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KEY POINTS
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Key Points

  • Defined as an increased distance between inner and outer canthi.

  • Prenatal sonographic measurements are obtained from either the outer-to-outer or inner-to-inner bony orbital margins.

  • Unknown incidence but rare.

  • Main concern is its association with median facial and/or brain defects as well as syndromes.

  • Offer karyotype and FISH analysis for 22q11.2 deletion (associated with autosomal dominant form of Opitz syndrome).

  • Prognosis depends on severity of associated anomalies and/or if a syndrome is present.

  • DNA analysis is available for a number of the single-gene disorders associated with hypertelorism.

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CONDITION
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Hypertelorism is a condition in which a larger-than-average distance exists between the orbits. The distances between the medial canthi and pupils are also increased (Kirkham et al., 1975). The term was first used by Greig in 1924, who described hypertelorism as a “great breadth between the eyes.” The orbits represent a bridge between the face and the cranium. Seven different bones are required to form the orbit (frontal, zygomatic, sphenoid, ethmoidal, maxillary, lacrimal, and palatine) (Dollfus and Verloes, 2004).

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Ocular hypertelorism is defined as an increased distance between the medial orbital walls. This can be demonstrated either radiographically or clinically by an increased interpupillary distance. If the interpupillary distance is greater than 2 SD above the mean for the patient’s age, hypertelorism is said to exist (Brodsky et al., 1990). More recently, it has been recommended that the diagnosis of hypertelorism be made radiographically by interorbital measurements. The difficulty with using intercanthal distance to define hypertelorism is that soft tissue changes of the face can increase the inter-canthal distance without affecting the interorbital distance (Trout et al., 1994). Telecanthus is an increased distance between the inner canthi. This can either be primary, defined as an increase in soft tissue with normal interpupillary and interbony distance, or secondary, which is really orbital hypertelorism, with an increased interbony or interpupillary distance (Murphy and Laskin, 1990). The major concern regarding the fetal finding of hypertelorism is its association with median facial and brain defects, such as encephalocele, facial cleft, and craniosynostosis.

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INCIDENCE
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Hypertelorism is rare. Its exact incidence is unknown. Hypertelorism may occur as an isolated condition or in association with other anomalies.

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SONOGRAPHIC FINDINGS
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Imaging of the fetal orbits and measurements of the interorbital distance are not routinely performed in most centers that offer targeted fetal sonographic studies. Measurement of the fetal interorbital distance is not included in either the American Institute of Ultrasound in Medicine (AIUM) or American College of Obstetrics and Gynecology (ACOG) guidelines for obstetrical sonography (American College of Obstetrics and Gynecology, 2008). Fetal orbital measurements should be performed in any pregnant woman known to have had a previously affected child with a condition associated with hypertelorism, such as Waardenburg, Opitz or Noonan syndromes. Detection ...

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