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Imaging of paranasal sinuses

paranasal sinuses

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Imaging of paranasal sinuses

  2. 2. SINONASAL PHYSIOLOGY  The normal secretions produced by the sinuses are cleared by the cilia lining the mucosa .  These drain the secretions towards the natural sinus ostia .  FRONTAL SINUSES – drain into the frontoethmoidal recess through the anterior ethmoid air cells into the anterior frontal recess of the middle meatus.  ANTERIOR ETHMOID – drain into the anterior aspects of the hiatus semilunaris .  MIDDLE ETHMOID – Through the ethmoid bulla , the posterior ethmoids drain into the superior meatus .  MAXILLARY SINUS – drains via the infundibulum into the ostium .  SPHENOID SINUS – into the sphenoethmoid recess posterior to the superior meatus .
  3. 3. Nasal Structures The nasal septum is a midline structure composed of both bone and cartilagenous tissue. Its deviation can cause partial obstruction in the nasal cavities unilaterally or on both sides depending on its shape. The lateral nasal wall has three projections superior, middle and inferior turbinates. These structures divide the nasal cavity into three air passages the superior, middle and inferior meatus. The inferior turbinate is the lower most projections arising from the lateral nasal bone and extending into the nasal cavity and running posteriorly toward the nasopharynx. The middle turbinate lies above the inferior turbinates. Anterosuperiorly, the middle turbinate attaches to the skull base just lateral to the cribriform plate. In its middle third it turns coronally and laterally to insert on the lamina papyracea and posteriorly to the roof of ethmoidal complex . The basal lamella is the portion of the middle turbinate where it attaches to the
  4. 4. Coronal CT image showing nasal structure. Middle turbinate (white arrow) and lamina papyracea (black arrow) Coronal CT at the level of OMC showing uncinate process (black arrow), agar nasi cells (short white arrow) and frontal recess(white long arrow)
  5. 5. Coronal section showing anterior draining pathway including frontal recess (white arrow), maxillary ostium (thin black arrow), infundibulum (thick black arrow), middle meatus (short black arrow) and maxillary sinus (star)
  6. 6. THE OSTEOMEATAL COMPLEX • Region where the frontal ,anterior and middle ethmoid and maxillary sinuses drain . • Includes the fronto ethmoidal recess , uncinate process , hiatus semilunaris , ethmoid bulla , the maxillary infundibulum and ostium and the ethmoid infundibulum . • Disease at the OMC is the major cause of recurrent acute/chronic sinusitis .
  7. 7. Frontal sinuses.
  8. 8. FRONTAL RECESS  The frontal recess is an hourglass like narrowing between the frontal sinus and the anterior middle meatus through which the frontal sinus drains  The frontal recesses are the narrowest anterior air channels and are common sites of inflammation. Their obstruction subsequently results in loss of ventilation and mucociliary clearance of the frontal sinus
  9. 9. SPHENOID SINUS  Sphenoid sinus develops in the body of the sphenoid sinus and drains via a sinus ostium into spheno ethmoid recess.  The degree of pneumatisation is variable and may extend into greater and lesser wing of sphenoid and pterygoid plates.  There are many important structures in relation to sphenoid sinus like vidian canal, optic nerve and foramen rotundum.
  10. 10. Ethmoid air cells  Thin walled air cavities in the lateral masses of the ethmoid bone. Varies from 3 – 18 in number.  Clinically divided into anterior ethmoidal air cells & posterior ethmoidal air cells, by basal lamella (lateral attachment of middle turbinate to lamina papyracea)  Anterior drain into- Middle meatus.  Posterior- sup.meatus & spenethmoidal recess.
  12. 12. PARADOXIC CURVATURE  Normally, the convexity of the middle turbinate bone is directed medially, toward the nasal septum.  When paradoxically curved, the convexity of the bone is directed laterally toward the lateral sinus wall.  The inferior edge of the middle turbinate may assume various shapes, which may narrow and/or obstruct the nasal cavity, infundibulum, and middle meatus.
