1. 4TH NERVE PALSY TROCHLEAR NERVE PALSY SUPERIOR OBLIQUE
PALSY
2. INTRODUCTION Thinnest and longest 75mm. Only CN that comes
out from the dorsal aspect of the brainstem. Only CN that crosses
completely to the opposite side. Thus originates from the
contralateral nucleus. Somatic motor component , innervates the
superior oblique of the contralateral orbit. Nucleus lies at the
level of the inferior colliculus
3. ANATOMY Anatomically Segments Nucleus Intracranial course
Extracranial course Central Cisternal Cavernous & Orbital * =
4th cranial nerve nucleus
4. ANATOMY From each nucleus, the nerve fibres run laterally
and emerge from the dorsal aspect of the midbrain Pass medially and
decussate (X) Thus it crosses completely before passing forward
Once the 4th CN exits from the brain from the dorsal side it turns
ventral and passes the Posterior Cerebral Artery and Superior
Cerebellar artery Then it pierces the arachnoid and enters the
subdural space on the posterior corner of the roof of the cavernous
sinus
5. ANATOMY - CONT In the cavernous sinus it runs on the lateral
wall below the Oculomotor nerve and above the 1st div of 5th CN
Before crossing the cavernous sinus it crosses the 3rd nerve
through the lateral part to enter the superior orbital fissure
Anatomy of the 4th cranial nerve
6. ANATOMY - CONT In the intraorbital part, the 4th CN doesnt
transverse through the annulus of zinn, it projects anteriorly,
superiorly and medially to it Travels temporal and inferior to
innervate the superior oblique muscle.
7. 4TH CN PALSY CASE HISTORY Initial observations: 1. Head tilt
on the affected side 2. Hypertropia-affected side 3. Facial
asymmetry General health: DM / HTN / Myasthenia gravis / IC tumours
/ TRAUMA Family history: Congential 4th CN palsy , Autosomal
dominant form Ocular history: Tx for diplopia, head posture in
childhood. Questions to ask further as a basis for investigation:
Diplopia? Vertical / horizontal ? Any torsion ? Duration ? Constant
or intermittent ? Worsen on reading or climbing stairs ? Neck pain
?
8. CAUSES OF AN ISOLATED 4TH NERVE PALSY I)CONGENITAL :
Congenital lesions are a common cause , although symptoms do not
develop until decompensation occurs in adult life. Children develop
a compensatory head tilt in order to compensate for underacting
superior oblique muscle, on the contralateral side. II) ACQUIRED :
1.TRAUMA : trauma is an important cause of 4th nerve palsy
accounting for 30% of accquired 4th nerve palsies, 4 th nerve is
the most commonly involved nerve in a traumatic palsy. Trauma
usually causes bilateral 4th nerve palsies due to an impact in the
area of the Anterior medullary vellum, where the two nerves
decusate.
9. 2.IDIOPATHIC : in about 20% of cases the cause is unknown.
3.VASCULAR AND NEUROLOGICAL : These account for about 5 % of
trochlear nerve palsies , in older individuals microvasculopathy
secondary to diabetes atherosclerosis or hypertension may cause an
isolated 4th nerve palsy. Aneurysms and tumors are rare causes.
Thyroid related orbitopathy and Myasthenia gravis may mimic as an
isolated 4th nerve palsy due to fibrotic inferior oblique ,
superior rectus.
10. SYNDROMES OF 4TH CN PALSY -Nuclear Most often due to
stroke, less often neoplasm, and almost never isolated; other
causes include demyelinative disease and trauma. -Fascicular Rare,
same associations as nuclear; may get contralateral Horners
syndrome; trauma (especially near anterior medullary velum) may
cause bilateral CN IV palsies. -Subarachnoid Space Usually due to
closed head trauma; rarely tumor, infection or aneurysm.
