Chiari malformation (CM) is a structural defect in the

cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebe ...

, characterized by a downward displacement of one or both

cerebellar tonsil The cerebellar tonsil (Latin: tonsilla cerebelli) is a rounded lobule on the undersurface of each cerebellar hemisphere, continuous medially with the uvula of the cerebellar vermis and superiorly by the flocculonodular lobe. Synonyms include: tonsi ...

s through the

foramen magnum The foramen magnum ( la, great hole) is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblonga ...

(the opening at the base of the skull). CMs can cause headaches, difficulty swallowing, vomiting, dizziness, neck pain, unsteady gait, poor hand coordination, numbness and tingling of the hands and feet, and speech problems. Less often, people may experience ringing or buzzing in the ears, weakness, slow heart rhythm, or fast heart rhythm, curvature of the spine ( scoliosis) related to spinal cord impairment, abnormal breathing, such as

central sleep apnea Central sleep apnea (CSA) or central sleep apnea syndrome (CSAS) is a sleep-related disorder in which the effort to breathe is diminished or absent, typically for 10 to 30 seconds either intermittently or in cycles, and is usually associated w ...

, characterized by periods of breathing cessation during sleep, and, in severe cases, paralysis. This can sometimes lead to non-communicating

hydrocephalus Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary i ...

as a result of obstruction of

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the b ...

(CSF) outflow. The cerebrospinal fluid outflow is caused by phase difference in outflow and influx of blood in the vasculature of the brain. The malformation is named after the Austrian pathologist Hans Chiari. A type II CM is also known as an Arnold–Chiari malformation in honor of Chiari and German pathologist Julius Arnold.

Signs and symptoms

Findings are due to

brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

and lower cranial nerve dysfunction. Onset of symptoms are less likely to be present during adulthood in most patients. Younger children generally have a substantially different presentation of clinical symptoms from older children. Younger children are more likely to have a more rapid neurological degeneration with profound brain stem dysfunction over several days. * Neurogenic dysphagia: Difficulty swallowing. Seen by poor feeding in patient. *

Cyanosis Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Body tissues that show cyanosis are usually in locations w ...

: Bluish discoloration of skin while feeding. * Weak crying * Facial weakness * Aspiration * Headaches aggravated by

Valsalva maneuver The Valsalva maneuver is performed by a forceful attempt of exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut while expelling air out as if blowing up a balloon. Variations of the maneuver can ...

s, such as yawning, laughing, crying, coughing, sneezing or straining, bending over, or getting up suddenly *

Tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...

(ringing in the ears) *

Lhermitte's sign Lhermitte phenomenon, also called the barber chair phenomenon, is an uncomfortable "electrical" sensation that runs through the back and into the limbs. The sensation can feel like it goes up or down the spine. It is painful for some, although oth ...

(electrical sensation that runs down the back and into the limbs) *

Vertigo Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...

(dizziness) * Nausea * Schmahmann syndrome *

Nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the invol ...

(irregular eye movements; typically, so-called "downbeat nystagmus") * Facial pain * Muscle weakness * Impaired gag reflex * Dysphagia (difficulty swallowing) *

Restless leg syndrome Restless legs syndrome (RLS), also known as Willis-Ekbom disease (WED), is generally a long-term disorder that causes a strong urge to move one's legs. There is often an unpleasant feeling in the legs that improves somewhat by moving them. This ...

* Sleep apnea * Sleep disorders * Impaired coordination * Severe cases may develop all the symptoms and signs of a

bulbar palsy Bulbar palsy refers to a range of different signs and symptoms linked to impairment of function of the glossopharyngeal nerve (CN IX), the vagus nerve (CN X), the accessory nerve (CN XI), and the hypoglossal nerve (CN XII). It is caused by a low ...

* Paralysis due to pressure at the cervico-medullary junction may progress in a so-called "clockwise" fashion, affecting the right arm, then the right leg, then the left leg, and finally the left arm; or the opposite way around. * Papilledema on fundoscopic exam due to

Increased intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury (mmHg) and at rest, is normally 7–15 mmHg for a supine adult. Th ...

