ACR Codes: 1.1
The Chiari I malformation is defined as inferior location/displacement of the cerebellar tonsils. Although mild cerebellar tonsillar ectopia appears to be of no clinical significance, tonsillar ectopia of greater than 5 mm is frequently associated with clinical symptoms. Patients with Chiari I malformations tend to present either with signs and symptoms of brain stem compression, exertional headaches, atypical facial pain, or signs and symptoms of syringohydromyelia. Symptoms of syringohydromyelia include segmental weakness and atrophy of the hands and arms with loss of tendon reflexes. Classically, patients have loss of pain and temperature sensation with preservation of sense of touch over the neck, shoulders, and arms. Films .2 - .4 demonstrate a patient with a Chiari I malformation and syringohydromyelia. The tonsils are slightly low and are pointed, indicating compression. The cervical and thoracic spinal cords are dilated, and a multiseptated syrinx is present within them. The syrinxes are most common near the cervical-thoracic junction but can extend anywhere in the cord from the craniocervical junction to the conus. The extension of the syrinx into the brain stem is a condition known as syringobulbia.