a 49-year - old man presented with a year - long history of 
 watering without sticky discharge on the left side . lacrimal sac syringing demonstrated a regurgitation of fluid 
 from the opposite punctum and a hard stop on probing . intraoperatively , the bony ostium was 
 fashioned in the conventional manner.8,9 it extended 
 from slightly anterior to the anterior lacrimal crest till near the 
 posterior crest of the lacrimal bone , upward till the medial 
 canthal tendon and downward up to the commencement 
 of the nasolacrimal duct . however , another layer of thick 
 bone was encountered just below and in a plane parallel 
 to this osteotomy [ figure 1].the bone was hard , unlike the 
 thin , brittle bone of ethmoid air cells . he was 
 asymptomatic with regard to watering from his eye at a routine 
 follow - up visit one year later . as the additional layer of hard bone was an unusual finding , 
 a 3d computed tomographic ( ct ) scan was performed to find 
 out what anatomical structure it may have been . the report 
 mentioned an accessory bony septum originating from the 
 antero - supero - medial wall of the maxillary sinus , lying in the 
 area of the anterior ethmoidal labyrinth , traversing deep to the 
 lacrimal sac and finally attaching to the floor of the frontal sinus . this was a variation in the uncinate process of the ethmoidal 
 bone which was rather anteriorly placed and attached 
 superiorly to the floor of the frontal sinus [ figures 2a - d ] . there was a prominent agger nasi cell and also a concha bullosa 
 ( pneumatized middle turbinate ) present on the left side . however , on 
 follow - up one year later , nasal endoscopy showed a patent 
 ostium [ figure 3 ] . the lateral ridge on the left was far more 
 prominent than on the right . adequacy of space for surgical maneuvers , the condition 
 of the mucosa and any anatomic variations are noted . select 
 patients such as those with recurrent cold or sinusitis , trauma 
 or surgeries in the nasal area , unusual nasal anatomy or nasal 
 problems are referred for an ent opinion . factors like deviated nasal septum or hypertrophied 
 nasal turbinates may narrow the space available in the nasal 
 cavity and also result in a greater incidence of postoperative 
 adhesions . with endonasal dcrs becoming a popular option for 
 patients , the external dcr has well - defined steps and landmarks8,9,12,13 
 but this is not so for endonasal dcr with different surgeons 
 choosing different surgical approaches to the lacrimal fossa ( for 
 example , some surgeons perform unciformectomy and some 
 dont ) and diverse technical variations.12 - 16 
 the underlying bony anatomy is revealed only after removing the overlying nasal 
 mucosa . also , in endonasal surgery , the surgeon works towards 
 the orbit and hence there is a greater chance of encountering 
 the delicate orbital structures . the uncinate process is a curved bone arising from the 
 anteroinferior part of the ethmoidal labyrinth and usually 
 commences just behind the lacrimal bone [ figures 4a and b ] . the cleft 
 formed between the uncinate process and the ethmoidal bulla 
 ( which is situated above it ) is termed the hiatus semilunaris . the infundibulum is the space bounded by the uncinate 
 process anteromedially , the ethmoid bulla posterolaterally 
 and the lamina papyracea anterolaterally . the frontal sinus often ends in the upper part of 
 the infundibulum . the maxillary sinus drains into this as also 
 the anterior and middle groups of ethmoidal air cells . the entire 
 area of the bulla , hiatus semilunaris , infundibulum , uncinate 
 process and the ostium of the draining sinuses - maxillary , 
 frontal , and anterior and middle ethmoidal cells is termed the 
 osteomeatal unit [ figures 5a and b].2 - 4 the superior part of the uncinate process may have one of 
 few possible sites of attachment [ figure 6].6,7 in one study of 144 
 patients,17 the variations in superior attachment were as follows : 
 52% to the lamina papyracea , 18.5% to the posteromedial wall 
 of the agger nasi cell , 17.5% to the lamina papyracea and the 
 junction of the middle turbinate with the cribriform plate , and 
 other less common attachments . the inferior border of the uncinate classically attaches to the 
 posterior edge of the inferior turbinate . however , it may also 
 attach along the anteroinferior margin of the inferior concha , 
 and then it is very closely approximated to the lacrimal bone.7 the anterior tip of the uncinate may be free or articulate 
 with superior structures . the posterior tip may be prolonged 
 and articulate with the palatine bone.7 various studies have measured the distances between 
 the important intranasal structures.17 - 20 one 
 study19 found 
 that the uncinate process was more frequently posterior 
