Cranial Nerve Palsy - VI : Abducens Nerve

Question 1

Anatomical Course of Abducens Nerve.

Answer 1

1. Originates at Pons.
2. Exits at Pontomedullary Junction and Enters SAH Space.
3. Pierces Dura’s Mater and travels through Dorello’s Canal.
4. Leaves at tip of Petrous Temporal Bone.
5. Enters Cavernous Sinus.
6. Enters Bony Orbit via Superior Orbital Fissure.

Question 2

Function of Abducens Nerve.

Answer 2

Innervates Lateral Rectus - Adduct Eyeball.

Question 3

Aetiology of Abducens Nerve Palsy.

Answer 3

1. Structural Pathology e.g. SOL, Stroke, Infection, Trauma.
2. Diabetic Neuropathy.
3. Thrombophlebitis of Cavernous Sinus (with other Nerves).

Question 4

Clinical Features of Abducens Nerve Palsy.

Answer 4

1. Horizontal Diplopia.
2. Affected Eye Rests in Adduction (Unopposed Activity of Medial Rectus).
3. Compensation : Rotation of Head.

Question 5

Why are Sixth Nerve Palsies known to be False Localising Signs?

Answer 5

Path of the sixth nerve within the brain, makes it easily compromised in a state of raised ICP.