IMAGING OF PARANASAL SINUSES

Speaker- Dr SharmaModerator- Dr W Jatishwor Singh

Nasal cavity is a passage from the external nose anteriorly to the nasopharynx posteriorly.

The frontal, ethmoid, sphenoid and maxillary sinuses form the paired paranasal sinuses and are situated around, and drain into the nasal cavity.

Approximately 2 L of water is produced daily by the serous glands of the sinonasal cavity and is used to humidify inspired air.

Development The nose is formed from five facial

prominences : the frontal prominence (bridge); the merged medial nasal prominences (crest and tip); and the lateral nasal prominences (alae).

Paranasal air sinuses develop as diverticula of the lateral nasal wall and extend into the maxilla, ethmoid, frontal, and sphenoid bones.

They reach their maximum size during puberty.

FP

LP

MP

The nasal cavity This is divided in two by the nasal

septum, is part. bony and part. cartilagenous.

The floor-- roof of the oral cavity , formed by the palatine process of the maxilla & palatine bone posteriorly.

The lateral walls- fromed by maxillary, palatine, lacrimal and ethmoid bones.

Nasal mucosa- vascular pseudostratified columnar ciliated epithelium that contains both serous and mucous glands.

Most superiorly a less vascular& nonciliated epthelium - the olfactory mucosa.

Lateral walls - three curved turbinates or conchae, divide the cavity into inferior, middle and superior meati.

Drainage: The sphenoid air-sphenoethmoidal

recess. Posterior ethmoidal air cells- superior

meatus. The frontal sinus- anterior opening of

the middle meatus. The anterior ethmoidal air cells and

maxillary sinus- middle meatus at the hiatus semilunaris, below the ethmoid bulla.

The nasolacrimal duct- inferior meatus.

Blood supply of the nasal cavity The sphenopalatine artery (max. artery). Greater palatine artery. Superior labial branch of the facial artery. Anterior and posterior ethamoidal

branches of the ophthalmic artery. Little's area/ Kasselbach plexus is a

vascular region of mucosa in the anterior and inferior part of the nasal septum, which is the site of majority of epistaxis.

The frontal sinuses Lie between the inner and outer

tables of the frontal bone. Vary greatly in size and are often

asymmetrical. They drain via the nasofrontal duct

into the anterior portion of the MM. Absent at birth and begin to develop

after the second year of life. In approx 5% of the population, they are absent.

At approximately 10 to 12 years of age, the final adult size is reached.

The ethmoid sinuses Labyrinth of bony cavities or cells

situated between the medial walls of the orbit and the lateral walls of the upper nasal cavity.

Enlargements anteriorly (agger nasi ) or below apex of orbit (Haller's cells).

Begin to develop in the 5th month of fetal life. Wide variation in the numbers and sizes of cells.

The anterior ethmoid air cells are more numerous. Pneumatization of the ethmoids is widely variable.

Concha bullosa- Pneumatization of MT.

The sphenoid sinuses Paired cavities in the body of the

sphenoid. May be subdivided further into smaller bony cells.

The sella turcica is superior and cavernous sinus & contents laterally.

Floor of sphenoid sinus- roof of the nasopharynx.

Begin to develop in the 4th or 5th fetal month from a posterior outgrowth of the nasal capsule. Major development in about the 3rd year of life and reaches adult size early in the 2nd decade.

The maxillary sinuses First sinus to form, begins at about 17th

day. By end of 1 year of life, the laterally extend into the medial portion of the floor of the orbit and reaches the infraorbital canal by the 2nd year.

The adult configuration-early second decade.

The maxillary sinuses are the largest PNS. They have a body and four processes: -orbital process, -zygomatic process, -alveolar process, -palatine process.

Medial wall, continued superiorly as a bony projection- uncinate process.

Maxillary ostium opens superiorly into the infundibulum, between the inferomedial aspect of the orbit laterally and the uncinate process medially.

The region of ostium, infundibulum and middle meatus is important clinically and is known as the ostiomeatal complex.

