Arnold-Chiari malformation

Definition

Arnold-Chiari malformation is a rare genetic disorder in which parts of the brain are formed abnormally. Malformations may occur in the lower portion of the brain (cerebellum) or in the brain stem.

Description

A German pathologist named Arnold-Chiari was the first to describe Arnold-Chiari malformation in 1891. Normally, the brain stem and cerebellum are located in the posterior fossa, an area at the base of the skull attached to the spinal cord. In Arnold-Chiari malformation, the posterior fossa does not form properly. Because the posterior fossa is small, the brain stem, cerebellum, or cerebellar brain tissues (called the cerebellar tonsils) are squeezed downward through an opening at the bottom of the skull. The cerebellum and/or the brain stem may extend beyond the skull or protrude into the spinal column. The displaced tissues may obstruct the flow of cerebrospinal fluid (CSF), the substance that flows around the brain and spinal cord. CSF nourishes the brain and spinal cord.

Although this malformation is present at birth, there may not be any symptoms of a problem until adulthood. For this reason, Arnold-Chiari malformation is often not diagnosed until adulthood. Women have a higher incidence of this disorder than men.

Other names for Arnold-Chiari malformation are Arnold-Chiari syndrome, herniation of the cerebellar tonsils, and cerebellomedullary malformation syndrome. When doctors diagnose Arnold-Chiari malformation, they classify the malformation by its severity. An Arnold-Chiari I malformation is the least severe. In an Arnold-Chiari I malformation, the brain extends into the spinal canal. Doctors measure the length of brain stem located in the spinal canal to further define the malformation.

A type II malformation is more severe than a type I. It is almost always linked with a type of spina bifida. A sac protrudes through an abnormal opening in the spinal column. The sac is called a myelomeningocele. It may be filled with part of the spinal cord, spinal membranes, or spinal fluid. Unlike many cases of Arnold-Chiari I malformation, Arnold-Chiari II malformation is diagnosed in childhood. Doctors have identified Arnold-Chiari III and IV malformations, but they are very rare.

Arnold-Chiari malformations may occur with other conditions. There may be excessive fluid in the brain (hydrocephalus), opening in the spine (spina bifida), or excessive fluid in the spinal cord (syringomyelia), but many people with Arnold-Chiari malformations do not have other medical problems.

Demographics

Arnold-Chiari malformations are rare; no data has been collected to demonstrate the incidence of Arnold-Chiari malformations. However, it is known that Arnold-Chiari malformations are the most common type of malformation of the cervico-medullary junction, the area where the brain and spine connect. About one percent of live newborns have a malformation in the cervicomedullary junction.

Causes and symptoms

Scientists do not know what causes Arnold-Chiari malformations. One hypothesis is that the base of the skull is too small, forcing the cerebellum downward. Another theory focuses on overgrowth in the cerebellar region. The overgrowth pushes the cerebellum downward into the spinal canal.

Some people with Arnold-Chiari I malformations have no symptoms. Typically, with an Arnold-Chiari I malformation symptoms appear as the person reaches the third or fourth decade of life. Symptoms of this disorder vary. Most symptoms arise from the pressure on the cranial nerves or brain stem. The symptoms may be vague or they may resemble symptoms of other medical problems, so diagnosis may be delayed.

One of the most common symptoms of Arnold-Chiari malformations is a headache. The headache generally begins in the neck or base of the skull and may radiate through the back of the head. Coughing, sneezing, or bending forward may bring on these headaches. The headaches can last minutes or hours and may be linked with nausea.

There may be pain in the neck or upper arm with Arnold-Chiari malformations. Patients often report more pain on one side, rather than equal pain on both sides. There may also be weakness in the arm or hand. Patients may also report tingling, burning, numbness, or pins and needles. Balance can be affected as well. A person may be unsteady on their feet or lean to one side.

Some people with Arnold-Chiari malformation may have difficulty swallowing. They may say that food 'catches' in their throat when they swallow. Another common complaint linked with Arnold-Chiari malformations is hoarseness.

People with Arnold-Chiari malformations may have visual problems, including blurred vision, double vision, or blind spots. There may be bobbing of the eyes.