  13. 13. Concha Bullosa  It is an aerated turbinate, most often the middle turbinate.  When the pneumatization involves the bulbous segment of the middle turbinate, the term concha bullosa applies.  If only the attachment portion of the middle turbinate is pneumatized, and the pneumatisation does not extend into the bulbous segment, it is known as a lamellar concha. Concha bullosa (arrow) causing partial obstruction of the middle meatus. Note le DNS
  14. 14. AGGER NASI AIR CELL  Its an ethmoturbinal remnant present in nearly all patients.  Located anterior to the vertical attachment of the middle turbinate to the skull base.  The degree of ANC pneumatization varies and has a significant effect on both the size of the frontal sinus ostium and the shape of the recess.
  15. 15. HALLER CELL  These are ethmoid air cells located anterior to the ethmoid bulla, along the orbital floor, adjacent to the natural ostium of the maxillary sinus, which may cause mucociliary drainage obstruction, predisposing to the development of sinusitis. Coronal CT image showing Haller cells (white arrows) along the roof of the maxillary sinus medially, causing narrowing of the infundibulum (black arrow)
  16. 16. Sphenoethmoid cell (Onodi cell)  This is formed by lateral and posterior pneumatization of the most posterior ethmoid cells over the sphenoid sinus.  The presence of Onodi cells increases the chance that the optic nerve and / or carotid artery would be exposed in the pneumatized cell. Coronal CT at the level of sphenoid sinus (asterix), showing Onodi cells lying superior to the sphenoid sinuses and in close relation to optic nerves (black arrows)
  17. 17. Accessory maxillary ostia  Accessory maxillary ostia are generally solitary, but occasionally may be multiple.  Such variation may be congenital or secondary to sinusal diseases.  Possible mechanisms involved in the development of such variation include:  main ostium obstruction, maxillary sinusitis or anatomical/pathological factors in the middle meatus, resulting in rupture of membranous areas.
  18. 18. VARIATIONS OF THE OPTIC NERVE  The optic nerve, carotid arteries, and vidian nerve develop prior to the paranasal sinuses, and are responsible for the congenital variations in the walls of the sphenoid sinus.  Delano, et al., categorized the various relationships between the optic nerve and posterior paranasal sinuses into four groups.  Type I: The most common type, it occurs in 76% of patients. Here, the nerve courses immediately adjacent to the sphenoid sinus, without indentation of the wall or contact with the posterior ethmoid air cell The nerve is seen to course immediately adjacent to the sphenoid sinus, without contact with the posterior ethmoid air cell
  19. 19.  Type II: The nerve courses adjacent to the sphenoid sinus, causing an indentation of the sinus wall, but without contact with the posterior ethmoid air cell
  20. 20.  Type III: The nerve courses through the sphenoid sinus with at least 50% of the nerve being surrounded by air
  21. 21.  Type IV: The nerve course lies immediately adjacent to the sphenoid and posterior ethmoid sinus
  22. 22. KEROS CLASSIFICATION  Method of classifying the depth of the olfactory fossa.  In adults, the olfactory recess is a variable depression in the cribriform plate. It contains olfactory nerves and a small artery.  The depth of the olfactory fossa is determined by the height of the lateral lamella of the cribriform plate.  Keros in 1962, classified the depth into three categories.  Type 1: 1-3 mm (26.3% of population)  Type 2: 4-7mm (73.3% of population)  Type 3: 8-16mm (0.5% of population)  The type 3 essentially exposes more of the very thin cribriform plate to potential damage from trauma, tumour erosion, csf erosion (in benign intracranial hypertension) and local nasal surgery or orbital decompression.  Thin bone in the skull base, especially the cribriform plate, is susceptible to erosion, encephalomeningocoele herniation and csf leaks
  23. 23. Imaging modalities
  24. 24.  X RAY  CT  MRI
  25. 25.  X ray – Water’s view & caldwell view.  CT – gold standard. Coronal & axial sections.  MRI is predominantly used for pre and post operative management of naso sinus malignancy.  The chief disadvantage of MRI is its inability to show the bony details of the sinuses, as both air and bone give no signal.