* Pupillary dilation *

Dysautonomia Dysautonomia or autonomic dysfunction is a condition in which the autonomic nervous system (ANS) does not work properly. This may affect the functioning of the heart, bladder, intestines, sweat glands, pupils, and blood vessels. Dysautonomia has ...

: tachycardia (rapid heart), syncope (fainting),

polydipsia Polydipsia is excessive thirst or excess drinking.Porth, C. M. (1990). ''Pathophysiology: Concepts of altered health states''. Philadelphia: J.B. Lippincott Company. The word derives from the Greek () "very thirsty", which is derived from (, " ...

(extreme thirst), chronic fatigue *

Apnea Apnea, BrE: apnoea, is the temporal cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are ( patency), there may ...

: Sudden pause of breathing, usually during sleep. *

Opisthotonos Opisthotonus or opisthotonos (from grc, ὄπισθεν, translit=opisthen, lit=behind and grc, τόνος, translit=tonos, lit=tension, label=none) is a state of severe hyperextension and spasticity in which an individual's head, neck and spinal ...

: Spasm of the head which causes head to arch backwards. More common in infants than adults. * Stridor The blockage of

(CSF) flow may also cause a syrinx to form, eventually leading to

syringomyelia Syringomyelia is a generic term referring to a disorder in which a cyst or cavity forms within the spinal cord. Often, syringomyelia is used as a generic term before an etiology is determined. This cyst, called a syrinx, can expand and elongate o ...

. Central cord symptoms such as hand weakness, dissociated sensory loss, and, in severe cases, paralysis may occur.

Syringomyelia

Syringomyelia is most often chronic progressive degenerative disorder characterized by a fluid-filled

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...

located in the spinal cord. However, there can be also cases where the syrinx in terms of size and extent of symptoms actually stays stable throughout a lifetime. Syringomyelia symptoms include pain, weakness, numbness, and stiffness in the back, shoulders, arms or legs. Other symptoms include headaches, the inability to feel changes in the temperature, sweating, sexual dysfunction, and loss of bowel and bladder control. It is usually seen in the

cervical In anatomy, cervical is an adjective that has two meanings: # of or pertaining to any neck. # of or pertaining to the female cervix: i.e., the ''neck'' of the uterus. *Commonly used medical phrases involving the neck are **cervical collar **cervic ...

region but can extend into the medulla oblongata and pons or it can reach downward into the thoracic or

lumbar In tetrapod anatomy, lumbar is an adjective that means ''of or pertaining to the abdominal segment of the torso, between the diaphragm and the sacrum.'' The lumbar region is sometimes referred to as the lower spine, or as an area of the back i ...

segments. Syringomyelia is often associated with type I Chiari malformation and is commonly seen between the C-4 and C-6 levels. The exact development of syringomyelia is unknown but many theories suggest that the herniated tonsils in type I Chiari malformations cause a "plug" to form, which does not allow an outlet of CSF from the brain to the spinal canal. Syringomyelia is present in 25% of patients with type I Chiari malformations.

Pathophysiology

Foramen magnum - inferior view - animation

The most widely accepted pathophysiological mechanism by which Chiari type I malformations occur is by a reduction or lack of development of the posterior fossa as a result of congenital or acquired disorders. Congenital causes include hydrocephalus,

craniosynostosis Craniosynostosis is a condition in which one or more of the fibrous sutures in a young infant's skull prematurely fuses by turning into bone (ossification), thereby changing the growth pattern of the skull. Because the skull cannot expand perpe ...

(especially of the lambdoid suture),

hyperostosis Hyperostosis is an excessive growth of bone. It may lead to exostosis. It occurs in many musculoskeletal disorders. See also * Diffuse idiopathic skeletal hyperostosis * Hyperostosis frontalis interna Hyperostosis frontalis interna is a common ...

(such as craniometaphyseal dysplasia,

osteopetrosis Osteopetrosis, literally "stone bone", also known as marble bone disease or Albers-Schönberg disease, is an extremely rare inherited disorder whereby the bones harden, becoming denser, in contrast to more prevalent conditions like osteoporosi ...

