OBJECTIVE: As   a   guide   to   the   clinical   practice   of   infiltration   of   local   anesthesia   into   the pterygopalatine fossa via the greater palatine canal, this study sought to determine and record the  mean  CT  scan  measurements  of  the  following:  1)  palatal  mucosal  thickness,  2)  length  and width  of  greater  palatine  canal,  and  3)  length  and  width  of  pterygopalatine  fossa  among  adult patients in a private tertiary hospital in Quezon City.
METHODS:
Design: Retrospective, Descriptive Study
Setting: Tertiary Private Hospital
Subjects: Paranasal Sinus (PNS) CT Scans of 113 adult patients from January 2014 to May 2014 were reviewed and evaluated. Excluded were images with pathology that distorted the anatomy of the sinuses and surrounding structures.
RESULTS: Our study showed average CT scan measurements of 5.98 mm palatal mucosal thickness, 16.99  mm  greater  palatine  canal  length,  18.75  mm  pterygopalatine  fossa  length,  2.37  mm greater palatine canal width and 2.58 mm pterygopalatine fossa width. Comparison of average measurements  by  sex  was  not  statistically  significant.  There  was  statistical  significance  when comparing the right palatal mucosal thickness of 5.86 mm with the left which was 6.11 mm with p-value of 0.001. Comparison between the length of the right pterygopalatine fossa of 18.48 mm with the  left side at 19.01 mm showed statistical significance with p-value of 0.01.
CONCLUSION: As the average measurement of the mucosal palatal thickness combined with the length of the greater palatine canal was 22.97 mm, we recommend bending the needle 23 mm from  the  tip  in  a  45  degree  angle  for  adult  patients  who  will  undergo  sinus surgery,  control  of posterior epistaxis, trigeminal nerve block and minor oral cavity surgeries.