Chiari Malformation in Children

If you've been diagnosed with a Chiari malformation, you may have found out by accident during an MRI for headaches. Most Chiari malformations are never symptomatic. But in patients who have the right combination of anatomy and symptoms, posterior fossa decompression surgery can be transformative.

What Is Chiari Malformation?

Chiari malformation type I is the most common form — the cerebellar tonsils extend more than 5 mm below the foramen magnum (the opening at the base of the skull). This can obstruct normal CSF flow between the brain and spinal canal. Most are found incidentally. In symptomatic patients, classic symptoms include Valsalva-type headaches (coughing, sneezing, straining) and syringomyelia (a fluid-filled cavity in the spinal cord).

Chiari malformation type II (Arnold-Chiari) is almost exclusively associated with myelomeningocele — the entire lower brainstem and cerebellum herniate through the foramen magnum. It requires a completely different approach.

At a Glance

Chiari I is cerebellar herniation through the skull base opening — the most common form; often found incidentally
Classic symptom: severe headache that worsens with coughing, sneezing, or straining (Valsalva-type)
Approximately 50-60% of symptomatic patients also have syringomyelia — a fluid cavity in the spinal cord
Surgery: posterior fossa decompression with duraplasty (opening the skull base and expanding the dura) to restore CSF flow
Surgery reliably stops symptom progression; headaches improve in approximately 70-80% of patients; syrinx often shrinks over months

Learn more about Chiari malformation in adults here.

Symptoms

Valsalva-Type Headaches

Severe headache at the back of the head (occiput/suboccipital) that worsens with coughing, sneezing, straining, or laughing
Typically short-lived but intense; can occur daily

Syringomyelia-Related Symptoms (When a Syrinx Is Present)

Cape-like dissociated sensory loss (loss of pain and temperature but preserved touch) across the shoulders and arms
Weakness in the hands or arms
Progressive scoliosis in children

Brainstem Compression Symptoms (In Severe Cases)

Dysphagia (trouble swallowing)
Hoarseness, vocal cord weakness
Sleep apnea or respiratory irregularity

Diagnosis

MRI of brain and cervical spine — measures tonsillar herniation, CSF flow around the foramen magnum, syrinx presence/size
Phase-contrast MRI CSF flow studies — shows obstructed pulsatile CSF flow at the foramen magnum (supports surgical indication)
Full-spine MRI — needed when a syrinx is present to assess extent

Important: Tonsillar herniation greater than 5 mm alone is not sufficient for surgery — symptoms must match.

Types

Chiari I — tonsillar herniation only; most common; may be symptomatic or asymptomatic
Chiari II (Arnold-Chiari) — brainstem and cerebellum herniation; nearly always associated with myelomeningocele
Chiari III — very rare; includes herniation of the brainstem and cerebellum through a posterior skull defect
Chiari 0 — syringomyelia without measurable tonsillar herniation; controversial diagnosis

Treatment

Observation

For asymptomatic or minimally symptomatic incidental findings. Annual MRI monitoring may be recommended if tonsillar herniation is significant but asymptomatic.

Posterior Fossa Decompression With Duraplasty

The standard operation. One to two centimeters of bone are removed from the back of the skull (suboccipital craniectomy), the upper part of the C1 lamina is removed, and the dura is opened and expanded with a patch (duraplasty) to enlarge the posterior fossa compartment. Most patients stay in the hospital for two to three nights. This procedure relieves CSF obstruction in approximately 85% of patients.

For Associated Syrinx

Syringomyelia usually resolves or substantially shrinks within six to 12 months after successful decompression. A separate shunt into the syrinx is almost never needed.

Outcomes

Outcome	Rate	Notes
Headache improvement	~70-80%	Valsalva-type headaches most responsive
Syrinx reduction or resolution	~60-80% at 1 year	Takes 6-12 months after decompression
Stability or improvement in sensory symptoms	~75-85%	Strength deficits recover less reliably
CSF flow normalization on phase-contrast MRI	~80-90%	Best predictor of good outcome
Reoperation for persistent symptoms	~5-15%	More common when duraplasty is not performed

References

Arnautovic A, et al. Pediatric and adult Chiari malformation type I surgical series 1965-2013: a review of demographics, operative treatment, and outcomes. J Neurosurg Pediatr. 2015;15:161-177. PMID: 25423028
Meadows J, et al. Asymptomatic Chiari type I malformations identified on MRI. J Neurosurg. 2000;92:920-926. PMID: 10839248
Holly LT, et al. Syringomyelia associated with Chiari I malformation: a review. Neurosurg Focus. 2001;11:E1. PMID: 16722638

Our Specialists

Arthur DiPatri, MD

Pediatric Neurosurgery

Martin Herman, MD, PhD

Neurosurgery

Mohamad Bydon, MD

Neurosurgery

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