, erythroid hyperplasia), X-linked vitamin D-resistant rickets, and neurofibromatosis type I. Acquired disorders include space occupying lesions due to one of several potential causes ranging from brain tumors to hematomas. Traumatic brain injury may cause delayed acquired Chiari malformation, but the pathophysiology of this is unknown. Additionally, ectopia may be present but asymptomatic until a whiplash injury causes it to become symptomatic. Some neurological experts believe that Chiari malformation type I is developed as a result of Filum Disease, an abnormal traction of the spinal cord caused by an excessively tense Filum terminale. This theory was first introduced by Dr. Miguel B. Royo Salvador in 1993.

Diagnosis

Diagnosis is made through a combination of patient history, neurological examination, and medical imaging. Magnetic resonance imaging (MRI) is considered the preferred imaging modality for Chiari malformation. The MRI visualizes neural tissue such as the cerebellar tonsils and spinal cord as well as bone and other soft tissues. CT and CT myelography are other options and were used prior to the advent of MRI, unfortunately the resolution of CT based modalities do not characterize syringomyelia and other neural abnormalities as well. By convention, the cerebellar tonsil position is measured relative to the basion-opisthion line, using sagittal T1 MRI images or sagittal CT images. The selected cutoff distance for abnormal tonsil position is somewhat arbitrary, as not every person will be symptomatic at a certain amount of tonsil displacement, and the probability of symptoms and syrinx increases with greater displacement; however, greater than 5 mm is the most frequently cited cutoff number, though some consider 3–5 mm to be "borderline,"; pathological signs and syrinx may occur beyond that distance. One study showed little difference in cerebellar tonsil position between standard recumbent MRI and upright MRI for patients without a history of whiplash injury. Neuroradiological investigation is used to first rule out any intracranial condition that could be responsible for tonsillar herniation. Neuroradiological diagnostics evaluate the severity of crowding of the neural structures within the posterior cranial fossa and their pressure against the foramen magnum. Chiari 1.5 is a term used when both

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

and tonsillar herniation through the foramen magnum are present. The diagnosis of a Chiari II malformation can be made prenatally, through ultrasound.

Classification

In the late 19th century, Austrian pathologist Hans Chiari 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. Since Dr. Chiari's original descriptions Chiari 0, 1.5, 3.5, and 5 have been described in the medical literature.

Types of Chiari malformation

Other conditions sometimes causally associated with Chiari malformation include hydrocephalus,

, spinal curvature, tethered spinal cord syndrome, and

connective tissue disorder A connective tissue disease (collagenosis) is any disease that has the connective tissues of the body as a target of pathology. Connective tissue is any type of biological tissue with an extensive extracellular matrix that supports, binds togeth ...

s such as Ehlers-Danlos syndrome and

Marfan syndrome Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with long arms, legs, fingers, and toes. They also typically have exceptionally flexible joints a ...

. Chiari malformation is the most frequently used term for this set of conditions. The use of the term "Arnold–Chiari malformation" has fallen somewhat out of favor over time, although it is used to refer to the type II malformation. Current sources use "Chiari malformation" to describe its four specific types, reserving the term "Arnold-Chiari" for type II only. Some sources still use "Arnold-Chiari" for all four types. Chiari malformation or Arnold–Chiari malformation should not be confused with Budd-Chiari syndrome, a hepatic condition also named for Hans Chiari. In Pseudo-Chiari Malformation, leaking of CSF may cause displacement of the cerebellar tonsils and similar symptoms sufficient to be mistaken for a Chiari I malformation.

Treatment

While there is no current cure, the treatments for Chiari malformation are surgery and management of symptoms, based on the occurrence of clinical symptoms rather than the radiological findings. The presence of a syrinx is known to give specific signs and symptoms that vary from dysesthetic sensations to algothermal dissociation to

spasticity Spasticity () is a feature of altered skeletal muscle performance with a combination of paralysis, increased tendon reflex activity, and hypertonia. It is also colloquially referred to as an unusual "tightness", stiffness, or "pull" of muscles. ...

and

paresis In medicine, paresis () is a condition typified by a weakness of voluntary movement, or by partial loss of voluntary movement or by impaired movement. When used without qualifiers, it usually refers to the limbs, but it can also be used to desc ...

