View
170
Download
5
Category
Preview:
Citation preview
Free Template from www.brainybetty.com 3
FUNCTIONAL COMPONENTS
• SOMATIC EFFERENT-concerned with movement of eye ball through SO.
• GENERAL SOMATIC AFFERENT-carries proprioceptive impulses from SO which are relayed in the mesencephalic nucleus of 5 th nerve.
Free Template from www.brainybetty.com 4
COURSE AND DISTRIBUTION
1)Fascicular part
2)Pre cavernous part
3)Intra cavernous part
4)Intra orbital part
Free Template from www.brainybetty.com 5
• SITUATION: at the level of inferior colliculus in the ventromedial part of central gray metter of midbrain dorsal to medial longitudinal bundle.
• Caudal & continous with 3rd nucleus complex.
Free Template from www.brainybetty.com 8
FASCICULAR PART:
• axons leave the nucleus
• curve posteriorly around the aquiduct in the central greymatter
• decussate in the anterior medullary velum.
Free Template from www.brainybetty.com 10
PRECAVERNOUS PART: leaves the brainstem on the dorsal surface
just caudal to inferior colliculus winds around brainstem runs forwards beneath the free edge of
tentorium pierces the dura on the posterior corner of
the roof of cavernous sinus to enter in to it.
Free Template from www.brainybetty.com 11
INTRACAVERNOUS PART:
Runs forwards in the lateral wall of the sinus,lying below 3rd nerve and above the 1st division of 5th nerve.
In the anterior part of the sinus, it rises,
crosses over the 3rd nerve
passes through the superior orbital fissure, above and lateral to annulus of zinn.
Free Template from www.brainybetty.com 13
INTRA ORBITITAL PART:
• Enters the orbit through lateral part of SOF
• Frontal & lacrimal nerves laterally, ophthalmic vein inferiorly.
• Divides in to fan shaped manner into 3 or 4 branches
• Ends by supplying SO on its orbital surface near lateral border.
Free Template from www.brainybetty.com 17
CONNECTIONS:
1)Cerebral cortex
Motor cortex - cortico nuclear tracts
Visual cortex - supeior colliculus & tactobulbar Frontal eye field. tracts.
2)Nuclei of 3rd ,6th&8th -MLF
3)Superior colliculi -descending predorsal bundle
4)Vertical & torsional gaze centres
5)Cerebellum - vestibular nuclei.
Free Template from www.brainybetty.com 18
UNIQUE CHARACTERS
• Only cranial nerve to emerge from dorsal aspect of brain.
• Only crossed cranial nerve
• Longest Intra cranial course(about 75 mm)& thinnest of all cranial nerves
Free Template from www.brainybetty.com 19
CLINICAL FEATURESSYMPTOMS:• Ac.onset of double vision,• Difficulty in going downstairs,• VertigoSIGNS: • Hyperdeviation ,limitation of depression in adduction,• Extorsion, vertical diplopia,• Hypertropia on opposite gaze• Charecteristic head posture- head tilted to opposite side face turned towards opposite side chin depressed
Free Template from www.brainybetty.com 22
PARK’S 3 STEP TEST:
STEP 1: Identify the HYPERTROPIC EYE in primary position.
depressors of hypertropic eye- SO,IR.
elevators of hypotropic eye-SR,IO.
STEP 2: Determine whether hypertropia is greater in Rt or Lt gaze.
on Lt gaze Lt SR, Rt.SO
on Rt gaze Rt IR, Lt IO
Free Template from www.brainybetty.com 23
STEP 3: Tilt the head towards each shoulder, look for vertical sqint.
BEILSCHOWSKY HEAD TILT TEST: same principle as the 3rd step of PARK TEST Pt fixates, head tilted Rt &Lt of Lt hypertropia on Lt head tilt- Lt SO of Lt hypertropia on Rt head tilt- Lt IR
Free Template from www.brainybetty.com 25
DOUBLE MADDOX ROD TEST :
For measuring the degree of cyclodeviation.
In unilateral palsy – cyclodeviation <10 deg
In bilateral palsy – cyclodeviation >10 deg
Free Template from www.brainybetty.com 27
Differential Diagnosis of Vertical Binocular Diplopia• Superior Oblique Palsy• Thyroid Ophthalmopathy• Myasthenia Gravis• Brown Syndrome• Orbital fracture with entrapment• Cyclovertical paresis or overaction• Skew Deviation/Ocular Tilt• Dissociated Vertical Deviation
Free Template from www.brainybetty.com 28
Isolated Superior Oblique Palsy
• Most common etiologies are congenital and traumatic
• Also vascular; less commonly tumor, demyelinating
• In absence of other neurological symptoms and presence of vascular risk factors, reasonable to observe
Free Template from www.brainybetty.com 29
TREATMENT• CONGENITAL:large hypertropia in PP treated by
SO tucking• ACQUIRED:
SMALL- ipsilateral IO weakening.
MODERATE- ipsilateral IO weakening with ipsilateral SR weakening .
PURE EXCYCLOTROPIA: without hypertropia –HARADA- Ito procedure
Splitting & ALT OF lateral half of SO tendon.
Recommended