prevalence of difficult laryngoscopic intubation is reported to range from 1.5 to 20% cases 

Unanticipated difficult airway remains a major concern for anaesthesiologists due to serious consequences of failed 

endotracheal intubation. The identification of patients with difficult airways is crucial during preoperative evaluations.

A variety of tests are used to evaluate potentially difficult airways in advance of the procedure . However, it is not clear 

which test has best sensitivity to predict difficult airway. 

   Commonly used tests are Modified Mallampati test with tongue protrusion (MMT-TP), modified mallampati test without 

tongue protrusion (MMT-NTP), inter incisor gap (IIG), thyromental distance (TMD), sternomental distance (SMD), 

mandible protrusion test (MPT) for prediction of difficult intubation relative to the Cormack Lehane grading for   

Laryngoscopic view.

Modified Mallampati Test (MMT) is the oldest bedside test that predicts difficult intubation by assessing mouth opening and 

visibility of pharyngeal structure.

For predicting difficult intubations, the mandible protrusion test is well established and relatively simple grading system.

Thyromental distance is measured along a straight line from the thyroid cartilage prominence to the lower border of the 

mandibular mentum with full head extension and mouth closed. It is a common method to predict difficult airways. The

 smaller the TMD is, the greater the probability of a difficult airway Sternomental distance (SMD is an indicator of head 

and neck mobility . IIG is a major single predictor for difficult airways. It reflects craniocervical extension, which is 

restricted in cervical spondylosis patients

.