Arnold-Chiari malformation

Arnold-Chiari malformation, sometimes referred to as Chiari II malformation or ACM, is a congenital malformation of the brain.

Arnold-Chiari Malformation (Chiari II malformation) occurs in almost all children born with both spina bifida and hydrocephalus. German pathologist Hans Chiari in the late 1800's described seemingly related anomalies of the hindbrain, the so called Chiari malformations I, II and III. Later, other investigators added a fourth (Chiari IV) malformation. The scale of severity is rated I - IV, with IV being the most severe. Arnold Chiari Malformation specifically refers to the Chiari II malformation.

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Cause

The cerebellar tonsils are elongated and pushed down through the opening of the base of the skull (see foramen magnum), blocking the flow of cerebrospinal fluid (CSF).

The brainstem, cranial nerves, and the lower portion of the cerebellum may be stretched or compressed.

Therefore, any of the functions controlled by these areas may be affected. The blockage of CSF flow may also cause a syrinx to form, eventually leading to syringomyelia. Many sufferers turn to The Chiari Institute in Long Island, NY for specialized medical attention and medication. Established in 2001, The Chiari Institute is a division of the Harvey Cushing Institutes of Neuroscience of the North Shore-Long Island Jewish Health System.

Presentation

In infants, the most common symptoms are stridor and swallowing difficulties. In older children, upper (and lower as age marches on) limb weakness and breathing difficulties may occur. Patients may experience no symptoms or remain asymptomatic until early adulthood, at which point they will often experience quick onset severe headaches and neck pain. Fatigue, dizziness, vertigo, neuropathic pain, pain at the point of tethering, visual disturbances, difficulty swallowing, ringing in the ears, sleep apnea, impaired fine motor skills, muscle weakness, and palpitations and excessive clearing of the throat with no obstructions are other common symptoms. Because of the complex combination of symptoms and the lack of experience with ACM1 had by many, even outstanding, neurologists and neurosurgeons, patients are frequently misdiagnosed.

Some patients may go an entire lifetime without having noticeable symptoms. Or, symptoms can be minimal, then turn severe suddenly due to head trauma which alters the condition of the spine, brain, or cerebellar tonsils and begins to cause more difficulties.

A Chiari malformation may be congenital or acquired. Research is still being done to determine its causes. In some cases it can be hereditary, and numerous cases exist of multiple members of one family having the condition.

It is common for adults to start showing noticeable symptoms when they are in the mid to late 30's. It is more common in women than in men.

Treatment

Once symptomatic onset occurs, the most frequent treatment is decompression surgery, in which a neurosurgeon seeks to open the base of the skull and through various methods unrestrict CSF flow to the spine. This treatment is well recognized and accepted with many studies published (involving a total of hundreds of patients) in well respected peer reviewed medical journals showing that about 80% of patients obtain improvement.

A small number of neurological surgeons believe that detethering the spinal cord as an alternate approach relieves the compression of the brain against the skull opening (foramen magnum) obviating the need for decompression surgery and associated trauma. However, this approach is significantly less documented in the medical literature with reports on only a handfull of patients. It should be noted that the alternative spinal surgery is also not without risk.

History

An Austrian pathologist, Hans Chiari, first described these hindbrain malformations in the 1890s. A colleague of Professor Chiari, Dr. Julius Arnold later contributed to the definition of the condition, and students of Dr. Arnold suggested the term "Arnold-Chiari malformation" to henceforth refer to the condition.^[1]

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