traumatic optic neuropathy ( ton ) is an impact injury to the optic nerve , usually secondary to blunt head trauma , resulting in partial or complete loss of vision .
a meta - analysis reported that both steroid administration and surgical decompression improved the prognosis of patients with ton .
after consideration of a lateral or medial orbitotomy , as well as transcranial approaches to the orbital apex and optic nerve canal , an endonasal transethmoidal - sphenoidal approach represents an alternative strategy for the treatment of ton .
the endoscopic anterior - to - posterior technique offers many advantages , including decreased morbidity , preservation of olfaction , rapid recovery time , more acceptable cosmetic results without external scars and no risk of injury to developing teeth in children .
however , despite its safety , effectiveness , and minimal invasiveness , the long - term effects of the iatrogenic trauma ( removal of uncinate process and anterior ethmoidal sinus ) resulting from the complete ethmoidectomy procedure used to gain full access to the optic nerve canal is unknown , and sequelae such as nasal synechia and sinusitis should not be ignored .
anatomically , the optic canal is just superolateral to the sphenoid sinus as a part of the lesser sphenoid wing .
the canal is wide with thin walls proximally toward the optic chiasm , and narrow with thick walls distally at the optic tubercle .
the optic tubercle is the thick bulge of the medial aspect of the bone surrounding the optic foramen .
depending on the degree of pneumatisation or the presence of superspheno - ethmoid ( onodi ) cellulae , the optic tubercle can be visualized within the sphenoid sinus or at the junction of the sphenoid and posterior ethmoid sinuses . in the case of high sphenoidal pneumatisation
, the use of an angled endoscope allows clear visualisation of the lateral sphenoidal wall and the orbit apex .
this raises the possibility that optic nerve decompression can be performed through a single trans - sphenoidal approach rather than using complete ethmoidectomy .
herein , we report five cases of ton in which a modified surgical procedure for endoscopic optic nerve decompression was performed , using a 45 endoscope . we include discussion of the operative events , along with the apparent advantages and limitations .
five patients with ton , all of whom were unresponsive to high - dose methylprednisolone ( 500 mg / day ) for more than 7 days , were enrolled to undergo modified endoscopic optic nerve decompression .
only patients with high sphenoidal pneumatisation and without onodi cellulae identified by preoperative fine - cut computed tomography ( ct ) scan [ figure 1 ] were included .
this study was approved by the ethical committee of our hospital , and a written informed consent was obtained from each subject .
demographics of five ton patients performed modified optic nerve decompression representative preoperative computed tomograpgy ( ct ) scan of a traumatic optic neuropathy ( ton ) patient ( a ) coronal view ; ( b ) horizontal view the surgical procedure was modified from what we have previously described .
briefly , patients were prepared in the routine manner for endoscopic sinus surgery under general anesthesia .
cotton pledgets soaked in epinephrine solution were placed in the nasal cavity to ensure vasoconstriction .
in contrast to the standard endoscopic ethmoidectomy procedure , we located the ostium of the sphenoid sinus by removing the superior turbinate [ figure 2a ] . when the sphenoid sinus was opened and the ostium was enlarged to the lateral wall , the optic nerve canal was clearly identified using a 0 or 45 endoscope [ figure 2b ] . in two cases ,
the posterior ethmoids were slightly opened retrograde from the sphenoid to improve the exposure of the optic nerve canal .
representative endoscopic view of optic nerve decompression using a modified trans - sphenoidal approach ( a ) sphenoidal ostium ; ( b ) optic nerve canal ; ( c ) optic nerve ; ( d ) intact middle meatus so , sphenoidal ostium ; st , superior turbinate ; onc , optic nerve canal ; on , optic nerve ; mt , middle turbinate the orbital apex was then dissected to expose the lateral wall of the sphenoid sinus . under endoscopic observation , a long - hand microdrill with a diamond burr was used to remove the medial wall of the bony optic canal . to avoid thermal injury to the optic nerve ,
the optic nerve canal was drilled 180 medially from the optic tubercle to near the optic chiasm until the bony canal became very thin .
a special instrument was then used to elevate the thin bony canal from its position over the optic nerve .
extreme care was taken to not exert pressure on the optic nerve with the elevator [ figure 2c ] .
we modified the routine procedure for endoscopic optic nerve decompression as follows : we used a endonasal trans - sphenoidal approach instead of a endonasal transethmoidal - sphenoidal approach to keep the anterior ethmoidal sinus and middle meatus intact [ figure 2d]we drilled off the distal bony wall of the optic nerve canal using a 0 endoscopewe drilled off the proximal bony wall of the orbital apex using a 45 angled endoscopewe maintained the integrity of optic nerve without incision of the optic sheath .
we used a endonasal trans - sphenoidal approach instead of a endonasal transethmoidal - sphenoidal approach to keep the anterior ethmoidal sinus and middle meatus intact [ figure 2d ] we drilled off the distal bony wall of the optic nerve canal using a 0 endoscope we drilled off the proximal bony wall of the orbital apex using a 45 angled endoscope we maintained the integrity of optic nerve without incision of the optic sheath .
