Trigonocephaly
Encyclopedia
Trigonocephaly is a congenital condition of premature fusion of the metopic suture (Greek: 'metopon' = forehead) leading to a triangular shaped forehead. The merging of the two frontal bones leads to transverse growth restriction and parallel growth expansion. It may occur syndromic involving other abnormalities or isolated.
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.
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.
Hermann Welcker
coined the term trigonocephaly in 1862. He described a child with a V-shaped skull and a cleft lip.
, Jacobsen syndrome
, Baller-Gerold syndrome and Say-Meyer syndrome. The etiology of trigonocephaly is mostly unknown although there are three main theories. Trigonocephaly is probably a multifactorial congenital condition, but due to limited proof of these theories this cannot safely be concluded.
suppletion in hypothyroidism
) or pharmaceutical (valproate in epilepsy
).
during birth.
Only one article gives valuable and reliable information regarding the incidence of metopic synsostosis 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.
Observatory signs of trigonocephaly are:
Imaging techniques (3D-CT, Röntgenography, MRI) show:
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:
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.
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 fase.
for surgery. Because of standardization of current surgical approaches there is no surgical mortality and complications are few to none.
The simple suturectomy is presently insufficient to adjust the complicated growth restrictions caused by metopic synostosis. 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.
Over the past few years distraction osteogenesis has been gradually acknowledged since it has a positive effect on hypotelorism. Expanding the distance between the orbits using springs seems to be successful. However, there are discussions whether hypotelorism really needs to be corrected.
The minimal invasive endoscopic surgery has been gaining attention since the early 90’s, however, it has technical limitations (only strip craniectomy is possible). Attempts have been made to reach beyond these limits.
History
In former times people born with malformed skulls were rejected based upon their appearance. This still persists today in various parts of the world even though the intellectual development is often normal. The Austrian physician Franz Joseph GallFranz Joseph Gall
Franz Joseph Gall was a neuroanatomist, physiologist, and pioneer in the study of the localization of mental functions in the brain.- Life :...
presented the science of phrenology
Phrenology
Phrenology is a pseudoscience primarily focused on measurements of the human skull, based on the concept that the brain is the organ of the mind, and that certain brain areas have localized, specific functions or modules...
in the early 19th century through his work The Anatomy and Physiology of the Nervous System in General, and of the Brain in Particular.
Hippocrates
Hippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...
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.
Hermann Welcker
Hermann Welcker
Hermann Welcker was a German anatomist and anthropologist who was born in Giessen. He was a nephew to philologist Friedrich Gottlieb Welcker ....
coined the term trigonocephaly in 1862. He described a child with a V-shaped skull and a cleft lip.
Etiology
Trigonocephaly can either occur syndromatic or isolated. Trigonocephaly is associated with the following syndromes: Opitz syndrome, Muenke syndromeMuenke syndrome
Muenke Syndrome, also known as FGFR3-related craniosynostosis, is a human specific condition characterized by the premature closure of certain bones of the skull during development, which affects the shape of the head and face. Muenke syndrome occurs in about 1 in 30,000 newborns...
, Jacobsen syndrome
Jacobsen syndrome
Jacobsen Syndrome, also known as 11q deletion disorder, is a rare congenital disorder resulting from deletion of a terminal region of chromosome 11 that includes band 11q24.1. It can cause intellectual disabilities, a distinctive facial appearance, and a variety of physical problems including heart...
, Baller-Gerold syndrome and Say-Meyer syndrome. The etiology of trigonocephaly is mostly unknown although there are three main theories. Trigonocephaly is probably a multifactorial congenital condition, but due to limited proof of these theories this cannot safely be concluded.
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 (9p22-24, 11q23, 22q11, FGFR1 mutation), metabolic (TSHThyroid-stimulating hormone
Thyrotrophin-stimulating hormone is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid gland.- Physiology :...
suppletion in hypothyroidism
Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...
) or pharmaceutical (valproate in epilepsy
Epilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
).
Fetal head constrain
The second theory says that synostosis begins when the foetal head gets hindered in the pelvic outletPelvic outlet
The lower circumference of the lesser pelvis is very irregular; the space enclosed by it is named the inferior aperture or pelvic outlet.-Boundaries:It has the following boundaries:* anteriorly: the pubic arch* laterally: the ischial tuberosities...
during birth.
