TITLE: Orbital Tumors
SOURCE: Grand Rounds Presentation, UTMB, Dept. of Otolaryngology
DATE: October 31, 2001
RESIDENT PHYSICIAN:Michael Underbrink, MD
FACULTY PHYSICIAN: Shawn Newlands, MD
SERIES EDITORS: Francis B. Quinn, Jr., MD and Matthew W. Ryan, MD
[ Grand Rounds Index | UTMB Otolaryngology Home Page ]
"This
material was prepared by resident physicians in partial fulfillment of
educational requirements established for the Postgraduate Training Program of
the UTMB Department of Otolaryngology/Head and Neck Surgery and was not
intended for clinical use in its present form. It was prepared for the purpose
of stimulating group discussion in a conference setting. No warranties, either
express or implied, are made with respect to its accuracy, completeness, or
timeliness. The material does not necessarily reflect the current or past
opinions of members of the UTMB faculty and should not be used for purposes of
diagnosis or treatment without consulting appropriate literature sources and
informed professional opinion."
INTRODUCTION
Although the orbital area is
generally considered within to fall within the domain of the ophthalmologist,
many orbital related disease processes require the involvement of other
subspecialties. Some related orbital
disease processes, such as paranasal sinus disease, may demand the involvement
of the otolaryngologist. In some cases,
patients with primary orbital lesions may present initially to the ENT
clinic. It is therefore, imperative
that we possess a basic understanding of the complex anatomy and potential
pathology of the orbit.
Anatomy
The orbit is a pyramidal or cone-shaped space
comprised of seven bones (frontal, greater and lesser wings of the sphenoid,
zygoma, maxilla, lacrimal, palatine, and ethmoid). The inferior wall, or orbital floor is composed mainly of the
orbital plate of the maxilla, the zygomatic bone anterolaterally, and the
orbital plate of the palatine bone posteriorly. The inferior orbital fissure separates the floor from the lateral
wall, providing passage for the maxillary division of CNV, the infraorbital
artery, branches from the sphenopalatine ganglion, and branches of the inferior
ophthalmic vein to the pterygoid plexus.
The lateral wall is composed of the frontal process of the zygoma and
the greater wing of the sphenoid lateral to the optic foramen. Along the lateral wall, we find Whitnall's
tubercle, a bony prominence just deep to the rim and just above the midpoint of
the lateral wall, where the lateral canthal ligament attaches. The superior orbital fissure demarcates the
lateral wall from the orbital roof. The
major orbital nerves and vessels pass through here (except the optic nerve and
ophthalmic artery which pass through the optic foramen). Posteriorly, the superior orbital fissure
communicates with the cavernous sinus and middle cranial fossa. The superior orbital wall, or orbital roof,
is comprised of the orbital plate of the frontal bone with a small
contribution, posteriorly, from the lesser wing of the sphenoid. Anterolaterally, the fossa of the lacrimal
gland creates a shallow depression, and
medially, there is a spine or depression for the trochlea about 5mm deep
to the rim. The medial wall is composed
of the frontal process of the maxilla, the lacrimal bone, the lamina papyracea
of the ethmoid, and a portion of the lesser wing of the sphenoid. Posteriorly, due it's somewhat eccentric
placement (medial and superior to the geometric apex), the optic foramen is
related to the posterior ethmoid air cells.
The foramina for the anterior and posterior ethmoid arteries lie within
the frontoethmoid suture line.
Anteriorly, the lacrimal fossa can be located between the anterior and
posterior lacrimal crests.
The orbit is compartmentalized by
several interconnecting fasciae. The
periorbita, or periosteum lining the orbital walls, is continuous with the dura
mater at the optic foramen and superior orbital fissure. Several septae pass from the periorbita to
divide the orbital fat into lobules.
There is a potential space between the periosteum and the bony walls
called the subperiosteal space.
Continuous with the periorbita at the orbital rim is a fibrous sheet
that extends across the entrance of the orbit called the orbital septum. It fuses with the levator aponeurosis in
the upper lid and the sheath of the inferior rectus in the lower lid. A firm fibrous sheath, known as Tenon's
capsule (bulbar fascia), surrounds the entire globe except for the cornea and
separates the eye from other orbital contents.
