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Arnold-Chiari Malformation


This is an area of particular interest for Neurosurgical Consultants with our experience encompassing over 200 successfully treated patients with this condition.

We now have experience with over 200 of these procedures with follow up ranging to 30 years. The operation that has been effective in our patients over these many years involves a Suboccipital Craniectomy (surgical opening of the bony compartment of the back of the head) to decompress the cerebellar tonsils with laminectomy of C1 and/or C2 (removal of the roof of the first two cervical vertebrae) to decompress the cervical spinal cord.

Introduction

This is a congenital anomaly of the cerebellum and brainstem. Although four types have been described, types I and II are more common. Type I is identified by excessive protrusion of cerebellar tonsils (the cerebellum is the balance and coordination center of the brain) through the foramen magnum (the passage way between the skull and the spinal canal through which the spinal cord travels to join the brainstem), down to the C1 or C2 level of the cervical spine. With the herniation of the Cerebellum, the brain stem and upper spinal cord can be compressed resulting in some potential serious damage. This condition may or may not be associated with syringomyelia (dilated areas within the center of the spinal cord) and as a consequence may also be associated with spinal cord mediated disabilities.

NOTE: Type II (the most common type of Arnold-Chiari malformation) is usually identified at birth since it is always associated with myelomeningocele (exteriorization of spinal contents near the base of the spine).

Symptoms

Arnold-Chiari type I malformation patients are usually identified as a consequence of symptoms beginning in the late teenage years or early in adulthood. Our patients have ranged from age 12 to 50 years. The most common symptoms are headache or neck pain (made worse by coughing, sneezing, or extension of the head and neck.) Other symptoms may include problems with balance, or visual motor problems which the patient notices as "distorted vision". For those patients who may also harbor the associated structural problem of syringomyelia, altered sensation or weakness of the arms and/or legs may add to their difficulties that bring them to our attention.

Diagnosis (including mention of technologies used)

The diagnosis of Arnold-Chiari malformation (and syringomyelia) is best made by MRI scan of the brain and/or cervical spine.

Treatment Alternatives & Risks

The only effective treatment for Arnold-Chiari malformation is surgery. The operation that has been effective in our patients over these many years involves a Suboccipital Craniectomy (surgical opening of the bony compartment of the back of the head) to decompress the cerebellar tonsils with laminectomy of C1 and/or C2 (removal of the roof of the first two cervical vertebrae) to decompress the cervical spinal cord. The dura mater (a tough leather-like covering of the brain and spinal cord) is also opened. It is important to microsurgically cut bands of adherent tissue inside the dura mater that attach to the spinal cord and brain stem. In addition, we invariably open the space between and separate the herniated cerebellar tonsil so as to re-establish more "normal" cerebrospinal fluid pathways. This is particularly important for patients with the additional problem of syringomyelia. (We strongly disagree with the concept of "amputating" or removing the cerebellar tonsils, a procedure practiced by some neurosurgeons.)

In order to maintain adequate decompression of the brain, brain stem and spinal cord in this region, it is imperative to sew in a decompressive graft as part of the closure of the dura mater. There are a number of materials that can be effectively used for this without adding any additional incisions or prolonging surgery by taking tissue grafts from the patient.

These patients are monitored post-operatively in the Intensive care unit and are discharged from hospital within a couple of days. Recovery to full function usually requires a couple of months since tissues must heal. Generally it takes three months for scar tissue to be firm and six months to be solid. While activities such as walking usually begins within one-two days of operation, some strenuous sports activities should be avoided until healing has been completed.

The results of this operation have been most encouraging with the vast majority of patients having resolved their pre-operative symptoms including the incapacitating pre-operative headaches and neck pain. Most of our patients with disabling pre-operative eye movement disorders have either resolved their movement disorder or recovered to the point of not being aware of the problem. Patients with syringomyelia are in a different category. Most of our patients have stabilized their pre-operative deficits with many enjoying some improvement. Part of the ultimate outcome for these patients is determined by the extent of their pre-operative neurological deficits.



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This page last edited on 2/20

All content ©2016 by Neurosurgical Consultants, P.A.
Author, Martin L. Lazar, MD, FACS
All Rights Reserved. See Usage Notices.