Coma

Question 1

What are the main causes of coma presentation to neurologists?

Answer 1

Coma can result from various causes, most often first seen in the emergency or ICU setting—due to metabolic, structural, or toxic causes.

Question 2

Can brain imaging be normal in coma?

Answer 2

Yes, MRI or CT may be normal—diagnosis often relies on clinical judgment.

Question 3

How quickly can comatose patients recover?

Answer 3

Some recover rapidly (e.g., after correcting hypoglycaemia), but others with structural brain injury may take days or remain prolonged.

Question 4

What are the two main components of consciousness?

Answer 4

1. Arousal – mediated by the brainstem reticular formation.
   
   2. Awareness – mediated by cortical networks

Question 5

What happens if arousal is disturbed?

Answer 5

Diminished alertness due to brainstem dysfunction.

Question 6

What happens if awareness is disturbed?

Answer 6

Diminished understanding or interaction with the environment due to cortical dysfunction.

Question 7

What is coma?

Answer 7

A state of complete unawareness and unresponsiveness to external stimuli, with absent eye tracking and only reflex motor responses to pain.

Question 8

Why should terms like stupor, obtundation, and somnolence be avoided?

Answer 8

They are vague—better to describe specific findings and compare them over time.

Question 9

What are the possible outcomes of coma?

Answer 9

1. Brain death
   
   2. Persistent vegetative state (PVS)
   3. Minimally conscious state (MCS)
   4. Full or partial recovery

Question 10

When do most comatose patients emerge from coma?

Answer 10

Within 1–2 weeks after onset

Question 11

What defines a Persistent Vegetative State (PVS)?

Answer 11

• No awareness of self/environment
• No purposeful or reproducible behaviour
• No language comprehension/expression
• Intact cranial nerve reflexes
• Sleep–wake cycles present
• Stable cardiorespiratory function
• Incontinence

Question 12

What defines a Minimally Conscious State (MCS)?

Answer 12

• Eye contact or head turning to voice
• Eye tracking or fixation
• Some emotional or verbal response
• Can hold or use objects when asked
• Partial awareness and purposeful actions

Question 13

What differentiates MCS from PVS?

Answer 13

MCS shows intermittent signs of awareness and purposeful behaviour, while PVS shows no evidence of awareness or purposeful response.

Question 14

What causes coma anatomically?

Answer 14

Interruption of the ascending reticular activating system (ARAS) in the midbrain/pons or its projections to the thalamus and cortex.

Key structures:
• ARAS (cholinergic & monoaminergic neurons)
• Thalamic intralaminar nuclei
• Posterior hypothalamus (arousal center)
• Cuneus/precuneus and anterior cingulate (involved in awareness and motivation)

Question 15

What are the 4 main categories of coma causes?

Answer 15

1. Structural (e.g., cerebral or brainstem injury, stroke)
   
   2. Metabolic/endocrine (e.g., hypoglycemia, hyponatremia)
   3. Diffuse physiological dysfunction (e.g., seizures, poisoning, hypothermia)
   4. Functional/psychogenic

Question 16

What are two major coma mimics?

Answer 16

1. Locked-in syndrome:
   • Eyes open, vertical gaze and blinking preserved
   • Lesion in ventral pons
   • Awareness intact
   
   2. Psychogenic unresponsiveness:
      • Normal reflexes
      • Avoids injury (e.g., hand drop test misses face)
      • Eyes resist opening or respond to tickling nose hairs

Question 17

What is the most universally used scale for initial neurological examination in coma?

Answer 17

The Glasgow Coma Scale (GCS)

Question 18

What is the FOUR score, and why is it used?
A: The FOUR score assesses coma with more n

Answer 18

The FOUR score assesses coma with more neurological detail than the GCS. It evaluates eye response, motor response, brainstem reflexes, and respiration.

Question 19

After coma scales, what is the next step in the neurological examination?

Answer 19

Assessment of cranial nerves and motor response to pain.

Question 20

What can fundoscopy reveal in a comatose patient?

Answer 20

Diagnostic findings such as:
• Subhyaloid haemorrhage → aneurysmal subarachnoid haemorrhage
• Acute papilloedema → increased intracranial pressure or hypertensive crisis

Question 21

What do small or pinhole pupils (<2 mm) indicate?

Answer 21

Pontine lesion or opioid intoxication.

Question 22

What do midsize, light, fixed pupils (4–6 mm) indicate?

Answer 22

A midbrain lesion.

Question 23

What do maximally dilated pupils (>8 mm) suggest?

Answer 23

Lesion of the third cranial nerve nuclei, mesencephalon, or compression of peripheral fibers of the third nerve. Drugs/toxins (e.g., lidocaine, amphetamines, cocaine) can also cause dilation.

Question 24

What does a unilateral fixed pupil indicate?

Answer 24

A third cranial nerve lesion, often due to compression of the midbrain.

Question 25

Which spontaneous eye movement abnormalities usually indicate bihemispheric dysfunction?

Answer 25

Ping-pong movements and ocular dipping.

Question 26

Which eye movement abnormality localises to the pons?

Answer 26

Ocular bobbing (rapid down, slow up).

Question 27

What do roving eye movements indicate?

Answer 27

That the brainstem is intact.

Question 28

What does skew deviation of the eyes suggest?

Answer 28

An acute brainstem injury

Question 29

What might horizontal deviation of the eyes to one side indicate?

