Head and Neck Imaging

Types

• • Conductive

    • Disruption of sound conduction that may be secondary to abnormalities in the EAC, TM, ossicles, or oval window

    • Common underlying causes: otitis, cholesteatoma, otosclerosis, trauma

  • Sensorineural

    • Evaluate inner ear, IAC

    • Common underlying causes: idiopathic, hereditary, vestibular Schwannoma, enlargement of vestibular aqueduct, labyrinthitis ossificans, otosclerosis (cochlear otosclerosis), trauma

Causes

• • Normal vascular variants

    • Aberrant ICA

    • Jugular bulb anomalies (high or dehiscent jugular bulb, diverticulum)

    • Persistent stapedial artery

  • Vascular tumors

    • Glomus jugulare paraganglioma

    • Glomus tympanicum

  • Vascular abnormalities

    • Skull base dural arteriovenous fistula/arteriovenous malformation (AVM)

    • Atherosclerotic carotid artery stenosis

    • Carotid-cavernous fistula (CCF)

    • ICA dissection or aneurysm at the petrous apex

    • Fibromuscular dysplasia

    • Dural sinus stenosis

    • Transverse-sigmoid sinus diverticulum

  • Other causes of tinnitus

    • Idiopathic intracranial hypertension

    • Paget disease

    • Otosclerosis

    • Ménière disease

Clinical Findings

• • Periauricular swelling and ecchymosis (Battle sign)

  • Bleeding into EAC or hemotympanum

  • Hearing loss

  • Tinnitus

  • Vertigo

  • Cerebrospinal fluid (CSF) leak

  • Facial paresis

Radiographic Features

Fracture Complications

• • Ossicular fractures or dislocations

  • TM perforation

  • Hemotympanum

  • CN VII paralysis

  • CSF otorrhea

  • Meningitis, abscess

  • Sinus thrombosis, rare

  • Labyrinthitis ossificans (late)

  • Also assess for associated cervical spine fracture or fracture extension to carotid canal.

Indications for Surgery in Temporal Bone Fractures

• • Ossicular fracture or dislocation: varied, conservative or surgery

  • Facial nerve injury: frequently conservative, but occasionally requires surgical decompression

  • Labyrinthine fistulae: surgery if persistent

  • CSF leaks: surgery if persistent

Potential Complications

• • Meningitis

  • Subdural empyema or epidural abscess

  • Dural venous sinus thrombosis

  • Petrositis (infection of petrous air cells)

  • Gradenigo syndrome (rare complication of petrositis: triad of otomastoiditis, sixth nerve palsy, and pain in the distribution of the fifth nerve)

  • Subperiosteal or Bezold (via defect at the mastoid tip) abscess

  • Focal encephalitis, brain abscess, otitic hydrocephalus

Radiographic Features

• • High resolution temporal bone CT first line, excellent for detailed bone evaluation; MRI can be helpful for complex cases and cholesteatoma distinction.

  • Soft tissue mass in middle ear

  • Borders may be well- or ill-defined.

  • Erosion of incus and otic spur (scutum) common

  • Bone resorption (collagenase) is typical and occurs most commonly in:

    • Ossicles

    • Lateral semicircular canal (fistula)

    • Tegmen tympani

    • Facial canal

  • Mastoid air cells may be underpneumatized and sclerotic secondary to chronic infection.

  • Labyrinthine fistula formation in lateral semicircular canal is less common.

  • It is often impossible to distinguish chronic middle ear infection from cholesteatoma in cases with little bone destruction on CT. However, MRI can be useful for distinction of cholesteatoma (restricted diffusion, no enhancement) from inflammatory changes or granulation tissue (enhances).

Complications of Acquired Cholesteatoma

• • Labyrinthine fistula (dehiscence of semicircular canals—most frequently lateral canal)

  • Facial nerve paralysis (involvement of facial nerve canal)

  • Invasion of tegmen tympani, petrous apex, or sigmoid plate

  • Automastoidectomy

Radiographic Features

• • Expansile erosive osseous lesion of the petrous apex

  • Smooth margins

  • CT: isodense relative to brain, no enhancement, no calcification

  • MRI: hyperintense relative to brain on T1-weighted (T1W) images because of methemoglobin and cholesterol crystals

  • Cholesterol granulomas retain their high signal on fat suppressed T1W images, distinguishing them from fatty lesions.

