Clinical Findings

Endoscopic Versus Open

Endoscopic craniectomy with a sagittal strip removal and biparietal anterior and posterior wedges followed by helmet therapy has proven to be very effective in this patient population when treated early (<6 months). The advantages of endoscopic minimally invasive treatment are decreased operating room (OR) time, hospital stay, decreased cost, decreased blood loss and transfusion rates, and a decreased reoperation rate. ^{, ,}

Cranial vault remodeling surgery is also effective for the treatment of sagittal synostosis; however, the disadvantages include increased length of hospital stay, increased blood loss and transfusion rates, increased OR time, and a later surgery date which permits the deformity and effects on the developing brain to persist for a longer period of time prior to operation. ^{, ,}

Both endoscopic and open groups have comparable aesthetic outcomes and both groups demonstrate equal regression at 3 years postoperatively.

Required Facial Surgeries

The frontal bossing which characterizes this deformity is usually corrected by the original cranial surgery. Additionally, the frontonasal angle tends to self-correct following the original cranial surgery, whether endoscopic or open.

As the child develops, they should continue to be monitored by the craniofacial team on a yearly basis. The facial deformities are generally mild; however, augmentation of the bitemporal areas may be desirable and this can be effectively accomplished with either cranial implants or bone cement. Awaiting near completion of cranial growth is recommended, i.e., after 5 years of age.

Cranial Findings

Trigonocephaly with posterior biparietal and bitemporal widening and anterior bitemporal narrowing. The anterior fossa is typically narrowed and shortened with a pseudoencephalocele-type formation resulting in frontal lobe growth restriction.

Facial Findings

Facial findings include: superolateral retraction of the bilateral superior orbital rim and brow, bitemporal narrowing/hallowing appearance, frontal metopic ridging, hypotelorism with or without presence of epicanthal folds, decreased width of choanae and nasal piriform aperture, and the ears are commonly prominent and overprojected. Little to no change of lower facial third is noted ( Fig. 2.3A–E ).

Intracranial Pressure Findings

Increased ICP is present in approximately 8% to 33% of metopic synostosis patients. ^{, , ,} The severity of the phenotype is not necessarily indicative of the severity of the pathology (raised ICP or associated developmental delays). Even in mild cases of nonsyndromic metopic synostosis, if clinical symptoms were also present, an increase in ICP was found in 91% of the patients tested.

Developmental Findings

Metopic suture synostosis is linked with a high percentage of neurodevelopmental delays at 57%. ^, Even mild metopic synostosis is known to be associated with language delay (most common in metopic synostosis), hyperactivity, autistic tendencies, self-mutilation, motor delay, panic, and irritability. Though debated, it has been demonstrated that even late repair will aid in ameliorating these symptoms; however, it has also been shown that earlier correction results in greater developmental recovery of the patient with very little recovery after the age of 8 years. ^, Generally, developmental delays in the mild metopic subgroup are not seen until after the first year of life.

Radiological Findings

Full fusion will go from nasion to bregma and typically causes hypotelorism and lateral superior orbital rim retraction ( Fig. 2.4A ). Typically, an endocranial ridge may be seen both in normally and prematurely fusing metopic sutures, whereas an endocranial notch is generally only seen in abnormally fusing metopic synostoses ( Fig. 2.4B ). When compared with control groups, there is a significant decrease in the intercoronal distance (ICD; distance between the outer surfaces of the coronal sutures), and the cephalic width (CW)/ICD ratio was indicative of which patients received surgery ( Fig. 2.4C ). A ratio of 1.25 was the average that received surgical treatment, whereas 1.19 was the average in the normal population and the observational cohort. In the more severe patients, interdacryon and inter-zygomaticofrontal suture distance are decreased when compared with controls, though this is not true for the mild and moderate group. The endocranial bifrontal angle has been shown to differentiate moderate trigonocephaly patients from the control group ( Fig. 2.4D ).

