# Analysis of Craniocervical Abnormalities in Osteogenesis Imperfecta during Growth
## 1 Introduction  
The craniocervical or cranioc vertebral junction (CCJ) is a complex transition between the skull and the cervical spine involving two essential neurological structures, which are the brain and the spinal cord; it is formed by the occipital bone and the first two cervical vertebrae [1, 2]. Osteogenesis Imperfecta (OI) is a genetic disease characterized by a reduction in bone mass with associated fragility. This bone alteration also affects the CCJ, which is one of the most important complications of OI. It is of special relevance since, in addition to the high prevalence of up to 37% in basilar anomalies in these patients as described in the literature, such deformations of the skull base can compress the brain stem with potentially severe neurological consequences, and they may even become lethal [3]. There are three common anomalies as follows: basilar invagination (protrusion of the odontoid process into the foramen magnum), basilar impression (position of the odontoid process above the caudal borders of the skull without penetrating the foramen magnum), and platybasia, which is defined as the flattening of the skull base [4]. Basilar invagination can be a solitary finding resulting from a number of developmental anomalies, or it can be associated with a more complex developmental process such as Chiari malformation. In the case of basilar impression, the malposition of the odontoid process is secondary to traumatic changes or bone softening in diseases such as OI among others [5]. Platybasia may be associated with basilar impression and basilar invagination. Platybasia alone does not usually cause symptoms unless it is associated with basilar invagination [6]. However, there are few studies in the literature on parallel measurements of structures in voluntary controls [7]. Although data on normal CCJ dimensions and changesin the growth of healthy children are a prerequisite for accurate diagnosis and a better understanding of the development of basilar anomalies, these are scarce. Knowledge of the normal variation in anatomical relationships and the effect of growth at the CCJ is crucial for the diagnosis of pathological conditions in this area. Basilar invagination and basilar impression may originate from skeletal alterations during infancy [3]. In fact, there is evidence that adolescence is the period when there may be progression of basilar impression in children susceptible to CCJ abnormalities, and early intervention may prevent the progressive progression of this anomaly leading to mortality [1]. Basilar impression is considered a frequent complication of OI although the number of cases published up to the 1980s was low [8] possibly because many were asymptomatic. Since the 1980s and 1990s, the neurological complications of OI in the form of basilar impression/invagination and their consequences have been recognized through a higher number of publications. Some of them report symptomatic cases with different neurological manifestations and their complications [9; 10; 11; 12; 13; 14]. Others reflect and emphasize their progressiveness to the point that they become another cause of lethality of the disease itself [8; 15; 16; 17; 18]. Some symptomatic cases presented very early on without any indication of such progressiveness may have also been reported [19]. Many of these cases justify the need for the early detection of such anomalies in order to avoid serious neurological consequences requiring neurosurgical interventions, which do not always limit progression in the affected group [20; 21; 22]. The most recent studies reflect a higher number of affected cases. [PERSON] and [PERSON] [23] in 1997 reported the presence of basilar invagination in the 18 patients included in their study based on a classic radiological diagnosis enhanced with computed tomography (CT) and magnetic resonance imaging (MRI). One year later, [PERSON] et al. [24] confirmed basilar impression in 19% of the children studied (8/42) by radiography and MRI. [PERSON] et al.