Coma

Question 1

What is the definition of a coma?

Answer 1

A state of unrousable psychological unresponsiveness in which the subjects lie with eyes closed and show no psychologically understandable response to external stimulus or inner need

Question 2

What does consciousness depend on?

Answer 2

• An intact ascending reticular activating system to act as the alerting or awakening element of consciousness
• A functioning cerebral cortex of both hemispheres which determines the content of that consciousness

Question 3

How is consciousness maintained?

Answer 3

• Arousal (Reticular activating system)
• Awareness of environment (Cerebral hemispheres)
  □ Lethargic/Stuporous/Obtunded/Coma

Question 4

What causes a decreased GCS?

Answer 4

- Toxic/metabolic states
□ Hypoxia/hypercapnia/sepsis/hypotension
□ Drug intoxication/renal or liver failure
□ Hypoglycemia, ketoacidosis
- Seizures
- Damage to reticular activating system
- Causes of raised intracranial pressure
□ tumour, stroke, EDH, SDH, SAH, hydrocephalus

Question 5

What is a persistent vegetative state?

Answer 5

○ A state in which the brain stem recovers to a considerable extent but there is no evidence of recovery of cortical function
○ There is arousal and wakefulness but the patient does not regain awareness or purposeful behaviour of any kind

Question 6

What is locked in syndrome?

Answer 6

○ The patient has total paralysis below the level of the third nerve nuclei and, although able to open, elevate and depress the eyes, has no horizontal eye movements and no other voluntary eye movement
○ The diagnosis depends on recognising that the patient can open their eyes voluntarily and signal numerically by eye closure

Question 7

What is the glasgow coma scale?

Answer 7

- Eye Opening
□ Spontaneous		       4
□ To speech		               3
□ To pain 		               2
□ None		                       1
- Best verbal Response
□ Orientated			       5
□ Confused			       4
□ Inappropriate words	       3
□ Incomprehensible sounds 2
□ None				        1
- Best motor response
□ Obeying Commands		 6
□ Localising to pain		 5
□ Withdrawing from pain        4		
□ Flexing to pain			 3
□ Extending to pain		 2
□ None				         1

Question 8

What are the causes of a coma without focal or lateralising signs and without meningism?

Answer 8

• Anoxic/ ischaemic conditions
• Metabolic disturbances
• Intoxications
• Systemic infections
• Hyperthermia/ Hypothermia
• Epilepsy

Question 9

What are the investigations for a coma without focal or lateralising signs and without meningism?

Answer 9

• Toxicology screen including alcohol level
• Measure blood sugar and electrolytes
• Assess hepatic and renal function
• Acid - base assessment and blood gases
• Measure blood pressure
• Consider carbon monoxide poisoning

Question 10

What are the causes of a coma with focal or lateralising signs and without meningism?

Answer 10

• Subarachnoid Haemorrhage
• Meningitis
• Encephalitis

Question 11

What are the investigations for a coma without focal or lateralising signs and with meningism?

Answer 11

• CT head scan
• Lumbar puncture
  □ Appearance
  □ Cell count
  □ Glucose level
  □ Capsular antigen tests

Question 12

What are the causes of a coma with focal brainstem or lateralising signs?

Answer 12

• Cerebral tumour
• Cerebral haemorrhage
• Cerebral infarction
• Cerebral abscess

Question 13

What are the investigations for a coma with focal brainstem or lateralising signs?

Answer 13

• CT or MRI obligatory
• If CT/MRI not diagnostic, then investigate as for other causes of coma e.g. including
  □ metabolic screens
  □ lumbar puncture
  □ EEG

Question 14

What are the causes of a coma lasting more than 5 hours?

Answer 14

○ 40% due to drug ingestion ± alcohol
○ 25% due to hypoxia e.g. secondary to MI
○ 20% due to cerebrovascular event, either haemorrhage or infarction
○ 15% metabolic e.g. diabetes, hepatic failure, renal failure, sepsis, hypercapnia/hypoxia