. These are important indications that decompressive surgery is needed for patients with Chiari Malformation Type II. Type II patients have severe brain stem damage and rapidly diminishing neurological response. Decompressive surgery involves removing the lamina of the first and sometimes the second or third

cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sa ...

and part of the occipital bone of the skull to relieve pressure. The flow of spinal fluid may be augmented 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. The alternative spinal surgery is also not without risk. Complications of decompression surgery can arise. They include bleeding, damage to structures in the brain and spinal canal,

meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...

, CSF fistulas, occipito-cervical instability and pseudomeningeocele. Rare post-operative complications include hydrocephalus and

compression by retroflexion of odontoid. Also, an extended CVD created by a wide opening and big duroplasty can cause a cerebellar "slump". This complication needs to be corrected by cranioplasty. In certain cases, irreducible compression of the brainstem occurs from in front (anteriorly or ventral) resulting in a smaller posterior fossa and associated Chiari malformation. In these cases, an anterior decompression is required. The most commonly used approach is to operate through the mouth (transoral) to remove the bone compressing the brainstem, typically the odontoid. This results in decompressing the brainstem and therefore gives more room for the cerebellum, thus decompressing the Chiari malformation. Arnold Menzes, MD, is the neurosurgeon who pioneered this approach in the 1970s at the University of Iowa. Between 1984 and 2008 (the MR imaging era), 298 patients with irreducible ventral compression of the brainstem and Chiari type 1 malformation underwent a transoral approach for ventral cervicomedullary decompression at the University of Iowa. The results have been excellent resulting in improved brainstem function and resolution of the Chiari malformation in the majority of patients.

Epidemiology

Congenital Chiari I malformation, defined as tonsilar herniations of 3 to 5 mm or greater, was previously believed to be in the range of one per 1000 births, but is likely much higher. Women are three times more likely than men to have a congenital Chiari malformation. Type II malformations are more prevalent in people of Celtic descent. A study using upright MRI found cerebellar tonsillar ectopia in 23% of adults with headache from motor-vehicle-accident head trauma. Upright MRI was more than twice as sensitive as standard MRI, likely because gravity affects cerebellar position. Cases of congenital Chiari malformation may be explained by evolutionary and genetic factors. Typically, an infant's brain weighs around 400g at birth and triples to 1100-1400g by age 11. At the same time the cranium triples in volume from 500 cm³ to 1500 cm³ to accommodate the growing brain. During human evolution, the skull underwent numerous changes to accommodate the growing brain. The evolutionary changes included increased size and shape of the skull, decreased basal angle and basicranial length. These modifications resulted in significant reduction of the size of the posterior fossa in modern humans. In normal adults, the posterior fossa comprises 27% of the total intracranial space, while in adults with Chiari Type I, it is only 21%. H. neanderthalensis had platycephalic (flattened) skulls. Some cases of Chiari are associated with platybasia (flattening of the skull base).

History

The history of Chiari malformation is described below and categorized by the year: * 1883: Cleland was the first to describe Chiari II or Arnold–Chiari malformation on his report of a child with spina bifida, hydrocephalus, and anatomical alterations of the cerebellum and brainstem. * 1891: Hans Chiari, a Viennese pathologist, described the case of a 17-year-old female with elongation of the tonsils into cone shaped projections which accompany the medulla and are crammed into the spinal canal. * 1907: Schwalbe and Gredig, pupils of German pathologist Julius Arnold, described four cases of meningomyelocele and alterations in the brainstem and cerebellum, and gave the name "Arnold-Chiari" to these malformations. * 1932: Van Houweninge Graftdijk was the first to report the surgical treatment of Chiari malformations. All patients died from surgery or postoperative complications. * 1935: Russell and Donald suggested that decompression of the spinal cord at the foramen magnum might facilitate the CSF circulation. * 1940: Gustafson and Oldberg diagnosed Chiari malformation with syringomyelia. * 1974: Bloch ''et al.'' described the tonsils position to be classified between 7 mm and 8 mm below cerebellum. * 1985: Aboulezz used MRI for discovery of extension

