Atlantoaxial instability (AAI) refers to excessive movement between the atlas (C1) and axis (C2) vertebrae, leading to potential spinal cord compression. It can be congenital (e.g., Down syndrome, skeletal dysplasias) or acquired due to trauma, inflammatory conditions (rheumatoid arthritis), infections (Grisel’s syndrome), or tumors. Patients may present with neck pain, restricted neck movement, headaches, neurological deficits (weakness, numbness), or signs of spinal cord compression like gait disturbances and bowel/bladder dysfunction in severe cases. Diagnosis is confirmed through X-rays (dynamic flexion-extension views), CT scans, and MRI to assess instability and spinal cord involvement. Treatment depends on severity; mild cases may require cervical immobilization with a collar, while severe cases with neurological symptoms need surgical stabilization (e.g., C1-C2 fusion).