|
|
Question: What does a fourth nerve palsy look like and what causes it?
 Answer: The trochlear nerve (CN4) only controls the superior oblique. This muscle has a funny course, and runs through a pulley at the superior-medial wall of the eye socket. Because of this change in direction, the superior oblique muscle works mainly as an intorter, though it does perform some vertical movement, especially when the eye looks medially.
Patients will often complain of a vertical diplopia, especially when looking away from the lesion. They may develop a head-tilt away from the affected eye. On cross cover testing, you’ll find a vertical hypertropia of the affected eye that worsens when that eye is looking medially toward the nose, especially when reading.
Fourth nerve palsies can occur from DM/HTN ischemia, like all palsies. They can also be:
- Trauma (that fourth nerve pops off the dorsally and has a long course to traverse)
- Congenital palsy that decompensates with age
- Tumor
Comments and Feedback
3 Comments
»
|
|
Hi Tim,
Im confused, I thought a lesion of CNIV would present with diplopia upon a downward gaze such as reading a book or walking downstairs. Do I have the sup. oblique confused with the inf. oblique?
JB Henderson
Comment by JB Henderson — January 14, 2009 @ 6:50 pm
|
 |
|
You are correct JB. A fourth nerve palsy causes diplopia when looking medialy. We tend to look medially when reading or walking down stairs.
In fact, before I was very comfortable with the eye-muscles, I used the “double vision with reading” mneumonic to help me understand this palsy. When we read, our eyes converge (turn inwards) and a superior oblique palsy will cause a verticle diplopia.
Comment by admin — January 15, 2009 @ 12:13 pm
|
|
|
The last optometrist gave me a 2 degree Base-down prism glasses which doesn’t help. I believe my exo phoria is much stronger than hyperphoria!. After less than 2 seconds of focusing my left eye sight starts to deviate to south east direction diagonally when I’m looking straightly or at a right object at most of gazes but not at all gazes my left eye deviates. And when I’m looking at left object the deviation is gradual to north east such as the shape of slash “/”. This is one my head is not moving, but it’s tilting. When I read the sentence by moving my head to follow it I can prevent deviation sometimes. Is this a fourth nerve palsy? What is the treatment for it?
Comment by Jim Jordan — May 30, 2010 @ 7:01 am
|
|
|
|
 |
|
 |
