External Auditory Canal (EAC)

• 
  
  
  
  
  
  • •
    

    Cartilaginous portion

    
    
  • •
    

    Bony portion

  
  

Middle Ear ( Figs. 7.1 – 7.2 )

Composed of air-filled spaces that contain the ossicles and are divided into:

• 
  
  
  
  
  
  • •
    

    Epitympanum (attic; above imaginary line between scutum tip and tympanic facial nerve)

    
    
  • •
    

    Mesotympanum (middle ear proper between epitympanum and hypotympanum)

    
    
  • •
    

    Hypotympanum (shallow space below imaginary line between tympanic annulus and cochlear promontory)

  
  

Boundaries of the middle ear are tympanic membrane (TM) laterally, the tegmen superiorly, and the inner ear medially. Posteriorly, there are three important structures (facial nerve recess, pyramidal eminence, and sinus tympani). The eustachian tube (pressure equalization) connects the middle ear with the nasopharynx. The lateral epitympanic recess (Prussak space) is a common location for retraction pockets and cholesteatoma. Three ossicles transmit sound waves from the TM to the oval window in the vestibule:

• 
  
  
  
  
  
  • •
    

    Malleus

    
    
  • •
    

    Incus

    
    
  • •
    

    Stapes (two crura, one footplate)

  
  

Inner Ear ( Fig. 7.3 )

The inner ear (labyrinth) consists of:

• 
  
  
  
  
  
  • •
    

    Three semicircular canals, which connect to vestibule

    
    
  • •
    

    Vestibule (utricle and saccule) between semicircular canals and cochlea

    
    
  • •
    

    Cochlea (sensorineural hearing), which connects to:

    
    
    
    
    • 
      

      Stapes → oval window

      
      
    • 
      

      Round window (allows for counterpulsation of fluid)

    
    

  
  

Internal Auditory Canal (IAC) ( Fig. 7.4 )

Left and right IAC should not differ >2 mm in diameter. Contents of IAC are divided by the falciform crest and Bill bar:

• 
  
  
  
  
  
  • •
    

    Facial nerve (anterior superior): cranial nerve (CN) VII (“7 up”)

    
    
  • •
    

    Cochlear part (anterior inferior): CN VIII (“Coke down”)

    
    
  • •
    

    Superior vestibular nerve (posterior): CN VIII

    
    
  • •
    

    Inferior vestibular nerve (posterior): CN VIII

  
  

Facial Nerve ( Figs. 7.5 – 7.6 )

Four main parts of the facial nerve:

• 
  
  
  
  
  
  • •
    

    Intraaxial segment

    
    
  • •
    

    Cisternal segment

    
    
  • •
    

    Intratemporal segment:

    
    
    
    
    • 
      

      Meatal (IAC) segment

      
      
    • 
      

      Labyrinthine segment

      
      
    • 
      

      Tympanic (horizontal) segment

      
      
    • 
      

      Mastoid (vertical) segment

    
    
    
    
  • •
    

    Extracranial segment:

    
    
    
    
    • 
      

      Exits the skull through the stylomastoid foramen

      
      
    • 
      

      Immediately gives off the posterior auricular branch/nerve

    
    

  
  

Main trunk courses through the parotid gland and gives rise to five terminal branches. The intratemporal segment of the facial nerve gives rise to three branches (see Fig. 7.6 ):

• 
  
  
  
  
  
  • •
    

    Greater superficial petrosal nerve

    
    
  • •
    

    Stapedius nerve

    
    
  • •
    

    Chorda tympani nerve

  
  

Hearing Loss

Pulsatile Tinnitus

Temporal Bone Fractures

Radiographic Features

TEMPORAL BONE FRACTURES ^a ( Fig. 7.7 )

Parameter	Longitudinal Fractures	Transverse Fractures
Frequency	80%	20%
Fracture line	Parallel to long axis	Perpendicular to long axis
Typically involves	Middle ear	Inner ear
Labyrinth	Typically spared	Commonly involved
Ossicles	Involved: conductive hearing loss	Commonly spared
Tympanic membrane	Involved	Frequently spared
Facial paralysis	Approx. 20%	Approx. 50%

 

More clinically relevant classification may be otic capsule (osseous labyrinth) violating versus otic capsule sparing. Otic capsule involvement increases the risk of sensorineural hearing loss, seventh cranial nerve injury, and cerebrospinal fluid leak.

a Fractures may also be characterized as oblique: mixed features of longitudinal and transverse fractures, cross the petrotympanic fissure.