Society and culture

The condition was brought to the mainstream on the series ''

CSI: Crime Scene Investigation ''CSI: Crime Scene Investigation'', also referred to as ''CSI'' and ''CSI: Las Vegas'', is an American procedural forensics crime drama television series that ran on CBS from October 6, 2000, to September 27, 2015, spanning 15 seasons. This wa ...

'' in the tenth-season episode "Internal Combustion" on February 4, 2010. Chiari malformation was briefly mentioned on the medical drama '' House M.D.'' in the fifth-season episode " House Divided", It was the focus of the sixth-season episode " The Choice." It is also the focus of ''Private Practice'' Season 4 episode 4, where a pregnant woman is diagnosed with it. It was the a cause of death on the reality television series ''Dr. G: Medical Examiner'' in the sixth-season episode "Bruised and Battered". It was also mentioned in the medical drama ''

A Gifted Man ''A Gifted Man'' is an American fantasy medical drama television series that premiered on CBS on September 23, 2011. The series is about a talented but self-absorbed surgeon ( Patrick Wilson) who starts questioning his purpose in life when he is v ...

'', in the first-season episode "In Case of Separation Anxiety". It is also featured in the 3rd and 4th episode of the 7th season of the series '' Rizzoli & Isles'' where Dr. Maura Isles is diagnosed with the condition.

Notable people

* Rosanne Cash – U.S. singer-songwriter; daughter of Johnny Cash *

Julia Clukey Julia Clukey (born April 29, 1985 in Augusta, Maine) is an American luger who started competing in 2002. Her best Luge World Cup season finish was 12th in women's singles in 2007–08. Clukey's best finish at the FIL World Luge Championships ...

– U.S. luge competitor for Team USA in 2010 Vancouver Winter Olympics *

Joanna David Joanna David (born Joanna Elizabeth Hacking; 17 January 1947) is an English actress, best known for her television work. Life David was born in Lancaster, England, to Davida Elizabeth (''née'' Nesbitt) and John Almond Hacking. In 1971, she ...

– British television and stage actress *

J. B. Holmes John Bradley "J.B." Holmes (born April 26, 1982) is an American professional golfer who plays on the PGA Tour. Early life Holmes, born in Campbellsville, Kentucky, began to play on the varsity golf team at Taylor County High School in Campbel ...

– U.S. professional golfer *

Marissa Irwin Marissa Irwin is an American model best known for her appearances on the cover of ''Bridal Guide'' and in '' Seventeen Magazine''. A native of Canton, Ohio, she received training from the Barbizon modeling school of Akron.Ehlers-Danlos syndrome * Bobby Jones – U.S. World Golf Hall of Fame golfer and founder of the Augusta National Golf Club *

Allysa Seely Allysa Seely (born January 4, 1989) is an American paratriathlete and gold medalist at the 2016 and 2020 Summer Paralympics. Background Seely was born on January 4, 1989. She grew up in Glendale, Arizona and graduated from Mountain Ridge High ...

– U.S. Gold Medalist at the 2016 Summer Paralympics in the paratriathlon * Leah Shapiro – U.S. drummer for the band Black Rebel Motorcycle Club * Michelle Stilwell – Canadian wheelchair racer and politician *

Rachid Taha Rachid Taha ( ar, رشيد طه, Latn, ar, Rashīd Ṭāhā, ; 18 September 1958 – 12 September 2018) was an Algerian singer and activist based in France described as "sonically adventurous". His music was influenced by many different styles ...

– Algerian singer * Sabre Norris – Australian skateboarder and surfer

References

{{DEFAULTSORT:Arnold-Chiari Malformation Congenital disorders of nervous system