Posttreatment Imaging of the Paranasal Sinuses Following Endoscopic Sinus Surgery





Endoscopic sinus surgery is a minimally invasive option for the treatment of several nonneoplastic indications, particularly for medically refractory sinusitis and polyposis. Numerous interventions can be performed through endoscopic sinus surgery, many of which may be performed together during the same procedure. There are also a variety of complications that can result from endoscopic sinus surgery. Radiological imaging plays an important role in the evaluation of patients after endoscopic sinus surgery. Thus, it is important to be familiar with the expected and complicated imaging findings associated with endoscopic sinus surgery, which are reviewed in this article.


Key points








  • Postoperative sinonasal diagnostic imaging techniques and protocols are reviewed.



  • The different types of endoscopic sinus surgery techniques are described and the corresponding expected postoperative findings are presented.



  • Complications resulting from endoscopic sinus surgery are summarized and selected examples of diagnostic imaging are presented.




Introduction


Endoscopic sinus surgery is a minimally invasive option for the treatment of several nonneoplastic indications, particularly for medically refractory sinusitis and polyposis. Numerous interventions can be performed through endoscopic sinus surgery ( Box 1 ), many of which may be performed together during the same procedure. There are also a variety of complications that can result from endoscopic sinus surgery ( Box 2 ). Radiological imaging plays an important role in the evaluation of patients after endoscopic sinus surgery. Thus, it is important to be familiar with the expected and complicated imaging findings associated with endoscopic sinus surgery, which are reviewed in this article.



Box 1

Types of endoscopic sinus surgery and related procedures





  • Uncinectomy/uncinotomy



  • Inferior and middle meatus antrostomy/fenestration



  • Ethmoidectomy (anterior and/or posterior)



  • Turbinectomy/turbinate medialization



  • Frontal sinusotomy



  • Sphenoidotomy/sphenoid drill-out/marsupialization



  • Polypectomy



  • Sinus stenting



  • Mucocele drainage



  • Sinonasal debridement



  • Balloon sinuplasty



  • Turbinate reduction/turbinoplasty



  • Septoplasty/septorhinoplasty



  • Approach for ophthalmic procedures, such as orbital wall decompression, and anterior skull base cerebrospinal fluid (CSF) leak repair




Box 2

Complications of endoscopic sinus surgery





  • Brain parenchymal injury and intracranial hemorrhage



  • Encephalocele and CSF leakage



  • Intracranial infection



  • Gossypiboma



  • Vascular injury (pseudoaneurysm)



  • Ophthalmic injury (intraorbital hemorrhage, extraocular muscle injury, optic nerve transection, nasolacrimal system disruption)



  • Periorbital lipogranuloma



  • Recurrent rhinosinusitis and polyposis



  • Retained septations



  • Neo-osteogenesis



  • Adhesions



  • Mucus recirculation phenomenon



  • Mucocele



  • Nasal septal perforation



  • Empty nose syndrome




Postoperative imaging techniques and protocols


The main radiological imaging modalities available for evaluating patients following endoscopic sinus surgery include computed tomography (CT), MR imaging, and angiography. High-resolution CT with multiplanar reconstructions is invaluable for a detailed depiction of the changes in bony anatomy and the presence of implants after surgery and can provide an overview of the extent of sinonasal opacification. CT can also be useful for screening orbital and intracranial complications. The administration of intravenous contrast with sinus CT is generally unnecessary, but can be helpful in cases of suspected orbital, facial, or intracranial infection. MR imaging often serves a complementary role to CT for optimal soft tissue characterization, particularly for delineating certain intracranial complications and further elucidating nonspecific findings on CT that are otherwise not readily amenable to endoscopic examination. Angiography, either in the form of CT angiography (CTA), MR angiography (MRA), or catheter angiography, is indicated for the evaluation of vascular complications. Notably, catheter angiography can serve as both a diagnostic and therapeutic modality in certain cases of postoperative hemorrhage. Fluoroscopy is mainly limited to guiding and verifying the completion of certain endoscopic procedures, such as balloon sinuplasty. Additional guidance for determining the appropriate imaging modalities can be found in the American College of Radiology Appropriateness Criteria for sinonasal disease. Protocol details for sinonasal CT and MR imaging techniques in adults are listed in Table 1 .



Table 1

Sinonasal CT and MR imaging protocol parameters in adults













Modality Parameters
CT Helical acquisition with 0.6-mm collimation at 200 mAs and 120 kVp in axial plane with 1-mm axial, coronal, and sagittal reformatted images using bone algorithm, and 3-mm axial, coronal, and sagittal reformatted images using soft tissue algorithm
MR imaging


  • Axial T1 (FOV, 240; slice thickness, 3 mm)



  • Coronal T1 (FOV, 160; slice thickness, 3 mm)



  • Axial T2 (FOV, 240; slice thickness, 3 mm)



  • Coronal T2 (FOV, 160; slice thickness, 3 mm)



  • Optional postcontrast axial and coronal T1 without or with fat suppression (if fat suppression is implemented, techniques such as mDIXON are useful for minimizing susceptibility artifacts)



  • Optional diffusion-weighted imaging (techniques such as FSE are useful for minimizing susceptibility artifacts)


Abbreviations: FOV, field of view; FSE, fast spin echo; kVp, kilovoltage peak.