The episcleral space is a potential surgical plane between the bulbar
fascia and the globe. Lastly, there is
a dense muscular fascia created by the fusion of the fibrous sheaths of the
extraocular muscles. Thickening of this
fascia from the medial and lateral recti form the medial and lateral canthal
tendons. Along with contributions from the
fascia of the inferior rectus these fascia form a fibrous sling which supports
the globe-the suspensory ligament of Lockwood.
Within the muscular cone formed by this fibrous sheath is the central
space. Outside the cone lies the
peripheral space.
The blood supply for the majority of
the orbit is via the ophthalmic artery, which branches off the internal carotid
artery and traverses through the optic foramen with the optic nerve. It gives off numerous branches, including the anterior and posterior ethmoid
arteries which exit at their respective foramina into the anterior cranial
fossa and eventually enter the nose.
Parts of the inferior orbit are supplied by the infraorbital artery,
which is a branch off of the internal maxillary artery. Parallel to the arteries run numerous veins
which eventually unite to form a superior and inferior ophthalmic vein. These vessels pass through the superior
orbital fissure and empty into the cavernous sinus. A branch off the inferior portion passes through the inferior
orbital fissure to communicate with the pterygoid plexus. There are no lymphatics or lymph nodes
within the orbit.
Another important aspect of the
orbit is the lacrimal system, which has a secretory and an excretory
system. The secretory system is
composed of the lacrimal gland (reflex secretor) and various basic secretors,
which include conjunctival goblet cells, accessory subconjunctival lacrimal
glands and oil secreting tarsal meibomian glands. The excretory system removes tears via the muscular contraction
of the eyelids which drive the lacrimal secretions medially. There is a punctum medially in each lid,
which empties into a canaliculus. These
canaliculi empty into the lacrimal sac, located in the lacrimal fossa, which
empties almost vertically into the nasolacrimal duct.
Evaluation
The approach to a patient with an
orbital tumor must be centered on ophthalmic evaluation. A good history and thorough physical
examination is essential to the development of a diagnosis. The history should include information
about the onset, duration, and progression of the orbital disease process. The most important clinical manifestation of
orbital disease is proptosis, however, this may not be the chief
complaint. Often, the patient will
first report changes in visual acuity, diplopia, eyelid droop/fullness,
discharge, and/or pain. A history of
allergies, sinus infections, epistaxis, nasal discharge or obstruction and
tearing should be elicited to rule out a sinonasal origin for the disease
process. It is also important to ask
about other medical illnesses, such as thyroid disorders, granulomatous
diseases, and autoimmune disorders.
The physical examination should pay
careful attention to visual acuity, visual fields, pupillary responses, ocular
motility and inspection of the external
surface of the globes, eyelids and surrounding structures. Exophthalmos can be most easily discerned
by visualizing the eyes from above or below.
Exophthalmos, or proptosis, is the most common sign of orbital disease,
occurring with about 90 percent of primary orbital tumors. Protrusion of an eye more than 21 mm beyond
the orbital rim or forward displacement of one globe 2mm greater than the other
is clinically significant and should raise suspicion for an orbital disease
process. Also, the direction of
displacement of the proptotic eye may clue the clinician to a possible
etiology. Displacement of the eye
downward and laterally may indicate frontal or ethmoid sinus disease. Tumors of the maxilla will displace the
globe upward. A purely axial
displacement may indicate pathology within the muscle cone, such as an optic
nerve glioma or Grave's ophthalmopathy.
Medial displacement of the eye may indicate a lacrimal gland tumor or
temporal fossa mass. Palpation of the
orbital contents is important and may help identify anterior pathology. A complete head and neck examination is
essential with focus on the nose, paranasal sinuses, nasopharynx and neck. Evaluation of cranial nerve function should
also be performed.
Laboratory evaluation with a
complete blood count, sedimentation rate and thyroid function tests should be
obtained for evidence of infection, inflammation or thyroid disease. Defining the extent and localization of
orbital tumors is most dependent on imaging techniques. Ultrasonography is a relatively inexpensive
and safe method of evaluating the orbit.
However, its use has been largely supplanted by computerized tomography
and magnetic resonance imaging. It is
still valuable as an office technique and as an adjunct to discriminate cystic,
solid, angiomatous, and infiltrative tissues.
CT scanning is currently the best available technique for detection and
localization of the extent of orbital lesions.