 ( 32% ) or adjacent ( 45.5% ) to the lacrimal fossa at the lower 
 part of the lacrimal fossa . the uncinate process was adjacent 
 to the maxillary bone [ i.e. further forward on the lacrimal 
 fossa ] ( 55.8% cases ) at the middle and adjacent to the middle 
 turbinate ( 61% ) at the upper levels of the lacrimal fossa . hence 
 in many cases of endonasal dcr it is necessary to perform an 
 unciformectomy16,19 to actually reach the lacrimal 
 fossa . the ethmoid sinuses consist of an anterior and posterior 
 group of ethmoid cells separated by the ground lamella of the 
 middle turbinate . the agger nasi is the most anteriorly 
 placed ethmoid cell lying below the lacrimal fossa . agger nasi 
 cells are believed to represent the remnant of the superiormost 
 nasoturbinal concha . depending on the degree of 
 pneumatization , agger nasi cells can be bounded anteriorly by 
 the frontal process of the maxilla , anterolaterally by the nasal 
 and lacrimal bones , posterolaterally by the lamina papyracea , 
 superiorly by the frontal sinus , inferolaterally by the uncinate 
 process , and posteriorly by the anterior ethmoid complex . knowledge of intranasal anatomy is very important when 
 performing a dcr , especially from the endonasal route . ethmoid air cells extend to the lacrimomaxillary suture in 32% 
 cases and completely across the fossa in 54%.21 one study found 
 that the lacrimal bones had underlying ethmoidal cells in 93% 
 cases.22 hence they are commonly encountered during dcrs 
 while fashioning the osteotomy . in our patient , the other possibilities considered as to what 
 structure the parallel plate of bone could be were : 
 unusually thick and large agger nasi cellthe outer wall of the concha bullosa 
  unusually thick and large agger nasi cell the outer wall of the concha bullosa the first option was a distinct possibility because the ct 
 scan did indeed show a large agger nasi cell on the right side . however , the structure we encountered arose from as far below 
 as the antero - superio - medial wall of the maxillary sinus and 
 was inserted on the floor of the frontal sinus . the wall of the 
 agger nasi does not arise so low nor is the insertion so superior . 
 however , it is a well - established fact that the uncinate process 
 contributes to the wall of the agger nasi cell , especially the 
 inferolateral part . the 
 likely possibility is that a large , thick , uncinate process arose 
 from its usual site , formed a part of the wall of the agger nasi 
 ( large space between two bones encountered at surgery ) and 
 then was inserted into the floor of the frontal sinus . the agger 
 cell was unusually large and the mucous lining was perhaps too 
 thin to be noticeable separately . these findings are very unusual 
 because both the agger nasi cell and the uncinate are normally 
 composed of very thin , easily breakable , fine bones . the second option ( b ) was ruled out because this structure 
 was found intact on the ct scan [ figure 7 ] . therefore , the most likely possibility was that the structure 
 was the uncinate process of the ethmoid bone . it must be 
 mentioned that the uncinate process normally is of very thin 
 consistency . however , our patient had an uncinate process 
 that was not only placed far anteriorly but was also unusually 
 thick . the uncinate process is a curved bone arising from the 
 anteroinferior part of the ethmoidal labyrinth and usually 
 commences just behind the lacrimal bone [ figures 4a and b ] . the cleft 
 formed between the uncinate process and the ethmoidal bulla 
 ( which is situated above it ) is termed the hiatus semilunaris . the infundibulum is the space bounded by the uncinate 
 process anteromedially , the ethmoid bulla posterolaterally 
 and the lamina papyracea anterolaterally . the frontal sinus often ends in the upper part of 
 the infundibulum . the maxillary sinus drains into this as also 
 the anterior and middle groups of ethmoidal air cells . the entire 
 area of the bulla , hiatus semilunaris , infundibulum , uncinate 
 process and the ostium of the draining sinuses - maxillary , 
 frontal , and anterior and middle ethmoidal cells is termed the 
 osteomeatal unit [ figures 5a and b].2 - 4 the superior part of the uncinate process may have one of 
 few possible sites of attachment [ figure 6].6,7 in one study of 144 
 patients,17 the variations in superior attachment were as follows : 
 52% to the lamina papyracea , 18.5% to the posteromedial wall 
 of the agger nasi cell , 17.5% to the lamina papyracea and the 
 junction of the middle turbinate with the cribriform plate , and 
 other less common attachments . the inferior border of the uncinate classically attaches to the 
 posterior edge of the inferior turbinate . however , it may also 
