Cranial Nerves, Clinical Aspects

Question 1

CN I disorders

Answer 1

Loss of smell = anosmia (difficult to clarify true dysosmia, or reduced smell, without multiple samples)

Question 2

Causes of CN I disorders

Answer 2

• Nasal causes - obstruction (eg., blood, URTI), local trauma or inflammation
• Drugs or toxins that damage high turnover cells of nasal olfactory mucosa – anti- histamines, antibiotics, chemotherapies
• Frontal head injury – shears nerve fibres through cribriform plate
• Compression of olfactory bulb (eg., tumour esp. meningioma; aneurysm)
• Lesion or degeneration of olfactory cortex (head injury, Parkinson’s disease)

Question 3

CN II disorders

Answer 3

1. Unilateral/monocular loss - optic nerve disorder (eg., glioma, optic neuritis)
2. Bitemporal hemianopia - pituitary lesion (eg., adenoma) as uniquely placed
3. Homonymous hemianopia - distal to optic chiasm (ie., LGN thalamus, whole optic radiation, occipital cx)
4. Homonymous quadrantanopia - upper or lower parts of optic radiation affect lower and upper quadrants, respectively

Question 4

CN III/IV/VI disorders

Answer 4

Eyelid disorders

1. Ptosis:
2. Constricted pupils (miosis)
3. Dilated pupils (mydriasis)
4. Horner’s syndrome

Question 5

Horner’s syndrome

Answer 5

ptosis, meiosis and anhydrosis of forehead on that side. Lesions at:

1. hypothalamus
2. brain stem
3. sp. cord to T1/2
4. T1/2 n. roots
5. lung apex
6. cervical sympa-
7. thethic chain
8. carotid sheath
9. orbit