Coronal and axial views of the orbit should be obtained, which help to
define the relationship of an orbital tumor to the optic nerve, extraocular
muscles, blood vessels, globe, sinuses and brain. CT scans provide more information regarding bony landmarks, and
are therefore, indispensable in surgical planning. Magnetic resonance imaging studies are particularly useful for
evaluating possible intracranial extension of orbital tumors. MR imaging is also better for delineating
vascular orbital lesions with the exception of orbital varices, which are
easier to detect with coronal CT
scan. Arteriography is useful for
differentiating hemangiopericytoma from cavernous hamangioma (encapsulated
venous malformations) and preoperative embolization of vascular tumors.
Pediatric Orbital Tumors
A child presenting with proptosis is
usually very disconcerting to all parties involved. The pediatric patient with an orbital tumor differs substantially
from the adult patient with a much greater incidence of congenital lesions,
higher frequency of infection, and unique benign and malignant tumors involving
the orbit. The most common orbital masses
in children are cystic lesions of the orbit, mainly dermoids. Vasculogenic lesions are the second most
common and include capillary hemangiomas, lymphangiomas, or cavernous
hemangiomas. The remaining number of
cases in any particular category is small, although a differential diagnosis
should include inflammatory lesions, adipose-containing lesions, lacrimal gland
masses, lymphoid tumors and leukemia, optic nerve and meningeal tumors, osseous
and fibro-osseous masses, rhabdomyosarcoma, and metastatic lesions (most
frequently neuroblastoma). The most
common malignant processes include rhabdomyosarcoma, metastatic disease,
lymphomas and leukemia. Most orbital
tumors in children are benign and familiarity with the more common orbital
lesions
and
their presentations will help the clinician make a timely and accurate
diagnosis.
Cystic Lesions (Dermoid cysts, Teratoma)
Dermoid cysts likely arise from
trapped embryonic ectoderm within the suture lines between the orbital
bones. The sequestered tissue forms a
cyst lined with keratinized epithelium and dermal elements. Cysts consisting of squamous epithelium
without adnexal structures are called epidermoids. The orbital dermoids can be classified into juxtasutural,
sutural, and soft-tissue types. The most
common type is the juxtasutural appearing in the superotemporal and superonasal
quadrants. Clinically, this type of
cyst presents in the preschool child as a painless mass in the superotemporal
area at the lateral portion of the eyebrow.
It is usually unattached to overlying skin, mobile, smooth and
nontender. Soft tissue or sutural
dermoids usually grow more slowly over a long period of time and often present
with proptosis. Most patients have no
visual symptoms. CT scan reveals a well
circumscribed lesion with a low density lumen and sometimes bony
remodeling. Deeper orbital lesions may
show complete bony defects with calcium deposition. Occasionally, episodes of inflammation can be seen with small
ruptures of the cyst wall. Management
is surgical with complete excision of the cyst lining taking care to avoid
rupture. Surgery is delayed until the
risk of accidental rupture from trauma outweighs the general anesthesia risks,
usually around 1 year of age. Smaller
cysts can be followed for signs of growth, visual disturbances, or cosmetic
deformity.
Teratomas are rare congenital
germ-cell tumors which arise from primordial germ cells. These tumors are characterized by the
presence of ectodermal, mesodermal and endodermal components. These tumors typically present at birth, and
although benign with no bone invasion, often cause orbital enlargement with
significant morbidity. With large
intraconal masses, massive proptosis accompanied by conjunctival keratinization,
exposure keratopathy and corneal ulceration may be seen. Massive teratomas traditionally are treated
by orbital exenteration, however salvage of the globe is possible with smaller
lesions (typically without subsequent normal visual acuity).
Vasculogenic Lesions (Capillary hemangioma, lymphangioma)
Capillary hemangiomas are common orbital
masses in the pediatric population. One
third are diagnosed at birth, and over 90% are visible by 6 months of age. The most common presentation is superficial involvement appearing as
tumor and telangiectatic vessels in the skin that with time develops the
typical strawberry-like appearance.
Deeper lesions may appear as raised, soft, purplish nodules. Deep orbital involvement may present solely
with proptosis and no skin changes.
Orbital hemangiomas frequently produce proptosis and globe displacement
and enlarge with Valsalva maneuvers or crying.
The typical course of these lesions isa normal appearance at birth, with
the lesion first noticed at one month and enlarging until the patient is 1 to 2
years of age. This is followed by a
period of stabilization and then spontaneous involution by age 4 to 8 years of
age. Long term cosmetic sequelae are
minimal following involution though visual complications such as amblyopia and
astigmatism from distortion of the globe are common. Major complications include superinfection, ulceration, and
necrosis with possible hemorrhage. Rare
but serious complications include Kasabach-Merritt syndrome and high-output
cardiac failure (large lesions).
