamina terminalis to anterior commissure: 
On CT:

{source}

Green: anterior cerebral artery

Purple: supposedly the anterior commissure as the LT is supposed to be too thin to see on CT 

9. {An amazing resource} of cistern anatomy, contents, imaging

10. Gas induction: 

- Good for kids, as it can be hard to get an IV in an awake kid

- Also helps you oxygenate-- as kids struggle, they increase their oxygen demand and make it harder for you to mask them; at least with a mask induction they get 100% oxygen at the same time as induction. 

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

High-yield executive summary of: Critical Care Management of Patients Following Aneurysmal Subarachnoid Hemorrhage: Recommendations from the Neurocritical Care Society’s Multidisciplinary Consensus Conference {source}

1. Rebleeding: 
- TXA/aminocaproic acid- short course only, initiate on diagnosis and stop after clipping/coiling, do not start if its been more than 72 hrs or continue past that. The risk of rebleeding is highest in first 72 hrs (5-10%), so the risk-benefit does not add up after that. Watch carefully for DVTs and other clots.
- SBP < 160, MAP <110. Use nimodipine or nicardipine.
- CTA is possibly better than angiogram in the acute setting.
2. Seizures: 
- Don't use dilantin
- Seizure prophylaxis may or may not be necessary; if given, should be given in a short course (3-7 days) and not a long course.
- If they seize once, treat with keppra for 3-6 months; no need for longer unless there are multiple seizure events
- Long term EEG for patients with SAH who fail to improve or who deteriorate for an unknown reason.
3. Cardiopulmonary:
- For an unknown reason, SAH may directly lead to myocardial stunning or injury, with elevated enzymes (~1/3 of patients) wall motion abnormalities (~1/4), arrhythmias (~1/3).
- Baseline enzymes, EKG, echo for all SAH patients
- Goal euvolemia (unless there is vasospasm, then all bets are off)
- BP/MAP goals per neurological needs, not cardiac
- Monitoring: do not get a central line for the sole purpose of monitoring CVP (i.e. get it if you need a central line for other reasons).
- Do not float a swan, the harms outweigh the benefits.
4. Fluid benefits
- Prophylactic triple-H therapy - no difference in rates of clinical or radiographic vasospasm but increased risk of complications demonstrated in two separate randomized clinical trials.
5. Effect of hypervolemic therapy on cerebral blood flow after subarachnoid hemorrhage : a randomized controlled trial. {Lennihan et al, Stroke. 2000}
BACKGROUND AND PURPOSE:
Cerebral blood flow (CBF) is reduced after subarachnoid hemorrhage (SAH), and symptomatic vasospasm is a major cause of morbidity and mortality. Volume expansion has been reported to increase CBF after SAH, but CBF values in hypervolemic (HV) and normovolemic (NV) subjects have never been directly compared.
METHODS:
On the day after aneurysm clipping, we randomly assigned 82 patients to receive HV or NV fluid management until SAH day 14. In addition to 80 mL/h of isotonic crystalloid, 250 mL of 5% albumin solution was given every 2 hours to maintain normal (NV group, n=41) or elevated (HV group, n=41) cardiac filling pressures. CBF ((133)xenon clearance) was measured before randomization and approximately every 3 days thereafter (mean, 4.5 studies per patient).
RESULTS:
HV patients received significantly more fluid and had higher pulmonary artery diastolic and central venous pressures than NV patients, but there was no effect on net fluid balance or on blood volume measured on the third postoperative day. There was no difference in mean global CBF during the treatment period between HV and NV patients (P=0.55, random-effects model). Symptomatic vasospasm occurred in 20% of patients in each group and was associated with reduced minimum regional CBF values (P=0.04). However, there was also no difference in minimum regional CBF between the 2 treatment groups.
CONCLUSIONS:
HV therapy resulted in increased cardiac filling pressures and fluid intake but did not increase CBF or blood volume compared with NV therapy. Although careful fluid management to avoid hypovolemia may reduce the risk of delayed cerebral ischemia after SAH, prophylactic HV therapy is unlikely to confer an additional benefit.
--Commentary: "there was no effect on net fluid balance or on blood volume measured on the third postoperative day" is an important sentence; the difference mean fluid intake between the two groups was relatively small, on the order of <1L per day, sometimes <0.5L per day.
6. Glucose: 
- Neither too high (inc risk of infection, possible increase in risk of vasospasm) nor too low (cerebral starvation, may increase risk of vasospasm).
- 80-200
7. NICE-SUGAR trial {NEJM} N=6000 ICU patients, randomized to either tight (80-110) or liberal (<180) glucose control. Those with tight sugar control had increased severe hypoglycemia (~6% vs <1%) and increased 90-day all-cause mortality.
8. Fevers:
- Common (40-70%) in SAH
- May cause increased metabolic demand of the brain, worsening infarcts.
- Treat with tyleonol/NSAIDs first line, and cooling blankets and devices secondary
- Prevent shivering (as that also increases metabolic demand)
- Look for + treat infectious source
9. DVT prophylaxis: 
- SCDs for everyone
- No chemoprophylaxis (ie. heparin/lovenox) for unruptured aneurysms that will undergo surgery
- Can be restarted 24h after surgery
- No heparin/lovenox 24 hrs before and after any intracranial procedures.
- Length of time to stay on chemoprophylaxis depends on the patient
10. Statins & SAH: 
Effects of statins-use for patients with aneurysmal subarachnoid hemorrhage: a meta-analysis of randomized controlled trials
Shao-Hua Su et al {Nature}
"...A total of 249 patients from six randomized controlled trials(RCTs) were subjected to meta-analysis. No significant decrease was found in the incidence of vasospasm(RR, 0.80; 95% CI, 0.54–1.17), with substantial heterogeneity (I2 = 49%, P = 0.08), which was verified by the further sensitivity analysis and subgroup meta-analysis. Furthermore, no significant difference was presented in the incidence of poor neurological outcome(RR, 0.94; 95% CI, 0.77–1.16), and potential side effects(RR, 2.49; 95% CI, 0.75–8.33). Nevertheless, significant difference was reported in the occurrence of DIND(RR, 0.58; 95% CI, 0.37–0.92) and mortality(RR, 0.30; 95% CI, 0.14–0.64). At present, although statins-use in the patients with aSAH should not be considered standard care at present, statins-use may have the potential effects in the prevention of mortality in patients with aSAH."

