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MIDLINE FACIAL LESIONS
DD of frontal midline masses
1) encephalocoeles
2) Dermoids -hamartoma contain skin and skin appendages,
sequestered along embryonic fusion planes, epithelial lined cavity.
3) Gliomas - (encapsulated collection of glial cells outside CNS)
4) Vascular malformations
5) Neoplasms
6) Cysts, polyps, fibromas, fibromyxomas, granulomas,lipomas.
mucoceles
Teratomas are made up of a variety of parenchymal cell types representative
of more than a single germ layer, usually all 3.
Choristoma - microscopically normal cells or tissues in abnormal locations
Hamartoma – excessive focal overgrowth of mature normal cell and tissue in
an organ composed of identical cellular elements. (abnormal architecture)
ENCEPHALOCOELES
A cystic congenital malformation with protrusion of cranial contents through a
defect in the skull
Meningocoele
meninges
Meningoencephalocoele
+ brain
Meningoencephalocystocoele
+ ventricles
Classification
 based on position in skull
1. Anterior (frontal, sincipital, and basal)
2. Posterior (infra- and supratorcular)
a. Torcular = confluence of sinuses
b. Occipial, Parietal, Sagittal, Occipitocervical
 Anterior encephaloceles are quite distinct from posterior lesions. The facial
defect is usually covered with normal skin and hydrocephalus is unusual.
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Anterior encephaloceles
1) Basal
o occur within the ethmoidal and sphenoidal bones.
o posteriorly located lesions, particularly those in the sphenoid sinus, are
more likely to contain structures such as the hypothalamus, pituitary
gland, optic nerves, and chiasm.
o Basal encephaloceles may remain hidden (clinically) for years.
i)
Transethmoidal (or, intranasal)- exits through the cribriform plate
into the superior meatus, extending medial to the middle
turbinate
ii)
Transphenoidal (or, sphenopharyngeal, presenting as mass in
the epipharynx) - herniates in the nasopharynx via defects
posterior to the cribriform plate
iii)
Sphenoethmoidal - exits through the cribriform plate, between
the posterior ethmoid cells and sphenoid, to present in the
nasopharynx
iv)
Spheno-orbital - enters the orbit via the superior orbital fissure
and may produce exophthalmos
2) Sincipital
occur between the fronto-midface junction. Defect is between frontal
bone(membranous) and ethmoid (cartilage) May have brain
deformities such as derangements of olfactory, optic nerves,
hypothalamus, mesencephalon, temporal lobes.
a) Frontoethmoidal (cranial defect is in the anterior cranial fossa at
the foramen caecum, position of the facial defect determines
subclassification)
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i.
Nasofrontal. The most common type; the defect lies in the
bregmatic region between the frontal and nasal bones. The
ostium is at the nasion between the orbits producing
hypertelorism. In addition, these children present with a
mass at the base at the glabella or the base of the nose.
ii. Nasoethmoidal. The osseous defect lies in the cribiform
plate of the ethmoid bone where brain tissue herniates into
the nasal cavity.
iii. Nasoorbital. The osseous defect lies between the frontal
process of the maxilla and the ethmoid bone. The
encephalocele passes into the medial wall of the orbit and
presents as an orbital mass.
b) Interfrontal
c) Craniofacial/atypical clefts (some have classified frontoethmoidal
and interfrontal encephaloceles as Cleft 14)
Aetiology
1. Multifactorial – racial/genetic/environmental/paternal factors.
a. Genetic component; occurring in families with spina bifida,
anencephaly.
2. Teratogens (X irradiation, trypan blue, vitamin A, arsenic) in animal models.
3. Warfarin
4. Amniotic band
5. Rubella infection
6. Syndromes: Meckel-Gruber, von Voss, Chemke, Roberts, and Knobloch ,
trisomy 18
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Less common than spinal bifida: 1/5000 to 1/10000 live births
Strong geographic differences are present.