Orbital involvement is best evaluated with CT or MRI which show a
diffusely infiltrating non-encapsulated mass, conforming to the surrounding
orbital structures. Bony erosion is not
seen, although expansion of the orbital walls is possible. Ultrasonography is also a valuable
noninvasive test. Lesions which do no
affect visual or orbital development can be observed. Indications of treatment include any of the complications
discussed previously. Medical therapy
involves the use of intralesional steroid injection, systemic steroids, or
interferon. Radiation therapy can be
very effective in the control of these lesions, however concerns regarding
radiation-induced malignancies in children has led to a reduction in its use. Surgical resection is reserved for well-circumscribed
lesions or those causing severe sequelae unresponsive to medical therapy. Complete surgical removal is often not
possible.
Lymphangiomas are benign congenital
vascular malformations which may affect the conjunctiva, eyelids or deep
orbit. Classically, they are viewed as
separate from the vascular system, although some overlap has been noted. Typically, the tumor is identified within
the first two decades of life. The
course may present as slow enlargement with increasing proptosis over many
years, or one of sudden proptosis from intralesional hemorrhage (chocolate
cyst). These tumors have been known to
show expansion during an acute upper respiratory infection. Superficial lesions are more common and have
a better prognosis for vision than deeper lesions. There is no enlargement of the tumor with Valsalva
maneuvers. Imaging studies include CT
and MRI, which both show the multi-compartmental nature of the venous-lymphatic malformations. MR imaging is preferred over CT because it delineates the
internal structure of the various cysts of the lesion. The management of orbital lymphangioma is
difficult due to the infiltrative nature of the tumor. Surgical debulking and cyst drainage is the
treatment of choice for significant proptosis, corneal exposure or optic nerve
compression. Complete surgical excision
is often not possible.
Rhabdomyosarcoma
This is the most common orbital malignant
tumor found in children. It presents
early in the first decade with rapid unilateral proptosis and displacement of
the globe. The eyelid may be
erythematous with conjunctival chemosis.
Occasionally ptosis, tearing, headache, and nosebleed are complaints. A palpable mass is present in about 25% and
with large intraconal lesions papilledema and retinal vascular congestion may
be seen. Sinusitis and epistaxis may
occur with extension of the mass into the paranasal sinuses. CT scan shows an irregular tumor with
moderately well-defined margins, soft tissue attenuation, and often evidence of
bony destruction (50%). MR imaging
demonstrates a signal similar to muscle on T1 and higher than muscle on
T2-weighted images. A complete blood
count is helpful to distinguish from orbital cellulitis and leukemia, and
biopsy of a suspected rhabdomyosarcoma should be performed as soon as possible
for a definitive diagnosis. During
biopsy, as much tumor as can be removed without violating critical structures
should be excised. Histologically, it
can be divided into four main types: embryonal , alveolar, pleomorphic, and
botryoid. The embryonal type is the
most common, occurring in 2/3 of cases.
The alveolar is second most common and is the most malignant with a high
frequency of metastases. The
pleomorphic type is the most differentiated type with the best prognosis. Once a tissue diagnosis is obtained, staging
of the disease with bone marrow biopsy, CXR, LFTs, CBC and lumbar puncture is required. With the recent advances in treatment using chemotherapy and
radiation, this once fatal disease now carries a much better prognosis. Localized disease (Group I & II) carries
a 90% 5-year survival. However,
disseminated or gross residual disease (Group II &IV) has a 35% 5-year
survival rate.
Optic Nerve Gliomas
Optic nerve glioma is the fifth most
common primary intraorbital tumor (1.5% to 3.5% of all orbital tumors) and the
third most common orbital tumor in children.
These tumors may occur randomly, but are often associated with
Neurofibromatosis type I (18 to 50% of cases), and are often bilateral when
occurring with this disease. The mean
age of presentation is about 8 years.
The typical presentation is proptosis and visual loss or visual field
changes. Intracranial extension may
produce headaches and pain. Upon eye
examination, optic disk swelling or atrophy may be noted as well as decreased
motility. Diagnosis can usually be made
based on clinical exam and radiography due to the characteristic appearance on
CT. Radiographically, they appear as
fusifom enlargement of the optic nerve which is isodense to brain. Intracranial extension into the optic canal
and chiasm is best evaluated with MRI.