Diagnosis

An Arnold-Chiari malformation is diagnosed with magnetic resonance imaging (MRI). An MRI uses magnetism and radio waves to produce a picture of the brain and show the crowding of the space between the brain and spinal cord that occurs with Arnold-Chiari malformations. In addition to an MRI, patients will also have a thorough neurologic examination.

Treatment team

Individuals who begin to experience symptoms from an Arnold-Chiari malformation are usually first seen by their primary care physician, who may send them on to a neurologist for further evaluation. If the patient is deemed to require surgery, a neurosurgeon will be consulted.

Treatment

The recommended treatment for an Arnold-Chiari I malformation is surgery to relieve the pressure on the cerebellar area. During the surgery, the surgeon removes a small part of the bone at the base of skull. This enlarges and decompresses the posterior fossa. This opening is patched with a piece of natural tissue. In some people with Arnold-Chiari malformation, displaced brain tissue affects the flow of cerebrospinal fluid. Doctors may evaluate the flow of cerebrospinal fluid during surgery for Arnold-Chiari malformation. If they find that brain tissue is blocking the flow of cerebrospinal fluid, they will shrink the brain tissue during surgery.

Recover and Rehabilitation

Individuals who are recovering from surgery to repair an Arnold-Chiari malformation may require physical and/or occupational therapy as they try to regain strength and fine motor control in their arms and hands. A speech therapist may be helpful in improving both speech and swallowing.

Clinical Trials

The National Institutes of Health are undertaking several research studies exploring aspects of Arnold-Chiari malformations. Efforts are being made to delineate a possible genetic defect leading to such malformations; studies are further exploring the anatomy and physiology of the malformations; and comparisons of the efficacy of various surgical treatments are being made.

Prognosis

Long-term prognosis for persons with Arnold-Chiari I malformations is excellent. Full recovery from surgery may take several months. During that time, patients may continue to experience some of the symptoms associated with Arnold-Chiari malformations.

Prognosis for Arnold-Chiari II malformations depends on the severity of the myelomeningocele and will be equivalent to that of spina bifida.

Resources

ORGANIZATIONS

American Syringomelia Project. PO Box 1586, Longview, Texas 75606-1586. (903) 236-7079.

National Organization for Rare Disorders (NORD). PO Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518 or (800) 999-6673. Fax: (203) 746-6481. http://www.raredisease.org.

World Arnold-Chiari Malformation Association. 31 Newton Woods Road, Newton Square, Philadelphia, PA19073. http://presenter.com?~wacma/milhorat.htm.

Lisa A. Fratt

Rosalyn Carson-Dewitt, MD

A congenital anomaly in which the cerebellum and medulla oblongata protrude down into the cervical spinal canal through the foramen magnum; it is almost always associated with meningomyelocele, spina bifida and hydrocephalus. Recorded in calves, sheep and dogs.

Arnold-Chiari
Classification and external resources
A T2-weighted sagittal MRI scan, from a patient with Chiari-like symptomatology, demonstrating tonsillar herniation less than 3 mm
ICD-10	Q07.0
ICD-9	741.0
OMIM	207950
DiseasesDB	899
MeSH	D001139

Arnold-Chiari malformation is a malformation of the brain. It consists of a downward displacement of the cerebellar vermis and the medulla^[1] through the foramen magnum, sometimes causing hydrocephalus as a result of obstruction of cerebrospinal fluid (CSF) outflow ^[2]. The cerebrospinal fluid outflow is caused by phase difference in outflow and influx of blood in the vasculature of the brain.

Contents 1 Terminology 2 Incidence 3 History and classification 4 Symptoms 5 Treatment 6 Prognosis 7 History 8 Notable people with the malformation 9 Research 10 See also 11 References 12 External links

Terminology

Chiari malformation is the most frequently used term for these types of malformations. The use of the term Arnold-Chiari malformation has fallen somewhat out of favor over time, although it is used by some to refer to the type II malformation. Some sources use "Chiari malformation" to describe four specific grades of the condition, reserving the term "Arnold-Chiari" for type II only.^[3] Some sources use "Arnold-Chiari" for all four types.^[4] This article uses the latter convention.

Chiari malformation or Arnold-Chiari malformation should not be confused with Budd-Chiari syndrome,^[5] a hepatic condition also named for Hans Chiari.