Ostiomeatal Unit It is the complex of middle meatus and

the ostia of draining sinuses. These are the frontal sinus, the anterior

ethmoid sinuses, and the maxillary sinus. Radiographic evaluation is therefore

directed toward assessing the patency of the maxillary sinus ostium, the ostia of the anterior ethmoid air cells, the hiatus semilunaris, and the middle meatus.

The coronal plane is best for demonstrating the anatomy of the ostiomeatal unit.

ethmoid bulla (b), concha bullosa©

Imaging of nasal cavity and paranasal sinuses

Conventional Radiography. CT Scan MRI. Angiography. PET. MRS.

Nasal bone Radiography:Pt sitting, median sagittal plane ll-el to cassette and the inter-pupillary line is perpendicular.

Occipito-mental(Water’s) View Patient seated, facing cassette with nose

and chin resting & open mouth. Orbito-meatal baseline 45-degree angle to the cassette holder. Horizontal CR through IOM.

450

Occipito-frontal(Caldwell) ViewPt seated facing the vertical Bucky, orbito-

meatal baseline is raised 15 degrees to horizontal, nasion is at centre, CR perpendicular to the vertical Bucky exits at the nasion.

150

Lateral View Sitting, median sagittal plane is parallel to the

Bucky and the inter-orbital line is perpendicular to Bucky, CR centred 2.5cm posterior to the outer canthus of the eye.

CT Scan CT scanning in either axial or coronal

planes. Particular attention to OM complex. The pneumatized sinuses should contain

nothing but air. Axial images, beginning at the alveolar

ridge and extending through the top of the frontal sinus. Coronal images are taken perpendicular to hard palate.

Advantage over plain film radiography. If surgical intervention is contemplated ,

overlapping thin sections with reconstruction are most useful.

CT is excellent for determining anatomic landmarks and variants, erosive processes , intraorbital extension of sino-nasal disease & other pathology.

CT is performed without contrast medium.

Opacified sinus with hyperdense contents, is usually a sign of benign disease.

Allergic Fungal Sinusitis- hyperdense material in posterior right ethmoid, b/L spheno-ethmoidal recesses, sphenoid sinus and there is involvement of the clivus.

MRI MRI is good at demonstrating the

sinuses by its multiplanar capabilities. Bone is seen as a low intensity structure sandwiched between high-intensity mucosal layers (t2).

MRI is extremely helpful in complicated sinonasal disease. MRI can identify secretions and mucosa from masses.

MRI is also useful for determining invasion of the skull base, foraminal extension & IC extension.

The use of gadolinium has been proposed as a method for differentiating sinonasal neoplasms from inflammatory masses.

The MRI protocol include T1- and T2-W images in axial and coronal.

Sagittal or off-sagittal images parallel to the optic nerve may be obtained if necessary.

Gadolinium (Gd-DTPA) may then be given, and repeat scanning can be performed if necessary.

Fungus usually has a high protein content of more than 28% and infection can mimic an aerated sinus because it is low on T1- and T2WI( 'pseudo-pneumatized sinus‘).

Infectious sinonasal disease.High signal content(proteinous) of the maxillary sinus with enhancement of the circumferential mucosa and not centre.

Congenital anomalies/normal varients.

Hypoplasia of the sinus -1% and 7% of the population and may be developmental or result from trauma, infection, surgical intervention, or irradiation.

Congenital first and second branchial arch anomalies such as Treacher Collins syndrome, with hypoplasia of one of the maxillary Sinuses.

MT showing exaggerated convexity directed toward the medial wall/nasal septum narrowing the middle meatus- paradoxical middle turbinate.

Ethmoid air cells extending inferiorly to the ethmoid bulla and roof of the maxillary sinus narrow the infundibuIum- Halle cells.

The anterior ethmoids,forming superior contour of the MM called ethmoid bullae may become enlarged blocking the infundibulum.

The uncinate process itself may be of varying sizes, shapes, and positions.

Deviated nasal septum to one side or another seen in more than 90% of people. When the deviation is significant or bone spur forms, obstruction MM may result.