Intrinsic brain malformation
The third theory predominates disturbed brain formation of the two frontal lobes as the main issue behind synostosis. Limited growth of the frontal lobes leads to an absence of stimuli for cranial growth, therefore causing premature fusion of the metopic suture.Epidemiology
The incidence of metopic synostosis is roughly between 1:700 and 1:15.000 newborns globally (differs per country). Trigonocephaly is seen more in males than females ranging from 2:1 to 6,5:1. Hereditary relations in metopic synostosis have been found of which 5,5% were well defined syndromic. Maternal age and a birth weight of less than 2500g may also play a role in trigonocephaly. 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 synsostosis 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.
Diagnosis
Diagnosis can be characterized by typical facial and cranial deformities.Observatory signs of trigonocephaly are:
- a triangular shaped forehead seen from top view leading to a smaller anterior cranial fossaAnterior cranial fossaThe floor of the anterior fossa is formed by the orbital plates of the frontal, the cribriform plate of the ethmoid, and the small wings and front part of the body of the sphenoid; it is limited behind by the posterior borders of the small wings of the sphenoid and by the anterior margin of the...
- a visible and palpable midline ridge
- hypotelorismHypotelorism-Causes:It is often a result of fetal alcohol syndrome caused by large alcohol intake in the first month of pregnancy.It can be associated with trisomy 8.It can also be associated with fragile X syndrome....
inducing ethmoidal hypoplasiaHypoplasiaHypoplasia is underdevelopment or incomplete development of a tissue or organ. Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia is similar to aplasia, but less severe. It is technically not the opposite of hyperplasia...
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 lateralLateralLateral may refer to:*Lateral , an anatomical direction*Lateral canal, a canal built beside another stream*Lateral consonant, an ℓ-like consonant in which air flows along the sides of the tongue...
view of the cranium on a röntgenograph
- a normal cephalic indexCephalic indexCephalic index is the ratio of the maximum width of the head multiplied by 100 divided by its maximum length ....
(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
- neurodevelopmental delays such as ADHD (Attention Deficit Hyperactivity Disorder), ODD (Oppositional Defiant DisorderOppositional defiant disorderOppositional defiant disorder is a diagnosis described by the Diagnostic and Statistical Manual of Mental Disorders as an ongoing pattern of disobedient, hostile and defiant behavior toward authority figures which goes beyond the bounds of normal childhood behavior...
), ASD (Autism Spectrum Disorder) and CD (Conduct DisorderConduct disorderConduct disorder is psychological disorder diagnosed in childhood that presents itself through a repetitive and persistent pattern of behavior in which the basic rights of others or major age-appropriate norms are violated...
). Many of these delays become evident at school age.
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.Fronto-supraorbital advancement and remodelling
A form of surgery is the so called fronto-supraorbital advancement and remodelling. Firstly, the supraorbital bar is remodelled by a wired greenstick fractureGreenstick fracture
A greenstick, buckle or torus fracture is a fracture in a young, soft bone in which the bone bends and partially breaks. A person's bones become harder and more brittle with age. Greenstick fractures usually occur most often during infancy and childhood when bones are soft...
to straighten it. Secondly, the supraorbital bar is moved 2 cm. forward and fixed only to the frontal process of the zygoma
Zygoma
The term zygoma generally refers to the zygomatic bone, a bone of the human skull commonly referred to as the cheekbone or malar bone, but it may also refer to:...
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
Parietal bone
The parietal bones are bones in the human skull which, when joined together, form the sides and roof of the cranium. Each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named from the Latin pariet-, wall....
and frontal bone
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
. Bone will eventually regenerate since the dura mater
Dura mater
The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...
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’ 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. 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.Other
- Suturectomy
- Distraction osteogenesisDistraction osteogenesisDistraction osteogenesis, also called callus distraction, callotasis and osteodistraction is a surgical process used to reconstruct skeletal deformities and lengthen the long bones of the body...
- Minimal invasive endoscopic surgery
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 fase.
Surgical
Trigonocephaly seems to be the most compliant form of craniosynostosisCraniosynostosis
Craniosynostosis is a condition in which one or more of the fibrous sutures in an infant skull prematurely fuses by ossification, thereby changing the growth pattern of the skull...
for surgery. Because of standardization of current surgical approaches there is no surgical mortality and complications are few to none.
The simple suturectomy is presently insufficient to adjust the complicated growth restrictions caused by metopic synostosis. 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.
Over the past few years distraction osteogenesis has been gradually acknowledged since it has a positive effect on hypotelorism. Expanding the distance between the orbits using springs seems to be successful. However, there are discussions whether hypotelorism really needs to be corrected.
The minimal invasive endoscopic surgery has been gaining attention since the early 90’s, however, it has technical limitations (only strip craniectomy is possible). Attempts have been made to reach beyond these limits.