Radiographic Features

• • Early findings may manifest as thickened mucosa of EAC and soft tissue swelling; more advanced disease can have bone erosion associated with the opacification.

  • Mastoiditis

  • Skull base osteomyelitis

  • Sinus phlebitis and thrombosis

  • Phlegmon or abscess in nearby soft tissues and spaces

Types

• • Glomus jugulare: origin at jugular bulb; more common

  • Glomus tympanicum: arises from paraganglia along inferior tympanic nerve (Jacobson nerve), frequently on the cochlear promontory

  • Glomus vagale

  • Carotid body tumor

Clinical Findings

• • Pulsatile tinnitus (most common)

  • Conductive hearing loss

  • Rarely, facial nerve paralysis

  • Other focal neurologic symptoms depending on location as well as systemic symptoms such as sudden blood pressure (BP) fluctuations if the tumor secretes catecholamines

Radiographic Features

• • Glomus tympanicum typically presents as a small enhancing soft tissue mass centered over the cochlear promontory. Enhancement distinguishes tumors from obstructive secretions.

  • Glomus jugulare (glomus jugulotympanicum) is centered in the region of the jugular foramen. Most common path of spread is to the middle ear. It is accompanied by permeative bone changes in the jugular foramen. Characteristic findings by MRI are multiple low signal intensity areas that represent flow voids in the tumor. This has a salt-and-pepper appearance.

  • Glomus vagale paraganglioma: arises from paraganglia in the nodose ganglion of the vagus nerve in the nasopharyngeal carotid (or poststyloid parapharyngeal) space; displaces carotid anteromedially, jugular vein posterolaterally, and does not splay the carotid bifurcation.

  • Carotid body paraganglioma: arises from carotid glomus bodies (paraganglia); splays the external carotid artery (ECA) and internal carotid artery (ICA).

  • Intense contrast enhancement by CT, MRI, angiography

  • Large tumors erode bone.

Types

• • Fenestral: sclerosis or spongiosis around oval window, including fixation of stapes. Diagnosis is usually made from clinical and audiometric findings (conductive hearing loss). Begins as radiolucent focus at the anterior margin of the oval window. Early disease may not be seen on imaging or may be very subtle.

  • Cochlear (retrofenestral) otosclerosis: involves pericochlear bony labyrinth. CT findings:

    • Deossification around cochlea (lucent halo)

    • Sclerosis occurs later in disease (mixed lucencies and densities)

  • Disease begins at fissula ante fenestram (fenestral); fenestral alone most common (85%, conductive hearing loss); approximately 15% progress to cochlear (mixed hearing loss).

Neoplasms: Benign and Malignant

• • Meningioma: classic locations olfactory groove and planum sphenoidale

  • Olfactory neuroblastoma (esthesioneuroblastoma): malignant tumor arising from olfactory mucosa in superior nasal cavity

    • Heterogeneously enhancing mass in upper nasal cavity

    • Larger tumors extend to the floor of anterior cranial fossa with erosive bone changes.

    • May have “waist” at level of cribriform plate

    • Peripheral tumor cysts at intracranial tumor-brain margin are highly suggestive of diagnosis.

  • Osteoma (sinonasal): well-defined nonaggressive bony mass, most common in frontal and ethmoid sinuses.

  • Metastasis: bone destruction, may involve dura or brain parenchyma

  • Sinonasal SCC: most common primary sinonasal malignancy, ethmoid sinus and nasal cavity primaries may extend to the anterior skull base.

