Neurosurgery

A rigid box, a fixed volume, and the physics of what happens when something extra wants in.

• Neurosurgery treats the brain and spine's surgical diseases: blood in the wrong compartment, cerebrospinal fluid that cannot circulate, and neural tissue under compression, all governed by one physical fact, the skull does not stretch.
• The Monro-Kellie doctrine is the specialty's physics: brain, blood and CSF share a fixed volume, so anything added (a haematoma, a swelling brain, trapped CSF) must displace something else, and when compensation runs out, pressure climbs fast.
• Its examinations are its monitoring: GCS, pupils and limb power, charted over time, are how a haematoma announces its growth, and a falling GCS is the specialty's crash call.
• The clock rules everything: an extradural evacuated in an hour is a walk-out; the same clot four hours later is a tragedy. Cauda equina applies the identical logic to the spine.

CT

What should I notice?

• Head injury with a lucid interval

  “A young man knocked out briefly at football, talking normally in the ED, now drowsy with a headache two hours later.”

  • Talk-and-deteriorate is the extradural haematoma's story: a torn middle meningeal artery fills the space between skull and dura while compensation lasts, then decompensates in minutes.
  • The pterion is the anatomy: the skull's thinnest junction, with the artery grooved into its inner surface, is why a temporal blow is never trivial.
  • CT now, not observation: the lens-shaped clot bounded by sutures is the picture, and the falling GCS is the timer.

  Live it as a case Craniotomy for extradural haematoma

• The elderly patient who is not themselves

  “Three weeks of increasing confusion and unsteadiness in an 82-year-old on apixaban; the fall that started it is barely remembered.”

  • Chronic subdural haematoma is the great impersonator of geriatrics: an atrophic brain stretches its bridging veins, a minor injury tears one, and the collection grows over weeks under anticoagulation's patronage.
  • The presentation is anything gradual: confusion, gait decline, headache, fluctuating drowsiness, or a stroke mimic, which is why elderly-plus-anticoagulant-plus-decline earns a CT.
  • The crescent-shaped collection on CT, often with fresh blood layered on old, makes the diagnosis; the anticoagulant makes the management conversation.

  Live it as a case Burr-hole drainage of chronic subdural

• Thunderclap headache

  “The worst headache of her life, maximal within seconds, with vomiting and neck stiffness: a 48-year-old smoker.”

  • Sudden-maximal is the phrase that matters: a headache at its worst within a minute is subarachnoid haemorrhage until proven otherwise, whatever it later proves to be.
  • CT within hours is highly sensitive; beyond that window the lumbar puncture question (xanthochromia) enters. The aneurysm behind it is found on CT angiography.
  • Once diagnosed, the enemies are three: rebleeding (the aneurysm is secured early by coiling or clipping), delayed cerebral ischaemia from vasospasm, and hydrocephalus from blood clogging the CSF's drains.

  Live it as a case

• Back pain with the wrong companions

  “Severe low back pain with new urinary difficulty, numbness where the saddle would touch, and progressive leg weakness.”

  • Cauda equina syndrome: the lumbosacral nerve roots are being crushed, usually by a massive disc prolapse, and the deficits at stake, bladder, bowel, sexual function, do not reliably recover once established.
  • The red flags are specific: saddle anaesthesia, painless retention or overflow, bilateral leg symptoms, and loss of anal tone. Ask about all of them, examine for all of them, document all of them.
  • The bladder scan is part of the neurological examination here: a silent post-void residual is objective evidence the history may not volunteer.

  Live it as a case

• The shunted patient with a headache

  “A 14-year-old with a ventriculoperitoneal shunt: two days of worsening headache, vomiting this morning, more sleepy than usual.”

  • A shunted patient with headache and vomiting has shunt malfunction until proven otherwise: blockage, disconnection or infection, and the history of 'just like last time it blocked' is high-grade evidence.
  • Compare, do not just image: today's ventricles against the last well scan, because some shunted ventricles never look normal and only the change convicts.
  • Drowsiness is the tipping point: a blocked shunt can decompensate quickly, and an external ventricular drain can buy controlled time when revision cannot happen at once.

  Live it as a case External ventricular drain insertion