Trigonocephaly

Trigonocephaly is a congenital condition due to premature fusion of the metopic suture (Template:Ety), leading to a triangular forehead. The premature merging of the two frontal bones leads to transverse growth restriction and parallel growth expansion. It may occur as one component of a syndrome together with other abnormalities, or in isolated form. The term is Template:Ety.

Cause

File:Trigonocephaly.png

Fused suture in trigonocephaly

File:Single suture synostosis.png

Trigonocephaly as a kind of craniosynostosis

Trigonocephaly can either occur in a syndrome or isolated, all by itself. Trigonocephaly is associated with the following syndromes: Bohring-Opitz syndrome, Muenke syndrome, Jacobsen syndrome, Baller–Gerold syndrome and Say–Meyer syndrome. The etiology of trigonocephaly is mostly unknown although there are three main theories.<ref name="StricklerM1990"/> Trigonocephaly is probably a multifactorial congenital condition, but due to limited proof of these theories this cannot safely be concluded.<ref name="vanderMeulenJJNM2009"/>

Intrinsic bone malformation

The first theory assumes that the origin of pathological synostosis lies within disturbed bone formation early on in the pregnancy. Causes can either be genetic<ref name="pmid9300656">Template:Cite journal</ref><ref name="pmid17621648">Template:Cite journal</ref><ref>Frydman M, Kauschansky A, Elian E. Trigonocephaly; a new familiail syndrome. Am J Med Genet 1984: 18: 55-9.Template:Cite journal</ref><ref name="pmid2282717">Template:Cite journal</ref> (9p22–24, 11q23, 22q11, FGFR1 mutation),<ref>Template:Cite journal</ref> metabolic<ref>Template:Cite journal</ref> (TSH suppletion in hypothyroidism)<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> or pharmaceutical<ref name=LajeunieE1998>Template:Cite journal</ref> (valproate in epilepsy).<ref>Template:Cite journal</ref><ref name="pmid3125743">Template:Cite journal</ref>

Fetal-head constraint

The second theory says that synostosis begins when the fetal head gets hindered in the pelvic outlet during birth.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Intrinsic brain malformation

The third theory predominates disturbed brain formation of the two frontal lobes as the main issue behind synostosis.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Limited growth of the frontal lobes leads to an absence of stimuli for cranial growth, therefore causing premature fusion of the metopic suture.Template:Citation needed

Other conditions and syndromes

Template:Multiple image Other conditions and syndromes with trigonocephaly include:

• Arthrogryposis, cleft palate, craniosynostosis, and impaired intellectual development
• Atypical glycine encephalopathy
• Blepharophimosis-intellectual disability syndrome, Verloes type
• Bohring-Opitz syndrome
• Coffin-Siris syndrome
• Greig cephalopolysyndactyly syndrome
• Holoprosencephaly
• Mandibulofacial dysostosis-microcephaly syndrome
• MEGF8-related Carpenter syndrome
• Microcephaly, primary autosomal dominant
• Mucolipidosis type II
• Orofaciodigital syndrome type 14
• Paris-Trousseau thrombocytopenia
• Potocki-Lupski syndrome
• Simpson-Golabi-Behmel syndrome type 1
• Trichothiodystrophy, photosensitive
• Trigonocephaly-bifid nose-acral anomalies syndrome

Diagnosis

Diagnosis can be characterized by typical facial and cranial deformities.<ref name="vanderMeulenJJNM2009"/><ref>Template:Cite journal</ref>

Observatory signs of trigonocephaly are:

• a triangular forehead seen from top view leading to a smaller anterior cranial fossa
• a visible and palpable midline ridge
• hypotelorism inducing ethmoidal hypoplasia

Imaging techniques (3D-CT, röntgenography, MRI) show:

• epicanthal folds in limited cases
• teardrop-shaped orbits angulated towards the midline of the forehead ('surprised coon' sign) in severe cases
• a contrast difference between a röntgenograph of a normal and a trigonocephalic skull
• anterior curving of the metopic suture seen from lateral view of the cranium on a röntgenograph
• a normal cephalic index (maximum cranium width / maximum cranium length) however, there is bitemporal shortening and biparietal broadening

The neuropsychological development is not always affected. These effects are only visible in a small percentage of children with trigonocephaly or other suture synostoses.

