Pediatric Chiari Malformation
What is a Pediatric Chiari I Malformation?
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Chiari I malformation, the most common and treatable type of
Chiari malformation, is a neurological disorder in which the
cerebellum – the part of the brain that controls balance – descends
out of the skull into the spinal canal. Specifically, the portions of
the cerebellum that descend lower than they should are called the
cerebellar tonsils (not to be confused with the tonsils located in
the throat). Normally, the cerebellum is located in an indented
space at the lower back of the skull above the foramen magnum,
a funnel-like opening to the spinal canal. Chiari I malformation
is diagnosed, usually by MRI, when part of the cerebellum is located
below the foramen magnum. Normally, only the spinal cord passes
through this opening.
Chiari I malformations may develop when
the indented space is smaller than normal,
causing the cerebellum to be pushed
downward into the foramen magnum and
the upper part of the spinal canal. The
result is pressure on the cerebellum that
may affect functions controlled by this
area of the brain and block the flow of
cerebrospinal fluid (CSF) to and from the
brain. CSF is a clear liquid that surrounds
and cushions the brain and spinal cord.
Symptoms of Pediatric Chiari I Malformation
Chiari I malformation may or may not
cause symptoms and usually is first noticed
in adolescence or adulthood, often during
examination for another condition. The most
common symptom is a specific type of headache
which occurs in the back of the head and may
involve the neck as well. Typically, these headaches
are short-lived and worsened with “valsalva
maneuvers” – when a person strains during
exercise, coughing or other activities. They are
often relieved when such activities are stopped.
Other symptoms may include:
- Balance problems
- Muscle weakness
- Numbness or other unusual feelings in the arms or legs
- Vision problems
- Ringing or buzzing in ears
- Difficulty swallowing
- Apnea (suspension or holding of breath)
Infants with Chiari malformation may have difficulty swallowing,
irritability when being fed, excessive drooling, a weak cry, gagging
or vomiting, arm weakness, breathing problems, developmental
delays and an inability to gain weight.
Other Conditions Associated with Pediatric Chiari I Malformation
Children and adolescents who have a Chiari I malformation may also
have hydrocephalus and syringomyelia.
Hydrocephalus is the excessive accumulation of cerebrospinal fluid (CSF)
in the brain causing increased pressure. If left untreated, loss of
mental and physical abilities, brain damage and even death may occur.
Early diagnosis and timely treatment are important to the successful
treatment and recovery of children with hydrocephalus. After birth,
infants with hydrocephalus may exhibit growth of the head at a faster
rate than normal due to the buildup of excess CSF. Older children
may experience the sudden onset of severe headaches accompanied
by vomiting as well as possible loss of bladder control, irritability,
sleepiness, seizures and loss of balance, motor skills and memory.
Syringomyelia is a disorder in which a fluid collection, called a syrinx,
forms within the spinal canal. When the syrinx grows, it expands and
puts pressure on the spinal cord, causing pain, weakness and stiffness
in the back, shoulders, arms or legs. Other symptoms may include
headaches and a loss of the ability to feel extremes of hot or cold,
especially in the hands. Some children and adolescents have severe
arm and neck pain.
If Chiari I malformation is suspected, the first step in diagnosis is
a physical examination which includes a complete neurological
examination. Your physician may also order an MRI, which uses radio
waves and a powerful magnetic field to produce a detailed 3-D image
of body structures, including tissues, bones and nerves. MRI scans
include images of the brain to assess the Chiari malformation and rule
out hydrocephalus or other conditions. They also include images of
the complete spine to look for a syrinx. Special MRI scans to assess the
flow of fluid around the brain and upper spinal cord, called CINE CSF
Flow studies, may help your child’s pediatric neurosurgeon determine
whether treatment is required.
MRI studies can take up to several hours and often require anesthesia
in children. To minimize the length of the imaging study, the pediatric
neurosurgery team at Children’s Memorial Hermann Hospital has
instituted an innovative “Quick Brain” MRI protocol. Quick Brain MRI
studies can be completed in less than five minutes, do not require sedation
and have no radiation exposure. Your child’s pediatric neurosurgeon
can tell you whether your child is a good candidate for this study.
Additional tests that your physician may order include somatosensory
evoked potentials (SSEPs) and brainstem auditory evoked responses
(BAERs). These tests assess the function of the spinal cord and
brainstem, respectively, and may provide information to help your
child’s physician determine the appropriate treatment plan.
Traditional and Minimally Invasive Surgery
Not all patients with Chiari I malformation
require surgery. When Chiari I malformation
is asymptomatic and does not interfere with
daily activities, your physician will recommend
observation without surgical intervention.
Medications may also be prescribed to ease
pain and other symptoms.
Surgery is the only treatment available
to improve symptoms directly attributed
to Chiari I malformation or to stop the
progression of damage to the central nervous
system. Posterior fossa decompression surgery creates more space
for the cerebellum and relieves pressure on the spinal column.
The procedure involves making an incision at the back of the head
and removing a small portion of the bottom of the skull to provide
additional space for cerebrospinal fluid (CSF) to flow normally.
The surgeon may also make an incision in the dura, a membrane
that covers the brain and spinal cord. A duraplasty may be performed,
in which a patch is sewn into the dura to create more space for the
flow of CSF. Whether or not to open the dura during decompression
surgery and perform a duraplasty is a source of controversy. A variety
of different materials can be used to perform a duraplasty, including
synthetic grafts and pericranium, a thick membrane that is attached
to the skull. Pericranium can be obtained through the same incision
required for the posterior fossa decompression.
When hydrocephalus occurs in
association with Chiari I malformation,
the ideal treatment is a minimally
invasive procedure called endoscopic
third ventriculostomy (ETV). This
procedure enables normal circulation of
fluid via a small incision on the top of
the skull. An endoscope (a small camera
with working ports) is inserted into the
ventricles (the fluid spaces of the brain)
and a hole is made in a membrane
called the floor of the third ventricle
which allows fluid to circulate normally.
Some patients may not be candidates for ETV and may require a
shunt, in which a flexible tube is inserted into the ventricle and fluid
is drained into the abdomen or another part of the body.
Treatment of Syringomyelia
Typically, posterior fossa decompression results in improvement
of symptoms and also causes either a decrease or stabilization of
an associated syrinx. If a syrinx persists despite posterior fossa
decompression, a shunt may be placed into the syrinx in order to
drain the syrinx into the space next to the spinal cord (called the
subarachnoid space) or into another compartment.
Collaboration with Parents and Referring Physicians
Parents are an integral part of the care team at Children’s Memorial
Hermann Hospital. Every effort is made to keep you fully informed
and involved in your child’s care and communication with your
pediatrician or referring physician about your child’s progress
throughout the evaluation, diagnosis and treatment process is a
priority. After all initial patient consultations, referring physicians
will receive a summary that includes the initial diagnosis, pending
tests and treatment options. Additionally, updates are provided to
the referring physician throughout all subsequent appointments.
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