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Traumatic Optic Neuropathy

2 / 17. Traumatic Optic Neuropathy. Is a devastating potential complication of closed head injury. The hall mark is a loss of visual function ? subnormal visual acuity, visual field loss and colour vision dysfunction and the presence of afferent pupillary defect ? prechiasmatic location.TON is see

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Traumatic Optic Neuropathy

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    1. September 2006 www.riogohchennai.ac.in 1 / 17 Traumatic Optic Neuropathy By Prof. N. Karthikeyan.

    2. 2 / 17 Traumatic Optic Neuropathy Is a devastating potential complication of closed head injury. The hall mark is a loss of visual function – subnormal visual acuity, visual field loss and colour vision dysfunction and the presence of afferent pupillary defect – prechiasmatic location. TON is seen in 2.5% of mid facial injury and 2.5% of closed head injury. At the Institute of Neurology, GGH, Chennai the incidence is about 0.1%.

    3. 3 / 17 History 18th century – recognized the relation between frontal trauma, vision loss in the absence of ocular injury. In 1879 Berlin described first the pathological examination of the optic nerve after head trauma. In 1890 Battle distinguished penetrating from non penetrating indidect optic nerve injury. 20th century – definition, classification, pathophysiology and traumatic optic nerve injury has been described. 1900 – transcranial unroofing of the optic canal was the surgical procedure for TON. In 1920 Sewell performed transethmoidal optic canal decompression. Recently endoscopic instrumentation has gained popular support for endoscopic transnasal optic nerve decompression.

    4. 4 / 17 Anatomy Orbit is pyramidal, base is anterior. Orbital walls converge posteriorly near SOF and OF. Optic canal is separated from the SOF by optic strut. Optic canal is about 6.5 mm in diameter and 8.1 mm in length.

    5. 5 / 17 Anatomy

    6. 6 / 17 Anatomy Optic nerve is 3.4 mm in diameter, measures 35 – 50 mm from the retina to optic chiasm.- intraocular 1 mm, intraorbital 20 – 30 mm, intracanalicular 5 – 11 mm and intracranial 3 – 16 mm. axons of the nerve have their origin from the nerve fibre layer of the Retina. Except intraocular segment the axons of the Optic nerve are myelinated. Pial branches of the ICA, ACA, Acom. A perfuse intracranial optic nerve. Intraorbital Optic nerve is supplied by perforating branches of the Ophthalmic artery.

    7. 7 / 17 Pathophysiology TON can occur anywhere along the nerve intraorbital or intracranial. It can be Direct – Optic nerve is avulsed, impinged, crushed or transected by penetrating wound with knife, pencil, bullets or pellets by extensive crush injuries displaced cranio orbital fracture by surgical repair of facial bone fractures

    8. 8 / 17 Pathophysiology Indirect – most common form after blunt trauma to superior orbital rim, lateral orbital wall or frontal area. Compression force from trauma transmitted via orbital bone to orbital apex and optic canal. Elastic deformation of the sphenoid bone allows the force to be transmitted to intracanalicular segment of the Optic nerve. Contusion of the intracanalicular Optic nerve axons and Pial vasculature produce localized Optic nerve ischaemia and oedema.

    9. 9 / 17 Diagnosis Essentially clinical. Suspect if there is midfacial injury, orbital, frontal bone fracture. A loss of best corrected V/A or VF accompanied by ipsilateral RAPD. Identify premorbid ocular condition that limits visual recovery.

    10. 10 / 17 Diagnosis Perform complete ophthalmic examination – Ocular adnexa – orbital rim wall fracture, orbital oedema, proptosis, EOM dysfunction, signs of penetrating injuries, extrusion of orbital contents. Visual acuity – serial assement Pupillary reaction – an afferent pupillary defect. IOP increase due to orbital haematoma, diffuse orbital haematoma, orbital emphysema, soft tissue oedema. Ophthalmoscopy – evaluate Retinal, Choroidal, ONH morphology and presence of Ring shaped haematoma adjacent to Optic nerve head.

    11. 11 / 17 Investigations

    12. 12 / 17 Investigations

    13. 13 / 17 Investigations PT, APTT, bleeding time CT Scan of orbit Perimetry Multifocal VEP Multifocal ERG – Identify subclinical loss.

    14. 14 / 17 Treatment Medical – observation, steroids, antioxidants Surgical – optic nerve decompression

    15. 15 / 17 Treatment Indications for surgical treatment - Clinical signs of optic nerve injury CT Scan / MRI Scan showing optic nerve sheath haematoma, optic canal fracture No improvement with high dose steroids

    16. 16 / 17 Treatment Surgical procedures – Intracranial subfrontal approach Extracranial external Ethmoidectomy Extracranial endoscopic Sphenoethmoidectomy

    17. 17 / 17 Other independent Trauma induced optic neuropathy Optic nerve avulsion due to – severe orbital trauma profound rotation of the globe fracture of the nerve at sclera-Lamina`cribrosa Optic nerve transaction Diffuse orbital haemorrhage diagnosed by CT / MRI Localized orbital haemorrhage Optic sheath haematoma Orbital emphysema

    18. 18 / 17 Other independent Trauma induced optic neuropathy

    19. 19 / 17 Other independent Trauma induced optic neuropathy

    20. 20 / 17 Other independent Trauma induced optic neuropathy

    21. 21 / 17 Other independent Trauma induced optic neuropathy

    22. 22 / 17 Thank you

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