> premature cranial suture(s) fusion followed by growth parallel (rather than perpendicular) to the suture (Virchow's law), seen in 1:2500 live births^[Knoll B, Persing J. Craniosynostosis. In: Bentz ML, Bauer BS, Zuker RM, eds. _Principles and Practice of Pediatric Plastic Surgery_. 2nd edition. Thieme; 2016.] ## Normal Skull Development → Ref [[Head and Neck Embryology#Cranium]] ## Etiology - Most common: 2/3 nonsyndromic - 1/5 are from the following syndromes: ▶ Mutations in FGFR2 (32%) ▶ FGFR3 (25%) ▶ TWIST1 (19%) ▶ Chromosomal abnormalities (15%) ▶ EFNB1 (7%) - coronal craniosynotosis has the highest likelihood of being linked to a mutation - 1/10 are other syndromes #### Pathophysiology - Cranial base - Synostoses result from abnormal tension exerted by cranial base through the dura - Theory does not account for isolated synostoses - Intrinsic suture biology - Synostoses result from the osteoinductive properties of dura mater, which contains osteoblast-like cells - Extrinsic factors - Synostoses result from extrinsic forces or systemic disease - In utero compression or ischemic event - Hydrocephalus decompression - Abnormal brain growth (e.g., microcephaly) - Systemic pathology (e.g., hypothyroidism or rickets) ### Diagnosis 1. Exam with abnormal cranial morphology 1. No expected movement in young infants 2. palpable ridge from synostosis 2. CT - often used for unclear cases, and for op planning ### Indications for treatment ^[Derderian C, Seaward J. Syndromic craniosynostosis. _Semin Plast Surg_. 2012;26(2):64-75. doi:[10.1055/s-0032-1320064](https://doi.org/10.1055/s-0032-1320064)] - ↗ [[Intracranial pressure (ICP)]] - cephalocranial disproportion - intracranial venous congestion - hydrocephalus - upper airway obstruction - more common w/ more suture synotoses^[Renier D, Sainte-Rose C, Marchac D, Hirsch JF. Intracranial pressure in craniostenosis. _J Neurosurg_. 1982;57(3):370-377. doi:[10.3171/jns.1982.57.3.0370](https://doi.org/10.3171/jns.1982.57.3.0370)] --- which also **↗ insidious mental impairment** - secondary Chiari I malformation - restoring head shape for smoother socialization ### Classification ![[Pasted image 20250120171325.png | 500]] #### → Nonsyndromic: ##### Sagittal synostosis (~1/2 of craniosynostosis) - Morph: Scaphocephaly ("boat shaped") + frontal bossing and occipital coning - Note: M:F 4:1 ##### Metopic synostosis (~1/4) - Morph: trigonocephaly ("triangular") - Note: ~10% has ↗ ICP ##### Unilateral coronal synostosis (~1/7) - Morph: anterior plagiocephaly (ipsilateral frontal and occipital-parietal flattening + contralateral frontal bossing + ipsilateral temporal convexity) - Ipsilateral harlequin deformity ##### Bilateral coronal synostosis (~1/15) - Morph: brachycephaly (broad flat forehead with recession of the supraorbital ridge) - → if untreated, lead to **turricephaly** (excessive skull height and vertical forehead) ##### Lambdoid synostosis (~1/35) - Morph: posterior plagiocephaly (ipsilateral occipital flattening and mastoid bulge) ##### Pansynostosis - Morph: Oxycephaly (pointed head + forehead retroverted and tilted back) ##### Kleeblattschadel (All sutures except squamous sutures) - Morph: cloverleaf deformity #### → Syndromic: - Crouzon’s syndrome (Autosomal dominant; FGFR2) - Normal extremities - Apert syndrome - Complex severe syndactyly, acne, common mental impairment - Pfeiffer syndrome (Autosomal dominant: FGFR2 or FGFR1) - Broad thumbs/halluces, usually no mental impairment - Saethre-Chotzen syndrome (Autosomal dominant, variable expression; TWIST-1) - Low hairline and eyelid ptosis, prominent crus helices - Muenke syndrome (Autosomal dominant; pro250Arg mutation in FGFR3) - Common cause of unicoronal and bicoronal craniosynostoses with high reoperation rate; family history common #### → Not synostosis (deform from unbalanced forces): ##### Plagiocephaly (1/300 in the general population) Morph: parallelogram - ipsilateral occipital flattening + frontal bossing - ipsilateral ear displaced anteriorly - **often mistaken for coronal or lambdoidal plagiocephaly** Etio: supine positioning or unequal rotational forces (torticollis, visual field def, vertebral abnormalities) ![[Pasted image 20250127125216.png| 500]] ## Surgical Treatment - In contrast to nonsyndromic, single-suture synostosis, syndromic patients see higher risk of ↗ ICP and will likely require multiple operations - Surgery earlier than 12 mo benefits from more malleable bones with less maladaptive growth and better healing, though synostosis recurrence is also higher ### Syndromic techniques ##### - Posterior vault expansion with distraction osteogenesis ^[Derderian CA, Bastidas N, Bartlett SP. Posterior cranial vault expansion using distraction osteogenesis. _Childs Nerv Syst_. 