Acquired Chiari Type 1 Malformation Secondary to Paget’s Disease of the Bone: A Case Report

Chiari type 1 malformations are characterised by caudal descent of cerebellar tonsil into foramen magnum. Usually it is congenital. Paget’s disease causing acquired chiari type 1 malformation is rare with only five reported cases in the literature. The diagnosis is primarily by Magnetic Resonance Imaging (MRI). Authors reported a case of acquired chiari type 1 malformation due to paget’s disease in a 58-year-old male patient diagnosed by MRI and Computed Tomography (CT). The patient presented with complaints of headache, unsteady gait, slow movements with weakness in all the four limbs, difficulty in walking which aggravated since three days and stammering of speech. Initially a diagnosis of motor neuron disease was suspected and the patient was subjected for MRI examination of brain and spine. MRI revealed platybasia with cerebellar tonsillar herniation with calvarial thickening and multiple vertebral collapse. The CT of brain and spine was done to evaluate bones specifically in view of thickened cranial vault and multiple vertebral collapse on MRI which revealed features of paget’s disease in the form of widened sclerotic bone with lytic areas and thickened trabeculae. Hence, diagnosis of paget’s disease causing acquired chiari type 1 malformation was made which correlated with biochemical findings. The management is different in primary and acquired chiari type 1 malformation and hence it is important to diagnose this condition which is relatively rare.