Where can I get more information? Chiari malformations are structural defects in the base of the skull and cerebellum, the part of the brain that controls balance. Normally the cerebellum and parts of the brain stem sit above an opening in the skull that allows the spinal cord to pass through it called the foramen magnum. When part of the cerebellum extends below the foramen magnum and into the upper spinal canal, it is called a Chiari malformation CM.
Chiari malformations may develop when part of the skull is smaller than normal or misshapen, which presses on the brain and forces the cerebellum to be pushed down into the spinal canal. The pressure on the cerebellum and brain stem may affect functions controlled by these areas and block the flow of cerebrospinal fluid CSF —the clear liquid that surrounds and cushions the brain and spinal cord. Some individuals with CM may not show any symptoms. Symptoms may change for some individuals, depending on the compression of the tissue and nerves and on the buildup of CSF pressure.
Symptoms may include:. CM Is most often caused by structural defects in the brain and spinal cord that occur during fetal development. This is called primary or congenital Chiari malformation. CM can also be caused later in life if spinal fluid is drained excessively from the lumbar or thoracic areas of the spine either due to traumatic injury, disease, or infection. This is called acquired or secondary Chiari malformation.
Primary Chiari malformation is much more common than secondary Chiari malformation. Chiari malformations are classified by the severity of the disorder and the parts of the brain that protrude into the spinal canal. Currently, no test is available to determine if a baby will be born with a Chiari malformation. There is no universally accepted theory explaining the Chiari malformation and its associated anomalies.
Even acquired forms of cerebellar tonsil herniation are recognised. Chiari I and II malformation tend to be more frequent in women and, in some subtypes of Chiari malformation, a genetic factor is beginning to be discussed. Two findings support the existence of a genetic factor: the familial association observed and the coexistence with genetic anomalies Klippel-Feil or achondroplasia.
Despite all these cases, no definitive conclusion can be drawn regarding the suspected existence of a genetic factor and the familiar association for this condition. In the Chiari I-syringomyelia complex, various pathogenic hypotheses are currently postulated, although the most accepted refer to a mechanical factor excessively small posterior fossa and an embryonic developmental anomaly [ 10 — 15 ].
The onset of Chiari syndrome symptoms usually occurs in the second or third decade age 25 to 45 years , although it is commonly earlier in patients with syringomyelia. Symptoms generally have an insidious onset and a progressive course. There is high clinical variability among patients, ranging from asymptomatic patients, patients with non-specific clinical manifestations, to patients with severe neurologic deficits.
Suboccipital headache is the most frequent symptom in these patients. The headache is located in the occipital and is of oppressive nature, increasing with Valsalva manoeuvres such as coughing, sneezing, or bowel movement. The headache can also have non-specific features or a tensional profile.
Neck pain is frequent and characterized by the absence of radicular distribution. It is associated to continuous, burning, deep-seated discomfort in the shoulders, nape, chest, and upper limbs. Neck pain usually increases with Valsalva manoeuvres. Vertigo can occur, particularly positional vertigo, or triggered by head movements.
Other otological symptoms present in these patients are tinnitus and aural fullness. Occasionally, mild neurosensorial hearing loss, with peripheral vestibulopathy is found in otological evaluations. Other frequent symptoms are ocular, often with unremarkable neuro-ophthalmologic examination. The most frequent ocular symptoms are: retro-orbital headache, diplopia, photopsia, blurred vision, and photophobia.
In very severe cases in which compression of the spinal cord or medulla oblongata occurs, symptoms of involvement of the motor or sensory pathways, or lower cranial nerves exist. Breathing-related sleep disorders were frequently reported in patients with craniocervical junction malformations. Chiari type I malformation should be considered in the differential diagnosis of central apnoeas in infants, especially when they are associated with other neurological sign or symptom.
Some authors considered the presence of sleep disorders as an earlier marker of progressive brain stem dysfunction. In cases associated to syringomyelia, levoscoliosis may be present. In these patients, the involvement of various nervous structures result in mixed physical signs:. First motor neuron : generalised hypereflexia, spasticity, and Babinski reflex, mostly in the lower limbs. Second motor neuron : atrophy, weakness, fasciculations, and areflexia, mostly in the upper limbs.
The following findings may exist: vocal cord paralysis, soft palate weakness, lingual atrophy, cricopharyngeal achalasia, facial hypoaesthesia, and absent gag reflex the most frequent physical sign indicating involvement of the lower cranial nerves. The delay from the onset of the disease to the diagnosis of any craneocervical junction malformation, before was significantly longer than after when magnetic resonance imaging became widely available in clinical practice.
That period of time usually was shorther in the pediatric group. The diagnosis of Chiari type I malformation in patients with or without symptoms is established with neuroimaging techniques; the preferred technique is magnetic resonance imaging MRI [ 20 ].