Despite their apparently benign and slow growth pattern, gliomas are
associated with significant morbidity and mortality, especially when the tumor
spreads to the optic chiasm, hypothalamus and brain. Because of this, these tumors must be excised while still
confined to the optic nerve. Once the
tumor has extended to the chiasm, surgery is not indicated. Radiotherapy at this point does not seem to
improve prognosis and chemotherapy is unproven. Gliomas are indolent enough to warrant conservative management
with serial radiographic studies when vision is intact. However, once the tumor extends to the optic
canal or the eye becomes blind and/or proptotic, surgical excision is
necessary.
Fibrous Dysplasia
This lesion is the most frequently seen
fibro-osseous tumor and develops almost exclusively in children during the
first 2 decades of life. This lesion is
characterized by the replacement of normal bone with abnormal tissue composed
of collagen, fibroblasts, osteoid and giant cells (immature woven bone). There are two types of fibrous dysplasia:
polyostotic (Albright's syndrome) and monostotic. Polyostotic fibrous dysplasia involves multiple bones, but not
generally the orbit, and is characterized by abnormal skin pigmentation and
precocious puberty. Monostotic fibrous
dysplasia occurs most often in the bones of the face and is the most common
type in the orbit. The orbital roof is
the most common site of orbital involvement.
Although the onset of disease is within the first couple of years of
life, the usual presentation is the adolescent child with proptosis, globe and
orbit displacement and facial asymmetry.
The CT will show thickened abnormal bone with sclerotic lesions with a
"ground-glass" appearance.
Biopsy is usually necessary to confirm the diagnosis and to rule out
more aggressive lesions. Conservative
management with close observation is the hallmark of treatment, since these
lesions usually stabilize after puberty.
Indications for surgical treatment are significant cosmetic deformity
and vision loss. Complete resection
followed by immediate craniofacial reconstruction is recommended, usually with
the neurosurgeon. If total resection is
not possible, removal of as much of the lesion as necessary to protect sight
and correct the cosmetic deformity should be performed.
Metastatic Tumors: Neuroblastoma
Neuroblastoma is the most frequent metastatic
orbital disease in children. Other encountered metastatic diseases include
Ewing's sarcoma, leukemia, and lymphoma.
Neuroblastoma is common in children and accounts for about 10% of all
malignancies. The majority of cases occur
before age 5 (median 22 months).
Bilateral disease is common with
eyelid ecchymoses and proptosis being the most common presenting
signs. Additional symptoms may include
abdominal fullness/pain, edema and hypertension owing to the primary lesion,
most commonly in the adrenal gland.
Urinalysis is positive for catecholamines in 90 to 95%. Incisional biopsy is necessary to confirm
the diagnosis. Children presenting with
orbital disease are stage IV, and have a survival rate of less than 15%. Therapy includes surgery, chemotherapy,
radiation therapy and bone marrow transplantation.
Adult Orbital Tumors
In the adult population, the more common types of
orbital tumors vary significantly from children. The most common tumor groups in this population include
carcinomas (paranasal sinus, secondary & metastatic), inflammatory masses
(pseudotumor), lacrimal gland tumors, cysts, lymphomas, meningiomas, and
vascular tumors (cavernous hemangiomas).
Secondary tumors commonly invade the orbit and include mucoceles,
squamous cell carcinoma, meningioma, vascular malformations and basal cell
carcinoma.
Paranasal Sinus Masses
A mass developing in the paranasal sinuses has the potential to extend into the
orbit and is a common cause of an orbital mass lesion. The most common mass lesion of the orbit
originating in the sinus is the mucocele.
Mucoceles often result from obstruction of a sinus ostium leading to an
enlarging fluid filled sinus which eventually may erode through the orbital
bony wall. The median age of
presentation is around 50 years, although they may present at any age. Most arise from the ethmoid and frontal
sinus. Patients will present with
unilateral proptosis with globe displacement away from the mass, lid swelling
and sometimes a palpable mass. CT scan
reveals a well-defined homogeneous mass extending into the orbit through a bony
defect associated with an opacified sinus cavity. Treatment involves drainage of the obstructed sinus and often
obliteration of the sinus.
