about nerve palsy

1. TESS JOSE

3. Unique features
 It is most slender cranial nerve, increasing its
vulnerability.
 It is the only cranial nerve to emerge from the dorsal
aspect of the brainstem.
 It is the only decussated (crossed) cranial nerve
(besides the optic nerve), so that left troclear nerve
contains fibers originating from right troclear nucleus.

7. Arise on the dorsal aspect of midbrain
Courses ventrally around cerebral peduncle
Enters the back of cavernous sinus
To the orbit through the superior orbital fissure

8. ANATOMY OF SUPERIOR OBLIQUE
 ORGIN: it arises from body of spenoid , above and
medial to optic canal till it reaches trochlea
 INSERTION: tendon of SO passes through trochlea,
below superior rectus, and inserted into sclera

9.  The trochlear nerve supplies only the superior oblique
muscle.
 Superior oblique muscle has following actions:
Depression
Abduction
Intortion

10.  Sup. Oblique muscle Primarily rotates the tip of the
eye towards the nose (Intorsion)
 Secondarily moves the eye downwards(depression)
 Tertiary function is to moves the eye outwards
(abduction)
 Trochlear nerve typically allows a person to view the
tip of his or her nose.
 In adducted position it act as a depressor.

11. Causes of isolated nerve palsy
 Congenitial
 Trauma. The long and slender nerves.
 Microvascular lesions
 Aneurysms cavernous sinus.
 Tumours

12. Clinical features
Left hypertropia
On looking staight (left palsy)

13. On looking down(left palsy)
Limitation in depression

14. On looking up
Normal elevation

15. Depression of eye in adducted position
Marked limitation in
depression

16.  Bilateral involvement
 Right hyperdeviation in left gaze
 left hyperdeviation in right gaze .

17.  A compensatory head posture avoids diplopia:
 vertical, torsional and worse on downgaze
 To compensate for weakness of intorsion there is
contralateral head tilt to the right.
 To alleviate the weakened depression of the eye the
chin is slightly depressed; as this is most marked
inadduction, the face may also be turned slightly to the
right.

20. Course
Emerges at pontomedullary junction.
Pierces the duramater.
Enters back of cavernous sinus.
Through the superior orbital fissure it enters the orbit
Supply the lateral rectus.

21. Clinical features
 Characterized by defective abduction of the eye from
the weakness of the lateral rectus .
 In a complete palsy ,there will be no abduction beyond
the midline
 In a partial palsy restriction will be less severe
 To avoid diplopia patient may adopt a face turn in the
field of action of the paretic muscle.
 A patient with right nerve palsy will turn the face to
the right.