There are two less common types of McGillivray syndromes are: Metopic synostosis (trigonocephaly). The metopic suture runs from your baby's nose to the sagittal suture. Premature fusion gives the scalp a triangular appearance. Another one is Lambdoid synostosis (posterior plagiocephaly). This rare form of craniosynostosis involves the lambdoid suture, which runs across the skull near the back of the head. It may cause flattening of your baby's head on the affected side. A misshapen head doesn't always indicate craniosynostosis. For example, if the back of your baby's head appears flattened, it could be the result of birth trauma or your baby's spending too much time on his or her back. This condition is sometimes treated with a custom-fit helmet that helps mold your baby's head back into a normal position.

First of all there is physical exam. Doctors examine baby’s head for abnormalities such as suture ridges and look the facial deformities. Also, they utilizes Computerized Tomography which scan of the baby’s skull. Fused sutures are identifiable by their absences. X-rays also may be used to measure precise dimensions of your baby's skull, using a technique called cephalometry.

Genetic testing. If your doctor suspects your baby's misshapen skull is caused by an underlying hereditary syndrome, genetic testing may help identify the syndrome. Genetic tests usually require a blood sample. Depending on what type of abnormality is suspected, your doctor may take a sample of your baby's hair, skin or other tissue, such as cells from the inside of the cheek. The sample is sent to a lab for analysis.

Radiographic analysis by performing a computed axial tomographic scan is the gold standard for diagnosing craniosynostosis.

Plain radiography of the skull may be sufficient for diagnosing a single suture craniosynostosis and should therefore be performed, but the diagnostic value is outweighed by that of the CT-scan. Not only can the sutures be identified more accurately, thus objectively demonstrating a fused suture, but also evaluation of the brain for structural abnormalities and excluding other causes of asymmetric growth are possible at the same time. In addition to this, CT-scanning can visualize the extent of skull deformity, thereby enabling the surgeon to start planning surgical reconstruction.

A clinical diagnosis of SCS can be verified by testing the TWIST1 gene (only gene in which mutations are known to cause SCS) for mutations using DNA analysis, such as sequence analysis, deletion/duplication analysis, and cytogenetics/ FISH analysis. Sequence analysis of exon 1 (TWIST1 coding region) provides a good method for detecting the frequency of mutations in the TWIST1 gene. These mutations include nonsense, missense, splice site mutation, and intragenic deletions/insertions. Deletion/duplication analysis identifies mutations in the TWIST1 gene that are not readily detected by sequence analysis. Common methods include PCR, multiplex ligation-dependent probe amplification (MLPA), and chromosomal microarray (CMA). Cytogenetic/FISH analysis attaches fluorescently labels DNA markers to a denatured chromosome and is then examined under fluorescent lighting, which reveals mutations caused by translocations or inversions involving 7p21. Occasionally, individuals with SCS have a chromosome translocation, inversion, or ring chromosome 7 involving 7p21 resulting in atypical findings, such as, increased developmental delay. Individuals with SCS, typically have normal brain functioning and rarely have mental impairments. For this reason, if an individual has both SCS and mental retardation, then they should have their TWIST1 gene screened more carefully because this is not a normal trait of SCS. Cytogenetic testing and direct gene testing can also be used to study gene/chromosome defects. Cytogenetic testing is the study of chromosomes to detect gains or losses of chromosomes or chromosome segments using fluorescent in situ hybridization (FISH) and/or comparative genomic hybridization (CGH). Direct gene testing uses blood, hair, skin, amniotic fluid, or other tissues in order to find genetic disorders. Direct gene testing can determine whether an individual has SCS by testing the individual's blood for mutations in the TWIST1 gene.

Up until recently, experts frequently disagreed on whether a patient had SCS, Crouzon syndrome, isolated craniosynostosis, or some other disease because the symptoms are so closely related, they literally had no way of differentiating between all of them. However, we now have direct gene testing, which allows for a more definitive diagnosis because it allows them to be differentiated from each other based on which gene is mutated in each condition. The following is a list of conditions commonly confused/misdiagnosed for SCS, some of their symptoms, and which mutated gene each contains:

The diagnosis of Jackson–Weiss syndrome is done via the following:

- Genetic testing

- Clinical presentation

The DDx for this condition includes metopic synostosis, as well as Lambdoida synostosis.

In a case of an adolescent with rear foot pain, the physical exam will reveal that the foot movement is limited. This is both because there is a physical blockade to movement and because the brain will 'turn on' the muscles around the area to stop the joint moving toward the painful 'zone'. X-rays will usually be ordered and, in general, if there is enough toughness to the tissue bridge that pain has begun – there will usually be enough bone laid down to show up in an x-ray.

