Type 1 Chiari malformation is the protrusion of the cerebellar tonsils (at the base of the brain) into the spinal canal. This results in crowding of the foramen magnum and obstruction of the normal flow of cerebrospinal fluid from the brain into the spinal canal. As a result, cysts form in the spinal cord called syringomyelia (or syrinx) in about 50% of patients.
Most cases of Chiari malformation are congenital and are asymptomatic until later in life. Average age of presentation is 45 years. A variety of symptoms occur including headache and neck pain. Numbness, weakness, and pain can affect the arms, legs, or trunk. The patient can have unsteadiness, double vision, trouble talking, ringing in the ears, or trouble swallowing. Syringomyelia can cause significant damage to the spinal cord resulting in disabling loss of spinal cord function.
Neurologic findings vary on the degree of brainstem compression and whether a syrinx is present. Findings include a “cape-like” distribution of numbness, weakness, spasticity, ataxia (problems with coordination), and dissociated sensory loss (loss of pain sensation but preservation of touch). Atrophy is an advanced finding of spinal cord injury and a poor indicator of outcome.
Magnetic resonance imaging (MRI) is the preferred study and should be a high quality cervico-brainstem junction study. MRI of the thoracic spine and contrast may be required to evaluate the extent of the syrinx and to exclude other associated pathology. The quality of MRI’s can vary between imaging centers and is usually less sharp with open MRI’s. Computed tomography (CT) with myelography can be done in special circumstances. Plain X-rays and bone scans are not useful in diagnosing Chiari malformation.
Most patients with Chiari malformation will worsen over time. There are some medications that can control symptoms but none will resolve the pathology. If the patient is asymptomatic, then observation may be indicated. Medication such as Neurontin can be tried for nerve damage, as well as other drugs for spasticity and pain. Medical therapy is best reserved for post surgical residual symptoms.
Indicated for patients who are symptomatic and/or have neurologic loss of function. Operative approach is a posterior fossa decompression with dural grafting and cervical laminectomy to resolve the crowding of the foramen magnum and upper spinal canal. In most cases, this procedure is enough, even when a syrinx is present. In my experience, when the brainstem is decompressed, the syrinx will often collapse and require no further treatment. For large unresolved syrinx, laminectomy with fenestration of the syrinx may be required, possibly with shunting.
Outcome of Surgery
The goal of surgery is to preserve neurologic function, and give the best chance for neural recovery. Improvement is most likely for symptoms of brainstem compression. Injury to the spinal cord from the syrinx is not likely to show much improvement. The syrinx may collapse after surgery and may require serial scanning and close monitoring. Recurrent symptoms from scarring are possible and may require repeat surgery, though this is generally unlikely. The overall chance of a complication is small in a healthy patient. Patients must balance the risk of surgery with the risk of further permanent injury. Surgery is usually very well tolerated. Most patients are up walking shortly after the surgery and go home the week of surgery. Long term outcome from surgery is generally excellent with very high satisfaction rates.
If you have a Chiari malformation, come see us for consultation. We take an aggressive approach to the treatment of Chiari malformation. We have extensive clinical and research experience for great outcomes with a personal touch.