Abstract

Background: Atlanto – occipital synostosis is a congenital condition in which the atlas the first cervical vertebra is partially or completely fused with the occipital bone.  The condition is also known by other names such as occipitalisation of atlas. Occipito - cervical synostosis, Atlanto- occipital fusion to name a few.  The terminology assimilation of atlas, refers to the complete fusion of the first cervical vertebra to the occipital bone.  It is a rare congenital anomaly with the incidence ranging from 0.14 - 0.75%.  The predilection of the condition is equal for both the sexes.  The condition is of clinical importance because of the compression of the neurovascular structure found along the upper margin of the atlas vertebra thus producing neurovascular deficits which usually produces symptom during the second decade of life.  Iatrogenic atlanto- occipital fusion has been tried as a mode of treatment for the management of atlanto- occipital osteoarthritis.  Hence, the present study aims to throw light on the importance of the incidence, symptomatology, clinical features and embryological basis of the condition.

Materials and Methods: Three hundred and fifty skulls were examined in the Institute of Anatomy, Madurai Medical College, Madurai.  Out of which 3 skulls showed partial occipitalisation of atlas.  The various dimensions were measured using digital vernier caliper.

Results: Three skulls showed partial occipitalisation of atlas, thus showing an incidence of 0.85%

Conclusion: Occipito- cervical fusion has a varied presentation ranging from asymptomatic features, neurovascular deficits to sudden death.  Hence the knowledge of the condition is important in the treatment of patients.

Keywords: Atlanto - occipital synostosis, atlanloaxial joint, osteoarthritis, sclerotome, neurovascular deficit, cervical myelopathy.