Chiari malformation is a structural abnormality of the craniovertebral junction characterized by downward displacement of the cerebellar tonsils through the foramen magnum, leading to compression of the brainstem and disruption of normal cerebrospinal fluid flow. Chiari type I is the most commonly encountered form in adolescents and adults and may be asymptomatic or associated with progressive neurological dysfunction.

Clinical manifestations vary widely and depend on the degree of hindbrain herniation and associated pathology. Common symptoms include occipital or suboccipital headaches, often exacerbated by coughing or straining, neck pain, dizziness, balance disturbances, sensory abnormalities, and motor weakness. Many patients develop syringomyelia, resulting in progressive spinal cord dysfunction, pain, and weakness.

Neurosurgical evaluation requires detailed neurological assessment and high-resolution MRI of the brain and cervical spine. Imaging confirms tonsillar descent, evaluates CSF flow dynamics, and identifies associated abnormalities such as syringomyelia or craniovertebral instability. Clinical correlation is essential, as radiological findings alone do not mandate surgery.

Surgical intervention is indicated in symptomatic patients with progressive neurological deficits, syringomyelia, or significant CSF flow obstruction. The primary goal of surgery is decompression of the posterior fossa to restore normal CSF circulation and relieve neural compression.

Posterior fossa decompression involves removal of bone at the craniovertebral junction, with or without dural expansion, depending on individual anatomy. Surgical technique is tailored to achieve adequate decompression while minimizing complications. Intraoperative decision-making is critical to balance efficacy and safety.

Postoperative recovery includes neurological monitoring and imaging follow-up to assess resolution of symptoms and syrinx regression. Long-term outcomes are favorable when surgery is performed for appropriate indications.

Chiari malformation surgery requires specialized neurosurgical expertise and careful patient selection to achieve durable neurological improvement.