  26. 26. PARIETOACANTHIAL PROJECTION: WATERS VIEW Extend neck, placing chin and nose against table/upright Bucky surface.  Head is adjusted so as to bring the orbito meatal line to a 45 degree angle to the casette holder.  Position the median saggital plane is perpendicular to the midline of grid or table/upright bucky surface.  Ensure that no rotation or tilt exists.  Centering is done at acanthion.
  27. 27. CALDWELL  Place patient's nose and forehead against upright Bucky or table with neck extended to elevate the OML 15° from horizontal. A radiolucent support between forehead and upright Bucky or table may be used to maintain this position.(alternate method if Bucky can be tilted 15°.)  Align MSP perpendicular to midline of grid or upright Bucky surface.  Centering is done at nasion, ensuring no rotation.
  28. 28. 1
  30. 30. CT procedures and techniques  CT is currently the modality of choice in the evaluation of the paranasal sinuses and adjacent structures.  Its ability to optimally display bone, soft tissue, and air provides an accurate depiction of both the anatomy and the extent of disease in and around the paranasal sinuses.  In contrast to standard radiographs, CT clearly shows the fine bony anatomy of the osteomeatal channels.
  31. 31.  SCAN LIMITS : From the ant margin of frontal sinus to post margin of sphenoid sinus
  32. 32. Coronal section procedure Coronal scans are performed by hyperextension of the patients head and angulation of the gantry The patient should preferably be in the prone position with the chin resting on a pad -KEEPS THE FREE FLUID OUT OF THE INFUNDIBULUM . In patients unable to do the above, the HEAD HANGING position should be acceptable .
  33. 33. The ideal scan thickness is 3-5 mm to cover the anterior margin of the frontal sinus to the posterior margin of the sphenoid sinus . The radiation dose is kept to the minimu by use of low mA with peak kV of 120. Images should be obtained at an intermediate setting of 2000-2500 HU window width and 200-350 HU window level as this provides details of bone and soft tissues on a single set of films .
  35. 35. 1.INFLAMMATORY SINUS DISEASE a) ACUTE SINUSITIS • Often due to secondary bacterial infection following an URTI of viral origin or a local infection . • The infection causes swelling of the mucosa which appears as an opaque rim around the periphery of the sinus . • Accompanied by an outpouring of the mucus into the sinus cavity , causing an opaque sinus on plain X-ray* . • Non specific sign ,although in most cases,denotes infection , a sinus filled with blood or new growth can give a similar appearance . • In any doubts about the presence of fluid , a tilted view should be obtained – to confirm the presence of a fluid level .
  36. 36. Inflammatory sinus disease. Coronal CT image of Inflammatory mucosal disease demonstrates maxillary (red arrows) and ethmoid (blue arrows) sinus mucosal thickening, and osteomeatal unit opacification (white arrows).
  37. 37. COMPLICATIONS 1. Osteomyelitis –May follow empyema which may rarely lead to bone involvement -Results in loss of outline of the sinus wall followed by frank osteolysis and bone sequestration. 2. Intracranial abscess- Spread of infection from the frontal or sphenoid sinuses may result in an intracranial abscess -CT/MRI will show the characteristic ring enhancement . 3. Orbital cellulitis – Commonly follows an ethmoiditis and may result in abscess formation , situated outside the perioribita adjacent to the infected sinus .
  38. 38. B) CHRONIC RHINOSINUSITIS • Chronic inflammatory disease of the paranasal sinuses and nasal cavity clinically represents recurrent acute sinusitis or a prolonged episode that has failed to respond to conservative management . • CT is the investigation of choice as this defines the degree and extent of involvement of the paranasal sinuses • Also provides the surgeon with a ‘roadmap’ of the anatomy before surgery . • FESS is usually the treatment for patients with chronic rhinosinusitis .