Neuropsychological signs are:

• problems in behaviour, speech and language
• mental retardation<ref name=ShillitoJ1968>Template:Cite journal</ref><ref name=AndersonFM1981>Template:Cite journal</ref>
• neurodevelopmental delays such as attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), autism spectrum disorder (ASD), and conduct disorder (CD).<ref name=CollmannH1996>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name="pmid3427566">Template:Cite journal</ref><ref>Template:Cite journal</ref> Many of these delays become evident at school age.<ref>Template:Cite journal</ref>

Treatment

Treatment is surgical with attention to form and volume. Surgery usually takes place before the age of one since it has been reported that the intellectual outcome is better.<ref name="DiRoccoC1989"/><ref name="DhellemmesP1986"/><ref name="ShillitoJ1968"/><ref name="AndersonFM1981"/><ref name="CollmannH1996"/><ref name=MarchacD1994>Template:Cite journal</ref><ref name=McCarthyJG1984>Template:Cite journal</ref><ref name=RenierD2000>Template:Cite journal</ref><ref name=WhitakerLA1987>Template:Cite journal</ref>Template:Citation overkill

Fronto-supraorbital advancement and remodelling

A form of surgery is the so-called fronto-supraorbital advancement and remodelling.<ref>Template:Cite journal</ref> Firstly, the supraorbital bar is remodelled by a wired greenstick fracture to straighten it. Secondly, the supraorbital bar is moved 2 cm. forward and fixed only to the frontal process of the zygoma without fixation to the cranium. Lastly, the frontal bone is divided into two, rotated and attached to the supraorbital bar causing a nude area (craniectomy) between the parietal bone and frontal bone. Bone will eventually regenerate since the dura mater lies underneath (the dura mater has osteogenic capabilities). This results in an advancement and straightening of the forehead.

'Floating forehead technique'

The so-called 'floating forehead technique'<ref name="vanderMeulenJJNM2009"/> combined with the remodelling of the supraorbital bar is derived from the fronto-supraorbital advancement and remodelling. The supraorbital bar is remodelled as described above.<ref name=MarchacD1978a>Template:Cite journal</ref><ref name="pmid11109361">Template:Cite journal</ref> The frontal bone is split in two pieces. Instead of using both pieces as in fronto-supraorbital advancement and remodelling, only one piece is rotated and attached to the supraorbital bar. This technique also leaves a craniectomy behind.<ref>Template:Cite journal</ref>

Other

• Suturectomy<ref name="vanderMeulenJJNM2009"/>

• Distraction osteogenesis<ref name="vanderMeulenJJNM2009"/>

• Minimal invasive endoscopic surgery<ref name="vanderMeulenJJNM2009"/>

These approaches are 2D solutions for a 3D problem, therefore the results are not optimal. Distraction osteogenesis and minimal invasive endoscopic surgery are yet in experimental phase.

Outcomes

Surgical

Trigonocephaly seems to be the most compliant form of craniosynostosis for surgery.<ref name="CollmannH1996"/> Because of standardization of current surgical approaches there is no surgical mortality and complications are few to none.<ref name="vanderMeulenJJNM2009"/><ref name=DiRoccoC1996a>Template:Cite journal</ref><ref>Galassi E, Giulioni M, Acciarri N, Cavina C, Pistorale T. Marchac procedure in the early treatment of metopic and coronal synostoses. Presented at the Consensus Conference on Craniosynostoses, Rome 1995.</ref> The simple suturectomy is presently insufficient to adjust the complicated growth restrictions caused by metopic synostosis.<ref name="vanderMeulenJJNM2009"/> On the other hand, the fronto-supraorbital advancement and remodelling and the 'floating forehead technique' create sufficient space for brain growth and result in a normal horizontal axis of the orbits and supraorbital bar. The fronto-supraorbital advancement and remodelling is the most used method nowadays.<ref name="DiRoccoC1996a"/> Over the past few yearsTemplate:When distraction osteogenesis has been gradually acknowledged since it has a positive effect on hypotelorism.Template:Citation needed Expanding the distance between the orbits using springs seems to be successful.<ref name="vanderMeulenJJNM2009"/><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> However, there are discussions whether hypotelorism really needs to be corrected.<ref>Template:Cite journal</ref> The minimal invasive endoscopic surgery has been gaining attention since the early '90s, however, it has technical limitations (only strip craniectomy is possible).<ref name="vanderMeulenJJNM2009"/> Attempts have been made to reach beyond these limits.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name="pmid16398483">Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Aesthetic

