Pathophysiology

  • Consciousness is closely related to the reticular activating system.
  • This means that many focal brain lesions above the level of the RAS will not affect consciousness – unless the lesion causes downward pressure

Intracranial causes of altered consciousness

Trauma
  • Head Injury
    • 2000 per 100 000 per year
    • 300 admitted to hospital per 100 000
    • 10 die per 100 000
    • The severity of the injury does not necessarily relate to the severity of the damage.
    • Battle’s sign – bruising over the mastoid process, a sign of fracture of the base of the skull.
    • Raccoon eyes – purple discolouration around the eyes due to fracture of the base of the skull.

Neoplasm

  • Most common brain tumour is GBM – glioblastoma. These are malignant. But benign tumours can also often be very dangerous due to location (compression, inoperable)
  • 50% of brain tumours are metastasis. 90% of these are in the posterior fossa.
  • Treatment of brain tumour
    • Surgery – Very hard to remove the whole thing – obvious you cant be generous with your excision boundary!
    • Radiotherapy
    • Chemotherapy

Infection

Seizures

Vascular

  • Haemorrhage (sub arachnoid, sub dural, extra dural)
  • Stroke

Diagnosing altered consciousness

  • ABC’s
    • Hypotension cannot result from sub-arachnoid haemorrhage! If the patient has suffered trauma, and has low BP, it is likely to be caused by some other injury (e.g. dissection of aorta,  femoral artery)
  • GCS – Glasgow coma score (below)
  • History
  • Bloods, electrolytes, toxicity
  • Core neurological exam
  • Herniation syndrome of posterior fossa lesion
  • Give Medications
    • Glucose?
    • Naloxone – to reverse opioid overdose
    • Thiamine – in alcoholics
  • Exclude meningitis
    • Do an LP if there is no evidence of raised ICP and no coagulation problems!
  • Treat seizures

Glasgow Coma Score – GCS

  • Out of 15
  • Minimum score is 3
  • It is important to give a detailed GCS – give a breakdown, don’t just give the number!
  • 8 or less is about the level at which a patient can maintain their own airway. Below 8 might be what a lay person would call ‘coma’. Below 8 you should urgently consider intubation to maintain the airway. Patients with a higher GCS are also frequently intubated for a whole range of reasons.

Eye Opening

  1. None
  2. To pain
  3. To speech
  4. Spontaneous

Verbal response

  1. None
  2. Sounds
  3. Words
  4. Confused
  5. Orientated

Motor Response

  1. None
  2. Extends to pain
  3. Flexes to pain
  4. Withdraws to pain
  5. Localises to pain
  6. Obeys commands

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