Incidence

The incidence of Chiari 1 malformation, defined as tonsilar herniations of 3 to 5 mm or greater, is approximately 1 in 1,200.^{[citation needed]} The incidence of symptomatic Chiari is less but unknown.

A prevalence of approximately 1 in 1000 has been described.^[6]

History and classification

The Austrian pathologist Hans Chiari in the late 1800s 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. Types III and IV are very rare.^[6]

Type	Presentation	Other notes
I	Is generally asymptomatic during childhood, but often manifests with headaches and cerebellar symptoms. Herniation of cerebellar tonsils.[7][8]	The most common form.
II	Usually accompanied by a myelomeningocele[9] leading to partial or complete paralysis below the spinal defect. Abnormal development of the cerebellar vermis and medulla oblongata occur, and they both descend into the foramen magnum. Hydrocephalus is frequently present.
III	Causes severe neurological defects. It is associated with an encephalocele.[10]
IV	Characterized by a lack of cerebellar development.[11]

Other conditions sometimes associated with Chiari Malformation include hydrocephalus,^[12] syringomyelia, spinal curvature, tethered spinal cord syndrome, and connective tissue disorders^[13] such as Ehlers-Danlos syndrome and Marfan Syndrome.

Symptoms

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 Cerebro-Spinal Fluid (CSF) flow may also cause a syrinx to form, eventually leading to syringomyelia. Chiari is often associated with major headaches, sometimes mistaken for migraines. Chiari headaches usually include intense pressure in the back of the head, aggravated by Valsalva maneuvers, such as yawning, laughing, crying, coughing, sneezing or straining. Chiari also includes muscle weakness, facial pain, hearing problems, and extreme fatigue. It also can cause insomnia cycles of sleep deprivation followed by inabilities to remain awake cycling between them. 15% of patients with adult Chiari malformation are asymptomatic.

Treatment

Once symptomatic onset occurs, a common treatment is decompression surgery,^[14] in which a neurosurgeon usually removes the lamina of the first and sometimes the second or even third cervical vertebrae and part of the occipital bone of the skull to relieve pressure. The flow of spinal fluid may be accompanied by a shunt. Since this surgery usually involves the opening of the dura mater and the expansion of the space beneath, a dural graft is usually applied to cover the expanded posterior fossa.

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 handful of patients. It should be noted that the alternative spinal surgery is also not without risk.^{[citation needed]}

Prognosis

The prognosis differs dependent on the type of malformation (i.e., type I, II, III, or IV). Type I is generally adult-onset and, while not curable, treatable and non-fatal.^[15] Types I and II sufferers may also develop syringomyelia. Type II is typically diagnosed at birth or prenatally.^[16] Approximately 33% of individuals with Chiari II malformation develop symptoms of brainstem damage within five years; a 1996 study found a mortality rate of 33% or more among symptomatic patients, with death frequently occurring due to respiratory failure.^[17] 15% of individuals with Chiari II malformation die within two years of birth.^[18] Among children under two who also have myelomeningocele, it is the leading cause of death.^[19] Prognosis among children with Chiari II malformation who do not have spina bifida is linked to specific symptoms; the condition may be fatal among symptomatic children when it leads to neurological deterioration, but surgical intervention has shown promise.^[20] Types III and IV are extremely rare and patients generally do not survive past the age of two or three.^[21]

History

An Austrian pathologist, Hans Chiari, first described these hindbrain malformations in the 1890s.^[22] A colleague of Professor Chiari, Dr. Julius Arnold, later contributed to the definition of the condition,^[23] and students of Dr. Arnold (Schwalbe and Gredig)^[24] suggested the term "Arnold-Chiari malformation" to henceforth refer to the condition.^[25][26]

Some sources credit the characterization of the condition to Cleland^[27][28] or Cruveilhier.^[29]

Notable people with the malformation

Rosanne Cash^[30]
Bobby Jones ^[31] - Legendary American golfer

Research

Considerable research has been directed towards improving methods used to diagnose Arnold-Chiari malformation. In particular, the traditional diagnosis method quantifying a 5 mm descent of the lower cerebellar tonsils through the foramen magnum may be insufficient for diagnosis in some patients. Research has been conducted to investigate the importance of cerebrospinal fluid velocities, other geometric parameters of the cranium, the importance of cranial and spinal canal compliance, and thickening of the filum terminale in assessment of Arnold-Chiari malformation.