More high-tech investigations such as CT scan will be required if proceeding to surgery. If the bridge appears to be mostly fibrous tissue, an MRI would be the preferred modality to use.

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 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

- neurodevelopmental delays such as ADHD (Attention Deficit Hyperactivity Disorder), ODD (Oppositional Defiant Disorder), ASD (Autism Spectrum Disorder) and CD (Conduct Disorder). Many of these delays become evident at school age.

The diagnosis of Muenke syndrome is suspected bases on abnormal skull shape and a diagnosis of coronal craniosynostosis. In 2006, Agochukwu and her colleagues concluded that “A distinct Muenke syndrome phenotype includes: uni or bilateral coronal synostosis, midface hypoplasia, broad toes, and brachydactyly.” Due to phenotypic overlap and/or mild phenotypes, clinical differentiation of this syndrome may be difficult. The suspected diagnosis is confirmed by a blood test to check for gene mutation. To establish the extent of disease in an individual diagnosed with Muenke syndrome, various evaluations are recommended.

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.

The prevention of the complications mentioned above plays an important role in the discussion about the timing of the surgery. The general consensus is now to perform surgery in late infancy, i.e. between six and twelve months. In this time frame the efficacy of surgery is enhanced due to several reasons:

- The bone is still more malleable and can be remodelled relatively 'simply' by greenstick fractures of the bone. At approximately one year of age the bone has become more mineralized and brittle and needs to be fastened to the surrounding bone with sutures or an absorbable plate.

- Reshaping of the cranial vault most commonly means excision of the bones and adjustment of the shape. Replacement of the bones can leave 'gaps' which are readily re-ossified before the age of one year, but need bony filling thereafter.

The reason why most surgeons will not intervene until after the age of six months is the greater risk that blood loss poses before this age. If possible it is preferred to wait until after three months of age when the anaesthetic risks are decreased.

Surgery is not performed in early childhood in every country. In some countries surgical intervention can take place in the late teens.

It is important that families seek out a Pediatric Craniofacial Physician who has experience with craniosynostosis for proper diagnosis, surgical care, and followup.

Radioulnar synostosis is one of the more common failures of separation of parts of the upper limb. There are two general types: one is characterized by fusion of the radius and ulna at their proximal borders and the other is fused distal to the proximal radial epiphysis. Most cases are sporadic, congenital (due to a defect in longitudinal segmentation at the 7th week of development) and less often post-traumatic, bilateral in 60%, and more common in males. Familial cases in association with autosomal dominant transmission appear to be concentrated in certain geographic regions, such as Sicily.

The condition frequently is not noted until late childhood, as function may be normal, especially in unilateral cases. Increased wrist motion may compensate for the absent forearm motion. It has been suggested that individuals whose forearms are fixed in greater amounts of pronation (over 60 degrees) face more problems with function than those with around 20 degrees of fixation. Pain is generally not a problem, unless radial head dislocation should occur.

Most examples of radioulnar synostosis are isolated (non-syndromic). Syndromes that may be accompanied by radioulnar synostosis include X chromosome polyploidy (e.g., XXXY) and other chromosome disorders (e.g., 4p- syndrome, Williams syndrome), acrofacial dysostosis, Antley–Bixler syndrome, genitopatellar syndrome, Greig cephalopolysyndactyly syndrome, hereditary multiple osteochondromas (hereditary multiple exostoses), limb-body wall complex, and Nievergelt syndrome.

Craniosynostosis (from cranio, cranium; + syn, together; + ostosis relating to bone) is a condition in which one or more of the fibrous sutures in an infant skull prematurely fuses by turning into bone (ossification). Craniosynostosis has following kinds: scaphocephaly, trigonocephaly, plagiocephaly, anterior plagiocephaly, posterior plagiocephaly, brachycephaly, oxycephaly, pansynostosis.

The goal of non-surgical treatment of tarsal coalition is to relieve the symptoms by reducing the movement of the affected joint. This might include non-steroidal anti-inflammatory drugs (NSAIDs), steroidal anti-inflammatory injection, stabilizing orthotics or immobilization via a leg cast. At times, short term immobilization followed by long term orthotic use may be sufficient to keep the area free of pain.

Surgery is very commonly required. The type and complexity of the surgery will depend on the location of the coalition. Essentially, there are two types of surgery. Wherever possible, the bar will be removed to restore normal motion between the two bones. If this is not possible, it may be necessary to fuse the affected joints together by using screws to connect them solidly. Cutting away the coalition is more likely to succeed the younger the patient. With age comes extra wear in the affected and adjacent joints that makes treatment more difficult.