Acute Inflammation

• 
  
  
  
  
  
  • •
    

    Otitis media (fluid in the middle ear cavity): acute, subacute, chronic forms

    
    
  • •
    

    Children: common

    
    
  • •
    

    Adults: less common; exclude nasopharyngeal carcinoma (NPC), which can cause eustachian tube obstruction and serous otitis media.

    
    
  • •
    

    Mastoiditis: fluid-filled mastoid cells are also often present but not specific for infection.

    
    
  • •
    

    Coalescent mastoiditis: occurs if medical treatment of acute otomastoiditis fails. Enzymatic resorption of mastoid septa and development of an intramastoid empyema seen as erosive changes on computed tomography (CT); comparison with the opposite side can be helpful in subtle cases.

    
    
  • •
    

    Labyrinthitis

  
  

Bell Palsy

Acute onset peripheral facial nerve palsy secondary to herpes simplex virus (HSV) that the majority of time resolves within 2 to 3 months. Imaging typically performed for atypical or persistent palsy. By magnetic resonance imaging (MRI), there is enhancement along the facial nerve involving intracanalicular (“fundal tuft”) and labyrinthine segments that normally do not enhance. Note that mild enhancement of the tympanic and mastoid segments of the facial nerve can be seen as a normal finding due to vascular supply. Facial nerve enhancement is nonspecific and can occur in other inflammatory and neoplastic conditions (especially if the nerve is enlarged, consider secondary to perineural spread of a tumor).

Acquired Cholesteatoma ( Fig. 7.8 )

Mass of stratified squamous epithelium and keratin debris. Cause: epithelial cells accumulate in the middle ear via a perforation of the TM. The most accepted theory is that they arise from TM retraction pockets resulting from decreased intratympanic pressure. Types:

• 
  
  
  
  
  
  • •
    

    Acquired (98%): chronic middle ear infection (common). Arise in attic (Prussak space; pars flaccida cholesteatoma), or from pars tensa (sinus tympani).

    
    
  • •
    

    Congenital (epidermoid; 2%): cholesteatoma arises from epithelial nests in middle ear, mastoid, or petrous bone, including the labyrinth (uncommon).

  
  

Congenital Cholesteatoma (Epidermoid)

Constitute approximately 2% of temporal bone cholesteatomas and may affect middle ear, EAC, mastoid, or petrous bone, including the labyrinth (uncommon). The most common location is the anterosuperior portion of the middle ear near the eustachian tube or stapes. The typical presentation is in a young patient with otherwise normal mastoid pneumatization and without history of chronic ear infections. Histologically, the cholesteatoma is made up of squamous cell lining, keratin debris, and cholesterol.

Cholesterol Granuloma (Cholesterol Cysts)

Mix of hemorrhage, cholesterol crystals, and granulation tissue that may be present in temporal bone, including the petrous apex or rarely the middle ear. Depending on the location of the expansile erosive lesion and involvement of critical structures, they can be associated with hearing loss, tinnitus, and CN palsies.

Malignant or Necrotizing External Otitis

• 
  

  Severe, life-threatening Pseudomonas aeruginosa infection in older adults with diabetes. Aggressive infection of EAC, adjacent soft tissues, and skull base that spreads via cartilaginous fissures of Santorini and can extend into:

  
  
  
  
  • •
    

    Middle ear and mastoid air cells

    
    
  • •
    

    Variable involvement of skull base, including osteomyelitis

    
    
  • •
    

    Phlegmon and abscesses may spread in any direction:

    
    
    
    
    • 
      

      Parapharyngeal, parotid, or masticator space

      
      
    • 
      

      Intracranially

      
      
    • 
      

      Anteriorly to temporomandibular joint (TMJ)

    
    

  
  

Labyrinthitis Ossificans

Ossification of the membranous labyrinth as a sequela of previous infectious, inflammatory, traumatic, or surgical injury to the inner ear. Seen as ossification within the membranous labyrinth on high resolution computed tomography (HRCT) and foci of low signal on T2-weighted (T2W) MRI within the otherwise high signal fluid of the membranous labyrinth.