    • Aggressive lesion with bone destruction

  • Sinonasal undifferentiated CA: rare, highly aggressive sinonasal malignancy

  • Sinonasal lymphoma: cephalad extension from nasal cavity through skull base

    • Typically, homogeneous lesions with relatively high density on unenhanced CT

    • Septal destruction, occasional bone remodeling

    • On MRI, relatively low signal on T2W images, homogeneously enhancing

  • Sinonasal melanoma: highly malignant, nasal cavity often site of origin

    • Bone destruction more frequent than remodeling

    • On MRI lesions may have intrinsically high signal on T1W and low signal on T2W images (paramagnetic properties of melanin)

    • Avid enhancement

  • Hemangiopericytoma: hypervascular lesion with aggressive growth pattern

    • Dural-based mass that may have internal flow voids

    • Intensely enhancing

  • Sinonasal nerve sheath tumor: benign neoplasm arising from peripheral nerve Schwann cells

    • Well-defined lesion with smooth remodeling

    • Enhancing sharply marginated mass, may have internal cystic changes

Nonneoplastic Lesions

• • Fibrous dysplasia: expansile developmental bone lesion

    • Classically ground-glass matrix (varies depending on amount of fibrous and ossified components)

    • Enhancing lesion, can be deceptively aggressive on MRI (suspect if very low signal on T1 and T2)

    • Obtain CT to demonstrate typical characteristics

  • Mucocele: expanded sinus from chronic obstruction

    • Variable signal depending on protein content of secretions

    • No solid enhancement (can see mucosal enhancement around the margins)

    • Nonaggressive with bone remodeling, MRI highly accurate for distinguishing higher density/proteinaceous secretions that are equivocal on CT from solid masses.

  • Meningocele and encephalocele: extension of meninges ± brain parenchyma through skull base defect into nasal cavity or ethmoidal labyrinth

    • CT frequently shows bone defect.

    • High resolution MRI for confirmation

    • Heavily T2W high resolution sequences can be helpful for clear demonstration of extension of meninges and/or brain through defect.

  • Nasal dermal sinus: midline developmental lesion anywhere from nasal tip to anterior skull base at foramen cecum, may be associated with nasal pit or repetitive bouts of meningitis clinically.

    • Look for tract from nasal lesion to anterior cranial fossa.

    • May see widened foramen cecum ± bifid crista galli

    • May have associated dermoid/epidermoid along tract

Neoplasms: Benign and Malignant

• • Metastasis: suspect in patient with known malignant neoplasm with new craniofacial pain or cranial neuropathy

    • Lytic destructive lesion

    • May have associated soft tissue mass

    • Look for multiple lesions

  • Meningioma: in addition to those with a classic appearance, occasionally lesions can be infiltrative, extend to extracranial spaces such as pterygopalatine and infratemporal fossa, or have intraosseous component.

  • Multiple myeloma: commonly lytic, multiple, may be indistinguishable from extensive metastatic disease with lytic pattern.

  • Lymphoma: may originate in bone or from dura, wide range of appearances.

    • Typically enhance uniformly

    • Can be dural-based

    • Can involve bone with lytic changes

    • Extensive soft tissue mass

    • Relatively restricted diffusion with low apparent diffusion coefficient (ADC) values

  • Pituitary macroadenoma: may occasionally extend inferiorly into clivus or sphenoid sinus.

  • Chordoma (clivus): rare, locally aggressive tumor arising from primitive notochord remnants

    • May present with headaches and diplopia secondary to CN VI involvement in Dorello canal, other nerves can be involved depending on extent.

    • Expansile destructive midline clival mass, may be near sphenooccipital synchondrosis

    • Classically high signal on T2W images secondary to high water content

    • Can also have mix of calcification, hemorrhage, and mucoid material with increased T1 and decreased T2 signal

    • Enhancing lesion, sometimes in a “honeycomb” pattern

  • Chondrosarcoma: arises in skull base fissures and synchondroses, most commonly petrooccipital fissure.

    • Typically eccentric (in contradistinction to chordoma)

    • Chondroid ring and arc-like calcifications on CT

    • Heterogeneously enhancing with high T2 signal with scattered hypointense foci (calcifications) on MRI

  • Langerhans cell histiocytosis: lytic enhancing lesion typically presenting in the first decade of life

Nonneoplastic Lesions

• • Fibrous dysplasia: relatively common expansile bone lesion

    • Classically ground-glass matrix (varies depending on amount of fibrous and ossified components)

    • Enhancing lesion, can be deceptively aggressive on MRI (suspect if very low signal on T1 and T2)

    • Obtain CT to demonstrate typical characteristics

  • Paget disease: primary metabolic bony disease, often asymptomatic, typically seen in older adults, more common in males

    • May be multifocal disease, with mixed lytic-sclerotic pattern

    • Well-defined lytic regions with bone expansion in early phase

    • “Cotton wool” appearance later in lytic-sclerotic phase

    • On MRI, hypointense on T1 and heterogeneous enhancement

  • Aneurysm: cavernous or other ICA segments

    • Rounded “mass,” low signal/flow void on MRI: must recognize!

