Chiari Malformations Report

8/3/2019 Chiari Malformations Report

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CHIARI

MALFORMATIONS

PGI Callejas, Jeanette


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General Data:J.P.12 days oldMale


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Cranial Ct Result:

1. Beaking of thetectum

2. Narrowing ofthe 4th ventricle

3. The lowermedulla is below

the foramenmagnum


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4. Scallopingof theposterior

border ofpetrousbones andclivus


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5. Lateral

ventricles arelarge, nearlyparallel, andhave pointed

occipital horns

Beaking of

the tectum


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Impression:Findings of hydrocephalus, tonsillarherniation , beaking of the tectum,enlarged pointed occipital horns,interdigitation of the gyri and narrowed4th ventricle are suggestive ofChiari IImalformation


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Anatomy of the brain

The forebrain orprosencephalon(supratentorial portion of

the brain) comprises thetelencephalon (the twocerebral hemispheres andthe midline structuresconnecting them) and the

diencephalon.


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Themidbrain or

mesencephalon lies betweenthe fore brain and the hindbrain. It passes through thetentorium cerebelli.

The hindbrain orrhombencephalon(infratentorial portion of thebrain) comprises the pons,the medulla oblongata(almost always called medullafor short), and the cerebellum.The mid brain, pons, andmedulla together make up the

brain stem.


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The Cerebellum isBrain's balance and

coordination center aswell as the controlcenter for fine tuningsmooth andcoordinated

movements of theentire body.

It is composed ofseveral parts. Thecenter portion is called

Vermis of

cerebellum

Vermis of

cerebellum

Tonsil of

cerebellum


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csf system AND VENTRICLES

q Cerebrospinal fluid (CSF) is a clear, waterysubstance that flows within and around the brain

and spinal cord.

q This circulating fluid is constantly being absorbedand replenished.

q The CSF is produced by the choroid plexus insidehollow channels in the brain called ventricles

q The CSF flows through the ventricles and out into

the venous sinus. The brain normally maintains a


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Ventricles and csf system

The ventricular

system is a setof structurescontaining

cerebrospinalfluid in thebrain. It iscontinuous withthe central canal

The system comprisesfour ventricles:

q right and left lateralventriclesq third ventricleq fourth ventricle


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There are several small holes or foramina thatconnect these ventricles,

NAME FROM TO

Right and LeftInterventricularForamina (Monroe)

Lateral Ventricles Third Ventricles

Cerebral Aqueduct(Sylvius)

Third Ventricle Fourth Ventricle

Median aperture(Magendie)

Fourth Ventricle Subarachnoidspace/ CisternaMagna

Right and LeftLateral Aperture Fourth Ventricle Subarachnoidspace/ Cistern of


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CHIARI MALFORMATIONS

q


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this can also causeCerebrospinal Fluid (CSF) tobe pushed down, underpressure, into the CervicalSpinal Cord's "Central Canal"to form a "Syrinx".

A Syrinx is an abnormal, fluidfilled, internal dilatation ofthe Spinal Cord's Central

Canal.


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types of chiari malformation

Type I Malformation

Most common form.Sometimes termed as

congenital tonsillar ectopia.That is unassociated withother congenital brainmalformations.

This type is usuallydiagnosed in adolescenceorearly adulthood whensymptoms most commonlyappear; however, with the

availability ofmagnetic


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Chiari I malformation is usually notassociated with other brainanomalies. However, spinal cord, skullbase and spine lesions are common inthis disorder.

Spinal Cord Accumulation ofcerebrospinal fluid within the spinalcord is frequent finding in patientswith chiari I

Hydromyelia

SyringomyeliaSyrinxSkull Base and Spine osseousanomalies are seen in about onequarter of all patients.Include atlantooccipital assimilation,

basilar invagination and fusedcervical vertebrae (Klippel Feil)


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Type II malformation

is more severe than Type I and


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the primitive ventricular system then


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The Chiari II malformationhas abnormalities of the

following:Skull and DuraHindbrain, cerebellum and

midbrainCerebrospinal fluid spaces

Cerebral hemispheresSpine and spinal cord


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Skull and Dura

There is focal calvarial thinning and a scoopedout appearance of the skull (lacunar skull)

Abnormally small and shallow posterior fossawith low lying transverse sinuses.

The foramen magnum is unusually large(gaping) and the posterior aspects of the

petrous temporal bones are often concave.The clivus also develops abnormally and is

often short, with a concave configurationsimilar to the petrous ridges.

The falx may be thinned, hypoplastic or

fenestrated.The interhemispheric fissure often has an

irregular, serrated appearance becauseapposing gyri cross the midline and eveninterdigitate.


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Hindbrain, cerebellum andmidbrain

The medulla and cerebellum are

displaced downward into the uppercervical canal for a variable distance.

The medulla is inferiorly kinked in 70% of all cases and may lies as low asthe upper thoracic canal

The displaced vermis and medullaform a cascade of displaced tissuethat protrudes through the gapingforamen magnum to lie behind thespinal cord

The cerebellar hemispheres andvermis also herniate upward (toweringcerebellum).