Glomus Tumors

Glomus tumors (chemodectomas) arise from chemoreceptor cells in multiple sites in the head and neck. The majority are benign and approximately 10% are multiple; thus it is important to check other common locations in the head and neck during imaging (glomus jugulare, vagale, and carotid body tumor). Glomus tympanicum represents the most common middle ear tumor.

Other Benign Temporal Bone Tumors

• 
  
  
  
  
  
  • •
    

    Meningioma

    
    
  • •
    

    Facial schwannoma may arise anywhere along the course of CN VII. In the IAC, the tumor may be indistinguishable from a vestibular schwannoma unless it can be seen to arise from the facial nerve.

    
    
  • •
    

    Osteoma

    
    
  • •
    

    Adenoma (ceruminoma), benign but locally aggressive, rare

    
    
  • •
    

    Endolymphatic sac tumor, benign but locally aggressive; permeative destructive lesion with spiculated calcified tumor matrix

    
    
  • •
    

    Epidermoid (primary cholesteatoma): not a true neoplasm

  
  

Malignant Temporal Bone Tumors

• 
  
  
  
  
  
  • •
    

    Carcinoma (CA) (most common malignant tumors)

    
    
    
    
    • 
      

      Squamous cell carcinoma (SCC) arising from the EAC

      
      
    • 
      

      Adenocarcinoma

    
    
    
    
  • •
    

    Lymphoma

    
    
  • •
    

    Metastases: breast, lung, renal, prostate; neuroblastoma and leukemia in children

    
    
  • •
    

    Chondrosarcoma, other primary bone tumors

    
    
  • •
    

    Rhabdomyosarcoma in children and late teens

  
  

Otosclerosis (Otospongiosis)

The osseous labyrinth (otic capsule) is the normal dense bone of the inner ear surrounding the cochlea, vestibule, and semicircular canals. In otosclerosis, the capsule is replaced by vascular, irregular bony trabeculae (lucent on CT) and later by new bone within the lucent areas in the late, chronic healing phase. Unknown cause, sporadic or autosomal dominant (AD) gene transmission, frequently bilateral. Patients (female > male) present with progressive conductive or mixed hearing loss.

Semicircular Canal Dehiscence Syndrome

CT shows a small defect or dehiscence in the bony wall of the superior or less commonly posterior semicircular canal. Seen as ≥2 mm dehiscence of roof of superior semicircular canal on coronal or ideally transverse oblique (Poschl) CT reformats for superior semicircular canal dehiscence. Clinically presents with dizziness and vertigo +/– nystagmus with loud sound or pressure (Tullio phenomenon). Clinical syndrome + positive CT = semicircular canal dehiscence syndrome. Can also be associated with inner ear conductive hearing loss. The cause is unknown, likely developmental, possibly also secondary to trauma.

Other Otodystrophies and Dysplasias

• 
  
  
  
  
  
  • •
    

    Paget disease

    
    
  • •
    

    Fibrous dysplasia

    
    
  • •
    

    Osteogenesis imperfecta

    
    
  • •
    

    Skull base osteopetrosis

    
    
  • •
    

    Craniometaphyseal dysplasia (Pyle disease)

    
    
  • •
    

    Craniodiaphyseal dysplasia and Camurati-Engelmann disease (progressive diaphyseal dysplasia)

    
    
  • •
    

    Cleidocranial dysostosis

  
  

Congenital Abnormalities of the Inner Ear

• 
  
  
  
  
  
  • •
    

    Cochlear incomplete partition type I: spectrum of abnormalities ranging from lack of internal structure of the cochlea to severe cystic cochleovestibular malformation

    
    
  • •
    

    Cochlear incomplete partition type II: incomplete partition with deficient interscalar septum between middle and apical turns (Mondini anomaly: historic terminology – incomplete partition type II + large vestibular aqueduct)

    
    
  • •
    

    Cochlear hypoplasia: small, underdeveloped cochlea, typically <2 turns

    
    
  • •
    

    Cochlear aplasia: absent cochlea with variable anomalies of other inner ear structures

    
    
  • •
    

    Labyrinthine aplasia: aplasia or hypoplasia of otic capsule, petrous apex hypoplasia, and other associated temporal bone abnormalities (Michel aplasia: historic terminology for complete labyrinthine aplasia)

    
    
  • •
    

    Common cavity malformation: undifferentiated cochlea and vestibule represented by a common cavity of variable size.