    • Pulsation artifact in phase encoding direction

    • CT or magnetic resonance (MR) angiography to confirm

  • Arachnoid granulation: lesions found along dural sinuses and dural surface, typically incidental but in patients with CSF leaks may represent the site of osteodural defect.

  • Basal cephalocele: uncommon, usually congenital

  • Persistent craniopharyngeal canal: developmental anomaly resulting in a persistent tract from nasopharynx to pituitary fossa.

    • Smoothly marginated midline canal between presphenoid and basisphenoid.

    • Typically incidental finding but may be associated with pituitary abnormalities, cephaloceles, midline craniofacial anomalies, or rarely even tumors arising from tissue within the canal.

  • Ecchordosis physaliphora: benign nodule of tissue in the dorsal clivus and/or prepontine cistern considered to represent ectopic notochordal remnant.

    • Benign clival variant of chordoma

    • Hyperintense on T2, but no enhancement (distinguishes from chordoma)

    • Often shows restricted diffusion

General

• • Spread of malignant tumor along sheath of large nerves

  • Most commonly along CN V and VII branches

  • Contiguous spread from the primary tumor site along nerve tracks via epineurium/perineurium distant from primary site, do not confuse with “perineural invasion” at site of primary tumor invasion on histopathology

  • Often retrograde but can also be antegrade

  • Important to identify for initial staging and management planning—carefully evaluate major nerve pathways according to primary tumor site

  • Some head and neck cancer types have particularly high propensity (e.g., adenoid cystic carcinoma [ACC]) but SCC is much more common therefore overall more commonly seen with SCC; can also be seen with desmoplastic melanoma and lymphoma

  • Subtle but may be seen on CT:

    • Asymmetry and soft tissue infiltration in PPF, neural foramina; widening of these structures when more advanced

  • Contrast-enhanced high resolution MRI is the optimal technique for evaluation of perineural spread of tumor.

  • May also see secondary findings: look for denervation changes

Differential Diagnosis (DDx)

• • Nerve sheath tumors

    • Tubular, fusiform, lobular mass along nerve or nerves

    • Typically larger than perineural tumor spread

    • No other primary head and neck tumor/malignancy

  • Skull base meningioma

    • Homogeneously enhancing dural-based mass

    • May extend into neural foramina, jugular foramen, or PPF

  • Invasive fungal sinusitis

    • Immunocompromised patients, including diabetics

    • Infiltrating disease but does not follow nerves exclusively

  • Sarcoidosis

    • Nerve involvement may mimic perineural tumor spread

    • Absence of primary head and neck malignancy

    • May have other associated findings such as dural-based inflammation, leptomeningeal component

Radiographic Features

• • Intraocular mass

  • High density (calcification, hemorrhage)

  • Dense vitreous, common (secondary to hemorrhage)

  • Calcifications ( Fig. 7.13 ) are common (90%); in absence of calcifications suspect other mass lesions:

    • Persistent hyperplastic primary vitreous (PHPV)

    • Retrolental fibroplasia (retinopathy of prematurity); calcium may be seen if advanced

    • Toxocariasis (no calcification acutely)

    • Coats disease

    

  • MRI findings:

    • T1: variable, mildly hyperintense compared with vitreous (unless hemorrhage in vitreous)

    • T2: hypointense relative to vitreous

    • T1 postcontrast: moderate to marked heterogeneous enhancement

  • Primary role of imaging is to determine tumor spread:

    • Scleral breakthrough

    • Optic nerve extension

    • Intracranial spread

Pearls

• • Tumors may occur bilaterally or trilaterally (bilateral + intracranial, pineal region tumor much more common than suprasellar)

  • Associated with other malignancies (osteosarcoma most common) later in life; also, risk of postradiation sarcoma in treatment field

