Atypical, abscessated nasopharyngeal polyp associated with expansion and lysis of the tympanic bulla

Abstract

A 5-year-old, male neutered domestic shorthair cat was referred for investigation of lethargy, weight loss, pyrexia and upper respiratory tract signs. On computed tomography, an expansile, osteodestructive lesion in the right tympanic bulla was identified. A soft tissue mass extended from the bulla into the nasopharynx, cranium and subcutaneous tissues. The nasopharyngeal mass ruptured during handling, liberating purulent material from which Pasteurella multocida was isolated in pure culture. The lesion was most likely an atypical, abscessated nasopharyngeal polyp. The cat was treated with bulla osteotomy and antibiotics, and made a complete recovery.

Figure 1

(a) Three-dimensional, volume-rendered computed tomography (CT) image of the caudoventral aspect of the skull (WL 344, WW 390) showing multiple, round-to-oval focal areas of lysis (black arrows) in the wall of the right tympanic bulla. The right epihyoid and stylohyoid bones (white arrow) are displaced laterally and ventrally by the enlarged right tympanic bulla. Crop and sculpt post-processing functions have been used to remove the image of the endotracheal tube that was superimposed on the tympanic bullae and hyoid bones in this view. The endotracheal tube is marked with a white asterisk. (b) Transverse, pre-contrast CT image of the skull at the level of the tympanic bullae made using a bone filter and viewed in a bone window (WL 500, WW 3500). The wall of the enlarged right tympanic bulla is thin and incomplete with a large defect in the lateral wall (white arrowhead) and multiple smaller defects in other regions of the wall. A defect is present in the right petrous temporal bone (white arrow) resulting in loss of the bony wall between the right tympanic cavity and the caudal fossa of the cranium. The right tympanic cavity is filled with soft tissue attenuating material and several small regions of gas. Soft tissue attenuating material is seen bulging into the nasopharynx (black asterisk), the right external ear canal is compressed and the right hyoid bones are displaced ventrolaterally (black arrow). (c) Transverse, post-contrast CT image at the level of the temporomandibular joints made using a soft tissue filter and viewed in a soft tissue window (WL 166, WW 545). Soft tissue attenuating material (white arrows) with moderate peripheral and ring-shaped regions of enhancement is seen filling the nasopharynx and causing severe ventral displacement of the soft palate. The endotracheal tube (white asterisk) is seen passing through the left side of the oropharynx. (d) Transverse, post-contrast CT image at the level of the caudal skull made using a soft tissue filter and viewed in a soft tissue window (WL 166, WW 545). The soft tissue attenuating material in the right tympanic bulla has a moderate heterogeneous contrast enhancement, with peripheral enhancement and multiple ring-shaped regions of enhancement (black arrows). A linear region of contrast enhancement is seen passing through the large defect in the right petrous temporal bone into the right ventral region of the caudal fossa of the cranium and there is mild leftward displacement of the brainstem (white arrow). Contrast-enhancing tissue is also seen passing ventromedially from the right tympanic bulla into the retropharyngeal region (white arrowhead). The endotracheal tube is marked with a white asterisk. R = right, L = left, white asterisk = endotracheal tube

Figure 2

(a) The soft palate has been retracted using a spey hook revealing the polypoid mass in the nasopharynx. (b) Rupture of the abscessated polyp during handling