Posterior are more common in Europe and North America (66-90%)
Anterior predominate in Southeast Asia, and Russia. (9.5:1)
in Aust, Nth America etc—pos encephalocoeles predominate
in Asia—frontal : pos=10:1
60% have other malformations and/or chromosomal anomalies
In fetuses spontaneously aborted before 20 weeks' gestational age, it is the
predominant neural-axis anomaly.
 F>M
Pathogenesis
1. Developmental arrest. Genetic or environmental factors interfering with
closure of anterior neuropore (approximately day 24) can cause lethal
conditions such as exencephaly or anencephaly. Therefore, less severe
degrees arrest could potentially cause sublethal conditions such as
encephaloceles. Therefore, according to some, encephaloceles are grouped
with abnormalities of dorsal induction, or primary neurulation
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2. Mesodermal insufficiency. Because encephaloceles usually contain
cerebellum or cerebral cortex, both which form after neural tube closure, the
presence of these tissues within the encephalocele sac is caused by their
herniation through a mesodermal defect. According to McComb, this occurs
between 8-12 weeks of gestation.
3. Adhesive Theory - Ectodermal adhesions between neuroectoderm and
ectoderm preventing mesoderm from surrounding the neural tube.
 In sincipital encephaloceles:
Early in embryogenesis diverticulae of dura project anteriorly through
fontanelle (fonticulus nasofrontalis) between frontal and nasal bones or
inferiorly into prenasal space. This normally regresses and nasofrontal
suture forms. if contacts skin—failure to regress
Clinical
 Present at or near glabella
 Bluish, soft, pulsatile, compressible, transilluminate
 Enlarge with crying, Valsalva and Furstenberg test (compress jugular
veins)
 Associated always with cranial defects. CSF leak/meningitis may occur
Deformity
1. Hypertelorism
2. Orbital dystopia
3. Long face
4. Dental malocclusion
5. Long nose (symmetric in nasofrontal, asymmetric in nasoorbital)
6. Trigonocephaly
7. Microcephaly (posterior)
Investigations
 elevated AFP 3% (not if skin intact)
 Plain films to examine C-spine and cranio-vertebral junction (posterior
encephaloceles)
 US – useful to follow ventricular size. Also prenatal detection
 CT scan
 MRI is the test of choice (+/- MRA) to determine if neural tissue is involved
and nature of adjacent vascular structures.
 Biopsy is strongly contraindicated due to risk of infection and meningitis.
Principles of Treatment
 Treatment involves surgical excision with repair of the bony defect.
 For frontonasal,, cranial vault and occipital encephaloceles, direct
extracranial repair may be feasible.
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 For nasoethmoidal and nasoorbital type, intracranial repair may be needed.
 Single stage surgery with neurosurgeons
 Open defects are a surgical emergency to avoid brain
infections/desiccation.
Principles
1) Wide exposure and dissection of sac
2) Isolate the neck
3) Amputation of excess tissue - herniated part of the brain is usually gliosed
and non-viable and can usually be safely amputate
4) Closure of dura- water-tight
5) Close bony defect if large
6) Skin closure
7) Shunting if associated hydrocephalus
Australian Cranial Facial Unit (David)
1) Frontoethmoidal different from other neural tube defects – absence of
familial pattern and geographic distribution
2) Intracranial abn common
3) Treatment with craniofacial technique best
4) Early surgery to allow developing brain and eyes to remodel
5) Established defects can be treated effectively with craniofacial
osteotomies.
6) Usually telecanthic not true hypertelorism
7) Frontal sinus region often requires repeat bone grafting and nasal bone
grafts often must be replaced as patients age.
8) Treatment of facial clefts should be delayed until growth completion
Craniofacial considerations
Transnasal cantoplasty to reposition medial canthi
Avoid long-nose deformity – nasal reconstruction with cantilever bone graft
Remove abnormal skin – attention to scar positioning
Correct trigonocephaly/telecanthus - lower supraorbital bar, rotate posterior
and medially, widen laterally
Surgery
• Usually elective as most are well covered by skin and mucosa.
