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The viva: operative surgery and surgical anatomy
Published in Vivian A. Elwell, Ramez Kirollos, Syed Al-Haddad, Neurosurgery, 2014
Vivian A. Elwell, Ramez Kirollos, Syed Al-Haddad
Three anatomical landmarks are identified on the patient’s face: The point supero-lateral to the zygoma and 3 cm in front of the tragus.The point at the intersection of the same axial plane and the midpupillary line.The point 3 cm lateral to the mouth’s corner on the bicommissural line. 5 mL of xylocaine 1% with adrenaline (epinephrine) is used as local infiltration.Placing your index finger inside the mouth, a 22G spinal needle is used to guide the needle toward the foramen ovale.X-ray guides the needle to the correct location in the trigeminal cistern.The foramen ovale is seen through the pterygomandibular and infratemporal space as an oval structure at the top of the petrous pyramid.The patient may wince when the needle penetrates the foramen.When the tip of the cannula is located inside the arachnoid of trigeminal cistern, there may be spontaneous egress of CSF.Iohexol is injected into the cistern as the table is tilted upward to outline Meckel’s cave.The inferior edge of the gasserian ganglion can be seen as the superior edge of the outlined space. The amount of iohexol to fill the cistern is measured by injecting until the dye overflows into the posterior fossa. The iohexol is withdrawn and anhydrous glycerol is injected into the same area to fill the cistern.
Acute Vision Loss as an Ophthalmic Complication of Dental Procedures
Published in Seminars in Ophthalmology, 2021
Cody Lo, Ashley H.S. Kim, Ahmed Hieawy, Nawaaz A. Nathoo
Compression of the optic nerve leading to vision loss as a complication of dental procedures can occur if air is introduced into the soft tissue planes of the orbit leading to increased intra-orbital pressure. High-speed rotary instruments are commonly used in dental extractions to facilitate the removal of impacted or diseased teeth.46 These cutting instruments utilize air to cool the bur when in operation, which may be directed back toward the bur.46 Anterograde flow of air can result in the introduction of air into the tissue planes of the oral cavity often referred to as “compressed air injury”.46 As established earlier in this review, there are multiple soft tissue planes connecting the face, neck, and chest.25 Positive-pressure events, such as Valsalva or sneeze, in combination with compromised oral mucosa and defects in the maxillary sinus wall can allow air to dissect along tissue planes to reach the orbital and periorbital tissues.22–24 Odontogenic dental infections can also result in emphysema if caused by gas producing organisms.25 The maxillary teeth are adjacent to the canine and infratemporal spaces, which can allow emphysema to spread to the orbit relatively easily through the maxilla.23 Mandibular teeth have a slightly more tortuous course through fascial planes leading to the orbit but the first, second, and third mandibular molars are particularly susceptible to this phenomenon as their roots communicate directly with the buccal space. This can allow emphysema to spread into the infratemporal space followed by the orbit. Orbital emphysema following dental procedures typically manifests over several days and is relatively obvious on examination with ipsilateral facial crepitus and proptosis.22 Previous reported cases with no radiological evidence of infection, normal visual acuity, and normal IOP have resolved spontaneously and there appear to be few examples where intervention was needed to evacuate air.22,24 A case reported by Fleischman et al (2014) attempted to decompress emphysema of the eyelid despite normal visual acuity and IOP using a 30-gauge needle but only relieved a small amount of air; despite this, the patient made a full recovery by day 7.23 These cases suggests that, regardless of intervention, full recovery is possible and that orbital emphysema can be monitored conservatively in the presence of normal ocular findings. However, there have been reported cases where there is not spontaneous resolution with persistent visual field deficits at least 5 months following orbital emphysema secondary to tooth extraction.5 Roelofs et al. (2019) has described an approach to orbital emphysema delineating that severe cases of orbital emphysema may require lateral canthotomy or needle decompression.25