Summary of Common Conditions Seen in OSCEs
Cranial Nerves
Write in your mnemonic and tick whether you think the nerve is motor/sensory or both. (Refer to the examination mark sheet for the answers).
Where Is the Lesion?
Upper Motor Neurone
| Cranial nerves | Site of pathology | Investigation |
| I–IV | Above (cranial nerves I and II) and within the midbrain | CT or MRI |
| V–VIII | Pons | |
| IX–XII | Medulla |
Lower Motor Neurone
| Cause | Investigation |
| Compression | Nerve conduction studies |
| Trauma | |
| Mononeuritis multiplex |
Common Eye Signs
Pupillary defects commonly turn up in finals, so know your differential diagnoses well.
| Large pupil | Small pupil |
| Palsy of cranial nerve III | Horner’s syndrome |
| Holmes–Adie syndrome (young women, absent ankle and knee reflexes) | Argyll Robertson pupil – neuro-syphilis: accommodates (on convergence) but does not react to light |
| Traumatic (may be irregular) | Age-related miosis |
| Drugs (dilating eye drops – tropicamide, atropine, illicit drugs (cocaine, ecstasy) | Drugs (opiates) |
| Anisocoria (difference in pupil sizes) |
Horner’s Syndrome
Identifying Horner’s syndrome is easy, but diagnosing the cause is much more difficult. The table below shows how you do it systematically according to the site of the lesion.
| Central lesion | Preganglionic lesion | Postganglionic lesion |
| Stroke | Pancoast tumour | Carotid artery dissection |
| Syringomyelia | Thyroidectomy | Carotid aneurysm |
| Multiple sclerosis | Trauma | Cavernous sinus thrombosis |
| Tumour | Cervical rib | Cluster headache |
| Infection |
Visual Field Defects
You should know the following information inside out by the time you sit finals.
Hearing
Air conduction (AC) should be louder than bone conduction (BC), i.e. AC > BC.
Start with a simple test by covering one of the patient’s ears with your finger and whispering a number into the other. Ask the patient to repeat what you have said.
Rinne Test
Use a 256 Hz tuning fork. Place it near the ear (air conduction). Tell the patient that this is sound 1.
Then place the tuning fork behind the ear (bone conduction). Tell the patient this is sound 2
Ask which was louder. Repeat it if necessary, and remember to test both ears.
Weber Test
Place a 256 Hz tuning fork on the centre of the patient’s forehead. Ask whether the sound is heard in the middle of the head or towards one side.
Interpreting the Rinne and Weber Tests
| Rinne test | Result | Findings |
| Normal | Rinne positive | Air > bone |
| Conductive | Rinne negative | Bone > air |
| Sensorineural | Rinne positive | Air > bone |
| Weber test | Findings |
| Normal | Heard in centre of head |
| Conductive | Lateralises to same side |
| Sensorineural | Lateralises to opposite side |
Hints and Tips for the Exam
Examination of the cranial nerves is testing to say the least. It is feared among students, and most students take longer to prepare for it than for examination of any other area. Yet doing it well will definitely distinguish you from other candidates.
Know the Names of the Cranial Nerves
The first step to learning this examination is to know the names of the 12 cranial nerves.
It is unlikely that you will have to examine the entire 12 nerves at one station, and you will most likely be directed by the blurb outside your station (e.g. ‘Examine this patient’s lower cranial nerves: V and VII–XII’ or ‘Examine this patient’s eyes’ – therefore implying nerves II–IV and VI).
But You Don’t Have to Examine in That Order
It is not necessary to examine the cranial nerves in the order I–XII. An alternative way to examine all the cranial nerves is to examine each part of the head separately in an orderly manner that covers all the cranial nerves (but not necessarily in numerical order). A possible order could be:
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