Orbital trauma
John Dudley Langdon, Mohan Francis Patel, Robert Andrew Ord, Peter Brennan in Operative Oral and Maxillofacial Surgery, 2017
At the orbital apex, the medially located optic canal passes through dense bone of the sphenoid bone transmitting the optic nerve together with the central artery of the retina. More laterally, the superior orbital fissure transmits branches of the ophthalmic division of the trigeminal nerve together with the third, fourth and sixth cranial nerves. The ‘superior orbital fissure syndrome’ comprises total ophthalmoplegia, upper lid ptosis and anaesthesia in the distribution of the ophthalmic division of the trigeminal nerve, ‘orbital apex syndrome’ includes these signs in conjunction with blindness. Within the orbit, the globe is supported by Lockwood’s suspensory ligament and moved by the extraocular muscles, it is enclosed in periorbital fat whose loss can contribute to enophthalmos. Anterior to the globe, the upper and lower tarsal plates are attached to the medial and lateral walls by the medial and lateral palprebal ligaments. This tense fascial sheath constitutes a ‘fifth wall’ of the orbital pyramid thereby forming a closed box. It is important to recognize this, for if orbital pressure increases following trauma, release of this fascial band by way of a lateral canthotomy can be sight saving, an important emergency surgical skill in the management of these injuries.
Clinical Neuroanatomy
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
Lesions in the optic canal readily cause visual disturbance and a central scotoma is often the first evidence of a lesion at this site. This may be followed by extraocular nerve palsies and very much later, proptosis. Meningiomas or neurofibromas are the most frequent tumours arising in the posterior orbit. Neoplastic infiltration from the paranasal sinuses and nasopharynx can occur and metastatic spread from remote sites, such as the prostate in adult males or suprarenal gland in children, are well recognized. In general, the tempo of development of the signs and the presence or absence of pain will indicate the likely diagnosis.9 The slow painless onset of symptoms usually indicates a benign lesion, while rapidly evolving symptoms, accompanied by pain, indicate a metabolic, neoplastic or infective process in the area.
Disorders of Sensation, Motion, and Body Schema
Rolland S. Parker in Concussive Brain Trauma, 2016
This is caused by forces that are transmitted at a distance from the optic nerve (e.g., blunt trauma to the forehead that results in a transmission of force through the cranium to the confined intracanalicular portion of the nerve). One cause is a deceleration injury of sufficient momentum, with the force of the impact directed to the ipsilateral forehead or mid-face region. Shearing injures the optic nerve axons and its sheaths, particularly within the optic canal, where it is tightly bound. Although evidence is obtained from serious trauma, optic neuropathy is associated with sphenoid bone fracture; forces applied to the frontal bone in a deceleration injury are transmitted to and concentrated in the region of the optic canal. Secondary trauma involves vasoconstriction and swelling of the optic nerve within the optic canal (leaving the orbit). The optic nerve is subject to secondary chemical traumata (Miller & Newman, 1999, p. 284).
Clinical Evaluation and Treatment Outcome of Traumatic Optic Neuropathy in Nepal: A Retrospective Case Series
Published in Neuro-Ophthalmology, 2018
Sanjeeta Sitaula, Hira Nath Dahal, Ananda Kumar Sharma
Another way to classify TON is based on the site of injury. Intraocular optic nerve injury resulting from violent rotation of the globe leads to avulsion of the distal end of the optic nerve and usually assumes a typical fundus picture of peripapillary haemorrhage and disruption of the choroid. In the orbit, the nerve is redundant and is cushioned by orbital fat, hence the less chance of indirect injury. Trauma in this region is mainly due to intraorbital haemorrhage or emphysema causing either ischaemia or elevated intraorbital pressure compromising the circulation of optic nerve known as orbital compartmental syndrome. Intracanalicular injury is the most common site for TON and is associated with high-momentum decelerating injuries, especially in frontotemporal region. Optic nerve is strongly tethered to bone at the orbital opening of the optic canal, in the canal itself, and at the intracranial entrance of the canal. Moreover, the optic canal has a mean subdural cross-sectional space of only 1.84 mm2. Thus, even small amounts of bleeding or oedema may infarct the nerve and the fracture of canal may injure the nerve. At both ends of the canal, the nerve is also subjected to shearing forces, because the brain and orbital contents are free to move, but the intracanalicular portion of the nerve is not. The intracranial optic nerve is the next most common site of injury, followed by injuries that also involve the chiasm that produces characteristic visual field changes.19
Neuro-Ophthalmic Literature Review
Published in Neuro-Ophthalmology, 2022
David A. Bellows, Noel C. Y. Chan, John J. Chen, Hui-Chen Cheng, Peter W. MacIntosh, Michael S. Vaphiades, Konrad P. Weber, Xiaojun Zhang
Among 92 patients with clinically diagnosed TED, 49 patients (98 orbits) were allocated to the TED-only group. DON was diagnosed in 43 patients, of which 76 orbits were allocated to the TED+DON group. Orbits of the unaffected eyes (10 orbits) in patients with unilateral DON were allocated to the TED+DON (unaffected) group. Forty orbits of 20 subjects were recruited as controls. Muscle volumes of each muscle were significantly higher in the TED+ON group than the TED alone group. However, the authors found that medial rectus (MR) muscle volume was the strongest predictor for the development of DON and they suggested patients with a MR muscle volume of >0.9 cm3 should be monitored more closely. This is most likely due to its close anatomical relationship with the optic nerve in the optic canal.
Aplasia of the Optic Nerve: A Report of Seven Cases
Published in Neuro-Ophthalmology, 2020
Yujia Zhou, Maura E. Ryan, Marilyn B. Mets, Hawke H. Yoon, Bahram Rahmani, Sudhi P. Kurup
MRI confirms the diagnosis and can provide information on other CNS abnormalities (Figure 2). In our review, the contralateral optic nerve appears unremarkable in unilateral ONA. The optic chiasm is either abnormal or hypoplastic in all cases (n = 7, 100%). The measurements of the optic canal and optic tracts are shown in Table 1. There may be small margins of error when measuring these small structures, as the MRI slice thickness is 2–3 mm, even though dedicated orbital images were used. In unilateral ONA, the ipsilaterally involved optic canal is smaller. The optic tracts are not detectable in bilateral ONA and are asymmetric in unilateral ONA. Interestingly in all cases of unilateral ONA (3 of 3, 100%), the optic tracts are larger on the side ipsilateral to the ONA. Such asymmetry was also reported in one previous study.5 On the other hand, the patient from another case report of unilateral ONA had symmetrical optic tracts.15 Due to the small sample size of our study and previous studies, it is difficult to conclude whether and how the size of the optic tract is related to the laterality of ONA, especially considering that there is partial decussation of the contralateral optic nerve at the optic chiasm.
Related Knowledge Centers
- Ophthalmic Artery
- Optic Nerve
- Sphenoid Bone
- Sympathetic Nervous System
- Chiasmatic Groove
- Optic Chiasm
- Orbit
- Ophryon