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HYPERTELORISM

INTRODUCTION

  • Telecanthus: increased distance between the medial canthi. The inter-orbital distance is normal.
  • Hypertelorism: increased distance between the orbits.
  • Orbital hypertelorism signifies an increased distance between both medial sides and lateral sides of the orbits.
  • Interorbital hypertelorism(bony telecanthus) denotes increased distance only between the inner orbital walls.
  • Interorbital hypertelorism - interorbital distance more than 2 standard deviations from normal mean, age and gender matched, with a normal outer orbital distance.
  • Orbital hypertelorism - both interorbital and outer orbital distances of more than 2 standard deviations from the normal mean

Embryology

  • Orbital hypertelorism occurs during the period prior to the 28-mm C-RL stage(approximately 50 days) of embryonic development.
  • The anomaly is not lateralization but failure of medialization of the entire orbits.
  • In contrast, interorbital hypertelorism more likely occurs during the period following medialization of the orbits.
  • A localized(field) defect(s) or sequence leading to abnormal development of the frontonasoethmoid complex could prevent primary medialization or cause excessive secondary lateralization of the medial orbital walls.

Assessment of Interorbital Distance

  • Inter-pupillary distance (IPD) unreliable because varies with extraneous conditions, eg squint. Inter-orbital distance should be used.
  • IOD – measured radiographically; the shortest distance between the medial walls of the orbits at approximately the level of the junctions of each medial angular process of the frontal bone with the maxillary and lacrimal bones.

1)the distance between the dacrya (dacryon = junction of frontal lacrimal bones), i.e., the interorbital distance

2)the distance between the lateral orbital rims at the horizontal level of the dacryon, i.e., the outer orbital distance.

  • Hypertelorism refers to increased interorbital distance

1)orbital hypertelorism - both interorbital and outer orbital distance increased

2)interorbital hypertelorism - interorbital distance increased but normal outer orbital distance.

  • Bony measurements on exaggerated Waters view or CT

CLASSIFICATION

Tessier

  • At birth, IOD = 16mm; at 12 years, IOD = 25mm; in adults, the normal inter-orbital distance is 25 mm in women and 28 mm in men.

1)1st degree hypertelorism: IOD = 30-34 mm

2)2nd degree hypertelorism: IOD = 35-40 mm

3)3rd degree hypertelorism: IOD > 40 mm

Gunther/Tessier based on standard deviation (SD)

1)first degree, interorbital distance 2 to 4 SDs

2)second degree, 4.1 to 8 SDs

3)third degree, more than 8 SDs greater than the normal mean.

  • Can also be classified according to the configuration of the medial orbital wall: parallel, divergent, bulging or convergent. The last 2 are the rarest and most difficult to Rx.

CAUSES

  • Traumatic.
  • Congenital

1)frontonasal malformation

  1. most common cause of hypertelorism
  2. also known as Median Cleft Face Syndrome, Frontonasal Syndrome, Frontonasal Dysplasia
  3. symmetrical, orbital type hypertelorism
  4. median cleft or bifid nose, median cleft upper lip and premaxilla, median cleft palate, widow's peak, anterior cranium bifidum occultum

(Above, left) Facies A: frontonasal malformation in a 4-year-old girl. Note the symmetrical second-degree interorbital hypertelorism, prominent widow's peak, and broad bifid nasal tip. She had resection of a nasal dermoid that extended intracranially.(Above, center) Facies B: frontonasal malformation (minor) with bipartate nasal tip and second-degree interorbital hypertelorism.(Above, right) Facies B: frontonasal malformation (major) in a 3-month-old girl. Note the symmetrical third-degree orbital hypertelorism, disjoined nares, median cleft lip/palate, and basal encephalocele. (Below, left) Facies D: frontonasal malformation in an 11-month-old girl with third-degree orbital hypertelorism, neurogenic blepharoptosis, alar colobomas with widely separated nasal openings, choanal atresia, and midfacial hypoplasia. She had an interfrontal encephalocele and mental retardation. Facies D is a combination of facies B(major) and facies C. (Below, center) Rugose frontonasal malformation in a 9-month-old girl. Note the thickened corrugated skin, short columella, poorly defined alar-cheek junctions, and symmetrical second-degreeinterorbital hypertelorism. (Below, right) Six-year-old girl with rugose frontonasal malformation and first-degreeinterorbital hypertelorism.