1. ETV overview: {image source}

2. ETV endoscopic view: {image source}

3. ETV steps: 

4. A common reason for failure of ETV is not perforating the liliequist membrane, which underlies the floor of the third ventricle {image source} 

(s- sellar, m- mesencephalic, d-diencephalic)

5. In the olden days, people used to do frontal craniotomies to fenestrate the lamina terminalis for management of hydrocephalus. The idea is you generate a communication between the third ventricle and the cortical subarachnoid space, but it probably doesn't work-- in this series of 15 patients who got LT fenestrations during aneurysm surgery in an attempt to reduce the incidence of hydrocephalus, there was no evidence of free flow of omnipaque contrast between ventricles and basal cisterns (vs a + control who got ETV). 

6. Lamina terminalis anatomy: 

7. The lamina terminalis represents the most rostral part of the neural tube from which the CNS is derived. It contains the OVLT (organum vasculosum of the lamina terminalis), which is one of the circumventricular organs. These neurons respond to the osmolality of the blood, and project to neurons that control the release of ADH. The OVLT is also stimulated by angiotensin II, as well. 

8. Thoughts about precedex/dexmedetomidine 

- Central a-2 agonist 

- Less risk of delirium upon awakening from anesthesia (good for people who have a record of this n the past) 

- Can induce bradycardia, esp in kids (a2 agonism...) 

- No risk of respiratory depression

- Can take a while for people to wake up 

- Expensive!!