See also

• Syringomyelia
• Hydrocephalus
• Ehlers-Danlos Syndrome
• Postural Orthostatic Tachycardia Syndrome
• Tethered spinal cord syndrome
• Spina bifida

References

1. ^ "urmc.rochester.edu". http://www.urmc.rochester.edu/neuroslides/slide169.html. 
2. ^ Rosenbaum, RB; DP Ciaverella (2004). Neurology in Clinical Practice. Butterworth Heinemann. pp. 2192–2193. ISBN 0-7506-7469-5. 
3. ^ "Dorlands Medical Dictionary:Chiari malformation". http://www.mercksource.com/pp/us/cns/cns_hl_dorlands_split.jsp?pg=/ppdocs/us/common/dorlands/dorland/nine/100011880.htm. 
4. ^ "Case Based Pediatrics Chapter". http://www.hawaii.edu/medicine/pediatrics/pedtext/s18c16.html. 
5. ^ "2008 ICD-9-CM Diagnosis 453.0 - Budd-Chiari Syndrome". http://www.icd9data.com/2008/Volume1/390-459/451-459/453/453.0.htm. 
6. ^ ^{a b} "Arnold Chiari Malformation". http://www.uscneurosurgery.com/Disorders_includes/arnchiari.html. 
7. ^ Kojima A, Mayanagi K, Okui S (February 2009). "Progression of pre-existing Chiari type I malformation secondary to cerebellar hemorrhage: case report" (^{[dead link]}). Neurol. Med. Chir. (Tokyo) 49 (2): 90–2. doi:10.2176/nmc.49.90. PMID 19246872. http://joi.jlc.jst.go.jp/JST.JSTAGE/nmc/49.90?from=PubMed. 
8. ^ O'Shaughnessy BA, Bendok BR, Parkinson RJ, et al. (January 2006). "Acquired Chiari malformation Type I associated with a supratentorial arteriovenous malformation. Case report and review of the literature". J. Neurosurg. 104 (1 Suppl): 28–32. doi:10.3171/ped.2006.104.1.28. PMID 16509477. http://thejns.org/doi/abs/10.3171/ped.2006.104.1.28?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dncbi.nlm.nih.gov. 
9. ^ "Neuroradiology - Chiari malformation (I-IV)". http://www.mir.wustl.edu/neurorad/internal.asp?NavID=123. 
10. ^ MeSH Arnold-Chiari+Malformation
11. ^ "Chiari Malformations - Department of Neurological Surgery". http://www.cumc.columbia.edu/dept/nsg/ct/chiari_malformation.html. 
12. ^ "Neuropathology For Medical Students". http://www.pathology.vcu.edu/WirSelfInst/neuro_medStudents/devdis.html. 
13. ^ Milhorat TH, Bolognese PA, Nishikawa M, McDonnell NB, Francomano CA (December 2007). "Syndrome of occipitoatlantoaxial hypermobility, cranial settling, and chiari malformation type I in patients with hereditary disorders of connective tissue". Journal of neurosurgery. Spine 7 (6): 601–9. doi:10.3171/SPI-07/12/601. PMID 18074684. http://thejns.org/doi/abs/10.3171/SPI-07/12/601?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dncbi.nlm.nih.gov. 
14. ^ Guo F, Wang M, Long J, et al. (2007). "Surgical management of Chiari malformation: analysis of 128 cases". Pediatr Neurosurg 43 (5): 375–81. doi:10.1159/000106386. PMID 17786002. http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=000106386. 
15. ^ "Chiari Malformation". http://www.lpch.org/DiseaseHealthInfo/HealthLibrary/neuro/chari.html. Retrieved 2009-09-21. 
16. ^ Sarnat, Harvey B.; Paolo Curatolo (2008). Malformations of the nervous system. 87. Elsevier Health Sciences. p. 97. ISBN 0444518967. "The most frequent of the Chiari malformations, Chiari II, is nearly always associated with lumbrosacral meningomyelocele, hence is diagnosed at birth if not prenatally." 
17. ^ Manto, Mario-Ubaldo; Massimo Pandolfo (2002). The cerebellum and its disorders. Cambridge University Press. p. 167. ISBN 0521771560. "About one-third of all patients with Chiari II malformation develop brainstem symptoms by the age of five, and one-third or more of these children die, often as a result of respiratory failure (Oakes, 1996)." 
18. ^ Incesu, Lutfi; Anil Khosla, Michael R. Aiello (October 1, 2008). "Chiari II Malformation". http://emedicine.medscape.com/article/406975-overview. Retrieved 2009-09-21. 
19. ^ Kumar, Praveen; Barbara K. Burton (2007). Congenital Malformations: Evidence-Based Evaluation and Management. McGraw-Hill Professional. p. 72. "The Chiari II malformation is the leading cause of death in infants with spina bifida under the age of 2 years." 
20. ^ Kumar and Burton, 74.
21. ^ http://www.asap.org/articles/batzdorf_sm_cm.pdf
22. ^ Chiari, H. Uber Veranderungen des Kleinhirns infolge von Hydrocephalie des Grosshirns. Dtsch. Med. Wochenschr. 17: 1172-1175, 1891.
23. ^ Arnold, J. Myelocyste, Transposition von Gewebskeimen und Sympodie. Beitr. Path. Anat. 16: 1-28, 1894.
24. ^ Ashwal, Stephen (1990). The Founders of child neurology. San Francisco: Norman Pub. in association with the Child Neurology Society. pp. 195. ISBN 0-930405-26-9. 
25. ^ Arnold-Chiari malformation at Who Named It?
26. ^ Bejjani GK (2001). "Definition of the adult Chiari malformation: a brief historical overview". Neurosurg Focus 11 (1): E1. doi:10.3171/foc.2001.11.1.2. PMID 16724811. http://thejns.org/doi/abs/10.3171/foc.2001.11.1.2?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dncbi.nlm.nih.gov. 
27. ^ Susman J, Jones C, Wheatley D (March 1989). "Arnold-Chiari malformation: a diagnostic challenge" (^{[dead link]}). Am Fam Physician 39 (3): 207–11. PMID 2923030. http://findarticles.com/p/articles/mi_m3225/is_n3_v39/ai_7621931. 
28. ^ Cleland (April 1883). "Contribution to the Study of Spina Bifida, Encephalocele, and Anencephalus". J Anat Physiol 17 (Pt 3): 257–92. PMID 17231474. 
29. ^ Pearce JM (January 2000). "Arnold chiari, or "Cruveilhier cleland Chiari" malformation". J. Neurol. Neurosurg. Psychiatr. 68 (1): 13. doi:10.1136/jnnp.68.1.13. PMID 10601393. http://jnnp.bmj.com/cgi/pmidlookup?view=long&pmid=10601393. 
30. ^ http://www.msnbc.msn.com/id/22220526/from/ET/
31. ^ http://www.csfinfo.org/bobby_jones_society

