Coma Flashcards
where does consciousness arise from
arousal - originates from reticular formation
content requires functioning hemispheres and diencephalon
what are the causes of a coma
impaired function of;
both cerebral hemispheres
reticular activating system in brainstem (or diencephalon)
cerebral hemispheres and reticular activating system
what can lead to a coma
structural lesion
metabolic
drug and toxins
CNS infections
stroke
describe a diffuse hemisphere coma
caused by trauma, ischaemia, hypoglycaemia/other metabolic disorders, infecting, drugs
can see bilateral changes after haemorrhage or infarction
brainstem compression after supra or infra tentorial mass lesions
dysfunction of brainstem due to ischaemia, haemorrhage or drugs
what are structural causes of coma
pressure on and displacement of diencephalon/brainstem (RAS)
this can be due to tumours, haematomas, abscesses etc
what is commonly seen in structural causes of comas
focal neurological signs (hemiparesis, papilloedema or 3rd nerve palsy)
describe uncal herniation
mass lesion pushes the brain through the uncus and compresses the medial temporal lobe which can cause 3rd nerve and brainstem compression
what is coning
progression of uncal herniation
which is measured by GCS
what are the 3 stages of coning
GCS=12, causes 3rd nerve palsy and hemiparesis of opposite
GCS=8, causes bilateral 3rds nerve palsy and loss of some p=brainstem reflexes
GCS=3, known as tonsil herniation, loss of reflexes leading to death
metabolic causes of coma
most common cause of medical/CT normal coma
major failure of any organ system
decreased O2 (esp hypoxic brian injury post cardiac arrest)
increased CO2 and other causes of acidosis
increased or decreased Na or Ca
diabetic coma due to increased/decreased glucose
decreased T4 and cortisol
hepatic encephalopathy
uraemia
hypothermia
how do drugs and toxins cause a coma
overdose
opiates (pinpoint pupils)
sedatives (benzodiazepines, antidepressants, anticonvulsants)
alcohol
carbon monoxide
poisons (ethylene glycol, paraldehyde)
other causes of coma
CNS infections/autoimmune (meningitis/encephalitis)
stroke (massive hemispheric infarction, brainstem or thalamic infarction, SAH venous sinus thrombosis)
trauma
seizures
management of coma
resuscitation
history - often limited, circumstances, informant history, medic alert bracelets
general examination
neurological examination
investigations
supportive and specific treatments
general examination
temperature (fever or hypothermia)
meningism (neck stiffness, Kernig’s sign)
trauma (blood, battles sign, ‘racoon eyes’)
skin (cyanosis, jaundice, purpuric rash, HIV lesiosn)
breath - alcohol, ketoacidosis, hepatic foetor
BP, murmur, bruits
what is Kernig’s sign
appearance of resistance or pain during extension of patients knee beyond 135degrees