Neoplasms of the paranasal sinuses
are uncommon, but frequently extend to involve the orbit when they do
occur. Both epithelial and mesenchymal
neoplasms may develop here. Benign
tumors tend to push the periorbita aside, while malignant lesions tend to
invade the periosteum. By far the most
common malignancy is squamous cell carcinoma.
This disease is usually advanced at presentation with orbital invasion
in almost two thirds of the patients.
Presentation with orbital extension imparts a poor prognosis, especially
with extension above an imaginary line from the medial canthus through the
angle of the mandible (Ohngren's line).
Glandular malignancies may arise from either minor salivary glands or
from the basal lamina of the respiratory epithelium. Adenocarcinomas arising from the ethmoid sinuses are frequently
associated with wood workers. Salivary
tumors are usually adenoidcystic or mucoepidermoid and are more common in the
antrum. Adenoid cystic carcinomas have
the propensity for perineural spread via the infraorbital nerve and have been
known to cause bilateral orbital invasion with blindness. Locally invasive neoplasms may arise from
the olfactory neuroepithelium-esthesioneuroblastoma. Due to the proximity to the ethmoid, early involvement of this
sinus is common. Orbital involvement is
a late finding, due to its indolent growth.
A benign paranasal neoplasm, not uncommonly seen, is the inverted
papilloma. This is a benign growth
arising from the lateral nasal wall in the region of the middle meatus, or from
the sinus mucosa. The tumor usually
involves the ethmoid and maxillary sinuses with gradual enlargement through the bony septa and sinus walls. Most patients present after nasal
obstruction or epistaxis have occurred.
True violation into the orbital fat is rare, however, compression of the
orbital contents can cause visual loss.
In 5 to 10% of cases, inverted papillomas are associated with SCCA so
aggressive surgical resection is mandatory.
Evaluation of the paranasal sinus
mass is best done radiographically with CT scan, because of the ability to
detect early lesions and note bony destruction with either orbital or
intracranial extension. MRI scans are
useful in detecting intracranial extension and distinguishing certain
neoplastic diseases from one another.
After radiographic evaluation, tissue should be obtained with biopsy prior
to definitive evaluation. This can
optimally be done in the operating room, especially when exploration of the
involved sinus is required. Biopsy
should not be performed in the case of juvenile angiofibroma, tumors with
direct cranial cavity communication, cerebrospinal fluid leak, or masses with
synchronous pulsations with the heart beat (i.e. encephalocele). Malignant tumors originating from the
paranasal sinuses will require radical resection with wide margins. Penetration through the periorbita is an
indication for sacrifice of the orbital contents. Postoperative radiation therapy often accompanies surgical
resection. Invasion of the orbit by a
malignancy of the paranasal sinuses usually carries a grave prognosis, and
often palliation is the primary treatment goal.
Orbital Pseudotumor (Idiopathic Orbital Inflammation)
This descriptive term was first used in 1905
by Birch-Hirschfield to describe an inflammatory condition of the orbit of
unknown etiology. It is now applied to
a large spectrum of non-specific idiopathic inflammations of the orbit and
ocular adnexa, excluding systemic diseases (sarcoidosis, Wegener's, thyroid
orbitopathy, etc.). It is now
restricted to lesions which show histological appearance of polymorphous
inflammatory infiltration of T&B cells, plasma cells, eosinophils and
neutrophils, with a variable degree of fibrous tissue proliferation. This disease is a common cause of proptosis
presenting anywhere from the 2nd to 7th decade of
life. Multifocal involvement is common
and any orbital structure may be involved.
The onset of symptoms is typically a few days, however, subacute or
chronic forms have been described. The
typical symptoms are dull orbital pain which is worse with eye movement. Proptosis is the most common finding
although eyelid swelling, chemosis, and diplopia commonly occur. Visual loss may occur with scleral, uveal,
or optic nerve inflammation. CT
findings show hazy enlargement of affected structures with enhancement after
intravenous contrast injection. MR
T1-weighted images show lesions with similar signal to muscle that enhance with
contrast. T2-weighted images have
increased signal similar or greater than fat.
A range of therapeutic options have been employed including surgery,
steroids, immunosuppressive agents, and radiation therapy. Symptom relief should be the goal. Surgery may be effective for localized
lesions, but is generally reserved for biopsy only as it may exacerbate the
inflammatory process. Steroid therapy
(oral prednisone 60-100 mg/day) is a mainstay of treatment and usually provides
symptomatic relief, however, relapse rates are high when discontinued. Some cases require immunosuppressive
medications, such as cyclophosphamide or cyclosporine. Radiation therapy is indicated for lymphoid
infiltrates and is effective in nonfibrotic lesions with marked cellularity or
prominent inflammatory features, and is an alternative when steroid therapy is
contraindicated or has adverse effects.
