- 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
- 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.
- 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!
- Haemorrhage (sub arachnoid, sub dural, extra dural)
Diagnosing altered consciousness
- 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)
- Bloods, electrolytes, toxicity
- Core neurological exam
- Herniation syndrome of posterior fossa lesion
- Give Medications
- 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.
- To pain
- To speech
- Extends to pain
- Flexes to pain
- Withdraws to pain
- Localises to pain
- Obeys commands