Endoscopic Versus Open

Open repair for metopic suture synostosis is generally performed between 6 and 12 months of age with the use of a fronto-orbital bandeau and anterior cranial vault remodeling. The older the patient the more stable the repair. Unfortunately, delaying may have untoward developmental affects and may also contribute to the persistence of orbital hypotelorism. However, satisfactory results with only slight residual deformities of the forehead and bitemporal hollowing being noted are possible. Residual hypotelorism is common. ^,

Endoscopic correction has the advantage of being able to be performed at a much younger age. Early treatment aids in near complete correction of orbital hypotelorism (93%), as well as providing earlier relief to a restricted brain. ^, Additionally, the endoscopic approach advantages include: decreased OR time, hospital stay, cost, blood loss and transfusion rate, and a decreased reoperation rate. ^,

Required Facial Surgeries

As the child develops, they should continue to be monitored by the craniofacial team on a yearly basis. The facial deformities are generally mild; however, augmentation of the lateral orbital region and bitemporal areas may be desirable and this can be effectively accomplished with either cranial implants or bone cement. Awaiting near completion of cranial growth is recommended, i.e., after 5 years of age. Cranial implants are preferable due to their lower infection rate, more reliable outcomes, and the ability to plan and fabricate virtually.

The persistent hypotelorism deformity seen in many of these patients is generally mild and late correction is not generally justified.

Cranial Findings

The cranial deformity that results from UCS includes: unilateral flattening of the frontal bone and elevation of the superior orbital ridge, roof, and sidewall ( Fig. 2.5A–E ). This results in orbital enlargement and retraction of the entire orbital frame on the affected side, contralateral bossing, and advancement of orbital roof on the unaffected side. The petrous portion may present with anterior displacement. Similarly the external acoustic meatus and glenoid fossa on the affected side are anteriorly displaced.

Facial Findings

Grossly, the deformity is characterized by ipsilateral forehead retraction and flaring superiorly, laterally, and posteriorly (harlequin eye deformity) ( Fig. 2.5A ). The root of the nose is deviated toward the affected side and the nasal tip is directed toward the unaffected side, as is the nasal septum. ^, Frontal bossing is noted on the contralateral side. The maxilla (though it appears projected anteriorly on the affected side) is actually hypoplastic. The projected appearance is secondary to the facial twisting or yaw of the maxilla ( Fig. 2.5E ). Orbital dystopia is present in 97% of presenting patients. Strabismus, astigmatism, and amblyopia are very common, affecting the majority of patients secondary to the orbital deformity. ^, On the affected side, the palpebral fissure is widened and the ear is often displaced anteriorly. There is generalized mandibular hypoplasia on the affected side, with an exception being vertical lengthening of the affected side ramus ( Fig. 2.5B ). This generalized mandibular hypoplasia is greater than the anterior displacement of the affected side glenoid fossa, generally resulting in slight deviation of the inferior border of the mandible toward the affected side. Interestingly, the mandibular chin point commonly appears deviated toward the unaffected side.

Intracranial Pressure Findings

Elevations of ICP may be present even in mild forms of unicoronal synostosis (up to 53%–71%). Therefore, surgery is recommended in this patient population not only to halt the progression of the cosmetic deformity but also the devastating effects of raised intracranial pressure on a developing brain. ^,

Developmental Findings

UCS has been shown to manifest with delays in speech, learning, intelligence, and behavior in 52% to 61% of children affected. Interestingly, it is also thought that the type of delay is dependent on whether there is left- or right-sided UCS present. Left-sided UCS is thought to be more likely associated with language-based learning disorders, and right-sided with nonverbal learning disorders. ^,

Radiological Findings

Understanding the radiological findings consistent with UCS is critical in understanding the resulting deformities. Typically, fusion of the unilateral coronal (frontoparietal) suture begins in the central portion of the suture. With time, this leads to narrowing and near obliteration of the sphenosquamosal, sphenofrontal, and sphenoethmoidal sutures ( Fig. 2.1A , B). As the fusion of the coronal suture proceeds, the sphenofrontal suture becomes progressively narrowed and may become fused as well. The sphenofrontal suture was patent in 100% of patients younger than 3 months, in 43% of those between 3 and 5 months, and 0% of patients after 5 months. ^{, ,}

Narrowing/fusion of the sphenoparietal, sphenofrontal, and sphenofrontal sutures leads to shortening of the anterior and middle cranial fossae, which results in the anterior displacement of the glenoid fossa. This anterior displacement of the seat of the mandibular condyle pushes the mandible forward on the affected side, generally leading to chin point deviation toward the unaffected side. The maxilla responds and will grow to the mandible, resulting in an increase in vertical growth of the maxilla on the affected side and an occlusal cant which is inferiorly displaced on the affected side ( Fig. 2.6A ).

