Craniofacial microsomia (CFM) is a heterogeneous disorder, causing a wide variety of facial malformations ranging in severity . After cleft lip and palate, CFM is the most common congenital craniofacial disorder, with an incidence of 1:3000 to 1:5000 live-births . The craniofacial anomalies found in CFM are believed to be related to the first and second branchial arches . In CFM, the mandible, zygoma, external and middle ear, facial musculature, facial nerve, and soft tissues can be affected. Although ear deformities are part of CFM, isolated microtia is generally not regarded as CFM . However, it is still discussed whether isolated microtia might be a minor form of CFM .

CFM is primarily known for its craniofacial malformations, but extracranial manifestations, such as vertebral, renal, heart, central nervous system, lung, and gastrointestinal defects may also occur . Goldenhar reported what he believed to be a specific variant of CFM; these patients have the clinical features of CFM in combination with epibulbar dermoids and vertebral anomalies . However, Vento and colleagues documented no association between these anomalies and refuted the existence of this variant . More recently Tuin et al. attempted to differentiate Goldenhar syndrome from CFM and concluded that the term Goldenhar syndrome was inconsequential . The most frequently seen vertebral anomalies in patients with CFM are hemivertebrae, fusion of the vertebrae, scoliosis, accessory vertebrae, occipitalization of the atlas, and spina bifida .

Several terms are used for CFM, such as oculo-auriculo-vertebral spectrum, hemifacial microsomia, lateral facial dysplasia, and first and second branchial arch syndrome. Presumably, these conditions are part of the CFM spectrum . In this article, the deformity is referred to as craniofacial microsomia (CFM), as this is currently the term most often used in the literature.

The exact origin of CFM is unknown. The most widely accepted theory is that CFM is the result of a disturbance in the embryological development of the first and second branchial arches during the first 6 weeks of gestation . During these first 6 weeks of embryological development, both the skull and spine are formed . Therefore, a common pathogenic mechanism is likely to be the basis of both craniofacial and vertebral malformations in patients with CFM.

Although the precise link between the facial and vertebral malformations has not been clarified, the deficiency presumably occurs during vertebral somite formation, resulting in incorrect formation of the vertebrae and the skull . This may lead to congenital scoliosis or instability of the cervical spine . Instability of the cervical spine may also be the result of abnormal development of the ligamentous structures and could cause compression of the spinal cord during movement . The clinical presentation of vertebral instability is largely variable and may or may not be associated with signs or symptoms . Symptoms of cervical spine instability include neck pain, torticollis, and limited neck movement, and neurological symptoms may occur if there is compression of the spinal column or vertebral artery . The cerebellum and cranial nerves can be involved, which may lead to a wide range of neurological symptoms, including ataxia, coordination disturbances, and diplopia . Basilar impression, which is associated with cervicovertebral anomalies, can cause similar symptoms . Excessive cervical spine manipulation, which may be induced by sports activities, may result in spinal cord impingement in patients with unrecognized cervical instability . Besides the possible neurological effects, fusion or underdevelopment of the vertebrae could also result in fractures of the ankylosed segments or in progressive scoliosis . It is important to keep these, often asymptomatic, vertebral anomalies in mind when performing surgery, as cervical spine instability can put these patients at risk of spinal cord injury during intubation or surgical manipulation .

Since vertebral anomalies occur in CFM patients and may cause serious complications, it is important that clinicians are aware of the possible anomalies and their consequences. The aim of this systematic review was to study the available literature on vertebral anomalies and their respective prevalence rates in patients with CFM.