The diagnosis of syringomyelia should be made by MRI of the complete spine cervical, dorsal, and lumbar. Cranial CAT is also useful for monitoring hydrocephalus. Asymptomatic patients who are diagnosed of Chiari type I malformation without syringomyelia should not be considered as candidates for surgery.
In asymptomatic Chiari type I malformation with syringomyelia, the opinion of neurosurgeons varies. In symptomatic patients, surgical treatment should be considered. Various techniques are used to treat this malformation, but they all involve decompression at the foramen magnum. As in all surgical procedures, decompression of the foramen magnum in Chiari malformation is not free from complications. These include CSF fistula, meningitis, hydrocephalus, or the progression of syringomyelia.
Most patients experience an improved quality of life after surgery. The symptoms that improve most are mainly headache and neck pain, followed by symptoms attributable to direct compression of the cerebellum or brain stem e. In contrast, the symptoms attributable to syringomyelia pain, scoliosis, and loss of sensitivity improve less. If syringomyelia persists, inadequate decompression of the craniocervical junction should be considered.
In post-traumatic syringomyelia Figure 2 , some authors [ 23 , 24 ] prefer to restore the canal, which avoids CSF blockade, and empty the cyst or leave a drainage tube in the subarachnoid space. Other authors support conservative treatment [ 25 ]. In cases of syringomyelic cysts associated to tumours, cyst reduction is generally achieved by excising the tumour [ 26 , 27 ]. Neuropathic pain is caused by the lesion of junctional structures between the cerebral base and the cerebellum, and the cervical spinal cord.
When a nervous system lesion occurs, different symptoms appear, some are due to loss of function when damage is severe and there is total disruption of nerve conduction; other symptoms are due to irritation Table 1. Allodynia: a painful response to a non-painful stimulus, such as, brushing the skin with a cotton wad or sponge.
Hyperalgesia: an excessively painful response to a mildly painful stimulus, such as a slight prick. Given the high variability in intensity, severity, and location of symptoms, each patient must receive individualized treatment.
Globally, there are two types of therapy: pharmacological and non-pharmacological. Neuropathic pain should be managed with a multifactorial approach using drugs that act on different components of pain, including disturbed neuronal activity anticonvulsants [ 28 — 32 ] and local anaesthetics [ 33 ] , potentiation of descending inhibitory pathways antidepressants [ 34 ] , or centres involved in the development and conduction of nociceptive responses analgesics [ 35 — 37 ].
Some of these drugs, their mode of action and side effects are described in Table 2. Neuropathic pain has traditionally been considered resistant to analgesics, specifically opiates, but it is now admitted that there is some response to these molecules, but less satisfactory than in nociceptive pain. Although the use of most of these drugs is backed by scientific evidence obtained in the treatment of other forms of neuropathic pain, evidence of their effect against the pain produced by Chiari syndrome or syringomyelia is limited due to the low incidence of these conditions and the lack of studies assessing non-surgical treatment for these patients.
Some studies suggest that the use of drug combinations, such as weak opiates with anticonvulsants, can be more effective in neuropathic pain and require lower doses. Spinal infusion of medications has been used for years, but there is little evidence of its efficacy in neuropathic pain and none in Chiari syndrome. Spinal infusion systems comprise an implantable pump system for controlled drug administration, and a catheter through which the medication is directly infused into the cerebrospinal fluid bathing the spinal cord.
Implantation of both elements allows prolonged therapy without complications. Drugs used most often with this system include morphine, bupivacaine, clonidine [ 38 ], and baclofen [ 39 ]. While little evidence is available to support pharmacological therapy for pain, there is no evidence at all on the effect of non-pharmacological therapies. Therapies that could benefit these patients are reserved for use when all other therapeutic options fail. When the symptoms of neuropathic pain are localized in a specific territory, such as one or both upper or lower limbs, electrical stimulation [ 40 ] is a potential option.
Although spinal stimulation has demonstrated its efficacy in certain types of neuropathic pain, this is not the case for central pain, and there is no evidence available in patients with Chiari syndrome. However, since this therapy is free of major side effects, and any side effect that could occur is reversible, it is an option to be considered before using more questionable therapeutic approaches. Peripheral stimulation has been used recently to treat certain conditions. For example, headache refractory to pharmacologic therapy has been treated with electric stimulation of the occipital nerves.
There is little evidence available on the efficacy of this therapy because the technique has been very recently developed, but it could be a therapeutic option for headache in patients with Chiari syndrome if no other treatment has been effective.