Radiographic Features ( Fig. 7.14 )

• • Thickening or irregularity of choroid (localized, polypoid, or flat)

    

  • Exophytic, biconvex mass lesion

  • Usually unilateral, posterior location

  • Retinal detachment, common

  • Contrast enhancement

  • MRI: T1W hyperintense, T2W hypointense (can vary based on pigmentation)

  • Poor prognostic indicators:

    • Large tumor size

    • Lack of pigmentation associated with aggressiveness

    • Infiltration of the angles, optic nerve, sclera, ciliary body

Radiographic Features

• • Small globe (microphthalmia)

  • Vitreous body hyperdensity along the remnant of the hyaloid artery

  • No calcification rare (in contrast to retinoblastoma)

  • Complications:

    • Retinal detachment

    • Chronic retinal hemorrhage

Radiographic Features

• • Unilateral (90%)

  • Retinal detachment (V-shaped contour)

  • Dense vitreous/subretinal exudates

  • Calcification uncommon

  • Hyperintense (T1 and T2) proteinaceous, hemorrhagic exudate

  • Nerve enhancement in advanced disease as a result of secondary glaucoma

Radiographic Features

• • Types of tumor growth: tubular, excrescent, fusiform widening of optic nerve

  • Enlargement of optical canal; >1 mm difference between left and right is abnormal.

  • Lower CT density than meningioma

  • Contrast enhancement variable

  • Calcifications rare (but common in meningioma)

  • Tumor extension best detected by MRI: chiasm → optic tracts → lateral geniculate body → optic radiation

Radiographic Features

• • Mass

    • Tubular, 65%

    • Eccentric (exophytic), 25%

    • Fusiform, surrounding the optic nerve, 10%

    • Calcification (common)

  • Enhancement

    • Intense contrast enhancement

    • Linear bands of enhancement (nerve within tumor): “tramtrack sign”

  • Other

    • Sphenoid bone and/or optical canal hyperostosis in advanced tumors

Clinical Findings

• • Visual loss

  • Pain on eye movement

  • Afferent papillary defects

Causes

• • Isolated (idiopathic)

  • Multiple sclerosis (MS)

  • Neuromyelitis optica (Devic syndrome)

  • Acute demyelinating encephalomyelitis (ADEM)

  • Pediatric optic neuritis: rare, may follow viral illness or vaccination, ADEM

  • 40%–60% of patients ultimately develop MS (and 70%–90% of MS patients develop optic neuritis at some point)

Radiographic Features (Acute Phase)

• • Coronal T2W or postgadolinium T1W with fat suppression best for diagnosis

  • T2W: obliteration of the perioptic space; increased T2 signal of the affected optic nerve

  • Enhancement of the optic nerve

Radiographic Features

• • Low CT attenuation and T1 hyperintensity (fat) are diagnostic.

  • Contiguous bone scalloping or sclerosis is common.

  • May contain debris (inhomogeneous MRI signal).

  • Calcification present occasionally.

Radiographic Features

• • Large, aggressive soft tissue mass (intraconal or extraconal)

  • Metastases to lung and cervical nodes

Radiographic Features

• • Periorbital cellulitis: soft tissue swelling

  • Postseptal infection (true orbital cellulitis)

    • Infiltration of extraconal, postseptal fat

    • Subperiosteal infiltrate or abscess

    • Lateral displacement of enlarged medial rectus muscle

    • Stranding of retrobulbar fat if intraconal extension

    • Proptosis

  • Evaluate paranasal sinuses for potential source

  • Bacterial infections can be complicated by cavernous sinus thrombosis.

Radiographic Features ( Figs. 7.18 – 7.19 )

• • Exophthalmos

    
    

  • Muscle involvement

  • Mnemonic for involvement: I'M SLow :

    • I nferior (most common)

    • M edial

    • S uperior

    • L ateral

  • Enlargement is maximal in the middle of the muscle and tapers toward the end (infiltrative, not inflammatory disease).

  • Spares tendon insertions (although may be involved in acute phase)

  • Often bilateral, symmetric

  • Other

    • Straightened or stretched optic nerve

    • Expansion of orbital fat

    • Lacrimal gland enlargement