• The indications for repair of frontal lesions is cosmetic. There is no need to
remove the lipomatous portion.
• For sincipital lesions, repair should be in the first few weeks to prevent
progression of bony deformities. Transcranial repair most effective. Although
the principle is to return cerebral components into the intracranial cavity, the
dysplastic neural tissue usually requires amputaion.
• For basal lesion, additional brain retraction is often required adding to
expected complications. Greater efforts must be made to preserve neural
tissue.
Prognosis
• The neurological outcome is usually normal.
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Clinical Presentation and Management
Twenty percent of all encephaloceles occur in the cranium. Of those, 15% are
nasal. Nasal encephaloceles can be divided into 2 types: sincipital (60%) and
basal (40%).
Further, the sincipital form is divided into subtypes as follows: (1) the
nasofrontal (40%), which exits the cranium between the nasal and frontal
bones; (2) the nasoethmoidal (40%), which exits between the nasal bones
and nasal cartilages; and (3) the nasoorbital (20%), which exits through a
defect in the maxilla frontal process. Sincipital encephaloceles typically
present as soft compressible masses over the glabella.
sincipital and basal encephalocoles vs gliomas:
1. expand with the Valsalva maneuver,
2. have a positive Furstenberg sign,
3. transilluminate
Patients may have a history of rhinorrhea or recurrent meningitis and may
have a broad nose or hypertelorism (dystopia canthorum).
Posterior Encephaloceles
 survival rates 55%
 often associated with Dandy-Walker malformation and Arnold-Chiari II
malformation. An occipital encephalocele may be high, above the foramen
magnum, or it may involve the upper cervical spine and occipital bone.
(The Chiari III malformation is a cervico-occipital encephalocele containing
most of the cerebellum.)
Surgery
 Timing influenced by status of sac and skin overlying defect. Early
treatment to prevent infection and deformity is the rule. General operative
considerations are maintaining normothermia and careful hemostasis in the
neonate.
 Often complex and should be performed thru a facial hemisection.
 Incision planned to preserve normal skin. Lesion is circumferentially incised
and dural covering is defined. The sac is then opened and the contents are
inspected. Dysplastic tissue is resected flush with the bony opening and the
dura closed. The skin is then closed without tension.
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Prognosis
 Meningoceles, although much less common, have better prognosis than
encephalomeningoceles (60-80% completely normal in the former
compared to 10-25% in latter).
 Existence and extent of neural tissue within the cephalocele, the
coexistence of hydrocephalus (60-70% of occipital encephaloceles develop
hydrocephalus), and the presence of microcephaly (<10th percentile,
present in at least 20% of occipital encephaloceles) are major prognostic
determinants.
GLIOMAS
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Encephaloceles which have lost their intracranial connections
15-20% still have a fibrous stalk that connects to intracranial space
Rarely have bony defect or CSF leakage
Reddish, firm, noncompressible, lobular with cutaneous telangiectasias
External gliomas usually appear at or just lateral to the nasal root
Intranasal gliomas usually arise from the lateral nasal wall and may cause
nasal obstruction or septal distortion.
DERMOID CYSTS
 The soft tissues of the face are formed by the convergence of three facial
processes (frontal, maxillary, and mandibular) – week 3-4.
 As a consequence, there are lines of fusion where islands of ectodermal
tissue may become submerged, later to secrete sebaceous material and
present as obvious cystic swellings known as dermoids.
 The commonest site for this phenomenon is at the upper lateral part of the
forehead (external angular dermoid), but other sites include the upper
medial part of the eye or along the midline of the face and neck.
