CASE REPOI~T

swimming. Nasal endoscopy revealed a Sphenochoanal right sided solitary polypoid mass with a slender pedicle extending from the polyp: sphenoethmoidal recess to the choana. An unenhanced CT scan of paranasal sinuses (5 x 5 mm coronal radiological scans) was performed on a GE 8800 scanner (Milwaukee, USA). A soft tis- sue polyp extending from the right diagnosis sphenoid sinus/sphenoethmoidal recess to the right choana was demonstrated. MWPak* Abstract Chronic right sphenoid sinusitis with FRCS(Ed) A sphenochoanal reactive sclerosis was seen. Inside the J Kew# polyp is seen as an sphenoid sinus there was a convex up- FFRad, (D) SA isolated soft tissue per margin to the soft tissue which in- * Division of Otorhinolaryngology, dicated the presence of either a mucous Depal1ment of Surgery, density mass that retention cyst or a polyp. The other # Depal1ment of Diagnostic Radiology and arises from the Organ Imaging, Prince ofWa/es Hosp/ta/, paranasalsinuseswere clear (Figures1-4). Chinese University of Hong Kong sphenoid sinus and The clinical and radiological findings extends to the choana indicated a sphenochoanal polyp. The on computed patient was admitted for excision un- tomograph ic scans. der general anaesthesia. Under endo- Distinction from its scopic control, the anterior wall of the more cornrnon sphenoid sinus was opened and the counterpart, polyp, together with its sphenoidal com- antrochoanal polyp ponent, was removed. No recurrence vvbich arises from the was noted two years after surgery. maxillary sinus, is essential prior to Discussion surgery. A case is A choanal polyp results from pro- presented to iII ustrate lapsed mucosa of an isolated paranasal that CT scan of sinus and accounts for 3-6% of nasal paranasal sinus plays polyps.P Characteristically, it passes an important role in through the enlarged sinus ostium and the identification of protrudes into the choana leading to the sinus of origin. unilateral nasal obstruction, rhinorrhea and sinusitis. Case report Choanal polyps from sphenoid si- nus are rare but share the characteristic A 47-year-old male presented to similarity with the more common coun- Prince of Wales Hospital with a one terparts which arise from the maxillary year history of right sided progressive sinus. They are invariablyunilateralin dis- nasal obstruction following an episode tribution and common in males between of upper respiratory tract infection. The the second and fourth decades.'? obstruction was worse on forced expi- Contrary to conventional nasal polyps, ration and more noticeable during choanal polyps are believed to be

topageB

7 SAJOURNAL OF RADIOLOGY. May 1998 (rom page 7

determine. If the sphenoid sinus is the only opaque sinus, a choanal polyp is prob- ably sphenochoanal, even if the connection cannot be demon- strated. If both the maxillary antrum and the sphenoid sinus are

Figure 1: Coronal CT scan showing normal opaque, continuity be- maxillary and ethmoid sinuses. No nasal polyposis Figure 4: Coronal CT scan showing the polyp in the right choana. tween the polyp and IS eVident and the osteomeatal units are patent. polyp may arise from the blocked aci- the correct sinus of ori- nous mucous gland and present as an gin isimportant to document. In the case extension of a mucocele.' However, of an antrochoanal polyp, the polyp can more evidence has suggested that the be followed passing between the mid- polyp is an extension of an asympto- dle turbinate and the lateral wall of the matic intramural cyst from within a si- nasal cavity. With a sphenochoanal nus through its natural ostium.' polyp, the polyp is between the nasal The sinus of origin can be identified septum and middle turbinate. The dif- clinically and radiologically. With a ferential diagnosis of a soft tissue mass 4 mm, zero degree nasal endoscope, the in the sphenoethmoidal recess/choana sphenochoanal polyp is readily recog- could include nasal polyp with sphenoid nized asa solitary polypoid mass extend- sinusitis,nasopharyngeal carcinoma and Figure 2: Coronal CT scan through the posterior ing posteriorly from the recess between lymphoma. maxillary sinuses which are clear. A soft tissue As simple avulsion of the intranasal opacity with a convex upper margin is seen in the septum and middle turbinate to the sphenoid sinus (arrowhead). There is soft tissue in choana. Further identification of a long portion alone is associated with recur- the sphenoethmoldal recess representing the stalk of the polyp (arrow). pedicle protruding through the rence of at least 20% within two years, sphenoid ostium in the the polyp should be resected together sphenoethmoidal recess is with the pedicle and its intrasphenoidal essential to confirm the di- portion. 1·3 To decrease the morbidity agnosis.Apart from endos- associated with external approaches to copy, CT scans of paranasal the sphenoid sinus, endoscopic removal sinus is indispensable to the of the polyp together with evaluation of an isolated na- sphenoidotomy remains the treatment sal polyp of unknown ori- of choice. gin. The radiological find- References 1. Heck WE, Hallberg 0, Williams HL. Antrochoanal polyp. ings of sphenochoanal pol- Arch Otolaryngol1950, 52: 538·548. yps are characteristic. The 2. Sirola R. Choana I polyps. Acta Otolaryngol (Stockh) 1996; 61: 42·48. CT appearance of the polyp 3. Hardy G. The choanal polyp. Ann Oto Laryngol Rhinol is of a hypoattenuated mass 1957; 66: 306·326. Figure ~: The polyp (arrow) Is seen in the right nasopharynx. The right 4. Mills CP. Secretory cysts of the maxillary antrum and sphenoid SinUS IS opaque and there Is associated reactive osteitis. arising from an isolated their relation to the development of antrochoanal polyp J Laryngol Oto 1959; 52: 84-1 DO. . opaque sphenoid sinus 5. Berg 0, Carenfelt C, Silfversward C, Sobin A. Origin of the choanal polyp. Arch Otolaryngol Head Neck Surg of inflammatory or infectious rather without evidence of bony erosion. The 1988; 114: 1270-1271. than allergic nature. 1·3 6. Hayes E, Lavelle W. Sphenochoanal polyp. CT findings natural ostium of the sphenoid sinus J Computer Assisted Tomography 1989; 13: 365-366.' The origin of the polyps is contro- is usually enlarged.ê? Occasionally, the 7. Weissman JK, Tabor EK, Curtin HD. Sphenochoanal polyps: Evaluation with CT and MR imaging. Radiology versial. Mills has suggested that the sinus of origin may be difficult to 1991; 178: 145-148.

a SA JOURNAL OF RADIOLOGY. May 1998