Disease and Clinical Features of Coma Flashcards
What is the definition of a coma?
State of unrousable unconsciousness
GCS of 8 or less
What is included in the GCS?
Eye opening /4
Motor response /6
Verbal response /5
Total: 15
What is the definition of arousal?
Level of consciousness/alertness
Function of the reticular activating system in pons and midbrain and its interaction with the thalamus
What is the definition of awareness?
Content of consciousness
Awareness of self environmnet
Function of multiple cortical areas
What is a unilateral cause for cortical damage leading to coma?
Large expanding mass lesions → raised ICP
e.g. haemorrhage, large MCA infarct
How can a single hemisphere or cerebellar lesion produce a coma?
Compression of the brainstem
What are the causes of coma?
Massive cortical damage
Brainstem lesion
Brainstem compression
Diffuse physiological brain dysfunction
Metabolic disorders, drugs and toxins, mass leasions, trauma, stroke and CNS disorders
How may brainstem compression lead to a coma?
Supratentorial mass lesion within the brain → inhibition of ARAS
Coning from brain tumour or haemorrage
Mass lesions within the posterior fossa are particularly prone to cause brainstem compression and hydrocephalus
How does diffuse physiological brain dysfunction arise to cause comas?
Generalised severe metabolic/toxic disorders depress cortical and ARAS function
Hypothermia/sudden hypertension, prolonged status epilepticus
Drugs, toxins, poisoning: Alcohol, sedatives, opiates, anaesthetics, uraemia, hypercapnia
Psychiatric
Metabolic - deranged Na/glucose, raised Ca, renal/hepatic failure
Endocrine: hypothyroidism, Addison’s, pan-hypopituitarism
What are two important coma mimics?
Locked in syndrome - de-efferented motor tracts
- complete paralysis except blinking and vertical eye movements intact in ventral pontine infarction (basilary artery)
- awareness and arousal retained (functioning cerebral cortex)
Psychogenic coma
What is the immediate management of coma?
ABC - intubate? oxygenation? correct hypotension/hypertension?
Blood glucose - if hypo, give glucose
Treat seizures with buccal medazolam
IV Abx for fever and meningism
IV naloxone if opiate OD, Flumazenil if benzo OD
Thiamine if Wernicke’s encephalopathy
How do the following give clues to the cause of coma?
Temperature
Odour of breath
Skin
RR
Pulse
BP
Temperature ↓: Cold, hypothyroid, alcohol, drugs, Addison’s; ↑: Infection/drugs
Odour of breath: Alcohol, Ketosis, Uraemia
Skin: Rash, Signs of liver disease, needle tracts, bruising (head injury)
RR - ↓: optiates; ↑: uraemia, pneumonia
Pulse - ↓: Hypothyroid, drugs, cold, Raised ICP; ↑:Infection, drugs
BP - ↓: Trauma, Shock, Cardiac failure, Drugs; ↑:Stroke, SAH, Raised ICP, Stimulants, Hypertensive encephalopathy
What should a neurological examination include for a patient in a coma?
Meningism - (neck stiffness, photophobia, headache) - SAH, meningitis
Fundi - look for papilloedema and retinal haemorrhages - raised ICP and SAH
Brainstem function - Pupils, Eye movements, Brainstem reflexes
Lateralising signs - Asymmetry of response to visual threat, face, tone, decerebrate and decorticate posturing, response to pain, tendon and plantar reflexes
What can the pupils show in a patient in a coma?
Dilation of one pupil that’s fixed → compression of CNIII (neurosurgical emergency)
Bilateral mid-point reactive pupils (normal) - metabolic/sedative drug coma
Bilateral light-fixed, dilated pupils → sign of brain death, deep coma
Bilateral light-fixed, pinpoint pupils → pontine lesions (pointine)/opiates
What can eye movements show in a patient in a coma?
Dysconjugate eyes - divergent ocular axes - brainstem lesion
Conjugate gaze deviation
- Towards lesion in frontal lobe (intact side pushing eyes away)
- Away from lesion in brainstem - PPRF in pons controls lateral gaze ipsilaterally
VOR - passive head turning produced conjugate ocular deviation away from direction of rotation - reflex disappears in coma, brainstem lesions, brain death