  39. 39. OSTEITIS. Axial CT image of chronic sinusitis indicated by left sphenoid sinus mucosal thickening and debris with adjacent osseous wall thickening (blue arrow). There is also scattered ethmoid air cell opacification (white arrow)
  40. 40. IMAGING FOR FESS(SSCT) • Particular attention is paid to the OMC , as most chronic rhinosinusitis is associated with disease in the middle meatus . • The CT will show the extent of mucosal thickening and the number of sinuses affected , and help confirm that the pathology is due to an inflammatory process . • CHRONIC DISEASE-will manifest with thickening and sclerosis of the bones. • Acute on chronic sinus secretions have a Ct density around 10-25 HU : watery or mucoid density . • Once the secretions have chronically thickened and concentrated , the Ct density will rise to 60-80 HU . • The MR appearance depends on the protein content of the secretion and hence can be quite variable . • MRI is reserved for difficult cases where there is a doubt about the pathology on SSCT or to assess any intracranial involvement .
  41. 41. • SSCT helps the surgeon avoid the known hazards of endoscopic surgery . • Shows the anatomical landmarks and the anatomical variants . • FIVE distinct patterns in which chronic rhinosinusitis presents itself : 1. Infundibular pattern – Obstruction of the maxillary infundibulum resulting in isolated maxillary sinusitis 2. Osteomeatal pattern – Middle meatus obstruction resulting in ipsilateral sinusitis affecting the frontal , anterior and middle ethmoids and the maxillary antrum 3. Sphenoethmoidal recess pattern – Obstruction results in posterior ethmoid and sphenoid sinusitis 4. Sinonasal polyposis – Sinonasal polyps are evident with opacification of various sinuses . 5. Sporadic pattern- retention cysts,mucoceles and mild mucosal thickening without mucosal obstruction
  42. 42. SINONASAL POLYPOSIS • Soft tissue pedunculated masses of edematous hyperplastic upper respiratory mucosa . • Specific polysaccharide material within the ground substance attracts excess fluid and electrolytes . • Commonest site – Ethmoids followed by maxillary antra and then the sphenoid sinus . • Plain Xrays and SSCT confirm the presence of a polpoidal mass : 1) Widening of the infundibulum 2) Opacification of the sinuses 3) Thinning of the sinus walls, nasal and ethmoid septa 4) Bulging of the lamina papyracea –Displacement of the eyeballs and hypertelorism
  43. 43. Extensive nasal polyposis (long white arrow) causing obstruction of anterior (short white arrow) and posterior (black arrow) drainage pathways causing pansinusitis
  44. 44. Multiple polyps in the maxillary sinus (white arrow) and in the sphenoid sinus (black arrow)
  45. 45. MUCOCELE  Defined as the end stage of a chronically obstructed sinus – an obstructed , airless, mucoid filled expanded sinus .  Most commonly affected is the frontal ( 66%) ; Sphenoid mucocele is rare .  On CT- Mucoid attenuation collection with remodelling of the wall -The bone may be locally thinned or eroded MRI is the optimum imaging modality – any intracranial or intraorbital extension can be assessed before surgery . Post contrast MRI typically shows peripheral enhancement of the mucosa with no enhancement of the secretions .
  46. 46. • FRONTAL SINUS MUCOCELE -Expansion of the sinus cavity with loss of the scalloped margin of the normal sinus . The sinus is more opaque than normal , due to secretions ,but may appear more radio-dense if bone destruction is marked . CT will show the full extent of the expansion and is usually enough to make the diagnosis MRI may be used to assess intracranial extension. ETHMOID MUCOCELE -Majority are found in the anterior ethmoid air cells -Usually more obvious clinically as most present with a palpable mass at the medial canthus . SPHENOID MUCOCELE -Has to be diagnosed and intervened early before vision is compromised -Involvement of the optic nerve , cavernous sinus and oculomotor nerve is common due to the proximity of these structures to the sinus . CT/MRI –shows partially rounded expansion of the sinus .