Coronal synostosis results in malformation of the orbit with associated ocular findings such as hypertropia, strabismus, malfunctioning, and/or abnormal orbital muscular attachment.

On axial slices, the anterior displacement of the glenoid fossa on the affected side is noted. Also visible is the illusion of anterior projection of the zygomaticomaxillary complex on the affected side secondary to the facial twist; however, in reality this area is hypoplastic ( Fig. 2.6B ).

Three-dimensional (3D) reconstruction of the facial skeleton assists in appreciating the deformity and twisting of the craniomaxillofacial complex. The persistent superolateral orbital deformity, despite correction as an infant, is commonly present ( Fig. 2.6A ). Nasal root deviation toward the affected side with twisting of the piriform aperture toward the unaffected side results in soft tissue nasal tip deviation toward the unaffected side. There is deviation of the vomer toward the affected side, with a decrease in the volume and size of the ethmoid air cells and bone as compared with the unaffected side. Contralateral compensation is also noted in the frontal bone, ethmoids, orbit, and maxilla.

Vertical lengthening of the maxilla on the affected side is likely exacerbated by the ipsilateral lengthening of the mandibular ramus. There is anterior displacement of the condyle on the affected side, with ramus lengthening and chin point deviation generally toward the unaffected side. This results in the affected-side downward occlusal cant which is seen in this patient population ( Fig. 2.6A ).

Endoscopic Versus Open

Timing is critical in ameliorating the ocular deformity associated with coronal synostosis. Anatomical evidence indicates near obliteration of associated cranial base sutures (“coronal ring” sutures) by 5 months of age. ^{, ,} This is consistent with surgical findings which have demonstrated that the orbitocranial deformity is likely permanently set by 9 months of age.

Early intervention before 8 months of age has been shown to decrease the progression and incidence of at least the orbital and visual issues that are present with a UCS. ^{, ,} Overall facial asymmetry is present even in infancy 33% of the time. The longer the synostosis remains present without correction, the more likely a significant facial deformity will occur that requires additional operations.

The stability of open procedures for UCS depends on the quality and strength of the bone present—greater relapse has been shown to occur when operating on younger patients. ^{, ,} Therefore, the ideal time to operate for open procedures is usually between 8 and 12 months of age. Unfortunately, this leads to a progression of the underlying pathology resulting in permanent facial deformities. The literature demonstrates that fronto-orbital advancement (FOA) does not reduce rates of amblyopia, astigmatism, or strabismus and the surgical procedure itself can lead to iatrogenic strabismus. Furthermore, relapse is common with the frontal bar and persistence/propagation of the facial deformities upon long-term follow-up is up to 46% to 90%. ^{, ,}

A study that reviewed 81 cases of nonsyndromic unicoronal synostosis reported the overall defect/relapse rate in patients following an FOA surgery to be 73%, with a total reoperation rate of 20%. Of note, 17% of the patients did not follow-up for more than 1 year—mean time to identification of relapse was 49.8 months—so if these patients are removed, then there was a relapse rate requiring surgery of 24%. Also, this study only looked at relapse of the supraorbital bar, forehead, and temporal hollowing and did not take into account resulting surgeries for mid and lower facial deformities that develop secondary to the synostosis.

Similarly, Machado and Hoffman looked at a series of 39 nonsyndromic UCS patients. Seven of the patients were operated on before the age of 1 month and nine after 1 year. They had a reoperation rate of 19% and noted that the only patients with poor results were operated on before 6 months of age. They also noted that in this group of patients with observed nasal deviation, 44% self-corrected following surgery. Additionally, they noted that 16% of their patients who had questionable immediate postoperative results improved over time, which they surmised was secondary to brain growth.

Owall et al. looked at 22 children with UCS with an approximately 7-year follow-up and noted severe facial asymmetries in 90% of patients who were significantly asymmetric when compared with controls. The areas most pronounced included the frontal bone and malar area; however, all areas of the face were affected including eyes, nose, mouth, and chin and were characterized by deformities seen in untreated individuals.

Types I and IIA will often need no additional surgery following initial correction as an infant; however, types IIB and III often have unsatisfactory long-term results and will need additional cranioplasty and likely facial surgery to correct the deformities present when the patient reaches skeletal maturity. Despite correction as an infant, the deformity of the cranial and maxillomandibular complex may persist and worsen as the child matures into adulthood ^, ( Fig. 2.6A–K ).

