THE CHIARI MALFORMATIONS AND
SYRINGOMYELIA: DEFINITIONS
Bermans J. Iskandar
Pediatric Neurosurgery
University of Wisconsin, Madison
ASAP Austin 2010
Standard
Chiari Type I
Chiari Type II
 Tonsillar descent >5mm below the plane
of the foramen magnum.
 Caudal descent of the vermis,
brainstem, and fourth ventricle.
 No associated brainstem herniation or
supratentorial anomalies
 Associated with myelomeningocele
and multiple brain anomalies
 Low frequency of hydrocephalus and
syringomyelia
 High frequency of hydrocephalus
and syringohydromyelia
Rare & Poor Prognosis
Chiari Type III
Chiari Type IV
 Occipital encephalocele containing
 Hypoplasia or aplasia of the cerebellum
 Dysmorphic cerebellar and brainstem
tissue
New & Controversial
Chiari 1.5
Chiari Zero
 Descent of tonsils & medulla
 Idiopathic syringomyelia that
responds to craniocervical
decompression
 Behaves like Chiari I
JNS:Peds 2004
JNS 1998
CHIARI I MALFORMATION



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
CHIARI I
CASE 1: BASIC SCENARIO
8 year old boy with headaches
 Syrinx
 1 cm tonsillar descent

CHIARI I
CASE 2: PSEUDOTUMOR CEREBRI
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

CASE 3: HYDROCEPHALUS
CHIARI I
CASE 4: ACQUIRED CHIARI I
10 year-old who underwent serial lumbar
punctures for a mild viral meningitis
 Develops lower cranial nerve symptoms
 MRI reveals new tonsillar herniation

CHIARI I
CASE 5: CHRONIC CRANIOCERVICAL
INSTABILITY
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

CHIARI II MALFORMATION

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 MALFORMATION

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)
CHIARI II MALFORMATION

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
SYRINGOMYELIA

Fluid-filled cavity
within the spinal cord

Other nomenclature
 Hydromyelia
 Syringohydromyelia
 Spinal
cord cyst
SIGNS AND SYMPTOMS
Dissociated sensory loss
 Central cord syndrome
 Brainstem symptoms
and signs
 Scoliosis
 Chronic pain

DIAGNOSTIC STUDIES
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.

TREATMENT - BASED ON ETIOLOGY

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
SPINA BIFIDA

The syrinx may be the result




Location of the syrinx within
the spinal cord may help to
dictate the treatment



Tethered cord from the
myelomenigocele repair scar
Chiari II malformation
Ventricular shunt malfunction.
Lumbar syrinx ??tethered cord
release
Cervical syrinx ?? VP shunt
revision
Check the shunt first!
CONGENITAL TETHERED CORD
(SPINA BIFIDA OCCULTA)
Diagnosis by MRI
 Treatment: Tethered
cord release
 If syrinx is large, it is
often drained at the
same surgery

ARACHNOIDITIS
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

TRAUMA
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
SPINAL CORD TUMOR
Diagnosis made on MRI
 High protein content
 Treatment:

 Tumor
resection
 It is rare to have to shunt the
syrinx in these situations.
IDIOPATHIC
NO IDENTIFIABLE CAUSE
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
PROGNOSIS AND OUTCOME
SYRINGOMYELIA RESOLUTION

Chiari decompression


Spina bifida



Focal – fair prognosis
Diffuse – poor, need to shunt the syrinx
Trauma


Excellent outcome when shunt is functional
Arachnoiditis


Excellent outcome
Poor outcome for syringomyelia and pain
Tumor:


Excellent outcome for syringomyelia
Overall Prognosis depends on tumor grade
CONCLUSIONS
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