External links

• Chiari Connection International--Chiari and Related Disorders Information http://www.chiariconnectioninternational.com/
• The Chiari Center Foundation - A 501(c)(3) Public Charitable Foundation http://www.chiaricenter.org/
• Chiari malformation: A handbook for patients and their families
• Chiari & Syringomyelia Foundation (CSF) http://www.csfinfo.org/
• Conquer Chiari
• World Arnold Chiari Malformation Association
• American Syringomyelia Alliance Project
• The Ann Conroy Trust (ACT)
• An insightful Huffington Post blog from a father whose son suffered from Chiari Malformation and the emotional roller coaster it created.

v • d • e Congenital malformations and deformations of nervous system (Q00-Q07, 740-742) Brain Neural tube defect Anencephaly (Acephaly, Acrania, Iniencephaly) · Encephalocele · Arnold-Chiari malformation Other Microcephaly · Congenital hydrocephalus (Dandy-Walker syndrome) other reduction deformities (Holoprosencephaly, Lissencephaly, Pachygyria, Hydranencephaly) Septo-optic dysplasia · Megalencephaly CNS cyst (Porencephaly, Schizencephaly) Polymicrogyria (Bilateral frontoparietal polymicrogyria) Spinal cord Neural tube defect Spina bifida · Rachischisis Other Currarino syndrome · Diastomatomyelia · Syringomyelia central nervous system navs: anat/physio/dev, noncongen/congen/neoplasia, symptoms+signs/eponymous, proc

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