2012;28(9):1551-1556. doi:[10.1007/s00381-012-1802-0](https://doi.org/10.1007/s00381-012-1802-0)] - Target: severe turricephaly and occipital flattening - Comparison: Greater change per millimeter of advancement than anterior vault remodeling - Cons: Single-stage procedures historically complicated by problems with healing and propensity to relapse from weight of head on construct. Outcomes improved with resorbable plate systems - Pros: - Maintains vascularity of bone flap - Provides new, vascularized bone - Limits dead space - Expands soft tissue envelope - Greater intracranial volume gain than single-stage procedures - Improvement in cerebellar anatomy - Decreased operative time - Still need fronto-orbital advancement for correction of retrusive brow, but can be delayed to a later age - Cons: - Need for second procedure to remove device - Potential device complications - Longer treatment time - **Technique**: 1. In prone position for posterior cranial vault exposure; coronal incision; posterior craniotomy performed with maintenance of dural attachments; barrel staves with out-fracture on inferior occipital segment 2. Place 2 distraction devices in parasagittal, collinear positions with uniform parallel vectors dictated by skull shape---distracter arms exit anterior scalp 3. Start distraction 72 hours postoperatively, 1 mm/day with range of 20-35 mm 1. Before removal, place patient in a consolidation phase for ~8 weeks 5. Obtain weekly XRay, then Head CT after removal of devices ##### Fronto-orbital advancement (FOA) - (I need to read up on this) - **Technique**: 1. Coronal incision, frontal craniotomy, removal of frontal bone, bandeau harvested and shaped 2. Advance the bandeau, which is secured with cranial bone graft and resorbable plates or sutures → Later in childhood, patient will likely need facial and orthognathic surgery ### Nonsyndromic techniques #### Scaphocephaly ##### Extended strip craniectomy with helmet - Target: isolated sagittal synostoses **<4 months of age** - Endoscopic approach minimizes scalp incision, blood loss, operative time, recovery^[Barone CM, Jimenez DF. Endoscopic craniectomy for early correction of craniosynostosis. _Plast Reconstr Surg_. 1999;104(7):1965-1973; discussion 1974-1975. doi:[10.1097/00006534-199912000-00003](https://doi.org/10.1097/00006534-199912000-00003)] - Wedge ostectomies made adjacent to coronal and lambdoid sutures allow for transverse expansion - Helmet molding applied postoperatively for up to 18 months ##### Spring-assisted cranioplasty - Target: sagittal synostosis (or those w/ symmetrical patterns) - Mech: Uses continuous spring force across an osteotomy, strip craniectomy, or patent suture - Cons: Requires brief, second procedure for device removal; little control of expansion rate/distance and opposing forces ##### Open cranial vault reconstruction - Clamshell: In children less than 1 year old, clamshell craniotomy with interleaving barrel-stave osteotomies may be used #### Other less common morphologies - **Plagiocephaly** and **brachycephaly**: Bifrontal craniotomy, FOA repositioning frontal bar, recontouring frontal bone, barrel staves - **Trigonocephaly**: Overcorrection of frontal dysmorphology and bitemporal constriction with bifrontal craniotomy, frontal reshaping, and expansion of supraorbital bar and frontal bone flaps with interpositional bone graft, wedge osteotomies, and bone grafting - **Lambdoid craniosynostosis**: Biparieto-occipital craniotomies, occipital switch, and contouring #Neurological #Plastics #clinicalscience #technique