Lacrimal Gland Tumors
Masses of the lacrimal fossa are
caused by numerous conditions.
Enlargement of this area with swelling and erythema often indicates
infection or inflammation of the gland.
However, inferior and medial displacement of the globe with no
inflammatory signs or symptoms should raise suspicion of a neoplastic
process. About half of the lacrimal
tumors are epithelial neoplasms, while the other half are lymphoproliferative
disorders. Lymphoid lesions include
benign lymphoid hyperplasia, malignant lymphoma and leukemias. Lymphoid lesions rarely cause bony changes
or destruction and appear as smooth enlargement of the gland on CT scans. Epithelial neoplasms appear more irregular
on CT and include pleomorphic adenomas (benign), adenoid cystic carcinoma,
adenocarcinoma, mucoepidermoid carcinomas, and undifferentiated
carcinomas.
Primary epithelial neoplasms of the
lacrimal gland are rare, and by far the most common of these is the pleomorphic
adenoma (benign mixed tumor). It occurs
in adults primarily between the ages of 20 and 50 years. The presenting symptoms are painless
proptosis with inferior and medial displacement of the globe that has been
present for many months or years. These
patients should undergo complete excisional biopsy of the gland for diagnosis
confirmation. There is a 32% rate of
recurrence with a chance for malignant degeneration over the patient's lifetime
if the capsule is incised without complete removal .
The most common malignant epithelial
neoplasm of the lacrimal gland is adenoid cystic carcinoma. In comparison to the benign mixed tumor,
malignant epithelial neoplasms will present with a more progressive onset of
proptosis and globe displacement. Pain
and numbness are also more common in malignant tumors. CT scans will often show bony destruction
and infiltration of the lacrimal mass.
An incisional biopsy is indicated for these findings before proceeding
with treatment. The mortality rate is
significant (>50%), and therefore aggressive surgical resection, many times
with exenteration and removal of soft
tissue and bone, followed by radiotherapy.
Lymphoid Tumors
Lymphoid tumors are one of the more common
orbital tumors despite the orbit not containing lymph nodes or a well defined
lymphatic vasculature. The incidence is
between 4 and 13% of all orbital tumors.
Orbital lymphomas may be primary or associated with systemic
disease. Although most orbital
lymphomas are localized to the orbit at diagnosis, many patients will develop
systemic lymphoma over time.
Approximately 20% of patients with lymphoid tumors of the conjunctiva,
35% of patients with orbital tumors and 67% with eyelid disease will eventually
develop systemic lymphoma. Orbital
lymphoma is an adult disease process usually presenting between the age of 50
and 70 years. The course is usually one
of an anterior mass which enlarges slowly causing progressive painless
proptosis over several weeks to months.
The classic lesion is a smooth, pink-orange mass ("salmon
patch") under an intact conjunctiva.
CT scan shows a homogeneous mass with well defined borders that does not
destroy surrounding structures or bone.
Most lesions are extraconal and in the superior orbit. The lacrimal gland may be affected but
enlarges with a normal shape unlike primary lacrimal gland tumors. To make a definitive diagnosis a generous
biopsy is needed and must be sent for immunohistochemical studies (fresh) as
well as permanent section (formalin).
Once a diagnosis of lymphoma is made, patients should be worked up for
systemic disease including a complete physical exam, a complete blood count,
bone marrow biopsy and CT scans of the thorax, abdomen and pelvis. Patients with localized lymphoma to the
orbit may be treated with primary XRT, and patients with systemic disease may
respond to a combination of orbital radiotherapy and systemic
chemotherapy. Consultation with an
oncologist should be obtained.
Orbital Meningiomas and Schwannomas
These are most common in adults
during the fourth to seventh decade of life and are rarely seen in
children. Although primary orbital
meningiomas may arise from the optic nerve, 70% invade the orbit from the
cranium. The most common presenting
symptom is proptosis, yet visual disturbances are usually the chief complaint. Other symptoms may include headache and
diplopia. Imaging studies usually make
the diagnosis. CT scan will reveal a
fusiform enlargement of the optic nerve, which is homogeneous, infiltrative,
and enhancing. The classic "railroad
track" describes calcifications of the tumor along the optic nerve in the
subarachnoid space. MRI is used to
evaluate intracranial extension, showing a hyperintense tumor after contrast
administration. In the older patient,
these tumors may be followed if no evidence of intracranial extension
exists. In the younger patient
(<40), these lesions are more aggressive and should be excised at an early
stage. Unfortunately, optic nerve
sheath meningiomas often cause severe visual deficits after removal.
