Presentations

Question 1

What is a coma?

Answer 1

Coma is a ‘state of unarousable unresponsiveness’.

• No evidence of arousal - there is no spontaneous eye opening, comprehensible speech, or voluntary limb movement.
• Unresponsive to external stimuli and surrounding environment, although abnormal postures may be adopted, eyes may open, or grunts may be elicited in response to pain.

Question 2

What are the causes of a coma?

Answer 2

Question 3

Describe the immediate management of a coma

Answer 3

1. Stabilize the patient (airway, breathing, circulation). Give O2 and IV fluids to correct hypotension.
   
   1. Open the airway by laying the patient on their side. Note the pattern of breathing. If there is apnoea or laboured or disturbed breathing, intubation and ventilation should be considered. Measure ABGs.
   2. Support the circulation. Correct hypotension with fluids and/or inotropes. If prolonged therapy is required, both require careful and frequent monitoring of CVP and/or pulmonary artery wedge pressure (PAWP). Search for any occult source of bleeding, e.g. intra-abdominal
   3. Treat seizures with usual drugs, but beware of over-sedation and hypotension.
   4. Take blood for glucose, U&Es, Ca2+, liver enzymes, albumin, clotting screen, FBC, and toxicology (including urgent paracetamol and salicylate levels). Urine should be saved for a toxicology screen.
2. Consider giving thiamine, glucose, naloxone (only if opioid intoxication is likely), or flumazenil (if benzodiazepine intoxication is likely).
3. Examine the patient. Is there meningism? Establish the GCS score. Is there evidence of brainstem failure? Are there focal or lateralizing signs?
4. Plan for further investigations.
5. Observe for signs of deterioration, and attempt to reverse them.

Question 4

What is the general approach to assessing limb weakness?

Answer 4

1. Ascertain if true limb weakness (i.e. not paraesthesia or pain)
2. Ascertain time course - anything not sudden onset or subacute is likely to only be seen by a neurologist
3. Localise the lesion - is it upper motor neurone, lower motor neurone etc.
4. Look for other neurological clues
5. Perform further investigation - i.e. fundoscopy and cardiovascular examination.

Question 5

Give an example of a lesion that can lead to a central scotoma

Answer 5

A central scotoma is caused by retinal pathologies such as macular degeneration.

Question 6

Give an example of a lesion that can lead to mononuclear vision loss

Answer 6

Mononuclear vision loss (loss of vision only in one eye) is caused by optic nerve lesions. Examples include:

• Central retinal artery/vein occlusion
• Retinal detachment
• Optic neuritis
• Optic atrophy
• Glaucoma

Question 7

Give an example of a lesion that can lead to bitemporal hemianopia

Answer 7

Bitemporal hemianopia is caused by lesions at the optic chiasm such as a pituitary tumour or craniopharyngioma

Question 8

Give an example of a lesion that can lead to contralateral homonymous hemianopia

Answer 8

Contralateral homonymous hemianopia (homonymous referring to the same side of visual field) is caused by lesions at the contralateral optic tract, such as a middle cerebral artery occlusion.

Question 9

Give an example of a lesion that can lead to inferior homonymous quadrantanopia and superior homonymous quadrantanopia

Answer 9

Homonymous quadrantinopia is caused by lesions at the optic radiation.

• Inferior quadrantinopia is caused by parenteral lobe lesions (as the tracts that supply visual information for the inferior fields run superior to those that supply the superior fields - upside down).
• Superior quadrantinopia is caused by temporal lobe lesions.

Question 10

Give an example of a lesion that can lead to homonymous hemianopia with macular sparing

Answer 10

Contralateral homonymous hemianopia that is macular sparing is usually caused by lesions in visual cortex such as due to a posterior cerebral artery occlusion.