Persistent proatlas with additional segmentation of the craniovertebral junction - The Tsuang-Goehmann-Malformation

摘要

Case study description and analysis of a complex craniovertebral dysplasia in an 8-year-old male patient, in which conventional cervical spine radiographs demonstrated a regularly differentiated occipital base, as well as the presence of two lateral masses of the proatlas vertebra and two lateral masses of the atlas vertebra. Further assessment included computed tomography of the occipital base and the upper cervical spine as well as three-dimensional reconstruction. Malsegmentation of the fourth occipital vertebra can result in various anomalies that are known as ‘manifestation of the proatlas’. The occurrence of a persistent proatlas with additional segmentation of the craniovertebral junction represents an extremely rare dysplasia. To our knowledge, it is the second report concerning the persistence of a complete human proatlas vertebra. We consider the biomechanical and embryological particularities of this complex dysplasia to represent sufficient basis for future differentiation from other malformations of the fourth occipital vertebra. Comprehensive literature review and discussion about the entity will be provided. Keywords: persistent proatlas, additional segmentation, manifestation of proatlas, manifestation of occipital vertebra, malformation, craniovertebral junction, cervical spine, occipital vertebra, atlas vertebra, computed tomography, CT scan, plain radiographs, X-ray, Sandberg-GutmannCASE REPORTThe complex craniovertebral dysplasia of an 8-year-old boy was analysed retrospectively. The child’s parents sought advice from a specialist in pediatric orthopedics because of movement restriction of the cervical spine, occasional headaches, attention deficits, and suspect posture. Diagnostics included conventional radiography the upper cervical spine and computed tomography (CT) of the occipital base and the upper cervical spine with three-dimensional (3D) reconstruction. Clinical neuro-orthopedic evaluation revealed moderate dysdiadochokinesia in both hands. No neurological deficits were observed. Inclination was decreased for the upper cervical range of motion.Radiological evaluation showed serious malformation of the upper cervical spine with formation of 8 upper cervical spine segments (Fig. 2?2–4). A persistent proatlas (persisting bone material of the sixth somite in formation of the craniovertebral junction) with two lateral masses of the proatlas vertebra and its posterior arch was present above the actual atlas vertebra (Fig. 1?1???–6, ?,88?8?–11). Anterior arches of proatlas and atlas vertebra had been replaced by connective tissue (Fig. 2?2–4, ?,8,8, ?,11).11). The lateral masses of the atlas vertebra were normally formed, while its posterior arch was hypoplastic without compression of the medulla spinalis (Fig. 2?2–4, ?,5,5, ?,1010–11). An os odontoideum was located above the dens axis (Fig. 2,?,55,?,77,?,88). Open in a separate windowFigure 1 Eight-year-old boy with persistent proatlas and additional segmentation of the craniovertebral junction.Technique: Plain a.p. radiograph according to Sandberg-Gutmann (75 kvp, 10 mAs).Findings: Additional lateral masses of C1 (black asterisks upper row) representing a complete persistence of proatlas vertebra and the “regular” lateral masses of C1 (black asterisks lower row).