Rehabilitation is a medical specialty that receives patients referred from both primary care and specialized care. Patients with Chiari malformation are often referred by a general practitioner with a diagnosis of chronic persistent neck pain, only to have the rehabilitation, specialist discover the malformation after obtaining a magnetic resonance imaging. Next, rehabilitation therapy is prescribed, including: medical, physical, and occupational therapy.
In rare cases, this type may also develop later in life. This is known as acquired or secondary Chiari malformation type I. The exact cause of a congenital Chiari malformation type I is not known. A problem during fetal growth may cause the defect.
It may be caused by contact with harmful substances during pregnancy. Or it may be linked with genetic problems that run in families. An acquired Chiari malformation type I happens to a person after birth. It is caused by excess leaking of spinal fluid from the lower back lumbar or chest thoracic areas of the spine. This can happen because of an injury, contact with harmful substances, or an infection. Alan Cohen , chief of pediatric neurosurgery, gives an overview of the different types of Chiari malformations and how they're treated.
Cohen also explains why not all cases will need surgery. Chiari malformations are associated with the formation of a syrinx, a fluid-filled pocket, or cyst, in the spinal cord. This condition also known as syringomyelia. As the cyst fills with cerebrospinal fluid, it expands, putting pressure on the spinal cord.
In some patients with a Chiari malformation, increasing pressure from a syrinx can affect neuromuscular function, causing limb weakness or difficulties with walking or breathing.
Some children will show signs of a spine syrinx, but others will not. In these situations, an MRI scan may be needed for a definite diagnosis. In children younger than 16 whose spines are still growing, the presence of a syrinx can also be associated with the development of scoliosis, an abnormal, lateral side-to-side curvature of the spine.
Toddlers, children and teens with undiagnosed type 1 Chiari malformations may develop headaches, which are typically located at the back of the head and neck, and are often made worse by exertion.
Type 2 Chiari malformations can also be associated with hydrocephalus, a condition in which there is an obstruction of the flow of cerebrospinal fluid that is found inside of the ventricles fluid-filled areas inside of the brain.
Sleep apnea is another problem that occurs in people with a Chiari malformation. This is a serious sleep disorder characterized by brief interruptions in breathing during sleep. A sleep study can confirm the presence of sleep apnea so a doctor can prescribe treatment.
If you have no symptoms, the problem may be found when you have imaging tests for other reasons. Swallowing study: Fluoroscopy XRays used to watch the internal swallowing process to determine if there is an abnormality suggestive of lower brainstem dysfunction. Brainstem auditory evoked potential BAER : An electrical test to examine the function of the hearing apparatus and brainstem connections.
This is used to determine if the brainstem is working properly. Myleogram: An X-ray of the spinal canal following injection of a contrast material into the CSF space; can show pressure on the spinal cord or nerves due to malformations. This test is performed less frequently now. Treatment of Chiari malformations and syringomyelia is very dependent on the exact type of malformation, as well as progression in anatomy changes or symptoms. Chiari I malformations that are asymptomatic should be left alone this involves the majority of Chiari malformations.
There is no indication for "prophylactic" surgery on these. If the malformation is defined as symptomatic, or is causing a syrinx, treatment is usually recommended. Chiari II malformations are treated if the patient is symptomatic, and physicians have determined that there are no complications from hydrocephalus.
In some patients, consideration of a tethered cord is also explored. In many infants who become symptomatic from a Chiari II malformation, the symptom onset and progression are severe and rapid, and this requires an urgent or emergency approach. Surgical treatment of these malformations depends on the type of malformation.
The goal of surgery is to relieve the symptoms or stop the progression of the syrinx or symptoms. Chiari I malformations may be treated surgically with only local decompression of the overlying bones, decompression of the bones and release of the dura a thick membrane covering the brain and spinal cord or decompression of the bone and dura and some degree of cerebellar tissue resection.
Occasionally some patients will also require cervical spinal fusion. Decompression is performed under general anesthesia. It consists of removing the back of the foramen magnum and often the back of the first few vertebrae to the point where the cerebellar tonsils end.
This provides more space for the brainstem, spinal cord and descended cerebellar components. A tissue graft is often spliced into this opening to provide even more room for the unimpeded passage of CSF. In some patients the descended cerebellar components are debulked or removed. Occasionally, the cavity within the spinal cord resulting from hydromyelia can be drained with a diverting shunt tube. This tube can divert the fluid from inside the spinal cord to outside the cord, or be directed to either the chest or abdominal cavity.
These procedures can be done together or separately. Chiari II decompression is treated similarly, but is usually restricted to decompressing the tissues in the spinal canal and leaving the back of the skull alone.
The benefits of surgery should always be weighed carefully against its risks. Although some patients experience a reduction in their symptoms, there is no guarantee that surgery will help every individual.
Nerve damage that has already occurred usually cannot be reversed.
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