9. Thoughts about propofol:

- Fast on fast off IF you give a bolus, but if you run a drip for say a 6 or 8 hour case, the levels increase in the blood and levels build up in the fat, and you can be sitting on the slow end of the elimination curve. 

10. Thoughts about the volatile inhaled agents

- Increase ICP at full dose, but less of an effect at lower doses

- Often used in combo with propofol in neuro cases as propofol alone may not be sufficient to induce deep anesthesia. 

1. Effects of statins-use for patients with aneurysmal subarachnoid hemorrhage: a meta-analysis of randomized controlled trials
Shao-Hua Su et al {Nature 2014}
"Aneurysmal subarachnoid hemorrhage (aSAH)-induced cerebral vasospasm and delayed ischemic neurological deficit (DIND) are the major causes of morbidity and mortality in patients with aSAH. The effects of statins-use for patients with aSAH remain controversial. Here,a total of 249 patients from six randomized controlled trials(RCTs) were subjected to meta-analysis. No significant decrease was found in the incidence of vasospasm(RR, 0.80; 95% CI, 0.54–1.17), with substantial heterogeneity (I2 = 49%, P = 0.08), which was verified by the further sensitivity analysis and subgroup meta-analysis. Furthermore, no significant difference was presented in the incidence of poor neurological outcome(RR, 0.94; 95% CI, 0.77–1.16), and potential side effects(RR, 2.49; 95% CI, 0.75–8.33). Nevertheless, significant difference was reported in the occurrence of DIND (RR, 0.58; 95% CI, 0.37–0.92) and mortality(RR, 0.30; 95% CI, 0.14–0.64). At present, although statins-use in the patients with aSAH should not be considered standard care at present, statins-use may have the potential effects in the prevention of mortality in patients with aSAH."
2. Thoughts on endoscopic sinus surgery:
- Insert endoscope, remove midline mucosa, drill out vomer and drill out midline bone in sphenoid sinus that divides it down the middle
- Hollow out the tumor to let any suprasellar element drop into the sphenoid sinus
- Go inferior and medial to avoid going into cavernous sinus/ICA
- Patch with mucosal graft, generally people do not attempt a primary dural closure with sutures as it is too cramped of a space.
3. Thoughts on closures:
- running skin stitch best watertight seal- good for posterior fossa crani's where you worry more about csf leak
- locked running stitch-- higher ischemia risk?
- probably OK to use modern gut for running stitch; the older stuff was reactive but the newer stuff probably isn't.
- vertical mattress gets you the best approximation- good for cases where you worry it won't heal (ie skin edges look like crap). Must stay in for a while, and are more painful to take out (vs staples).
- When you close the galea, if you take it low without any overlying fat you'll get a more symmetric/more perfectly approximated close.
4. Thoughts on meningiomas:
- 2/3s are avascular, 1/3 are hemorrhaghic and bleed (a lot!). Unfortunately no way to tell the difference on imaging... no BBB so these things always light up on perfusion imaging. Just go in slowly and carefully when you go to resect.
- If you see blood coming out of the skull before opening.. this is not a good sign.
- Can cause changes/growth of the overlying bone.. you have to drill it out.
5. Intraop brain swelling
- Some surgeons diurese at least 1L off before they enter the dura to avoid herniation
- If the brain herniates through durotomy/skull defect, you can get ischemia
- Manage with increasing venous drainage (look at the neck to make sure no veins are kinked, put bed in reverse trendelenburg)
- Have anesthesia hyperventilate to an end tidal of 25 to 35, depending on how much swelling and how concerned you are about it.
- Diurese: Mannitol 1gm/kg bolus, lasix
- Etiologies: bleeding - extraparenchymal or intraparenchymal, hypercarbia, venous outflow obstruction, diffuse edema
6. Post op orders - crani 
Monitoring
- Admit to ICU
- Vital signs and neuro checks q1
- I+O q1
Vitals
- Goal SBP <160
- PRN labetalol/hydralazine vs nicardipine drip
- Goal afebrile: use tylenol (big studies show modest effect) and cooling blankets.
Drugs
- Keppra 500 BID (supratentorial surgery only-- people don't seize from infratentorial pathology). Maintain for 2-3 months.
- Dex 4q6 (ISS/Accuchecks/Pepcid). If already on steroids, give stress dose steroids
- Ancef 24 hours, if they have a drain then ancef for as long as the drain is in.
Labs
- CBC, BMP postop and in the AM
Imaging
- MRI in AM (for tumor)
- CT postop (if any concern for postop hemorrhage)
- DVT prophylaxis: SCD boots/stockings
- Diet: NPO except for meds
- Activity: HOB 20-30, bed rest
7. Postop deterioration ddx: 
- Bleed (HCT, back to OR)
- Seizure (EEG, keppra/dilantin)
- Ischemia
- Hydrocephalus (HCT, EVD)
- Penumocephalus (just having air in the skull can cause neuro symptoms even without tension... lethargy, confusion, HA, n/v, seizures... air usually resorbs with improvement in sx in 1-3 days)
- Edema (HCT, steroids)
- Persistent anesthesia effects - unlikely if someone got better initially and then deteriorated. You can try naloxone if you think its opiate induced... be careful though.. if people go nuts that can cause elevated ICP
- Vasospasm
8. New {guidelines} on acute spinal cord injury: joint report by AANS and CNS: class 1 evidence - no steroids.
"Administration of methylprednisolone
(MP) for the treatment of acute spinal cord injury is
not recommended. Clinicians
considering MP therapy should bear in
mind that the drug is not FDA
approved for this application. There is
no Class I or Class II medical evidence
supporting the clinical benefit of MP in
the treatment of acute SCI. Scattered
reports of Class III evidence claim
inconsistent effects likely related to
random chance or selection bias.
However, Class I, II, and III evidence
exists that high-dose steroids are
associated with harmful side effects
including death."
9. Vertebral osteomyelitis and spinal epidural abscess often go together (the former often causes the latter) so finding one should prompt a search for the other.
10. Vertebral osteo: Risk factors
- IV drug use
- Diabetes (weird bacteria/fungal)
- Immunocompromised- AIDS, chronic steroids, alcoholism
- Dialysis patients (radiographic changes that look like osteo can occur even without infection)

- Postop 

- Endocarditis 

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.

1. Indications for neurosurgical admission for blunt head injury in kids: 
- GCS <15
- Significant mechanism of injury (fall > 3 body lengths, MVA, etc)
- LOC, amnesia, any focal neurological deficits
- Multisystem injury requiring surgical management for any reason
2. Management of above injury: 
- NPO
- Preop labs (T+S, coags, CBC. BMP)
- Repeat CBC/BMP in the AM
- Isotonic fluids
- Consider mannitol 0.25 to 1 gm/kg IV, start low and titrate up.
3. If you need intracranial monitoring: EVD if you can, bolt if the ventricles are small/you can't get the EVD to work.
4. Temporal lobe: 

5. Temporal lobectomy: 

- measure from tip of temporal lobe 3.5 cm back (L side) or 4 cm back (R side) to determine how much to cut

- Preserve the superior temporal gyrus, as it has part of wernicke's area on it, as well as the primary auditory cortex 

6. Cauda equina symptom: 

- Urinary retention is often the first sign, incontinence follow later (overflow incontinence) 

- Loss of lower extremity reflexes is a very sensitive sign 

7. Dens fractures: 

8. Management of Type I Dens fractures: 

- Extremely rare, little evidence. 

- May indicate underlying atlanto-axial instability. 

- 6-8 weeks in a collar, unless there is instability at occiput-C1, or disruption of alar ligaments, in which case you go to surgery 

9. Management of type II dens fractures: 

- Controversial, still no good way of predicting who will heal with immobilization alone and who will need surgery 

- Nonunion with immobilization alone estimates range from 5 to 75% in the literature-- according to greenberg, 30% is probably a good estimate, 10% for those with displacement <6mm

- Some authors think displacement <4mm indicates likelihood of fusion, >6mm associated with high risk of non-union (70% regardless of age or direction of displacement) 

- Kids (esp <7) almost always heal with immobilization, while older people (age cutoff in literature ranges 40 to 65) are less likely to heal. 