all patients received regular follow - up care including visual acuity and field chart testing 10 days postoperatively .
a patient 's vision was considered to have improved if they showed any of the following : an improvement from no light perception to light perception or better ; an improvement from light perception to hand motion or better ; an improvement from hand motion to finger counting or better .
five patients with ton , all of whom were unresponsive to high - dose methylprednisolone ( 500 mg / day ) for more than 7 days , were enrolled to undergo modified endoscopic optic nerve decompression .
only patients with high sphenoidal pneumatisation and without onodi cellulae identified by preoperative fine - cut computed tomography ( ct ) scan [ figure 1 ] were included .
this study was approved by the ethical committee of our hospital , and a written informed consent was obtained from each subject .
demographics of five ton patients performed modified optic nerve decompression representative preoperative computed tomograpgy ( ct ) scan of a traumatic optic neuropathy ( ton ) patient ( a ) coronal view ; ( b ) horizontal view
briefly , patients were prepared in the routine manner for endoscopic sinus surgery under general anesthesia .
cotton pledgets soaked in epinephrine solution were placed in the nasal cavity to ensure vasoconstriction .
in contrast to the standard endoscopic ethmoidectomy procedure , we located the ostium of the sphenoid sinus by removing the superior turbinate [ figure 2a ] . when the sphenoid sinus was opened and the ostium was enlarged to the lateral wall , the optic nerve canal was clearly identified using a 0 or 45 endoscope [ figure 2b ] . in two cases ,
the posterior ethmoids were slightly opened retrograde from the sphenoid to improve the exposure of the optic nerve canal .
representative endoscopic view of optic nerve decompression using a modified trans - sphenoidal approach ( a ) sphenoidal ostium ; ( b ) optic nerve canal ; ( c ) optic nerve ; ( d ) intact middle meatus so , sphenoidal ostium ; st , superior turbinate ; onc , optic nerve canal ; on , optic nerve ; mt , middle turbinate the orbital apex was then dissected to expose the lateral wall of the sphenoid sinus . under endoscopic observation , a long - hand microdrill with a diamond burr was used to remove the medial wall of the bony optic canal . to avoid thermal injury to the optic nerve ,
the optic nerve canal was drilled 180 medially from the optic tubercle to near the optic chiasm until the bony canal became very thin .
a special instrument was then used to elevate the thin bony canal from its position over the optic nerve .
extreme care was taken to not exert pressure on the optic nerve with the elevator [ figure 2c ] .
we modified the routine procedure for endoscopic optic nerve decompression as follows : we used a endonasal trans - sphenoidal approach instead of a endonasal transethmoidal - sphenoidal approach to keep the anterior ethmoidal sinus and middle meatus intact [ figure 2d]we drilled off the distal bony wall of the optic nerve canal using a 0 endoscopewe drilled off the proximal bony wall of the orbital apex using a 45 angled endoscopewe maintained the integrity of optic nerve without incision of the optic sheath .
we used a endonasal trans - sphenoidal approach instead of a endonasal transethmoidal - sphenoidal approach to keep the anterior ethmoidal sinus and middle meatus intact [ figure 2d ] we drilled off the distal bony wall of the optic nerve canal using a 0 endoscope we drilled off the proximal bony wall of the orbital apex using a 45 angled endoscope we maintained the integrity of optic nerve without incision of the optic sheath .
all patients received regular follow - up care including visual acuity and field chart testing 10 days postoperatively .
a patient 's vision was considered to have improved if they showed any of the following : an improvement from no light perception to light perception or better ; an improvement from light perception to hand motion or better ; an improvement from hand motion to finger counting or better .
the cause of ton included motorcycle accidents ( 4/5 ) and a fall ( 1/5 ) .
after performing a direct sphenoidotomy through the natural ostium of the sphenoid sinus rather than a complete ethmo - sphnoidectomy , we found that the endonasal trans - sphenoidal approach provided adequate access to the optic nerve canal and the apex using a 45 angled endoscope .
successful decompression of the canal optic nerve was performed trans - sphenoidally in all five patients using an angled endoscope .
no surgical complications occurred , and none of the patients suffered from anterior ethmoidal sinus or skull base damage .
in this study , we successfully developed a modified endoscopic optic nerve decompression procedure for five patients with ton with severe sphenoidal pneumatisation and without onodi cellulae .
our results suggest that modified endoscopic optic nerve decompression is a safe , effective , and minimally invasive strategy for specially selected ton patients .
ton is an important cause of severe visual impairment following blunt or penetrating head trauma .
treatment options include steroids , surgical decompression , or both , with no consensus on the optimal protocol .
the use of high - dose steroids after optic nerve injury became more common during the 1980s , following the rationale that steroids may reduce post - traumatic edema , contusion necrosis , and vasospasm , and thus aid functional recovery .
