The Chiari Malformations and syringomyelia: Definitions

Bermans J. Iskandar

Pediatric Neurosurgery

University of Wisconsin, Madison ASAP Austin 2010

Chiari Type I Tonsillar descent >5mm below the plane of the foramen magnum.

No associated brainstem herniation or supratentorial anomalies

Low frequency of hydrocephalus and syringomyelia

Chiari Type II Caudal descent of the vermis, brainstem, and fourth ventricle.

Associated with myelomeningocele and multiple brain anomalies

High frequency of hydrocephalus and syringohydromyelia

Standard

Chiari Type IV Hypoplasia or aplasia of the cerebellum

Chiari Type III Occipital encephalocele containing

Dysmorphic cerebellar and brainstem tissue

Rare & Poor Prognosis

New & Controversial

Chiari Zero Idiopathic syringomyelia that responds to craniocervical decompression

Chiari 1.5 Descent of tonsils & medulla

Behaves like Chiari I

JNS:Peds 2004 JNS 1998

Diagnosis made on MRI Treatment: posterior fossa

decompression. If the syrinx does not

resolve: Re-explore the posterior fossa

and expand the decompression

Consideration of subtle craniocervical instability

Consideration of benign intracranial hypertension

Consideration of shunting the syrinx directly

8 year old boy with headaches Syrinx 1 cm tonsillar descent

30 year-old with 1.5 cm tonsillar descent and severe symptoms

Posterior fossa decompression fails LP monitoring reveals elevated ICP VP shunt Symptoms resolve

10 year-old who underwent serial lumbar punctures for a mild viral meningitis

Develops lower cranial nerve symptoms

MRI reveals new tonsillar herniation

12 year-old with Chiari I, syringomyelia, and basilar invagination

Posterior fossa decompression

Symptoms and syrinx don’t resolve until craniocervical fusion a year later

Likely Etiology In utero CSF leak through the

myelomeningocele opening, causing caudal traction on brain structures

Clinical Presentation Infants: usually asymptomatic Children: signs of lower brainstem

compression: stridor, apnea, dysphagia, aspiration

Chiari II: leading cause of death in spina bifida patients in the recent past

30% of patients: brainstem symptoms by age 5 (1/3 of these die)

Most dangerous period: 2-3 months of age (sometimes up to 2 years)

Current understanding VP shunt malfunction most likely

cause of deterioration, rather than the Chiari

Ventricle size may not change Number of Chiari II decompressions

has decreased significantly since more aggressive shunt revisions

Fluid-filled cavity within the spinal cord

Other nomenclature

Hydromyelia Syringohydromyelia Spinal cord cyst

Dissociated sensory loss

Central cord syndrome

Brainstem symptoms and signs

Scoliosis Chronic pain

Spinal MRI will show a dilated cavity with the same intensity of CSF.

A complete brain and spinal MRI with and without Gadolinium is needed to determine the primary pathology.

Cine MRI may also help in diagnosing abnormal CSF flow patterns. So far results have been conflicting.

Rarely, myelography may help to sort some of the more difficult cases.

Asymptomatic patients with small syrinx cavity and no obvious etiology are best managed with watchful waiting and serial imaging

Large syrinx: Treat the cause of the syrinx, not the syrinx itself

The syrinx may be the result Tethered cord from the

myelomenigocele repair scar Chiari II malformation Ventricular shunt malfunction.

Location of the syrinx within

the spinal cord may help to dictate the treatment Lumbar syrinx ??tethered

cord release Cervical syrinx ?? VP shunt

revision Check the shunt first!

Diagnosis by MRI Treatment:

Tethered cord release

If syrinx is large, it is often drained at the same surgery

Diagnosis made on MRI Treatment: Dissection of the arachnoid

scar (often difficult or impossible) Goal: Reestablish normal CSF flow Difficulties: If the arachnoiditis is so

diffuse that it becomes impossible to achieve a good dissection, shunt the syrinx to the pleural or peritoneal cavities

Post-traumatic syrinx is difficult to treat successfully

Possible causes Arachnoiditis and blockage of

flow causing expansion of the cord, or

Atrophy long term after cord contusion

Treatment: arachnoidal dissection, or syrinx shunt into the pleura or peritoneum

Diagnosis made on MRI High protein content Treatment:

Tumor resection It is rare to have to

shunt the syrinx in these situations.

In a large percentage of patients, the syrinx has no identifiable cause

Difficult to treat If large, syrinx shunting Rarely, posterior fossa decompression

(Chiari zero) It is so far impossible to predict which

patient with idiopathic syringomyelia would respond to posterior fossa decompression

Chiari decompression Excellent outcome

Spina bifida Excellent outcome when shunt is functional

Arachnoiditis Focal – fair prognosis Diffuse – poor, need to shunt the syrinx

Trauma Poor outcome for syringomyelia and pain

Tumor: Excellent outcome for syringomyelia Overall Prognosis depends on tumor grade

Standard basic definitions Complicating factors: hydrocephalus,

pseudotumor cerebri, instability, etc. Treatment controversies

When to treat What to do When to do it

Goals: Recognize basic concepts; recognize controversial areas; be prepared to bring these points up with your physician