  47. 47. Mucocele of the ethmoid sinus. Plain X- ray Water’s view (A) shows an expanded and opaque left ethmoid sinus. Coronal non-contrast CT (B) shows the expanded sinus containing soft tissue densities. The wall of the sinus are thickened but are intact
  48. 48. A left sided ethmoidal mucocele (A) encroaching on the left orbit. Left globe in proptosed. T2W MR axial and coronal sections (B) of the same patient showing hyperintense fluid contents of the mucocele
  49. 49. FUNGAL DISEASE • Usually diagnosed when an apparent routine infection fails to respond to normal antibiotic treatment . • Aspergillus fumigatus – most common • The ethmoids and the maxilla antra are commonly involved. The frontal are rarely affected . • The findings vary from non specific mucosal thickening without bone involvement to an opacified sinus with a central mycetoma with reactive new bone formation or even erosions . • On CT- High density central mass separated by mucoid separations . -Areas of calcification may be present . -Calcifcation may be diffuse , nodular or linear -Accompanied by bone expansion and bone destruction in the invasive form of the disease . MRI- Signal hypointensity is the distinctive feature of aspergilloma Due to the paramagnetic effect of heavy metals present in the fungal ball .
  50. 50. CT images coronal and axial showing diffuse nasal and sinus mucosal thickening with hyperdensities (black arrows) causing expansion and blockage of the sinuses. On bone window, the ethmoid lamellae and sinus walls are remodelled and eroded (white arrow)
  51. 51. Invasive fungal sinusitis: Axial T2WI (left) and T1WI (right) images showing soft tissue in the frontal, ethmoid and sphenoid sinuses which is isointense on T1WI and hyperintense on the T2WI
  52. 52. GRANULOMATOUS DISEASE • Majority are infectious • Include Tuberculosis , Syphilis, leprosy, rhinoscleroma and actinomycosis . • Non specific findings on imaging . • Most of these start in the nasal cavity with soft tissue masses and chronic non specific pan sinusitis . • A diagnosis of granulomatous disease should be considered when there is evidence of nasal septal mass with septal erosion on imaging .
  54. 54. RETENTION CYSTS • Occur as a result of obstruction of the ducts of the mucosal glands . • Usually small, have a well defined outline • CT- Smooth , broad based soft tissue mass with a well defined outline . • MRI – Low intensity on T1 and bright on T2 but may appear bright on T1 depending on the concentration of entrapped secretions .
  55. 55. TUMOURS OF THE PARANASAL SINUSES • BENIGN TUMOURS -OSTEOMA – • Benign slow growing tumours containing mature compact or cancellous bone . • Occur most frequently in the frontal sinus, followed by ethmoid and maxillary sinuses • May block the drainage of a sinus resulting in recurrent infection and/or mucocele . • Large frontal osteomas can erode the inner table to the frontal bone which may allow the infection to spread intracranially and pneumocephalus will be seen . • Posterior extension may lead to the compromise of the optic nerve .
  56. 56. • Plain film and CT – Well defined very dense lesion (if it contains mature bone) • Less ossified if it contains cancellous bone Osteoma of the left frontal sinus. Axial and coronal CT scans showing a dense bony lesion of the left sinus occupying much of the sinus cavity leaving only a thin rim of air around it.
  57. 57. PAPILLOMA • The mucosal lining of the nose is derived from ectoderm and is called the schneiderian membrane . • Can give rise to three types of papillomas : (a) FUNGIFORM – Arises from the nasal septum,usually anteriorly . (b) INVERTED- Commonest usually originate (c) CYLINDRICAL CELL from the lateral wall . -Inverted papillomas – Characterestically arises from the lateral nasal wall near the middle turbinate and extend into the sinuses ,usually involving the maxillary and ethmoid sinuses . SYMPTOMS – Nasal obstruction , epistaxis and anosmia .
  58. 58. INVERTED PAPILLOMA of the right antrum and ethmoids. Noncontrast CT scan shows a hyperdense soft tissue lesion in the right ethmoid and nasal cavity extending into the right antrum. The middle turbinate is destroyed and the septum shows focal erosion. The floor and medial wall of the orbit is eroded at places
  59. 59.  Imaging appearance can vary from a small nasal polypoid mass to an expansile mass with remodelling of the nasal cavity  May extend into the sinuses with secondary obstructive sinusitis .  The nasal septum usually remains intact but may be remodelled with bowing of the septum .  INVERTED PAPILLOMAS – usually multicentric .  ADENOMAS – may simulate a nasal polyp but are locally invasive and local recurrence occurs if they re not completely excised .