Synostosis (plural: synostoses) is fusion of two bones. It can be normal in puberty, fusion of the epiphysis, or abnormal. When synostosis is abnormal it is a type of dysostosis.

Examples of synostoses include:

- craniosynostosis – an abnormal fusion of two or more cranial bones;

- radioulnar synostosis – the abnormal fusion of the radius and ulna bones of the forearm;

- tarsal coalition – a failure to separately form all seven bones of the tarsus (the hind part of the foot) resulting in an amalgamation of two bones; and

- syndactyly – the abnormal fusion of neighboring digits.

Synostosis within joints can cause ankylosis.

It is sometimes possible to correct the problem with surgery, though this has high failure rates for treatment of post-traumatic radioulnar synostosis.

To treat the trigonocephaly, expanding the distance between orbits using springs seems to work. It allows enough space for the brain to grow and it creates a normal horizontal axis of the orbits and supraorbital bar. The endoscopic surgery started to become popular since the early 90's, but it has some technical limitations (only strip cranictomy is possible). There have been few attempts to go beyond the limits.

Aesthetic outcomes of metopic surgery have been good. Surgery does not have a perfect outcome because there will most likely be minor irregularities. Sometimes reoperations are needed for the severe cases. Trying to hollow out the temporal, and the hypoterlorism are very hard to correct. The hypotelorism usually stays not corrected and in order to correct the temporal hollowing, a second operation is most likely needed.

Congenital radioulnar synostosis is rare, with approximately 350 cases reported in journals, and it typically affects both sides (bilateral) and can be associated with other skeletal problems such as hip and knee abnormalities, finger abnormalities (syndactyly or clinodactyly), or Madelung's deformity. It is sometimes part of known genetic syndromes such as triple X-Y (XXXY), Apert's, William's, or Holt-Oram. It has been reported to run in families typically following an autosomal dominant inheritance pattern which means children of an affected parent have a 50% chance of having the condition. When associated wth amegakaryocytic thrombocytopenia this inheritance has been found to be caused by mutations to the "HOXA11" gene.

The treatment of Muenke syndrome is focused on the correction of the abnormal skull shape and mirrors the treatment of coronal craniosynostosis. The abnormal growth patterns continue throughout the growing years; therefore, intervention, accurate diagnosis, and a customized, expertly carried-out treatment plan should be a primary concern. The treatment of Muenke syndrome is focused on correction of the abnormal skull shape and mirrors the treatment of non-syndromic coronal craniosynostosis. Although the timing of surgery can be highly individualized, surgical correction of the bicoronal craniosynostosis is most often done between 6 and 12 months of age. Surgery is usually performed through a scalp incision that lies concealed within the hair of the head. Your craniofacial surgeon will work in concert with a pediatric neurosurgeon in order to safely remove the bones of the skull. Then, the craniofacial surgeon reshapes and repositions those bones to give a more normal skull shape.

A dysostosis is a disorder of the development of bone, in particular affecting ossification.

Examples include craniofacial dysostosis, Klippel–Feil syndrome, and Rubinstein–Taybi syndrome.

It is one of the two categories of constitutional disorders of bone (the other being osteochondrodysplasia).

When the disorder involves the joint between two bones, the term "synostosis" is often used.

The growth retardation dates from the intrauterine period (development in the uterus.) The long-term developmental growth and outcome is not known, but the early childhood development is known, which is said to be moderately delayed. Craniosynostosis is usually rare among the X-Linked Intellectual Disability Syndromes, but when it is present, it affects the metopic structure (forehead).

Tsukuhara syndrome is an infrequently occurring skeletal dysplasia characterised by a caudal synostosis of the vertebra at birth.

Hypotelorism is a medical condition in which there is an abnormally decreased distance between two organs or bodily parts, usually pertaining to eyes (orbits), also known as orbital hypotelorism.

Cenani–Lenz syndactylism, also known as Cenani–Lenz syndrome or Cenani–syndactylism, is an autosomal recessive congenital malformation syndrome involving both upper and lower extremities.

It is often a result of fetal alcohol syndrome (FAS) caused by large alcohol intake in the first month of pregnancy.

It can be associated with trisomy 13 which is also known as Patau syndrome, as well as hereditary neuralgic amyotrophy.

It can also be associated with fragile X syndrome and Prader-Willi syndrome.

Metopic synostosis, the early closure of metopic suture during skull development in children, can also cause hypotelorism.