A case of spinal arterio-venous malformation (AVM) initially diagnosed as unilateral cerebral palsy (CP) is reported. The presentation was of a long-standing spastic monoparesis of the left leg, with initial response to Botulinum toxin injections to the calf and tibialis posterior muscles. This was followed by progressive deterioration occurring over a 3-month period before further investigation and definitive diagnosis at 7 years. Imaging demonstrated a large extra-medullary spinal AVM compressing the mid-thoracic cord. This was successfully managed by embolisation with a non-adhesive polymer: ethylene-vinyl alcohol copolymer injected into the dominant feeding vessel. This case highlights the need to consider alternative diagnoses when a child with a diagnosis of CP presents with atypical clinical features such as monoparesis and has worsening or altered clinical signs. Moreover, a normal magnetic resonance imaging brain scan and the absence of ipsilateral upper limb neurological signs or functional impairment should raise suspicion even in the context of static lower limb signs. A literature review was performed on the management of spinal AVM in children and this will be is discussed.