  60. 60.  NASAOPHARYNGEAL ANGIOFIBROMA -Rare histologically benign but locally aggressive tumour . -Highly vascular polypoid mass-usually in males (10-18) -Almost all tumours originate from the posterior choanal tissue near the pterygopalatine fossa and the sphenopalatine foramen . -They fill the entire nasopharynx and frequently extend into the pterygolpalatine fossa causing widening of the fossa and anterior bowing of the posterior ipsilateral antral wall . -Intracranial extension occurs uncommonly in 5-20%-----Superior orbital fissure widening is seen as an indication .
  61. 61. ANGIOFIBROMA LATERAL X-RAY OF SKULL - showing anterior bowing (small arrow) of the posterolateral wall of the maxillary sinus due to the angiofibroma (open arrow)
  62. 62. Angiofibroma: Contrast enhanced axial CT sections show a well-defined mass in the nasal cavity and in the pterygomaxillary fissure which is wide. Posterolateral wall of the antrum is pushed anteriorly (Arrow). Coronal sections shows widening of the pterygomaxillary fissure
  63. 63. • In addition , a soft tissue nasopharyngeal mass and opacification of the sphenoid sinus may be seen . • Cross sectional imaging may demonstrate an avidly enhancing mass . • Multiple flow voids will be seen within the tumour on T1 and T2 weighted spin – echo sequences . • The internal maxillary artery and the ascending pharyngeal artery are the major feeding vessels which will be demonstrated on angiography • Pre operative embolisation may be used to aid subsequent surgery .
  64. 64. ANGIOMATOUS POLYP - Located in the nasal fossa and NOT the NASOPHARYNX , unlike the nasopharyngeal angiofibroma . - Does not extend into the pterygopalatine fossa or intracranially . - The vascular supply of these lesions is less extensive than angiofibromas . - Does not enhance avidly following intravenous contrast and vascular flow voids are not seen on MRI .
  65. 65. LYMPHOMAS  Forty-seven percent of non-Hodgkin’s lymphomas are found in the head and neck; 90 percent of these are in the cervical lymph nodes.  Though the nasopharyngeal region surrounded by the Waldeyer’s ring is a potential site of lymphoma, actual involvementof the sinonasal cavity is rare.  Lymphomas arising in the nose and PNS are of the non-Hodgkin’s type and are seen in cases of disseminated lymphoma.  Lesions may be mistaken for sinusitis, polyposis and granulomatous processes.  On CT and MR - bulky masses which show moderate enhancement.  The osseous changes include remodeling, expansion, erosion and infiltration of the sinus walls.  Primary lymphoma of the paranasal sinus is uncommon.
  66. 66. MALIGNANT TUMOURS  Plain radiographs are no longer recommended for screening for sinonasal malignancy  Cross-sectional imaging is required to stage these tumours in order to visualise the extent of tumour beyond the sinuses.  The areas of particular concern are the intraorbital cavity, pterygomaxillary fossa, pterygopalatine fossa, infratemporal region and intracranial extension  CT acquisition is much faster with helical and multislice scanners , is sensitive to bone destruction and is more readily available.  Gadolinium-enhanced MRI is better than CT for the detection of intracranial and perineural tumour extension.  Nodal disease may be assessed by either CT or MRI.  Intravenous contrast enhancement allows identification of rim enhancement and central necrosis, which is often seen in squamous cell carcinoma.  Extracapsular spread of nodal disease is better assessed by CT than MRI.
  67. 67.  Ideally scans should include the first and second oral draining nodes.  Tumours involving the maxillary antrum drain initially to the retropharyngeal nodes but level 2 (upper internal jugular) and level I (submandibular) groups may be involved and these should therefore be included within the scan.  Collimation should be 5 mm or less.  Direct coronal and axial scans should be obtained with both bone and soft-tissue algorithm.  On MRI a slice thickness of 4 mm or less should be used.  Sagittal T1-weighted fatsaturated scans after gadolinium enhancement may also be useful in assessing perineural and intracranial extension.