Endoscopic treatment has demonstrated advancement of the frontal deformity with near complete normalization of the frontal asymmetries present at 36 months following surgery. Additionally, follow-up lateral radiographs demonstrate increasing advancement postoperatively that is similar or greater than what is achievable with an open FOA (30 mm) ( Fig. 2.7 ).

In a large series reviewing unicoronal synostosis, 115 patients were treated using minimally invasive endoscopic craniectomy with postoperative helmet therapy. This study demonstrated 51% of patients obtained 100% correction of orbital dystopia. Overall, 65% of the studies patients achieved greater than 80% correction. The lowest amount of correction achieved was 38%, and all patients with less than 50% correction were older than 8 months of age. ^, Additionally, only 4% of patients needed corrective ocular muscle surgery to correct residual strabismus. The ability to intervene early using endoscopic strip craniectomy with helmet therapy and its positive results in decreasing the orbital, visual, and nasal deformities ^{, , ,} has provided hope that it may also ameliorate the other facial deformities noted with unicoronal synostosis.

Minimally invasive endoscopic craniectomies with subsequent helmet therapy have demonstrated a low incidence of reoperation when compared with open procedures. ^, In a 2020 study looking at 500 minimally invasive endoscopic surgeries for craniosynostosis, only a 2.8% reoperation rate was noted. When separated into syndromic versus nonsyndromic, the rate of reoperation was 1.2% and 29%, respectively. Of these only 0.6% required reoperation secondary to an unfavorable cosmetic deformity. Of this 0.6%, all were noted preoperatively to have multisuture synostosis with a severe cosmetic deformity. Additionally, the endoscopic approach advantages include: decreased OR time, hospital stay, cost, blood loss and transfusion rate, and a decreased reoperation rate. ^{, ,}

Cranial findings

Turribrachycephaly (towering forehead and anteroposterior cranial shortening) are the most characteristic cranial findings associated with bicoronal synostosis. Additionally, profound widening of the bitemporal and biparietal regions is observed.

Facial findings

Exorbitism with significant retrusion of the supraorbital bar is seen due to the inability of the anterior cranial vault to advance and descend. Mild hypertelorism is present due to the compensation of the metopic and pterional fontanels. The entire midface is shortened resulting in a superiorly displaced midface with a short nose and anteverted nares. The face is symmetric secondary to the symmetric nature of the deformity.

Midface hypoplasia is common in NSBCS but not facial stenosis as seen in many of the SBCS.

Intracranial Pressure Findings

An increase in ICP is common in NSBCS but not nearly as common as in patients with SBCS.

Additionally, hydrocephalus resulting in the need for surgery, though present in approximately 17.3 % of SBCS, only occurs in 3.3% of NSBCS.

Developmental Findings

Fifty-five percent of children with NSBCS present with associated developmental delays.

Radiological Findings

NSBCS presents with turribrachycephaly, flattening and elongation of the frontal bone, shortening of the anterior cranial fossa, asymmetric bone deposition along the squamosal sutures, an increase in bitemporal width, and retrusion of the supraorbital bar ( Fig. 2.8E ).

Endoscopic Versus Open

Surgical repair is often unsatisfactory in this patient population. Bastidas et al. reviewed their use of an open technique with FOA for a 20-year period and noted an 80% revision rate when followed for at least 10 years. Additionally, 29% required surgery for strabismus.

Endoscopic treatment has demonstrated hopeful results for this patient population. In a series with an average 61 months of follow-up, 38 nonsyndromic bicoronal patients were treated endoscopically with postoperative helmet therapy. A reduction in brachycephaly by 26% was observed, resulting in a decrease in bitemporal width. Orbital normalization with correction of the downturned palpebral fissures and mild hypertelorism was noted. No patients in this series required additional cranial surgery.

Correction of Facial Deformities

Thankfully facial deformities associated with NSBCS are much less severe when compared with SBCS. Very few of these patients will require a midface advancement as compared with SBCS, where the majority of patients require midface advancement. The most common facial surgery performed is implants and bone cement to aid in contour of the remaining forehead deformities, often secondary to their initial open cranial surgery.