Inflammatory Diseases-1.Acute Rhinosinusitis

Acute inflammation in nose and paranasal sinuses.

One of most common medical problem.

Mostly viral or bacterial origin. Dental etiology in abt 10-20%. Symptoms are variable. Sinus

tenderness may be noted.

Imaging Features Nodular or smooth mucosal thickening

or complete sinus opacification. Contrast-enhanced inflamed mucosa

lining; variable amounts of submucosal edema and surface secretions.

Air-fluid level esp. maxillary sinus. T1-weighted MRI: low to int. SI T2-weighted MRI: high signal of

inflamed mucosa and fluid. T1-weighted post-Gd MRI: intense

enhancement of inflamed mucosa; no enhancement of fluid.

Fluid-level in max. sinuses and mucosal thickening of ethmoid cells bilaterally

Opacification of the maxillary sinuses and sphenoid sinuses

Chronic Sinusitis Develops from either persistent

acute inflammation or repeated episodes of acute or subacute sinusitis.

Allergic sinusitis Vasomotor rhinitis Fungal sinusitis (90% Aspergillus

fumigatus; maybe fulminant and invasive in immunosuppressed patients)

Chronic rhinosinusitis tends to present in Five distinct patterns:

1. Infundibular pattern - obstruction of the maxillary infundibulum.

2. Ostiomeatal unit pattern- middle meatus obstruction resulting in ipsilateral sinusitis .

3 Sphenoethmoid recess pattern- post. ethmoid and sphenoid sinusitis.

4. Sinonasal polyposis pattern- sinonasal polyps with opacification.

5. Sporadic or unclassifiable pattern- includes retention cysts, mucoceles and mild mucosal thickening without obstruction.

Imaging Features Varying mucosal swelling, smooth/

irregular d/t edema and secretion. Thickened, sclerotic, fibrotic sinus

walls, esp. maxillary sinuses. Dystrophic calcification. T1-w MRI: low to interm. T2-wMRI: usually high signal of

inflamed mucosa, low signal of sclerosis and fibrosis.

Inspissated mucus can be dark on all sequences resulting in false-negative MR diagnosis of chronic sinusitis.

Chronic sinusitis- surgical maxillary defects b/l , opacification of left sinus, and thickening with sclerosis of sinus walls b/L.

Opacification of ethmoid sinuses bilaterally.

Fungal Infections. The most common and most important of

these include mucormycosis, histoplasmosis, and candidiasis and dis- eases caused by Aspergillus.

The radiographic features are nonspecific and include opacification of the sinus as well as a sclerotic bony reaction.

Fungal RS-calcifications & high densities in ethmoid and sphenoid .

Fungus ball- rt sphenoid opacity, calcifications & sclerosis. Fungus ball extends through spheno-ethmoidal recess.

Mucormycosis Esp. in imunocompromised. 50 to 75% have

poorly controlled or uncontrolled diabetes mellitus.

Organisms are invasive - spread rapidly from the nasal cavity to the PNS & blood vessels.

May cause thrombosis, venous cerebral infarcts, Invasion of the orbits, cavernous sinuses, and ophthalmic veins, and Intracranial extension.

Because fungi tend to bind Ca, Mn, and other heavy metals- PNS may appear hyperdense on CT scans and of low SI on MRI.

Latter stages- bony destruction may mimic an aggressive tumor such as sq. cell ca.

Aspergillus infection Occur in otherwise healthy

patients. May show Opacification of a single

paranasal sinus, a hyperdense paranasal sinus on CT scans, hypointense signal -on T2-weighted MRI studies from heavy metal, and osseous destruction mimicking aggressive tumor in the later stages.

May cause vasculitis and cerebral thrombosis.

Chronic aspergillus sinusitis

opacification of right maxillary & ethmoid. T1-w- high signal in max. & low si in ethmoid. Heterogeneous contrast enhancement

Tuberculosis.

Tuberculosis may involve the paranasal sinuses secondary to pulmonary infection.

