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4th nerve palsy

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4th nerve palsy

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4th nerve palsy

  1. 1. 4TH NERVE PALSY TROCHLEAR NERVE PALSY SUPERIOR OBLIQUE PALSY
  2. 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. 3. ANATOMY Anatomically Segments  Nucleus  Intracranial course  Extracranial course  Central  Cisternal  Cavernous &  Orbital * = 4th cranial nerve nucleus
  4. 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. 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. 6. ANATOMY - CONT • In the intraorbital part, the 4th CN doesn’t 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. 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. 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. 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. 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 Horner’s 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. 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. 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. 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. 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. 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. 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. 17. In Right SO palsy , on right head tilt RSR will work thus the eye will move upwards
  18. 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. 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. 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. 21. ACTIONS OF SUPERIOR OBLIQUE 1. Intorsion 2. Depression 3. Abduction
  22. 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:
  23. 23. THANK YOU

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