- Soft guidelines for surgery: Displacement >5mm, instability even with halo, age >51 (increases rate of non-union with halo alone 21 times), disruption of transverse ligament (associated with delayed instability), 

- Odontoid screw: acute fractures with intact/attached transverse ligament and no risk factors for non-healing (osteopenia, old person, old non-healed fracture)

- Posterior fusion: for everyone else, fuse either C1-C2 or O-C1-C2. 

- No indication for surgery: 10-12 weeks of immobilization; some data that halo vest (fusion rate 72%) is the best. 

- NB: Old (>6 weeks) fractures: unlikely to heal an odontoid screw. So old people with old fractures- soft collar rather than surgery (hard collars are an aspiration risk in old people) 

- Type III: traction, 8-12 weeks in a halo 

10. Management of type III dens fractures: 

- 90% heal with 8-14 weeks of immobilization. Halos fuse better than collars. 

1. Menigiomas on the anterior sagittal sinus are safer to resect than those on the posterior; on the anterior, if you get into the sinus you can ligate it, posteriorly it may lead to mortal bleeding.
2. Sight & Sound: 
- Superior colliculus & Lateral geniculate body- vision
- Inferior colliculus & medial geniculate body  - hearing.
- Brodmann's 41 = primary acoustic cortex.
3. About pain drugs
- morphine 1 = dilaudid 0.2
- morphine is renally cleared
- rigid chest syndrome when bolusing fentanyl (esp kids, anaesthesia dosing rather than analgesic dosing)
- fentanyl patch - steady state 12-24 hours, effect lasts for 14-24 hrs after taking it off
- take off transdermal patches before entering MRI- some have aluminum layer that helps contain the drug and can cause burns
- methadone: half life 15-60 hours (ie can take a long time to reach steady state, as its 5 half lives), can cause QT prolongation
- nalbuphine (nubain): partial agonist/antagonist, 0.05mg/kg pruritis, 0.1 mg/kg analgesia, at doses >0.15mg/kg can reverse opiate effects - don't give in opiate tolerant people
4. Osteoid osteoma vs osteoblastoma:
- Histologically identical. Distinguish by SIZE and BEHAVIOR
- Osteoid osteomas are by definition smaller (<1cm), never have malignant transformation, appear mostly in the lamina of the lumbar spine but occ cervical (not thoracic), can appear in pedicle or facet too, have more bony sclerosis around them, 10% in the spine.
- Osteoblastoma are bigger (>1cm), more locally destructive/invasive, may have contralateral spondylolysis, more often will present with neurologic symptoms, can appear anywhere in the spine, tend to occur in pedicle primarily but frequently multi-part (incl lamina, etc) very rarely will transform into osteosarcoma, about a third will occur in the spine.
- Cure with complete resection - no role for radiation
- Quick word on osteosarcoma- rarely appear in the spine, but when they do, tend to be 40 y/o M with hx of paget's or osteoblastoma.
5. Vertebral hemangioma - 
- most common primary bone malignancy in spine.
- Causes "striped" (sagittal/coronal) or "polka-dot" (axial) or honeycomb vertebral body on CT
- Don't light up on bone scan (vs mets, which do)
- Highly vascular
- Primarily in women post puberty - rarely beforehand, possibly bigger with pregnancy/hormones although this has not been proven.
- Rarely present with sx, and when they do its usually from compression fracture
- Rarely change over time
- Don't do anything unless its symptomatic.
- Small ones tend to be hyperintense on T1 and T2, tend to become hypointense as they grow bigger.
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 is met, most common primary is hemangioblastoma
10. CPA Tumors
- 7/9 vestibular Schwannoma aka acoustic neuroma
- 1/9 meningioma
- 1/18 epidermoid cyst (diffusion restricts)