The sinus disease is again nonspecific.

Retention Cysts(Mucous and Serous)

Mucous retention cyst: d/t obstruction of submucosal mucinous gland, thus cyst wall have duct epithelium and gland capsule.

Serous retention cyst: d/t accumulation of serous fluid in submucosal layer of sinus mucosa, thus have cyst lining of elevated mucosa.

Imaging Features Smooth, spherical soft tissue mass. Retention cysts found incidentally in 10–

35% of patients, MC in maxillary sinus, but can occur in any sinus.

Frequently small, may become large but always contain some air in sinus.

Normal bone in almost in every case. T1-weighted MRI: low to intmd. SI. but

show high signal if high protein content. T2-weighted MRI: high signal.

Retention cyst in max sinus without expansion of sinus walls. T2-w MRI shows retention cyst with high signal in patient with

osteosarcoma of right maxilla

Polyps D/T Expansion of fluids in deeper lamina

propria of Schneiderian mucosa in nasal fossa and paranasal sinuses.

MC expansile condition in nasal cavity. About 4% in general population. Associated with allergy, but may result

from infectious rhinosinusitis, vasomotor rhinitis, cystic fibrosis, diabetes mellitus, aspirin intolerance, and nickel exposure.

When seen in children, cystic fibrosis should be ruled out.

Imaging Features Smooth, spherical soft tissue mass If multiple, complete opacification of

nasal cavity and sinuses. T1-weighted MRI: low to interm.SI T2-weighted MRI: high signal. Heterogeneous MR signal characteristic

in chronic polyps; and can also enhance.

Eth Polyps- Complete opacification of nasal cavity and all paranasal sinuses.

Polyps bulging through OM complex & mucosal thickening in ethmoid and maxillary sinuses

Antrochoanal polyp- polyp in nasopharynx. Lat view with contrast in nose polyp blocks nasopharynx.

Mucoceles Collection of mucoid secretions surrounded

by mucus-secreting respiratory epithelium. Develops due to obstruction of sinus

ostium or a compartment of a sinus with the sinus mucosa and always have expanded sinus walls.

Clinical Features Most common expansile condition in PNS MC in frontal sinuses (60–65%); Wide range of age: 20 to 60 years. Ostial obstruction may be caused by

inflammatory scar, trauma, or tumor.

Imaging Features Initially, intact /remodeled, expanded bone. With progressive growth sinus wall will be

destroyed and Completely airless sinus. CT scans- expanded sinus filled with

homogeneous material low atten. (-15 HU) MRI : variable signals, depending on protein

content, state of dehydration, and viscosity. Mostly high signal on T1 and T2, or moderate-to-marked low signal on T1 and T2, or low to intermediate T1 and high T2.

T1-w post-Gd MRI: no enhancement except of thin peripheral rim.

Frontal sinus mucocele- ovoid well-defined soft tissue mass in right orbit with displacement of globe laterally down with bone expansion.

Frontal mucocele- T2-w intm signal expansive mucocele. T2-w axial- expansion into cranial fossa . Post-Gd no enhancement except in thin peripheral rim.

Wegener’s Granulomatosis Noninfectious Destructive Sinonasal

Disease

Clinical Features Diagnosis difficult to establish early in

disease course. Chronic, nonspecific inflammatory

process of nose and sinuses for more than a year.

Nasal septum affected in more than 90%, with ulceration and perforation (‘saddle nose’ deformity).

Imaging Features Nasal involvement precedes sinus

disease. May have soft-tissue mass of nasal

septum and septal erosion. Sinuses affected in more than 90% cases

with nonspecific inflammation and mucosal thickening.

Bones of nasal vault and affected sinuses may be thickened and severely sclerotic d/t chronic inflammation, osteomyelitis or necrosis.

Wegener’s granulomatosis - destruction of nasal cavity structures, and chronic sinusitis

Sag. CT image shows destruction of nasal bone, saddle nose.

Tumors and Tumor-like Conditions

Papilloma Benign tumor of nasal cavity composed

of vascular connective tissue covered by well-differentiated stratified squamous epithelium.