2)craniofrontonasal dysplasia (Cohen Syndrome, Craniofrontal Dysplasia, Craniofrontonasal Dysostosis, Craniofrontonasal Syndrome)

  1. second most common cause of hypertelorism
  2. all have coronal synostosis, unilateral or bilateral
  3. frontonasal anomalies were (1) short nose, broadened and flat nasal root with a variable degree of tip bifidity (also seen in minor forms of frontonasal malformation), and (2) symmetrical or asymmetrical orbital hypertelorism, usually third-degree severity (in contrast to frontonasal malformation
  4. narrow or high-arched palate
  5. thick, curly, orfrizzy hair that evolved during childhood
  6. narrow/sloping shoulder girdle deformity comprising variably a short, webbed neck, small, prominent, S-shaped or partially absent clavicles, axillary webbing, and prominent, asymmetrical or elevated scapulae (Sprengel deformity)

3)craniofacial cleft(s)

  1. Asymmetrical orbital hypertelorism associated with paramedian facial cleft(s): Tessier nos. 2-12 and 3-11, either unilateral or bilatera

4)Encephalocele/tumors

  1. Frontoethmoidal, Naso-frontal, Naso-ethmoidal, Naso-orbital
  2. Interorbital hypertelorism in patients with nasofrontal encephalocele was symmetrical, but it was asymmetrical in those with asymmetrical naso-orbital encephalocele.
  3. Elongation of the midface, particularly the nose, was symmetrical in the nasofrontal type and asymmetrical in naso-orbital encephalocele
  4. Tumors: Dermoid cysts, gliomas

5)Miscellaneous - well-described, mostly chromosomal or syndromic disorders.

  1. Craniosynostosis eg Apert’s syndrome
  2. Bilateral cleft-lip palate

Right naso-orbital (sincipital) encephalocele with asymmetrical midfacial and nasal elongation.

Asymmetrical orbital hypertelorism with right-sided Tessier no. 2-12 cleft in a 10-year-old girl

TREATMENT

  • patient with orbital hypertelorism requires transcranial translocation of the entire orbital complex, whereas translocation of the medial orbital walls can suffice for interorbital hypertelorism, depending on the position of the cribriform plate
  • Correction is subcranial or combined intracranial/extracranial.
  • Subcranial may be either

1)Medial orbital wall migration: maximum correction 10 mm.

  1. Complete ethmoidectomy followed by bilateral medial canthopexy

2)Four wall (classic Tessier)

  1. Best for adults
  2. Inferior orbital nerve is sacrificed
  3. Modification by Converse preserves the cribriform plate

3)Three wall (Inverted U) osteotomy

  1. mobilising the medial, lateral and superior orbital walls en block
  2. maximum correction 15 mm.
  3. best for children during primary or mixed dentition, or for asymmetric orbital shapes
  4. inferior orbital nerve is preserved

4)facial bipartition

5)Lammelar split orbital osteotomy

  1. Outer table split from inner table
  2. Does not correct true hypotelorism, useful as an adjunct to refine the orbital contour post 3-4 wall osteotomies
  • Intracranial correction is indicated in severe cases (cribriform plate below fronto-nasal suture). Using the method of Tessier as modified by Converse (to prevent anosmia), the entire orbit is mobilised as a box allowing total control of the orbital contents.
  • Ortiz Monasterio sections the whole midface vertically in half (facial bipartition) which allows approximation of the orbits, elongation of the midface to correct a short nose and lowers the dental arch to minimise an anterior open bite.

4 wall

Facial bipartition with cranial vault remodelling

COMPLICATIONS

  • Early:
  • Infection
  • Haemorrhage (including retrobulbar haematoma)
  • Sensory disturbances (eg SON, ION)
  • Anosmia
  • Wound dehiscence
  • Late:
  • Canthal drift
  • Enophthalmos.exopthalmos
  • Lacrimal duct damage
  • Ptosis
  • Temporal depression
  • Abnormal orbital configuration – over-correction / under-correction
  • Blindness