2.1 Literature search for data collection
We have performed extensive search through PubMed, Cochrane Library, Web of Science, EMBASE, Biomedical Literature Database (CBM) and Clinicaltrials.gov with reference to PPS tumors. Articles meeting the search criteria with keywords such as ‘parapharyngeal space’ or ‘transmandibular’ or ‘benign parapharyngeal space tumor’ or ‘trans-cervical’ or ‘lip split mandibulotomy’ or ‘mandibular swing’ were included in the first instance and concluded on 25.05.2019. The analysis included systematic reviews, retrospective studies, literature reviews pertaining to open surgical management of primary parapharyngeal space tumors published from 1989 to 2019. No focused publication was found on the management of benign parapharyngeal space tumors due to rarity of the disease. The studies with management of parapharyngeal space tumors including series with patients not less than 10 were also incorporated. Data was collected including patient’s age, gender, year of publication, histopathological classification, surgical approaches and complications. The criteria for exclusion was case reports /series addressing malignant pathology only, treatment modalities other than surgery, single case reports or case series having less than 5 patients, non-primary parapharyngeal space tumors, tumors with nasopharyngeal, intracranial, infratemporal fossa extensions, studies comparing approaches such as robotic / lateral skull, studies that provide data using single modality with no comparisons, letter to the editors, meeting abstract and editorials.
Robotic and endoscopic approaches have not been included in the review as majority of the published literature have addressed PPS tumors with open surgical access. Further, the endoscopic approaches may still need to be validated for reproducibility and effectiveness to be labelled as the standard of care. We had to incorporate different benign histologies as the numbers are very few and surgical management of these tumors have been based more on the location of the tumor rather than tissue of origin.