 Central facial dermoids occur in three patterns:
1. brow
2. orbital
3. nasaoglabellar
 Rarely, there may be a communication through the calvarium and two
dermoid elements occurring on either side of the bone to resemble a dumbbell tumour. Any suspicion that a dermoid may be fixed to the bone should
prompt an x ray examination or even computed tomography to test this
possibility. Dermoids should be treated by excision.
Histology
Lined by stratified squamous epithelium. Its walls contain sweat, sebaceous
glands and hair follicles.
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(cf epidermoid cyst – lined by same epithelium but no appendages)
Clinical
 Firm, noncompressible, nonpulsatile, May be lobulated
 50% will have a pit/sinus (pathognomic if see hairs protruding out
from pit)
 Tracts connecting the dermal sinus to dermoid cysts are referred to as a
dermal fistulas or sinus tracts. Sebaceous discharge can be expressed or
can spontaneously drain.
 The sinus tracts have transcranial connections in up to 45 percent of
patients.
Surgery
Great care must be taken to excise all sinus elements to prevent recurrence.
Use of dye-injection techniques or probing to find tract
Common sites of cervicofacial dermoids
1.Between outer border of eye and hair line (external angular dermoid)
2.Nasal bridge
3.Under chin (sub-mental)
4.Superficial to sternum
NB: Rarely Floor of mouth (1.6%)
Nasal Dermoids
 Nasal dermoid cysts, usually seen at or shortly after birth, are congenital
tumors of ectodermal origin without any malignant potential.
 The incidence is 1 in 20,000 live births, 1 percent of all dermoids, and 12
percent of head and neck dermoids.
 The cause of nasal dermoids is still unclear, and among the various
theories, two receive the most attention.
1. prenasal space theory, which postulates that as the dura mater
recedes from the prenasal space via foramen caecum, it pulls
nasal ectoderm upward to form a sinus or cyst.
2. superficial theory, which explains the nasal dermoid as the ectoderm
of the fused right and left medial nasal processes that are pulled
in to form a sinus tract or trapped to form a cyst.
 Nasal dermoids differ from other dermoids because they have the
potential to involve deeper structures and extend intracranially.
 Intracranial extension, which ranges from 1 to 45 percent, is mainly an
attachment to dura or within the leaves of the anterior falx; however,
involvement of brain parenchyma has been also reported.
 Although it is rare, a nasal dermoid should be suspected when a child
presents with a swelling on the nose.
 The differential diagnosis of such midline lesions include epidermoid cyst,
dermoid cyst, glioma, and meningoencephalocele.
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Investigations
1. CT
a. Bifid nasal bones, a thickened or bifid nasal septum, and
circular translucency under the nasal bones patent foramen
caecum or a bifid crista galli
b. false negative and false positive results with CT scans are not
uncommon
2. MRI
a. emonstrate marked hyperintensity on short TR/TE images due to
their fatty content, which consists of triglycerides and unsaturated
fatty acids
b. demonstrates the nasal dermoid with better tissue contrast than the
CT scan
c. sagittal plane imaging can allow visualization of the cyst and its
extension intracranially.
d. Definite diagnosis of intracranial extension is of great importance for
planning surgery; thus, with increasing frequency, MRI scanning
has become the preferred initial diagnostic tool.
Management
 When the dermoid is diagnosed, the proper treatment involves complete
surgical excision to avoid complications.
 Improper or delayed management can cause progressive enlargement of
the lesion, with distortion of skeletal structures, or infection resulting in
meningitis or brain abscess. Incision and drainage, aspiration, curettage,
and insufficient excision frequently fail to eradicate the lesion, resulting in a
recurrence rate of 30 to 100 percent, infection, further surgery, and
deformity.
 The cyst must be removed intact because even a small epithelium
remnant can lead to recurrence.
 Therefore, the first operation is the best opportunity for definitive treatment.
- accurate MRI scan showing the extent of the cyst, total resection, if
necessary involving an intracranial approach with the help of a
neurosurgeon, should be performed.