Basilar Invagination: Causes, Symptoms & Treatment Options

Basilar invagination (BI) is a craniovertebral junction anomaly where the clivus/occiput invades the foramen magnum, compressing the brainstem and upper cervical cord. Also called basilar impression or platybasia.

Etiology

• Congenital: Chiari I, achondroplasia, osteogenesis imperfecta, Klippel-Feil, ligamentous laxity (Down, EDS).
• Acquired: Rheumatoid arthritis (pannus erosion), trauma, Paget’s, osteomalacia, tumors.

Symptoms

• Suboccipital headache, neck pain
• Brainstem: dysphagia, dysarthria, nystagmus, vertigo
• Cord: myelopathy (weakness, spasticity, sensory loss)
• Cerebellar: ataxia, dysmetria
• Autonomic: syncope, blood pressure lability

Diagnosis

• MRI (gold standard): neural compression, syrinx.
• CT: bony anatomy, Chamberlain’s line, McRae’s line, McGregor’s line measurements.
• Dynamic flexion/extension films for instability.

Treatment

• Conservative: Cervical collar, PT, pain management — for mild, stable cases.
• Surgical: Posterior occipitocervical fusion ± decompression (C1 laminectomy, transoral odontoidectomy). Indicated for progressive deficit, instability, or severe compression.

Multidisciplinary neurosurgery/orthopedics/rheumatology care optimizes outcomes.