Fungiform papillomas make up approximately 50% of all papillomas.

-Arise from the nasal septum, -are usually solitary and unilateral, and -may have an irregular surface much like

other papillomas but not premalignant.

Inverted papillomas (endophytic papillomas)

-50% of all sinonasal papillomas. -Middle-aged men. -Arise from lateral nasal wall at root of

the middle turbinate, and may extend laterally into the paranasal sinuses.

-Infolding of mucosa in underlying stroma without crossing BM.

-The rate of malignancy assd about 15%. Postoperative recurrence 35–40%.

-Mostiy degenerate into sq. cell ca, but rarely mucoepidermoid and adeno ca.

Imaging Features CT- soft tissue density mass with non-

homogenous contrast enhancement. Bone remodeling that may deviate, but

intact nasal septum. Mass may extend into ethmoid or

maxillary sinuses MRI- ‘septated striated’/’convulated

cerebriform’ or ‘columnar’ pattern. T1-w MRI: low or intermediate T2-w MRI: interm. to high, usually high. T1-fs post-Gd MRI: some enhancement.

T2-w MRI- Displacing and remodeling the posterolateral wall. Parallel columnar pattern of the inverted papilloma. Expansion

of nasal cavity &Thinning of the bony periosteal covering of the posterolateral maxillary sinus.

Inverted papilloma- soft-tissue mass in right nasal cavity with some deviation of nasal septum extending into nasopharynx.

Osteoma Benign tumor of normal mature bone. Usually an incidental finding.Imaging Features MC in frontal, followed by ethmoid and

maxillary sinuses May occlude sinus ostia causing sinusitis

or mucocele formation. Described as "ivory" or highly dense

bone, obvious on both plain film and CT. May cause obstruction or erosion from

the frontal or ethmoid sinus into the cranial cavity, causing CSF leak.

Frontal/ethmoid osteoma- CT shows well-defined bone mass in right frontal and ethmoid sinuses crossing midline.

Sphenoid/ethmoid osteoma CT - mass involving ethmoid and sphenoid sinuses extending to sells turcica.

Fibrous Dysplasia Benign bone disease; where medullary

bone is replaced by a poorly organized and loosely woven bone that is expanded.

May involve maxilla and mandible with Painless swelling and deformity.

Imaging Features Radiolucent and/or radiopaque areas,

depending on amount of fibrous tissue. Ground-glass appearance typical with

expansion of the middle table blending into the inner and outer tables.

Fibrous dysplasia- 3D CT shows expanded right maxilla and zygoma with elevated orbital floor.

Axial CT shows ground-glass appearance .

Juvenile angiofibroma(nasopharyngeal angiofibroma)

Highly vascular and nonencapsulated polypoid mass that is benign but aggressive.

Mostly males in the 2nd decade. Origin- thought to be nasopharyngeal region

at the pterygopalatine fossa or sphenopalatine foramen. Involvement of the pterygopalatine fossa seen in 90% of cases.

Tendency for growth in submucosal plane and early bone invasion.

May extend into the maxillary and ethmoid sinuses or orbit &cranial fossa.

Highly vascular and can cause profuse hemorrhage.

Angiogram demonstrates major feeding vessels, most often the internal max artery and asc pharyngeal artery. Preoperative embolization of these branches greatly reduce blood loss at surgery.

Contrast enhanced CT or MRI reveals a polypoid and infiltrating enhancing mass that involves the nasopharynx and pterygopalatine fissures.

Juvenile angiofibroma CT- Lesion displaces maxillary sinus wall. Involvement of pterygoid process &spread deep to the nasopharyngeal roof.

Post-contrast MR extension of the tumor towards the sphenopalatine foramen (arrows) and erosion of the pterygoid process (arrowheads)

Neurogenic Tumor Schwannomas are benign, encapsulated,

slowly growing tumors of the nerve sheath. Seen rarely in PNS.

When plexiform neurofibromas arise from the soft tissues or subcutaneous tissues, may infiltrate within the paranasal sinuses.