 attach along the anteroinferior margin of the inferior concha , 
 and then it is very closely approximated to the lacrimal bone.7 the anterior tip of the uncinate may be free or articulate 
 with superior structures . the posterior tip may be prolonged 
 and articulate with the palatine bone.7 various studies have measured the distances between 
 the important intranasal structures.17 - 20 one 
 study19 found 
 that the uncinate process was more frequently posterior 
 ( 32% ) or adjacent ( 45.5% ) to the lacrimal fossa at the lower 
 part of the lacrimal fossa . the uncinate process was adjacent 
 to the maxillary bone [ i.e. further forward on the lacrimal 
 fossa ] ( 55.8% cases ) at the middle and adjacent to the middle 
 turbinate ( 61% ) at the upper levels of the lacrimal fossa . hence 
 in many cases of endonasal dcr it is necessary to perform an 
 unciformectomy16,19 to actually reach the lacrimal 
 fossa . the ethmoid sinuses consist of an anterior and posterior 
 group of ethmoid cells separated by the ground lamella of the 
 middle turbinate . the agger nasi is the most anteriorly 
 placed ethmoid cell lying below the lacrimal fossa . agger nasi 
 cells are believed to represent the remnant of the superiormost 
 nasoturbinal concha . depending on the degree of 
 pneumatization , agger nasi cells can be bounded anteriorly by 
 the frontal process of the maxilla , anterolaterally by the nasal 
 and lacrimal bones , posterolaterally by the lamina papyracea , 
 superiorly by the frontal sinus , inferolaterally by the uncinate 
 process , and posteriorly by the anterior ethmoid complex . knowledge of intranasal anatomy is very important when 
 performing a dcr , especially from the endonasal route . ethmoid air cells extend to the lacrimomaxillary suture in 32% 
 cases and completely across the fossa in 54%.21 one study found 
 that the lacrimal bones had underlying ethmoidal cells in 93% 
 cases.22 hence they are commonly encountered during dcrs 
 while fashioning the osteotomy . in our patient , the other possibilities considered as to what 
 structure the parallel plate of bone could be were : 
 unusually thick and large agger nasi cellthe outer wall of the concha bullosa 
  unusually thick and large agger nasi cell the outer wall of the concha bullosa the first option was a distinct possibility because the ct 
 scan did indeed show a large agger nasi cell on the right side . however , the structure we encountered arose from as far below 
 as the antero - superio - medial wall of the maxillary sinus and 
 was inserted on the floor of the frontal sinus . the wall of the 
 agger nasi does not arise so low nor is the insertion so superior . 
 however , it is a well - established fact that the uncinate process 
 contributes to the wall of the agger nasi cell , especially the 
 inferolateral part . the 
 likely possibility is that a large , thick , uncinate process arose 
 from its usual site , formed a part of the wall of the agger nasi 
 ( large space between two bones encountered at surgery ) and 
 then was inserted into the floor of the frontal sinus . the agger 
 cell was unusually large and the mucous lining was perhaps too 
 thin to be noticeable separately . these findings are very unusual 
 because both the agger nasi cell and the uncinate are normally 
 composed of very thin , easily breakable , fine bones . the second option ( b ) was ruled out because this structure 
 was found intact on the ct scan [ figure 7 ] . therefore , the most likely possibility was that the structure 
 was the uncinate process of the ethmoid bone . it must be 
 mentioned that the uncinate process normally is of very thin 
 consistency . however , our patient had an uncinate process 
 that was not only placed far anteriorly but was also unusually 
 thick .
variations in the bony components of the nose are often 
 encountered . 
 one such variation was found in a 49-year - old male 
 who had undergone conventional external dacryocystorhinostomy 
 for adult onset nasolacrimal duct blockage . 
 intraoperatively , a 
 thick bar of bone was seen beneath and parallel to the lacrimal 
 sac fossa after a complete osteotomy had been made . another 
 osteotomy had to be fashioned in this bone to reach the nasal 
 cavity . 
 postoperative 3d computed tomographic scan revealed 
 the bone to be an anatomical variation of the uncinate process 
 of the ethmoidal bone which was rather anteriorly placed , much 
 thicker than usual , and attached to the nasal roof.the uncinate process is thin , curved and its anterior edge may 
 frequently overlap some part of the lacrimal fossa . however , to 
 our knowledge , the presence of such a large and thick uncinate 
 process necessitating an additional large osteotomy has not been 
 reported .