Cerebrospinal Fluid spaces

Abnormalities of the ventricles are


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Spine and Spinal Cord

Various spine and cord anomalies are associated with theChiari III malformation

Myelomeningocele is present in virtually all cases.

Syringohyromyelia and diastematomyelia also oftenaccompany Chiari II malformation.


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In Type III malformationOccurs rarely.

Parts of the cerebellum and the brain stemprotrude into a spina bifida defect located at thebase of the skull, on the neck.

Some neurologists do not consider it a Chiarimalformation but rather a specific type of spinabifida called an encephalocervical meningocele.


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Type IV malformation

Consists of an underdevelopment of the cerebrumand involves no herniation of brain tissue into thespinal area.

As with Type III malformation, many neurologistsdo not consider this a Chiari malformation but rather

cerebellar hypoplasia (underdevelopment).Both Type III and IV Chiari malformations are

extremely rare, and this term is not often used indiagnosis of these conditions.


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demographics

The true incidence is unknown.

Most researchers agree that the rate of both TypeI and Type II Chiari malformation is approximately1 percent of all live births. Of those with Type Imalformation, approximately 25 percent alsohave syringomyelia. However, the majority of all


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Who is affected?

Chiari I malformation has been on imagingstudies in patients of all ages. However, patientstypically seek medical attention in their 20s and30s.

Three times more women than men areaffected. Some genetic studies show that thiscondition runs in some families.


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SIGNS AND SYMPTOMSHeadaches aggravated byValsalva maneuvers, such asyawning, laughing, crying,coughing, sneezing orstrainingTinnitusDizziness and vertigoNauseaNystagmusFacial painMuscle weakness

Impaired gag reflexRestless Leg SyndromeSleep ApneaDysphagiaBreathing abnormalitiesNeck pain


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diagnosis

Diagnosis is made through a combination ofpatient history, neurological examination, andMagnetic Resonance Imaging (MRI).

Other imaging techniques involve the use of 3-D

CT imaging of the brain and cine imaging (amovie of the brain) can be used to determine ifthe brainstem is being compressed by thepulsating arteries that surround it.[
http://c/Users/jeanette/Desktop/chiari/Arnold???Chiari_malformation.htm#cite_note-Chiari_Institute_Videos-20http://c/Users/jeanette/Desktop/chiari/Arnold???Chiari_malformation.htm#cite_note-Chiari_Institute_Videos-20


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Magnetic Resonance Imaging (MRI) scan is a

noninvasive test used to evaluate the patientsbrain, spinal cord and surrounding CSF. MRIstudies will identify the extent of cerebellarherniation, from several millimeter to centimeter.

The herniation may reach to the level of the firsttwo vertebra of the cervical spine. As a result ofthe herniation, other anatomical abnormalitiesmay be seen at C1 and C2. in some patients, MRIcan also detect an abnormal accumulation of CSF

within the spinal canal. This fluid-filled cavity(syrinx) is surrounded by stretched tissues of thespinal cord.

Cine MRI is a special type of study performed toobserve and detect obstruction of CSF flow.
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treatmentTreatment options vary depending on the severity of symptoms,the extent of tonsilar herniation, and the presence of associatedconditions such as hydrocephalus, syringomyelia, and disorders of

the skull and spine.

OBSERVATION:Mild or no symptomsMonitoring by regular exam may be recommended.

If there are symptoms of pain, pain medication may provided

relief.Avoid chiropractic manipulation as it can make the herniationworse or aggravate the brain injury.

SURGERY:In patients whose pain are severe or a syrinx is present

In general , the goals of surgery are to relieve the progression ofsymptoms caused by the herniation of the cerebellar tonsils and
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Posterior Fossa Decompression is a surgical

procedure that removes bone at the back of theskull and spine to widen the foramen magnum.The dura overlying the tonsils is opened and adural patch is sewn to expand the space andrestore normal CSF flow.

Shunt in some cases shunt is inserted intothe syrinx cavity to reroute the cerebrospinal

fluid from the spinal cord.
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prognosisThe prognosis differs dependent on the type of malformation (i.e.,type I, II, III, or IV). Type I is generally adult-onset and, while notcurable, treatable and rarely fatal.Types I and II sufferers may also develop syringomyelia.Type II istypically diagnosed at birth or prenatally. Approximately 33% ofindividuals with Chiari II malformation develop symptoms ofbrainstem damage within five years; a 1996 study found a mortalityrate of 33% or more among symptomatic patients, with deathfrequently occurring due to respiratory failure. 15% of individuals withChiari II malformation die within two years of birth.

Among children under two who also have myelomeningocele, it is the

leading cause of death. Prognosis among children with Chiari IImalformation who do not have spina bifida is linked to specificsymptoms; the condition may be fatal among symptomatic childrenwhen it leads to neurological deterioration.

Types III and IV are extremely rare and patients generally do not

survive past the age of two or three
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Chiari Malformations Report