Odontogenic tumors Arise from the alveolar ridge and may

extend to the maxillary sinus. Approximately 10% to 15% of all

maxillary sinus inflammatory and neoplastic diseases have an odontogenic origin.

The most common odontogenic lesions involving the maxillary sinus are odontogenic cysts

Squamous Cell Carcinoma 50–80% of all malignant sinus masses. >60% originate in max. sinuses, followed by

nasal cavity & ethmoid sinuses. Most are low-grade tumors. Paucity or mild symptoms- mis/under

diagnosed. Imaging Features Usually advanced when detected; bone

destruction in 80%. Alveolar bone destruction in half of patients. Tumors enhance very little. Gd MR study may

be useful for differentiating neoplastic from inflammatory masses.

Sq cell ca left maxillary sinus- T2-w coronal seq shows a solid mass extending into the nasal fossa and the ethmoid.

Glandular carcimoma 10% of tumors of the sinonasal tract are

glandular in origin. These include tumors that arise from

minor salivary glands such as adenoid cystic carcinomas and mucoepidermoid carcinomas and adenocarcinoma.

Adenoid cystic carcinomas are unusual because of their course.

Most adenocarcinomas arise from the ethmoid air cells.

Ethmoid adenocarcinoma- CT PC shows well-defined, dense mass in left ethmoid sinus and expanding into nasal cavity and orbital wall. Incidental retention cyst.

Olfactory Neuroblastoma Uncommon tumor, originates from neural

crest cells of olfactory mucosa. Bimodal pattern- 2nd & 6th decade. Polypoid tumor may be soft or firm but

may be friable and bleed profusely. Relatively slow-growing with some

expansion and remodeling of bone. Propensity for intracranial extension

through the dura at cribriform plate.

Olf. NB Postcontrast- Extension into orbital apices, suprasellar & nasal cavity. Left carotid artery is encased.

Lymphoma Most common sarcomas involving the

sinonasal tract. Majority are NHL types. It is one of the MC malignancies in HIV

pts. But PNS involvement is rare. Grossly, bulky soft tissue masses that

may enhance following gd. ,tend to remodel bone and occ. erode bone rather than destroying.

The nasal cavity and maxillary sinus are the most common sites of origin.

Soft-tissue mass in infratemporal fossa, invades maxillary sinus with bone destruction - plasmablastic lymphoma

Osteosarcoma Maxillary osteosarcoma- Axial CT & T2 fs image

shows large soft-tissue mass in maxillary sinus with destruction of most of sinus wall.

Ewing sarcoma Coronal CT image shows enormous tumor destructions of maxilla,

zygoma, orbital floor, and nasal cavity expanding maxillary sinus. Axial T1-w fs huge exophytic tumor.

MISC. Conditions: Foreign body- Axial CT image shows piece of

calcified mass in ethmoid sinus.

Oroantral fistula- Opening between oral cavity and maxillary sinus and minimal mucosal thickening.

Maxillary sinusitis due to displaced tooth root. Mucosal thickening root in alveolar part of sinus.

TRAUMA Fractures of the nasal bone are the most

common fracture of the facial skeleton. These may be isolated or associated with other injuries. Plain film examination with oblique cone-down views of the nasal bones is the most sensitive.

Maxillary Fracture is classified ,as described by Le Fort in 1900 as:

Le Fort I, II, and III.

Le Fort

Fractures

Imaging of Maxillary Fracture

Initial- Standard OM View and True lateral view, cantered at maxilla.

CT-Axial slice- for maxillary fracture Coronal slice- for orbital fracture. MDCT with 3D recons. – for facial

skeleton and before reconstructive surgery.

THANK YOU

REFERENCES:•Hagga: CT/MRI Imaging.•Larheim/ Westesson: Maxillofacial Imaging.•Hodler :Imaging of Brain/head/Neck(IDKD).•Grainger: Diagnostic Radiology.•Sutton: Radiology & Imaging.•Radiographics, AJR.