Cranial Nerve Palsy - IV : Trochlear Nerve

Question 1

Anatomical Course of the Trochlear Nerve (5).

Answer 1

1. Trochlear Nucleus - posterior aspect of Midbrain.
2. Anterior and Inferior within SAH space.
3. Pierce dura mater adjacent to Posterior Clinoid Process of Sphenoid Bone.
4. Runs along lateral wall of Cavernous Sinus (with III, IV, VII and ICA).
5. Enters Orbit via Superior Orbital Fissure.

Question 2

Motor Function of Trochlear Nerve.

Answer 2

ONLY Superior Oblique - contralateral muscle : depress and introit the eyeball.

Question 3

Clinical Features of Palsy of Trochlear Nerve (4).

Answer 3

1. Vertical Diplopia - Defective Downward Gaze.
2. Torsional Diplopia (Subjective Tilting).
3. Contralateral Head Tilt - Compensatory.
4. Look Straight : Affected Eye Deviates Upwards and Rotates Outwards.

Question 4

When do patients typically notice Vertical Diplopia? (2)

Answer 4

1. Reading a Book.

2. Going Downstairs.

Question 5

Aetiology of Trochlear Nerve Palsy (2).

Answer 5

Commonest :

1. Ocular Trauma.
2. Diabetes Mellitus/HTN - Microvascular Damage.