Neurosurgery

Shared operative foundations taught once, the room they happen in, the instruments on the tray, and the anaesthetic that makes it possible.

• Intracranial pressure & the Monro-Kellie doctrine

  One idea explains the specialty's emergencies, examinations and operations: the skull is a fixed box holding brain, blood and CSF, and any addition must be paid for. Taught once here; every haematoma, hydrocephalus and head-injury decision assumes it.

  1. 01The doctrine. Brain (~80%), blood (~10%) and CSF (~10%) fill a rigid container: add a mass and CSF and venous blood are squeezed out first. That is compensation, and it is finite.
  2. 02The curve. Pressure-volume compensation is a cliff, not a slope: early additions cost little, then the buffers exhaust and each further millilitre spikes the pressure. The lucid interval is a walk along the flat part.
  3. 03Perfusion arithmetic. The brain is perfused by the difference between arterial and intracranial pressure: as ICP climbs, perfusion falls, ischaemia swells the brain further, and the spiral tightens.
  4. 04Herniation. Pressure gradients move brain across dural edges: the uncus over the tentorium crushes the third nerve (the blown pupil), the tonsils descend through the foramen magnum, and Cushing's response (hypertension, bradycardia, irregular breathing) is the late flag.
  5. 05The countermeasures. Head up, sedation, osmotherapy, controlled CO2, CSF drainage via EVD, and surgical evacuation: every ICP treatment is an application of the same equation, removing volume or slowing its cost.

  Used byBurr-hole drainage of chronic subduralCraniotomy for extradural haematomaExternal ventricular drain insertion

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  Chronic subdural hematoma management

  Who gets burr holes, who gets watched, and what recurrence means.

  Watch for

  • The membrane and why the collection is liquid
  • Burr hole placement over the thickest part
  • The drain and the flat bed afterwards

  Source: Johns Hopkins Medicine · Watch on YouTube
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  CNS Neurosurgery 100: epidural hematoma

  The society's core teaching on the lentiform bleed and the craniotomy that treats it.

  Watch for

  • The middle meningeal artery and the pterion
  • Flap placement over the clot
  • Tacking the dura up to stop it recurring

  Source: Congress of Neurological Surgeons · Watch on YouTube
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  External ventricular drain (EVD)

  Why the drain goes in, where Kocher's point is, and how the height of the bag sets the pressure.

  Watch for

  • Kocher's point and the trajectory
  • Zeroing the transducer at the tragus
  • What a blocked drain looks like

  Source: Cleveland Clinic · Watch on YouTube

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