Discussion
We have found only one study (PubMed search) reporting four PMA cases.6 However, in our series PMAs represented 14,3% of DNIs, suggesting that this entity is not uncommon, and in “real world” practice may be underdiagnosed or misdiagnosed as parapharyngeal abscesses. PMA is supposed to be mainly associated with pharyngeal mucosa’s infections; while infections of the teeth, major salivary glands, or other foci lateral to pharyngeal constrictor can hardly result in PMA.6 Our results support this, since none of our cases had odontogenic or salivary source of infection.
Symptoms of PMAs are similar to those of DNIs. Dysphagia was consistent symptom in all patients, with odynophagia and sore throat lagging behind. Skoulakis et al6, did not report trismus and neck swelling in their cases. In our series, mild trismus noticed in 20,75% of patients; but this finding was significantly lower than other DNIs. Neck swelling, secondary to neck lymphadenitis, even though significantly lower than other DNIs, was recorded in 24,53%. The rest of PMA symptoms were not significant different from other DNIs. Fever was noted in half of our patients, whilst mean WBC and CRP values were raised.
Lateral pharyngeal wall edema was a constant physical examination finding in all cases, while in some of them edemas in other oropharyngeal parts coexisted. In 43(40,6%) patients with abscess extension to hypopharyngeal part of PMA, edema was extended to pyriform sinus; while in those where pus reached the most inferior part of PMS, arytenoid or aryepiglottic fold edema coexisted. No other findings from laryngeal endoscopy were recorded, while follow up of the 5 cases with epiglottic edema and the 2 cases with the true vocal cord edema revealed the presence of epiglottic retention cysts and Reinke edema respectively. Tenderness during palpation of larynx (bilateral movement) was also a constant finding in all patients. Similar findings were reported by Skoulakis, et al.6
CT-scan with contrast (figure 1) is the “gold standard” to set PMA diagnosis6. Abscess protrusion into pharyngeal lumen may give the impression of parapharyngeal abscess; however, PMS is located to the lateral pharyngeal wall among pharyngeal mucosa and pharyngeal constrictors, extends under the hyoid bone and passes medial to it; in contrast other spaces pass lateral to (e.g. carotid space) or end to the hyoid bone (e.g. parapharyngeal space). MRI may also be used, while ultrasonography cannot identify PMS adequately.6
Streptococcus pyogenes and Staphylococcus aureus were the commonest bacteria species in our series. Microbiology of PMA seems to be similar to other DNIs and related to pharyngeal microflora.3,6 However, we had only a small number of positive cultures, so on these grounds safe and generalized conclusions cannot be made. Empirical therapy with IV-ampicillin/sulbactam combined with metronidazole or clindamycin seemed to be effective in our practice.
Skoulakis et al, suggested that “the abscess, as a rule, is drained spontaneously6. In our series spontaneous drainage was noted in 49,1% of patients, and the mean time until spontaneous drainage was 1.8±0.8 days from admission. In all instances spontaneous opening was small and the flow of pus was slow allowing the patient to swallow it; we believe this was the main reason why no compilation related to tracheobronchial pus aspiration was noted in any of these patients. PMS lying just deep to pharyngeal mucosa while dense connective tissue is present only in its deeper border, hence hindering infection spread towards deeper spaces and facilitating pus drainage intraluminal in case of PMA by virtue of least resistance. Furthermore, pharyngeal constrictor’s pressure on the abscess during the pharyngeal peristaltic wave facilitates spontaneous drainage through the “vulnerable” mucosa. Transoral drainage under local anesthesia or aspiration may also be performed in order to shorten hospital-stay.
In our series, no major adverse event was noted and no further surgical intervention was needed. Superficial PMS location in pharyngeal lumen and dense deep border together with spontaneous drainage may be the reasons why abscesses constrained in PMS fare better than other DNIs.
Even though our data withdrawn from a prospectively collected database, retrospective nature of our study is the main limitation. On the other hand, we believe that the relatively large number of cases minimizes bias and present meaningful results.
In conclusion, our study suggests that PMAs, are not so rare as they are considered to be; however, there is a lack of literature on this space abscesses. PMAs have much in common with other DNIs but they are less dangerous than their deep-seated counterparts, since its superficial location renders them amenable to spontaneous drainage, aspiration, incision and drainage intraorally obviating spread to deeper structures.
Conflict of interest: None to declare.
Data availability statement: The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.