A schwannoma, or neurilemoma, is a
benign, noninvasive, peripheral nerve tumor that may arise from any nerve
within the orbit. They are relatively
rare and usually occur in adults from age 20 to 70 years. These patients present with painless
proptosis and diplopia. Rarely,
progressive visual loss or a relative afferent pupillary defect may occur. Diagnosis is made with CT and/or MR
imaging. CT shows a well-circumscribed,
homogeneous, elongated ovoid mass displacing surrounding structures. The tumor is hypointense on T1-weighted
images of MRI, and hyperintense on T2-weighted images. The tumor may be extraconal when associated
with the trochlear nerve (IV), but is more commonly intraconal. The definitive therapy is complete surgical
excision and the prognosis is excellent with rare recurrences.
Cavernous
Hemangioma (Encapsulated Venous Malformation)
An encapsulated venous
malformation, commonly referred to as the cavernous hemangioma, is a relatively
common vascular lesion in the orbit. It
is the most common vascular lesion of adults and is the most common primary
intraconal orbital lesion in adults.
The peak incidence is during
middle age with the average age of onset around 40 years. It is generally more common in women (70%)
than men (30%) and is generally unilateral.
These lesions present with a slowly progressive painless proptosis over
a perod of several years.
Interestingly, these malformations are isolated from the orbital
vascular system and therefore do not enlarge with Valsalva maneuvers. It is thought that these lesions are formed
from pre-existing vascular malformations, the vessels of which are initially
collapsed outside of the fibrous capsule.
Once these vessels enlarge due to changes in the systemic circulation
pressures, they become enlarged and eventually incorporated by a newly formed
reactive fibrous capsule.
Imaging with either CT or MRI
reveals a well-defined mass with an oval shape. Most are intraconal, but occasionally can be found outside the
muscular cone. On CT they are homogeneous
with increased density. With MRI they
appear homogeneous and isointense to muscle on T1-weighted images and
hyperintense on T2-weighted images.
Following contrast addition, the lesions enhance inhomogeneously. The treatment of choice is complete surgical
excision of the tumor and capsule with an excellent prognosis. Recurrences are very rare even with
incomplete resection.
Metastatic Tumors
Metastasis is an important cause of orbital
disease in the adult, representing approximately 8% of all orbital tumors. Orbital metastases may signal either
reactivation of treated disease or new systemic malignancy. Breast carcinoma is the most common
metastatic tumor found in women followed by lung carcinoma. In men the most common are lung and
prostate. The common presenting
symptoms are proptosis, diplopia, pain and vision loss. Physical examination may reveal upper eyelid
ptosis and a palpable mass. The average
age at presentation is in the 7th decade, most being female (due to
the higher incidence of breast metastasis - 50% of all mets). On CT, the most common finding is a
well-defined, contrast enhancing, intraconal mass. The orbital bony walls are also a common site for metastasis,
especially with prostate cancers.
Biopsy may be necessary for diagnosis and the prognosis with orbital
metastasis of systemic cancer is very poor (avg. survival - 10 months). Radiation therapy is the usual modality of
treatment for orbital metastasis with chemotherapy and hormonal therapy
occasionally used.
Conclusion
The orbit has a very complex anatomy in close
association with the paranasal sinuses and cranial vault. A wide variety of lesions may develop in the
orbit with significant variation according to the age of the patient. It is not uncommon for these patients to
present to the otolaryngologist either primarily or via consultation from
another subspecialty. It is therefore
important for the otolaryngologist to possess a basic understanding of the
anatomy of the orbit and the more common disease processes which may affect it. Since vision is of primary concern with disease
processes of the orbit, it is always advisable to involve the ophthalmologist
in the management of orbital tumors. In
some cases it may be necessary for several specialties to manage these diseases
together. A combined approach with the help of
neurosurgeons, oncologists, radiation therapists, otolaryngologists and
ophthalmologists will often give the best outcome to the patient afflicted with
an orbital tumor.
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