    
    
  • •
    

    Large vestibular aqueduct: ≥1 mm diameter at midpoint and/or ≥2 mm at operculum perpendicular to long axis of vestibular aqueduct; rule of thumb—abnormal if larger than the posterior semicircular canal. High incidence of associated cochlear abnormalities (also see incomplete partition II above).

    
    
  • •
    

    Small IAC

  
  

Petrous Malformations Associated With Recurrent Meningitis

• 
  
  
  
  
  
  • •
    

    The presence of a fistula in the petrous portion of the temporal bone may lead to otorrhea, pneumocephalus, meningitis, or abscess; rare.

    
    
  • •
    

    Acquired lesion of the petrous apex can potentially have similar complications depending on extent and violation of adjacent structures.

  
  

Overview of Syndromes

Anterior and Central Skull Base Anatomy

• 
  
  
  
  
  
  • •
    

    Anterior skull base: broadly consists of floor of anterior cranial fossa and the roof of the nose, ethmoid air cells, and orbits.

    
    
  • •
    

    Central skull base: broadly consists of floor of middle cranial fossa, roof of sphenoid sinus, and greater wing of sphenoid.

    
    
  • •
    

    Anterior and central skull base boundary:

    
    
    
    
    • 
      

      Medially: posterior margin of planum sphenoidale (tuberculum sellae)

      
      
    • 
      

      Laterally: lesser wing of sphenoid/sphenoid

    
    

  
  

Central Nervous System (CNS), Foramina, and Cavernous Sinus ( Figs. 7.9 – 7.10 )

• 
  
  
  
  
  
  • •
    

    CN I: olfactory nerve

    
    

    
    

    
    

    

    
    

    
    

    
    

    

    
    
    
    
  • •
    

    CN II: optic nerve

    
    
  • •
    

    CN III: oculomotor nerve

    
    
  • •
    

    CN IV: trochlear nerve

    
    
  • •
    

    CN V: trigeminal nerve

    
    
  • •
    

    CN VI: abducens nerve

    
    
  • •
    

    CN VII: facial nerve

    
    
  • •
    

    CN VIII: auditory nerve

    
    
  • •
    

    CN IX: glossopharyngeal nerve

    
    
  • •
    

    CN X: vagus nerve

    
    
  • •
    

    CN XI: spinal accessory nerve

    
    
  • •
    

    CN XII: hypoglossal nerve

  
  

Pterygopalatine Fossa (PPF) (see Fig. 7.10 )

• 
  
  
  
  
  
  • •
    

    Important space and potential route of spread of disease in the deep face

    
    
  • •
    

    Contents:

    
    
    
    
    • 
      

      Pterygopalatine ganglion

      
      
    • 
      

      Maxillary nerve (V2) via foramen rotundum

      
      
    • 
      

      Distal internal maxillary artery via pterygomaxillary fissure

    
    
    
    
  • •
    

    Relations and boundaries:

    
    
    
    
    • 
      

      Anterior: posterior maxillary sinus wall

      
      
    • 
      

      Posterior: pterygoid plates and inferior part of lesser wing of sphenoid

      
      
    • 
      

      Superior: inferior orbital fissure

      
      
    • 
      

      Inferior: tapers into the greater palatine canal

      
      
    • 
      

      Medial wall: perpendicular plate of palatine bone, sphenopalatine foramen superiorly

      
      
    • 
      

      Lateral wall: pterygomaxillary fissure (vertical communication with infratemporal fossa)

    
    

  
  

Orbital Spaces ( Figs. 7.11 – 7.12 )

• 
  
  
  
  
  
  • •
    

    Intraconal space: space inside the rectus muscle pyramid

    
    

    
    

    
    

    

    
    

    
    

    
    

    

    
    
    
    
  • •
    

    Extraconal space: space outside the rectus muscle pyramid

    
    
  • •
    

    Preseptal space

    
    
  • •
    

    Postseptal space

    
    
  • •
    

    Lacrimal fossa

  
  

Orbital Structures

• 
  
  
  
  
  
  • •
    

    Globe (anterior chamber, posterior chamber, lens, vitreous, sclera/choroid/retina)

    
    
  • •
    

    Intraconal, extraconal fat

    
    
  • •
    

    Optic nerve and sheath

    
    
  • •
    

    Ophthalmic artery and vein

    
    
  • •
    

    Rectus muscles

  
  

Orbital Septum

• 
  
  
  
  
  
  • •
    

    Fascia arising from orbital rim periosteum

    
    
  • •
    

    Attaches to outer margins of bony orbit and deep tissues of lids

    
    
  • •
    

    Separates structures in the orbit from soft tissues in the face (postseptal vs. preseptal)

  
  

Retinoblastoma

• 
  
  
  
  
  
  • •
    

    Malignant tumor that arises from neuroectodermal cells of retina. Clinical: leukokoria (white mass behind pupil). Age: <3 years (70%)

    
    
  • •
    

    30% bilateral, may also be multifocal within one eye

    
    
  • •
    

    60% sporadic, 40% hereditary, 10% of patients have a positive family history

  
  

Melanoma

• 
  
  
  
  
  
  • •
    

    Most common (75%) primary ocular malignancy in adults. Arises from pigmented choroidal layer; retinal detachment is common.

  
  

Persistent Hyperplastic Primary Vitreous (PHPV) ( Fig. 7.15 )

Caused by persistence of portions of the fetal hyaloid artery and primary vitreous in Cloquet canal. Associated with ocular dysplasias (e.g., Norrie disease = PHPV, seizures, deafness, low intelligence quotient [IQ]). Clinical findings of blindness, leukokoria, and microphthalmia. Unilateral more common. Rare.

Retrolental Fibroplasia (Retinopathy of Prematurity)

Toxic retinopathy caused by oxygen treatment (e.g., for hyaline membrane disease [HMD]). A retinal vasoconstriction leads to neovascularization and fibrovascular proliferation of the posterior vitreous and retina. Typically bilateral, retinal detachment common, may have associated hemorrhage, calcification rare except in advanced stages.

Coats Disease

Primary vascular abnormality (exudative retinopathy) causing lipoprotein accumulation in retina, telangiectasia, neovascularization, and retinal detachment (pseudoglioma). Age: typically first decade, male predominance. Rare.

Drusen

Focal calcification in hyaline bodies in the optic nerve head. Usually bilateral and asymptomatic but may be associated with macular degeneration. Blurred disk margins may be mistaken for papilledema. On CT, seen as punctate hyperdensity most commonly at optic nerve head or macula.

Globe-Shape Abnormalities ( Fig. 7.16 )

• 
  
  
  
  
  
  • •
    

    Coloboma: focal outpouching involving retina, choroid, iris; caused by deficient closure of fetal optic fissure; located in region of optic disc. Associated with various congenital globe, CNS, and other systemic anomalies.

    
    

    
    

    
    

    

    
    
    
    
  • •
    

    Staphyloma: acquired defect of globe wall with thinning of posterior sclera-uveal rim and protrusion of choroid or sclera. On imaging, see elongated globe with focal deformity, usually posterior, but not as pronounced as coloboma.

    
    
  • •
    

    Axial myopia: anteroposterior (AP) elongation but no protrusion

    
    
  • •
    

    Buphthalmos: congenital glaucoma, anterior ocular chamber drainage problem.

    
    
  • •
    

    Enlarged globe, increased depth of anterior chamber.

  
  

Leukokoria

Leukokoria refers to a white pupil. Clinical, not a radiologic, finding. Underlying causes:

• 
  
  
  
  
  
  • •
    

    Retinoblastoma

    
    
  • •
    

    PHPV

    
    
  • •
    

    Congenital cataract

    
    
  • •
    

    Toxocariasis

    
    
  • •
    

    Other

    
    
    
    
    • 
      

      Sclerosing endophthalmitis

      
      
    • 
      

      Coats disease

      
      
    • 
      

      Retrolental fibroplasia

      
      
    • 
      

      Trauma

      
      
    • 
      

      Chronic retinal detachment

    
    

  
  

Retinal Detachment ( Fig. 7.17 )

Separation of the sensory retina from the outer pigmented epithelium. Appears in a characteristic V shape, with the apex of the detachment at the optic disc. The presence of retinal or choroidal detachment may be caused by an ocular mass.

Choroidal Detachment (see Fig. 7.17 )

Usually results after ocular surgery, trauma, or uveitis, causing fluid to accumulate in the choroidal space. Characteristic appearance spares the posterior third of the globe (region of the optic disc) in contradistinction with retinal detachment.

Optic Nerve Glioma

Most common cause of diffuse optic nerve enlargement, especially in childhood. Pathology: childhood lesions most commonly low grade astrocytomas (grade I pilocytic astrocytoma > grade II fibrillary astrocytoma). In patients with neurofibromatosis type 1 (NF1), pathology may be perineural arachnoid gliomatosis (PAG) rather than true astrocytoma. In adults, commonly high-grade astrocytomas. Clinical findings include loss of vision, proptosis (bulky tumors). Most common in first decade of life. In NF1 the disease may be bilateral.

Optic Nerve Meningioma

Optic nerve sheath meningiomas arise from arachnoid rests in meninges covering the optic nerve. Age: fourth and fifth decades (female predominance in adults); younger patients typically have neurofibromatosis type 2 (NF2). Progressive loss of vision.

Optic Neuritis

Vascular Lesions

• 
  
  
  
  
  
  • 
    

    Orbital cavernous venous malformation (previously/commonly known as cavernous hemangioma ): adults, not a true neoplasm, rather vascular malformation; true capsule, benign, most common vascular orbital mass in adults

    
    
    
    
    • •
      

      Most commonly in lateral intraconal space

      
      
    • •
      

      Well-defined nonaggressive mass

      
      
    • •
      

      Hyperintense on T2W images

      
      
    • •
      

      Progressive enhancement “fill-in”

    
    
    
    
  • 
    

    Orbital infantile hemangioma (capillary hemangioma): benign vascular tumor of infancy, no capsule

    
    
    
    
    • •
      

      Lobular or infiltrative hypervascular, intensely enhancing mass

      
      
    • •
      

      On T2W images: hyperintense, flow voids may be visible.

      
      
    • •
      

      Most frequently superficial extraconal location, may have postseptal extension, uncommonly presents as exclusively retrobulbar mass

      
      
    • •
      

      Grows for <1 year and then typically involutes

    
    
    
    
  • 
    

    Venous, lymphatic, or venolymphatic malformations: vascular malformation with or without lymphatic component

    
    
    
    
    • •
      

      Multiloculated, transspatial lesions

      
      
    • •
      

      Those with significant lymphatic component tend to be more cystic and have propensity to hemorrhage with fluid-fluid levels.

      
      
    • •
      

      Those with predominantly venous component tend to have more homogenous enhancement.

    
    
    
    
  • 
    

    Venous varix: distensible venous channel with systemic connection

    
    
    
    
    • •
      

      Dynamic enlargement of lesion with provocative maneuver (e.g., Valsalva)

      
      
    • •
      

      May not be visible when patient relaxed

      
      
    • •
      

      May present with thrombosis or hemorrhage

    
    
    
    
  • 
    

    Hemangiopericytoma: uncommon, slow-growing vascular neoplasm that can be benign or malignant

    
    
    
    
    • •
      

      Well-circumscribed or invasive when high grade

      
      
    • •
      

      May remodel or erode bone

      
      
    • •
      

      Avidly enhancing

      
      
    • •
      

      Flow voids common on T2W images

    
    
    
    
  • 
    

    Other vascular lesions: AVM, dural arteriovenous fistula, and cavernous carotid fistula

  
  

Dermoid Cyst

Common orbital tumor in childhood. Age: typically present in the first two decades.