Answer 29

Non-convulsive status epilepticus, ipsilateral hemispheric stroke, or contralateral pontine stroke

Question 30

Which breathing pattern is least localising and can occur with any reduced alertness?

Answer 30

Cheyne–Stokes breathing.

Question 31

Which breathing patterns indicate bihemisphere or pontine lesions?

Answer 31

Cluster breathing and central neurogenic hyperventilation.

Question 32

Which breathing pattern indicates a lesion in the lateral tegmentum of the lower pons?

Answer 32

Ataxic breathing.

Question 33

How are motor responses in coma elicited?

Answer 33

By painful stimuli: supraorbital nerve, temporomandibular joint, or nailbed compression.

Question 34

How are decorticate responses defined?

Answer 34

Slow flexion of elbow, wrist, and fingers.

Question 35

How are decerebrate responses defined?

Answer 35

Adduction and internal rotation of shoulder, arm extension, wrist pronation, and fist formation.

Question 36

What does foul breath suggest in a comatose patient?

Answer 36

• Dirty toilet smell → uraemia • Fruity → ketoacidosis • Musty/fishy → acute hepatic failure • Onion → paraldehyde poisoning • Garlic → organophosphate poisoning

Question 37

What does skin bullae indicate?

Answer 37

Barbiturate poisoning.

Question 38

What does dry skin indicate?

Answer 38

Barbiturate poisoning or anticholinergic toxicity

Question 39

What does profuse sweating indicate?

Answer 39

Cholinergic poisoning, neuroleptic malignant syndrome, or serotonin syndrome.

Question 40

What does hypotension suggest in a comatose patient?

Answer 40

Deliberate overdose with antihypertensives.

Question 41

What does hypertension suggest?

Answer 41

Amphetamine intoxication, cocaine use, or other recreational drugs.

Question 42

What does hypothermia (<35°C) suggest?

Answer 42

Alcohol intoxication or overdose with barbiturates/tricyclic antidepressants.

Question 43

What does hyperthermia (>40°C) suggest?

Answer 43

Cocaine, tricyclic antidepressants, phencyclidine, or salicylate intoxication.

Question 45

Which toxins commonly cause cardiac arrhythmias?

Answer 45

Tricyclic antidepressants, cocaine, and ethylene glycol

Question 46

What can hypothermia (<35°C) indicate in a comatose patient besides cold exposure?

Answer 46

Hypothyroidism, Addison’s disease, hypoglycaemia, or may herald brain death.

Question 47

What can hyperthermia (>40°C) indicate in coma?

Answer 47

Fulminant systemic infection, endocarditis, or CNS infection.

Question 48

What does hypotension suggest in a comatose patient?

Answer 48

Early sepsis or fulminant acute meningococcal meningitis.

Question 49

What does hypertension suggest in coma?

Answer 49

Acute hypertensive encephalopathy or Cushing reflex from catastrophic intracerebral haemorrhage (especially pons or cerebellum).

Question 50

What questions should be asked to determine if coma is due to anoxic–ischaemic insult?

Answer 50

• How was the patient found? • Was the patient breathing on arrival? • Was cardiac arrest documented? • Duration of resuscitation efforts? • Noticeable blood loss? • Did the patient deteriorate during transport?

Question 51

What questions help identify basilar artery embolus?

Answer 51

History of atrial fibrillation, cardiac disease, recent warfarin discontinuation, or poorly controlled hypertension

Question 52

How is an intrinsic brainstem lesion recognised?

Answer 52

Skew deviation, internuclear ophthalmoplegia, small/unequal pupils, absent oculocephalic responses.

Question 53

How is brainstem displacement by supratentorial lesions recognised?

Answer 53

Wide, fixed pupils, abnormal motor responses, otherwise intact brainstem reflexes

Question 54

How is brainstem displacement by infratentorial lesions recognised?

Answer 54

Small pupils, absent corneal reflexes, abnormal/absent oculocephalic responses.

Question 55

What does a normal CT scan with intrinsic brainstem syndrome suggest

Answer 55

Basilar artery embolu

Question 56

What does an abnormal CT with intrinsic brainstem syndrome suggest?

Answer 56

Brainstem haemorrhage, traumatic injury, tumour, or infection.

Question 57

What does a brainstem displacement syndrome with abnormal CT suggest?

Answer 57

Massive hemispheric stroke, contusion, large subdural/epidural hematoma, malignant tumour, or abscess with oedema.

Question 58

What are the findings in bihemispheric syndrome?

Answer 58

Few localising signs, gaze preference may appear, brainstem reflexes usually intact.

Question 59

What does normal CT in bihemispheric syndrome suggest?

Answer 59

Toxin, status epilepticus, CNS infection, endocrine/metabolic derangement, or anoxic–ischaemic injury.

Question 60

What does abnormal CT in bihemispheric syndrome suggest?

Answer 60

Cortical lesions, white matter lesions, hydrocephalus, brain oedema, cerebral haemorrhage, or posterior reversible encephalopathy syndrome (PRES).

Question 61

What can myoclonic status epilepticus indicate?

Answer 61

Hypoxic–ischaemic brain injury after CPR

Question 62

How is brain death recognised?

Answer 62

Absent eye opening to pain, no motor response to pain, absent pupil and corneal reflexes.

Question 63

When is brain death declared?

Answer 63

When brainstem reflexes, motor responses, and respiratory drive are absent in a normothermic, non-drugged comatose patient with an irreversible widespread brain lesion of known cause and no contributing metabolic derangements.