-Intracavernous Space Due to cavernous sinus disease from
inflammation (sarcoidosis), infection (fungal), or neoplasm
(lymphoproliferative, meningioma, pituitary macroadenoma); usually
associated with CN III, V, and VI findings and sympathetic
abnormalities. -Orbital Trauma, inflammatory or
11. FEATURES OF 4TH NERVE PALSY The features of nuclear ,
fasicular and peripheral 4th nerve palsies are clinically identical
except that nuclear lesions produce CONTRALATERAL superior oblique
weakness. SYMPTOMS : DIPLOPIA : Acute onset of a vertical diplopia,
which is more on downward gaze ,it is noted by patients while
coming down stairs and while doing near work. SIGNS : 1)HYPERTROPIA
the involved eye is higher as a result of weakness of the superior
oblique muscle, which becomes more prominent when the head is
tilted towards the ipsilateral shoulder 2)RESTRICTED OCULAR
MOVEMENTS: there is limitation of depression on adduction.
3)ABNORMAL HEAD POSTURE: to avoid diplopia ,head takes a posture
towards the action of the superior oblique muscle, face is slightly
turned to the opposite side, chin is depressed, and head is tilted
towards the opposite side.
12. COMPENSATORY HEAD POSTURE IN LEFT 4TH NERVE PALSY HEAD IS
TILTED TO THE RIGHT. FACE IS TURNED TO THE RIGHT.AND CHIN IS
DEPRESSED.
13. SPECIAL TESTS USED IN DIAGNOSIS OF 4TH NERVE PALSY : 1)
PARKS BIELSCHOWSKY THREE STEP TEST. 2) DOUBLE MADDOX ROD TEST.
Park-Bielschowsky 3 step test
14. PARK-BIELSCHOWSKYTHREE STEP TEST: STEP 1 :( to assess which
eye is hypertropic in the primary gaze.) In case of left
hypertropia, the following four muscles could be involved: 1)
Depressors of the left eye i.e superior oblique and inferior
rectus. 2) Elevators of the right eye i.e the superior rectus or
inferior oblique. In a 4th nerve palsy the involved eye is always
higher.
15. STEP 2 : (which lateral direction has worse hypertropia )
If the left hypertropia increases on right gaze implicates a left
superior oblique or right superior rectus involvement. Increase in
the left gaze implicates that either the right inferior oblique or
left inferior rectus are involved. In 4th nerve palsy the deviation
IS WORSE ON OPPOSITE GAZE . (WOOG)
16. STEP 3: ( in which head tilt direction is the hypertropia
worse ) The head tilt test is performed with the patient fixating
at a straight ahead target at 3 mts. Increase in left hypertropia
on left head tilt implies the left superior oblique is involved ,
and increase in right hypertropia on left head tilt indicates the
right inferior rectus is involved. In 4th nerve palsy the deviation
is BETTER ON OPPOSITE TILT(BOOT).
17. In Right SO palsy , on right head tilt RSR will work thus
the eye will move upwards
18. 4TH CONFORMATORY STEP: (is the hypertropia worse in upgaze
or downgaze) If the left hypertropia increases on down gaze it
confirms that the left superior oblique is involved . Helps to rule
out mimickers like myasthenia and thyroid disease.
19. DOUBLE MADDOX ROD TEST A unilateral 4th nerve palsy is
characterized by less than 10 degree of cyclodeviation, while a
bilateral palsy will have more than 20 degree of
cyclodeviation.
20. CHECKING 4TH CN FN IN 3RD CN PARESIS Vertical actions
cannot be tested as there is 3rd N involvement (adduction) To solve
this , note a limbal or conjunctival landmark. Ask the pt to look
down. The pt will not be able to look down as the eye is abducted
and not adducted. But the eye should intort as the SO works. Check
for the conjunctival landmark to see if the eye is intorting. If
the conjunctival landmark is moving the eye is intorting thus the
4th CN is intact.
21. ACTIONS OF SUPERIOR OBLIQUE 1. Intorsion 2. Depression 3.
Abduction
22. MANAGEMENT Occlusion: Double vision is restricted to the
downward gaze, occlude the lower third of the spectacle lens before
the affected eyewith semi opaque tape. Surgical: