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Other forms of Chiari
malformations include Type II, which is associated with myelomeningocele
(spina bifida), and Type III, which is associated with an occipital encephalocele.
There is also, technically, a type IV Chiari Malformation, which is described
as hypoplasia of the cerebellar hemispheres. Many authors have eliminated
this entity as a part of the Chiari group.
Signs
and Symptoms of the Chiari I Malformation
The signs and symptoms
associated with a Chiari I malformation are quite varied. The list of symptoms
include headache, pain, weakness, sensory changes, clumsiness, respiratory
dysfunction, dysrhythmias, dysphasia, dysarthria, hoarse voice, facial numbness,
hiccups, severe snoring, drop attacks, and urinary incontinence. A list of
signs would include weakness (more common in the upper extremities than the
lower extremities), hemiparesis and quadriparesis, atrophy, sensory loss,
hyporeflexia, hypereflexia, lower extremity clonus, Babinski response, ataxia,
nystagmus, absent gag reflex, facial sensory loss, tongue atrophy, and vocal
cord palsy. The headaches seen with the Chiari I malformation are often associated
with exertion and can sometimes be relieved by head extension. Diagnosis
is often delayed in patients with a Chiari I malformation, which of course
is understandable considering the wide range of signs and symptoms that can
be attributed to this malformation. The delay in diagnosis is usually more
prolonged in the adult population than in the pediatric population.
 The
MRI image on the left shows hydro/syringomyelia, also called a syrinx. Syrinx
formation is frequently associated with the Chiari I malformation. With a
syrinx, the patients are more likely to develop scoliosis. Many patients
with scoliosis, either with or without a syrinx, arrest the progression of
their curve following decompression of their Chiari Malformation. An MRI
scan is the imaging procedure of choice for diagnosing Chiari malformations.
The availability of MRI has reduced the delay in diagnosis ten fold. An MRI
cine scan, a gated study that documents CSF flow, can be performed at the
time of the MRI. This study enables one to determine whether CSF flow in
the region of the foramen magnum is impaired.
Surgical
Treatment
There are now two accepted
types of surgical decompression for Chiari I malformation. The first is a
suboccipital craniectomy with removal of the ring of C1, as well as removal
of a tight band of dura in the area. The dura is not opened. This procedure
seems to give symptomatic relief for many patients. In addition, intraoperative
ultrasound has been a valuable intraoperative adjunct to this procedure.
If fluid is seen on ultrasound around the herniated tonsils, and there is
decreased pistoning of the tonsils after decompression, the likelihood of
a successful procedure is high. The second type of surgical decompression
includes the above procedure, followed by opening the dura and placing a
patch graft. This is especially important if a spinal cord syrinx is present.
This procedure has been proven over the years to relieve signs and symptoms
associated with Chiari malformation. On the postoperative MRI, decompression
of the syringomyelic cavity is frequently noted. In addition, ascension of
the cerebellar tonsils to a normal level can also be seen.
Over the last 7 years
we have surgically treated close to 100 children with Chiari malformation
at our institution with excellent results. The majority of children have
demonstrated improvement or complete resolution of their symptoms.
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