Aesthetic outcome of metopic synostosis surgery is persistently good with reoperation hazards below 20%.<ref name=GreenbergBM2006>Template:Cite journal</ref><ref>Template:Cite journal</ref> In 1981 Anderson advised that craniofacial operations for synostosis should be as extensive as necessary after a study of 107 cases of metopic and coronal synostosis.<ref name="AndersonFM1981"/> Surgery does not provide a 100% natural outcome, mostly there will be minor irregularities. Reoperations are usually performed on more severe cases (including syndromic metopic synostosis). The hypotelorism and temporal hollowing are the most difficult to correct: the hypotelorism usually remains under corrected and a second operation is often needed for correction of temporal hollowing.<ref name="GreenbergBM2006"/><ref>Template:Cite journal</ref>

Neurological

The highest rate of neurological problems of single suture synostosis are seen in patients with trigonocephaly.<ref name="vanderMeulenJJNM2009"/> Surgery is performed generally before the age of one because of claims of better intellectual outcome.<ref name="DiRoccoC1989"/><ref name="DhellemmesP1986"/><ref name="ShillitoJ1968"/><ref name="AndersonFM1981"/><ref name="CollmannH1996"/><ref name="MarchacD1994"/><ref name="McCarthyJG1984"/><ref name="RenierD2000"/><ref name="WhitakerLA1987"/> Seemingly surgery does not influence the high incidence of neurodevelopment problems in patients with metopic synostosis. Neurological disorders such as ADHD, ASD, ODD and CD are seen in patients with trigonocephaly. These disorders are usually also associated with decreased IQ. The presence of ADHD, ASD and ODD is higher in cases with an IQ below 85. This is not the case with CD which showed an insignificant increase at an IQ below 85.<ref name="vanderMeulenJJNM2009"/>

Epidemiology

The incidence of metopic synostosis is roughly between 1:700 and 1:15,000 newborns globally (differs per country).<ref name="LajeunieE1998"/><ref name="pmid9041871">Template:Cite journal</ref> Trigonocephaly is seen more in males than females ranging from 2:1 to 6.5:1.<ref name=FriedeH1990>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name=DiRoccoC1989>Template:Cite journal</ref><ref name=DhellemmesP1986>Template:Cite journal</ref> Hereditary relations in metopic synostosis have been found of which 5.5% were well defined syndromic.<ref name="LajeunieE1998"/> Maternal age and a birth weight of less than 2500g may also play a role in trigonocephaly.<ref>Template:Cite journal</ref> These data are based on estimations and do not give factual information.

Only one article gives valuable and reliable information regarding the incidence of metopic synostosis in the Netherlands. The incidence in the Netherlands showed an increase from 0.6 (1997) to 1.9 (2007) for every 10,000 live births.<ref>Template:Cite journal</ref>

History

In former times people born with malformed skulls were rejected based upon their appearance.<ref name=StricklerM1990>Strickler M, van der Meulen J, Rahael B, Mazolla R. Craniofacial malformations. Edinburgh, London, Melbourne, New York: Churchill Livingston, 1990.</ref><ref name="pmid6406099">Template:Cite journal</ref> This still persists today in various parts of the world even though the intellectual development is often normal.<ref name=vanderMeulenJJNM2009>Template:Cite book</ref> The Austrian physician Franz Joseph Gall presented the science of phrenology in the early 19th century through his work The Anatomy and Physiology of the Nervous System in General, and of the Brain in Particular.<ref name=Phrenology>Phrenology. http://www.phrenology.org/</ref>

Hippocrates described trigonocephaly as follows: Men's heads are by no means all like to one another, nor are the sutures of the head of all men constructed in the same form. Thus, whoever has a prominence in the anterior part of the head (by prominence is meant the round protuberant part of the bone which projects beyond the rest of it), in him the sutures of the head take the form of the Greek letter 'tau', τ.<ref>Hippocrates. On injuries of the head. Med classics 1938: 3: 145-60.</ref><ref name="pmid16331180">Template:Cite journal</ref>

Hermann Welcker coined the term trigonocephaly in 1862. He described a child with a V-shaped skull and a cleft lip.<ref>Welcker H. Untersugungen uber wachtsum und bau des menschlischen Schädels. Leipzig: Engelmann, 1862.</ref>

Popular culture

Via a photo shown on a Facebook page, the mother of a child previously diagnosed with this condition recognised the symptoms and reported them to the family involved, resulting in an immediate diagnosis that medical professionals had overlooked in all earlier consultations.<ref>Template:Cite news</ref>