previous studies have reported improvement in between 44% and 82% of patients following steroid therapy . however , in other studies , 57% of untreated patients showed improvement in visual acuity , indicating spontaneous remission . the indications for endoscopic optic nerve decompression are also cause for debate .
it has been suggested that such surgery should only be performed following failure of high - dose steroid therapy .
some authors suggested that endoscopic optic nerve decompression be performed if vision fails to improve after 72 hours of methylprednisone therapy ; or if progressive visual loss during steroid therapy is observed .
additionally , complete blindness with ct evidence of optic nerve compression was also put forth as an indication for surgery . despite the lack of evidence showing a clear benefit for either steroids or surgery or combined therapy , patients with ton have a strong desire for endoscopic optic nerve decompression for vision salvage . in this study , we sought to develop a novel , less invasive surgical approach rather than to address the clinical efficacy of and indications for endoscopic optic nerve decompression .
currently , a traditional transethmoidal - sphenoidal approach is generally performed to gain wide access to the optic nerve canal and optic apex by means of a complete endoscopic ethmoidectomy and sphenoidotomy .
however , the complete endoscopic ethmoidectomy includes removal of the uncinate process and anterior ethmoidal sinus , and the long - term effects of this trauma are unknown . additionally , common postoperative sequelae such as nasal synechia and sinusitis should not be ignored . to avoid iatrogenic trauma as much as possible
, we developed a modified surgical procedure that leaves the uncinate process , ethmoidal bulla , and middle meatus intact . in this study
, we modified the endonasal transethmoidal - sphenoidal approach by using an endonasal trans - sphenoidal approach to avoid removing the uncinate process and anterior ethmoidal sinus . in cases of high sphenoidal pneumatisation
, we were able to drill off the distal bony wall of the optic nerve canal using a 0 endoscope , and drill off the proximal bony wall of the orbital apex using a 45 angled endoscope .
in addition , the modified endonasal trans - sphenoidal approach may be especially appropriate for patients with lamina papyracea bony fragments , in whom the orbital fat herniating into the ethmoidal sinus typically blocks access to the sphenoidal sinus and orbit apex .
we successfully conducted trans - sphenoidal decompression of the canal optic nerve in all five patients .
the decision to perform nerve sheath incision during optic nerve decompression is also under debate .
based on our unpublished data , we found no additional optic vision improvement following incision of the optic sheath .
thus , we made a second modification by maintaining the optic nerve intact without incision of the optic sheath .
consequently , we showed that incision of the optic sheath is not a prerequisite for successful optic nerve decompression .
first , although the uncinate process and anterior ethmoidal sinus were kept intact , the posterior ethmoids were slightly opened retrograde from the sphenoid to improve the exposure of the optic nerve canal in two of five cases ; thus , the minimal trauma of this approach can not be over - interpretated for some patients .
it is also worthwhile to note that all five patients had high sphenoidal pneumatisation without onodi cellulae ( identified by a preoperative fine - cut ct scan ) , as the optic nerve canal may not be accessible in the case of onodi cellulae .
additionally , when the ostium of sphenoidal sinus is enlarged to the lateral wall , the optic nerve canal need to be identified using a 45 endoscope to gain appropriate access to the lateral sphenoidal wall and orbit apex , which may increase the technical difficulty of the surgery .
our study demonstrates that a modified trans - sphenoidal optic nerve decompression is a feasible , safe , effective , and minimally invasive approach for ton patients with high sphenoidal pneumatisation and without supersphenoid - ethmoid cellulae . in cases of high sphenoidal pneumatisation
, the use of an angled endoscope allows for easy access to the optic nerve canal and the orbit apex using a trans - sphenoidal approach while keeping the uncinate process and anterior ethmoidal sinus intact .
 background : although the endoscopic anterior - to - posterior technique offers many advantages , the long - term effects of the iatrogenic trauma ( removal of the uncinate process and anterior ethmoidal sinus ) resulting from the complete ethmoidectomy procedure used to gain full access to the optic nerve canal is unknown , and sequelae such as nasal synechia and sinusitis should not be ignored.aims:the aim of our study is to develop a less invasive procedure for endoscopic optic nerve decompression.materials and methods : we proposed a modified trans - sphenoidal surgical procedure for endoscopic optic nerve decompression in five patients with traumatic optic neuropathy ( ton ) , all with high sphenoidal pneumatisation and without onodi cellulae.results:after performing a direct sphenoidotomy through the natural ostium of the sphenoid sinus rather than a complete ethmo - sphnoidectomy , we found that the modified approach provided adequate access to the optic nerve canal and the apex using a 45 angled endoscope . 
 successful decompression of the canal optic nerve was performed trans - sphenoidally in all five ton patients using an angled endoscope . 
 no surgical complications occurred , and none of the patients suffered from anterior ethmoidal sinus or skull base damage.conclusions:the modified trans - sphenoidal approach is a feasible , safe , effective , and minimally invasive approach for ton patients with high sphenoidal pneumatisation and without supersphenoid - ethmoid cellulae . 