Lacrimal Gland Tumors

• 
  
  
  
  
  
  • 
    

    Lymphoid

    
    
    
    
    • •
      

      Benign reactive lymphoid hyperplasia

      
      
    • •
      

      Lymphoma

    
    
    
    
  • 
    

    Epithelial tumors

    
    
    
    
    • •
      

      Benign mixed (pleomorphic) tumor (most common epithelial tumor)

      
      
    • •
      

      ACC

      
      
    • •
      

      Mucoepidermoid CA

      
      
    • •
      

      Malignant mixed tumor (carcinoma ex pleomorphic adenoma)

    
    

  
  

Rhabdomyosarcoma

Most common malignant orbital tumor in childhood. Mean age: 7 years.

Metastases

Adults: breast, lung, renal cell, prostate CA, melanoma. Breast metastasis to the orbit may have retractile fibrotic stroma and paradoxically be associated with enophthalmos. There can also be direct extension of malignant sinonasal tumors to the orbit. Children: rare, neuroblastoma, leukemia.

Orbital Infection

The orbital septum represents a barrier to infectious spread from anterior to posterior structures. Common causes of orbital infection include spread from infected sinus and less commonly trauma.

Thyroid Ophthalmopathy

Orbital pathology (cellular infiltration, deposition of glycoproteins and mucopolysaccharides in the orbit, fibrosis) caused by autoantibodies targeting thyrotropin receptors found in orbit (in addition to thyroid). Clinical: painless proptosis; patients may be euthyroid, hypothyroid, or hyperthyroid. Functional classification (clinical severity and risk):

• 
  
  
  
  
  
  • •
    

    Mild: eyelid lag and retraction with proptosis in setting of active hyperthyroidism

    
    
  • •
    

    Moderate: soft tissue inflammation and intermittent myopathy; stabilizes without major sequelae

    
    
  • •
    

    Severe: rapid and fulminant, greater mass effect, severe sequelae including optic nerve compromise

  
  

Treatment: prednisone → radiation therapy → surgical decompression; surgery or ¹³¹ iodine (I) for thyroid.

Idiopathic Orbital Inflammation (Orbital Pseudotumor)

Inflammation of orbital soft tissues of unknown origin

Erdheim-Chester Disease

Lipid granulomatosis (non-Langerhans histiocytosis) with retroorbital deposition or mass, xanthelasma of eyelids, skeletal manifestations (medullary sclerosis, cortical thickening), and cardiopulmonary manifestations as a result of cholesterol emboli. Rare. Diffuse infiltrative mass most commonly involving intraconal space or other area in orbit, bilateral.

Ocular Manifestations of Phakomatoses

• 
  
  
  
  
  
  • 
    

    NF1

    
    
    
    
    • •
      

      Lisch nodules

      
      
    • •
      

      Optic pathway glioma

      
      
    • •
      

      Optic nerve sheath ectasia

      
      
    • •
      

      Sphenoid bone dysplasia

      
      
    • •
      

      Choroidal hamartoma

      
      
    • •
      

      Plexiform neurofibroma

    
    
    
    
  • 
    

    NF2 (orbital involvement rare)

    
    
    
    
    • •
      

      Meningioma

      
      
    • •
      

      Schwannoma

    
    
    
    
  • 
    

    Sturge-Weber (encephalotrigeminal angiomatosis)

    
    
    
    
    • •
      

      Choroidal angioma

      
      
    • •
      

      Buphthalmos

      
      
    • •
      

      Glaucoma

      
      
    • •
      

      Abnormal ocular enhancement on MRI, thickest over posterior portion of the globe

    
    
    
    
  • 
    

    Tuberous sclerosis

    
    
    
    
    • •
      

      Retinal hamartomas

      
      
    • •
      

      Punched out areas of retinal depigmentation

      
      
    • •
      

      Angiofibromas of the eyelids

      
      
    • •
      

      Colobomas.

    
    
    
    
  • 
    

    Von Hippel-Lindau (VHL)

    
    
    
    
    • •
      

      Retinal hemangioblastomas