The sequence of investigations depends on clinical suspicion:
Signs of raised ICP or focal neurological signs Meningism
Urgent CT SCAN"^
(but see suspected meningitis, page 472)
LUMBAR PUNCTURE - CSF EXAMINATION
Suspected drug abuse or metabolic disease No signs of raised ICP No meningism No focal neurological signs
Urea and electrolytes Blood glucose Blood gases/PH Drug screen If not
Liver function tests diagnostic Blood cultures (if pyrexia)
- serum calcium
- serum phosphate
- serum magnesium
- thiamine, B12
- folic acid
- serum amylase
- serum Cortisol
SKULL X-RAY - may reveal an unsuspected fracture, pineal shift, calcification or an osteolytic lesion.
CHEST X-RAY - may reveal a bronchial carcinoma.
ELECTROENCEPHALOGRAPHY - may provide evidence of - subclinical epilepsy
- herpes simplex encephalitis
- metabolic encephalopathy.
MRI - has a limited role in the investigation of coma. More sensitive than CT scan in demonstrating small ischaemic changes and early encephalitis.
Although conscious level examination does not aid diagnosis, it plays an essential rôle in patient management and along with the duration of coma, pupil response and eye movements provides valuable prognostic information. Non-traumatic coma tends to carry a better prognosis (see page 210).
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