Types of surgery and imaging findings


Ostiomeatal Unit Endoscopic Sinus Surgery


The goal in treating an obstructed ostiomeatal unit via endoscopic surgery is to improve mucociliary clearance by removing anatomic obstacles. The procedure most typically involves uncinectomy and middle meatal antrostomy, which creates a wide neoinfundibulum that is best delineated on coronal CT images ( Fig. 1 ). Variable degrees of ethmoidectomy and middle turbinectomy may also be performed, depending on the extent of disease; for example, medial deviation of the lamina papyracea with or without posterior repositioning of the globe frequently occurs after ethmoidectomy because of the loss of buttressing effects ordinarily provided by the ethmoid septations. The medial bowing of the lamina papyracea can be observed on postoperative CT and is generally on the order of a 1-mm to 3-mm decrease in the interorbital distance ( Fig. 2 ). Another less commonly implemented option for treating patients with ostiomeatal unit complex diseases is inferior antrostomy, which provides an alternate drainage pathway and can be useful in cases of severe disease that cannot be addressed through the usual uncinectomy and middle meatal antrostomy. This procedure results in a defect in the inferior nasoantral wall that can mimic a secondary ostium ( Fig. 3 ).




Fig. 1


Osteomeatal unit complex functional endoscopic surgery. Preoperative coronal CT image ( A ) shows opacification of the left osteomeatal unit complex. Postoperative coronal CT image ( B ) shows interval left uncinectomy and middle meatus antrostomy with a wide neoinfundibulum ( oval ), left ethmoidectomy, and left middle turbinectomy.



Fig. 2


Lamina papyracea medialization after ethmoidectomy. Preoperative coronal CT ( A ) shows an interlaminar distance of 22.8 mm. Postoperative coronal CT ( B ) shows interval partial bilateral internal ethmoidectomy with interval medial bowing of the lamina papyracea and a decreased interlaminar distance of 20.7 mm.



Fig. 3


Inferior meatal antrostomy. Coronal CT image shows a defect in the inferior nasoantral wall ( arrow ) in addition to uncinectomy and middle meatus antrostomy. There is mild mucosal thickening in the left maxillary sinus.


Frontal Sinusotomy and Stenting


Frontal sinusotomy is indicated when frontal sinus disease persists despite more conservative endoscopic approaches directed at the infundibulum and anterior ethmoid region. The Draf classification describes various types of endoscopic frontal sinusotomy based on the extent of surgical resection of the regional sinonasal skeleton ( Table 2 ). The postoperative status of the frontoethmoid recess is best delineated on sagittal and coronal CT images. For example, frontal sinus stenting is indicated if the neo-ostium measures less than 5 mm in width, and CT can be useful for verifying the position of the stents ( Fig. 4 ) and assessing surrounding anatomy if further surgery is contemplated.



Table 2

Draf classification for frontal sinusotomy
















Category Findings
Draf 1 Simple drainage: complete resection of the anterior ethmoid cells and uncinate process surrounding the frontal recess to the frontal ostium
Draf 2 Extended drainage: resection of the floor of the frontal sinus from the nasal septum medially to the lamina papyracea laterally (can be difficult to distinguish from Draf 1 on CT)
Draf 3 (modified Lothrop procedure) Resection of the superior nasal septum and entire frontal sinus floor



Fig. 4


Frontal sinus stent. Coronal CT image shows a right frontal sinus self-retaining stent ( arrow ) that empties into the nasal cavity. There is extensive sclerosis of the sinonasal region associated with the patient’s underling Wegener granulomatosis.


Sphenoidotomy


Endoscopic sphenoidotomy is commonly performed to address disease that involves the sphenoid sinus and can be achieved without or with ethmoidectomy and other endoscopic sinus surgery. The main approaches for accessing the sphenoid sinus include widening the natural ostium or creating a second opening through the posterior ethmoid sinuses. In either case, CT can show a widened communication between the sphenoid and ethmoid sinuses, which is most conspicuous on axial and sagittal reformatted images ( Fig. 5 ). Marsupialization is another option for treating chronically infected sphenoid sinus and consists of exteriorizing the affected sinus. Furthermore, sphenoid drill-out may also be performed for chronic sinusitis and can be considered as an intermediate procedure between sphenoidotomy and sphenoid marsupialization. Regardless of the technique that is implemented, the goal is improved aeration of the sphenoid sinus.




Fig. 5


Sphenoidotomy. Axial ( A ) and sagittal ( B ) CT images show a wide right sphenoid ostium ( arrows ).


Balloon Sinuplasty


Balloon sinuplasty is a minimally invasive endoscopic treatment that involves dilating the paranasal ostia while minimizing mucosal damage. The inflated balloon delicately displaces, microfractures, and molds the bone surrounding the sinus outflow and may be used alone or in combination with conventional endoscopic surgery. Fluoroscopic imaging guidance can be used to visualize the position and expansion of the contrast-filled balloon, which appears radio-opaque ( Fig. 6 ).




Fig. 6


Balloon sinuplasty. Fluoroscopic image shows an expanded radio-opaque contrast-filled balloon ( arrow ) that extends from the nasal cavity into the maxillary antrum ( asterisk ).


Mucocele Drainage


Endoscopic techniques can be effective for treating paranasal sinus mucocele, including those with orbital extension, thereby often obviating an trans-orbital approach. In addition to clearing the affected paranasal sinus contents of the mucocele, packing material, stents, or spacers are sometimes placed and may be observed on imaging obtained soon after surgery ( Fig. 7 ). Postoperative CT can be useful to evaluate for residual mucocele components and the status of the paranasal sinus walls, whereas MR imaging can be appropriate for delineating intracranial or intraorbital extension. Following successful mucocele drainage, remineralization of the affected paranasal sinus walls can be observed and associated proptosis can diminish.


May 18, 2021 | Posted by in NEUROLOGICAL IMAGING | Comments Off on Posttreatment Imaging of the Paranasal Sinuses Following Endoscopic Sinus Surgery
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