New York Chiari Malformation Malpractice

What is Chiari Type I Malformation?

Chiari malformations are structural defects in the base of the skull that cause the lowest part of the cerebellum (called the cerebellar tonsils) to protrude through an opening in the skull where the brain connects to the spinal cord (the foramen magnum). The skull opening is widest at the bottom of the cerebellum where the dura (dense covering of the brain and spinal cord) narrows as it enters into the spinal region like a funnel. Only a small amount of brain tissue can fit through the funnel without causing serious problems.

The cerebellum is responsible for movement, balance, coordination, and precision of movement, posture, and speech. When the cerebellar tonsils herniate into the spinal canal, there is not enough space. This may put pressure on nearby structures and partially obstruct the flow of cerebrospinal fluid (CSF) that bathes the brain and spinal cord.

Types of Chiari Malformation

Depending on the severity and the parts of the brain being affected by the structural defect, individuals are classified with Chiari Type I, Type II, Type III, or Type IV. Classifications are based on the degree or amount of cerebellar tissue that goes into the funnel towards the spinal cord.

Type I:

Chiari Type I malformation is the most common form of this defect. It may be diagnosed in infancy, but may also go unnoticed or undiagnosed until adolescence or adulthood. Chiari malformation Type 1 is characterized by congenital hypoplasia of the posterior fossa and caudal displacement of the cerebellar tonsils below the foramen magnum. The most common symptoms are occipital headache (back of the head) aggravated by coughing, laughing or bending. Other common symptoms include diplopia (double vision), dizziness, ringing in the ears, pain in the neck and shoulders, upper extremity weakness, clumsiness, sleep apnea, poor fine motor movements, and episodic nausea and vomiting. Since these symptoms are common to other conditions as well, Chiari I formation may go undiagnosed for years, leaving patients to suffer with ineffective treatments.

Type II malformations are known to develop before birth with most individuals starting to experience or notice symptoms during early childhood. Type II symptoms are more severe than those associated with Type I, and these symptoms start as complications during early childhood but can quickly become life threatening without the required surgery. Type II is also associated with a form of spina bifida which is characterized by an undeveloped spinal cord and brain. This severe form of spina bifida is Myelomeningocele and is the result of a severe defect in the backbone and spinal cord which causes the spinal canal to not close properly after birth. About 1 to 5 children in every 1,000 born in the United States have a myelomeningocele.

Type III & Type IV:

Chiari Type III and Type IV are both considered extremely rare and are typically quite severe. Type III is identified when portions of the cerebellum protrude through an irregular opening in the back of the skull. This malformation leads to extreme neurological complications and is often diagnosed at the time of birth or through an ultrasound. Type IV malformations are the result of an undeveloped cerebellum, and children born with the condition rarely survive beyond infancy.

Signs and Symptoms of Chiari I Malformation

The symptoms of Chiari I are the result of 3 conditions from the disordered anatomy: 

(1) Compression of the medulla (a portion of the brain stem), located beneath the cerebellum and upper spinal cord 

(2) Compression of cerebellum 

(3) Blockage of the CSF flow through the opening of the skull. 

The pressure of the cerebellum may cause symptoms such as:

• abnormal walking, 
• loss of balance, 
• stumbling, 
• swaying, 
• speech abnormalities, 
• eye movement irregularities. 

Disruption of CSF flow causes pain in the majority of cases. The pain can result from neck pain or due to headaches. Headaches and neck pain can also be aggravated by coughing and straining or lifting. Hand weakness and lack of sensation or numbness may be other symptoms. 

Diagnosis

Magnetic Resonance Imaging (MRI) is the most accurate diagnostic test for diagnosing Chiari malformations.  Chiari Type I is characterized by tonsillar herniation below the foramen magnum as small as 3 millimeters to as large as 25 millimeters or larger. Some of the most symptomatic patients may have relatively small tonsillar herniations. CSF flow analysis may also help to predict if surgery will be helpful. Myelography (a test that infuses dye into the CSF fluid) is also helpful if someone cannot undergo an MRI, CT scan, or regular x-rays. The presence of cerebellar or brain stem compression consistent with Chiari I malformation should correlate with the clinical signs and symptoms before surgery is considered. For example, If there are significant symptoms causing nerve dysfunction, muscle weakness, gait abnormalities, and headaches, surgery may be indicated. Mild or unclear symptoms warrant more extensive testing before surgical intervention is undertaken. There are other causes for the cerebellum pushing into the spinal canal, such as tumors, or patients with CSF disorders.

Treatment

Medical Management

Chiari I malformations in patients with mild symptoms can be treated with medications such as pain relievers, muscle relaxers, or a support collar. Symptomatic patients should be offered surgery as long as the diagnosis is confirmed.

Surgical Management

Numerous studies have shown that early surgical intervention for symptomatic Chiari I malformation results in better neurological outcomes. In one study of 158 patients who underwent surgery, 70 percent had an improvement in their symptoms, which continued for 4-7 years. After seven years, there was a decline to 61 percent who had sustained improvement. Those with spinal cord symptoms such as muscle weakness and sensory loss did not do as well, with only 58 percent showing improvement.

In younger patients who underwent surgery due to symptoms, ages ranging from 9 months to 18 years, 75 percent were clinically improved and 87.5% showed resolution of their syringomyelia (fluid-filled cyst of the spinal cord). Of those who were managed medically, only 41.7% saw improvement.  

Most knowledgeable surgeons in the field recommend surgical decompression, including suboccipital craniectomy, duraplasty, reduction of the cerebellar tonsils and C1 laminectomy. Dura is the tough membrane covering the brain and spinal cord. In some cases, removing bone and loosening the fibrous band that constricts the skull opening may be sufficient to relieve symptoms and reduces the chance of CFS leakage.

Complications

As in all surgery, there are potential risks and complications from surgical procedures for Chiari malformation, primarily CSF leakage and the formation of cysts. Wound infection and meningitis may also occur and warrant antibiotics and other treatment. Rare, but serious complications such as neurologic dysfunction, cessation of breathing, and bleeding from a vertebral artery may occur immediately after surgery and necessitate close observation and potentially emergency intervention.

Outcome and Prognosis

The long-term outlook for Chiari I malformation depends upon a variety of factors, particularly the severity of neurological problems at the time of diagnosis. Those with less severe neurologic symptoms tend to recover best. When symptoms have been prolonged, progressive and severe prior to diagnosis and surgery, the outcomes are less favorable. For this reason, early diagnosis and surgery for Chiair I malformation offers the best chance to restore normal cerebellar function and cessation of symptoms.

Medico-legal Implications

When a physician fails to properly diagnose Chiari I malformation, the patient’s symptoms may continue to progress and the chances of successful surgical management may become significantly diminished. In such a case, the physician may be held responsible for malpractice. Depending upon the severity of the patient’s injuries, damages may be assessed for pain, suffering, loss of enjoyment of life, loss of earnings and medical expenses. 

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References

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