  68. 68.  Squamous cell carcinomas show little contrast enhancement.  However, contrast administration is necessitated in CT evaluation of these tumors because it can help to differentiate (1) Fluid from areas of necrosis (2) involvement of normal structures from tumors especially in the orbit (3) and to delineate intracranial extent of the tumor  Limitations of CT scan include: 1. Inability to distinguish between inspissated and retained secretions from tumors 2. Detect involvement of the periorbital structures especially the lamina papyracea and the adjacent structures 3. To differentiate soft tissues involvement by tumors versus swelling due to edema.  On MRI inflammatory tissue and retained secretions can be differentiated with some degree of confidence from tumors as the latter have a higher water content and thus appear to be of high intensity on T2WI and low intensity on T1WI
  69. 69. Coronal MRI images showing mass to be isointense on T2WI which enhances on post contrast images (black arrow). MR show extensive lesion with aggressive behavior infiltrating into the right orbit, frontal sinuses and frontal bone diploe. Also seen are intensely bright maxillary sinuses (short white arrow) on T2WI which does not enhance suggestive of postobstructive changes. Note normal thin mucosal enhancement of maxillary sinuses (long white arrow)
  70. 70.  These tumours often present at an advanced stage.  The commonest tumour is squamous cell carcinoma, which accounts for 80% of all sinus malignancies.  Approximately 50-65% arise in the maxillary sinuses,10-25% in the ethmoid sinuses and 15-30% in the nasal cavity.  Small tumours will mimic the appearances of chronic sinusitis and nasal polyposis, thus many patients will be diagnosed at a late stage of their disease.   The Primary tumour shows little if any enhancement on CT following intravenous contrast.  On MRI, the tumours are of intermediate T, signal intensity and slightly higher signal intensity on T,-weighted images.  Larger tumours may have areas of necrosis and haemorrhage altering the signal intensities within them.  They also enhance slightly following intravenous gadolinium.
  71. 71. SQUAMOUS CELL CARCINOMA OF THE RIGHT MAXILLARY SINUS. Noncontrast CT scan shows soft tissue mass of intermediate attenuation with central necrosis filling the right antrum. The lesion extends beyond the bony walls of the sinus, bone window setting show extensive lytic destruction of the walls
  72. 72.  Intestinal-type adenocarcinomas of the sinonasal cavities are especially common in individuals with a previous exposure to hardwood dust  The histology of the high-grade tumours resemble colonic and gastric carcinomas.  In these patients metastatic disease from gastrointestinal primaries should be ruled out before making the diagnosis, but this is a rare occurrence.
  73. 73. MALIGNANT MELANOMAS  Occur more commonly in the sinonasal cavities.  When they do occur, involvement of the nose is more common than the sinus.  Local recurrence or metastatic disease within the first year is seen in up to 65% of patients, metastases affecting the lungs, nodes, brain, adrenal glands, liver and skin.  These tumours enhance more avidly than squamous cell carcinomas on postcontrast scans.  Some lesions willexhibit high signal intensities on T,-weighted sequences owing to the presence of haemorrhage and/or melanin.
  74. 74. OLFACTORY NEUROBLASTOMA  Arises from the olfactory epithelium of the nasal cavity and is a tumour of neural crest origin.  Epistaxis and nasal obstruction  The prognosis is related to the extent of disease at presentation.  These lesions are hypointense to brain on T,-weighted images and  hypertense to brain on T2 -weighted images.  Coronal and sagittal scans are usual to determine the relationship of the tumour to the cribriform plate and intracranial extension.  The tumours enhance with intravenous contrast on both CT and MRI.  Metastatic disease is seen in up to 38% of patients, with involvement of cervical lymph nodes, parotid glands, skin, lung, liver, eye, spinal cord and spinal
  75. 75. Olfactory neuroblastoma: Axial and coronal contrast enhanced CT section showing a uniformly enhanced mass in the right nasal cavity extending from the superior nasal fossa upto the inferior turbinate, the thinned out nasal septum bulges to the left. There is erosion of the right fovea ethmoidalis and the cribriform plate