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Pediatric Chiari Malformations

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This presentation is about the signs, symptoms, types, and surgical treatment options for Chiari Malformations.

TYPES OF CHIARI MALFORMATIONS

  1. occurs during fetal development and is characterized by downward displacement by more than four millimeters, of the cerebellar tonsils beneath the foramen magnum into the cervical spinal canal.
  2. characterized by downward displacement of the medulla, fourth ventricle, and cerebellum into the cervical spinal canal, as well as elongation of the pons and fourth ventricle. This type occurs almost exclusively in patients with myelomeningocele.
  3. a form of dysraphism with a portion of the cerebellum and/or brainstem pushing out through a defect in the back of the head or neck. These malformations are very rare and are associated with a high early mortality rate, or severe neurological deficits in patients that survive
  4. the most severe form and the rarest. The cerebellum fails to develop normally. There may be other associated malformations of the brain and brainstem. Most babies born with this malformation do not survive infancy.

CHIARI I MALFORMATION

CHIARI I MALFORMATION SYMPTOMS

  • Severe head and neck pain
  • An occipital headache felt at the base of the skull that is made worse by coughing, sneezing, or straining
  • Loss of pain and temperature sensation of the upper torso and arms (as a result of a syrinx)
  • Loss of muscle strength in the hands and arms (as a result of a syrinx)
  • Drop attacks – collapsing to the ground due to muscle weakness
  • Spasticity
  • Dizziness
  • Balance problems
  • Double or blurred vision
  • Hypersensitivity to bright lights
  • Brain stem findings, e.g. swallowing or breathing difficulties

DIAGNOSIS IS RADIOGRAPHIC

Diagnosis is Radiographic

Once the Diagnosis is Made….

  • Referral for Neurosurgical Evaluation if Symptoms May be Due to Chiari
  • History
  • When walked
  • When potty trained
  • Swallowing or respiratory issues
  • Pain(where, when)
  • Motor Skills
  • Gross Motor
  • Fine Motor

Physical Examination

  • Gait
  • Reflexes
  • Tone
  • Cutaneous stigmata of neural tube defect
  • Sensory disturbance(temperature, proprioception)
  • Scoliosis

Rule of 20s

  • 20% of Scoliosis patients will have an intradural anomaly
  • 20% of Chiari patients will have additional neural axis anomalies
  • Syrinx
  • Tethered Cord
  • Fatty Filum Terminale
  • Diastematomyelia
  • Dermal tract

DECISION TO OPERATE BASED ON SYMPTOMATOLOGY

  • Head-aches, classically sub-occipital, worsened by a Valsalva maneuver
  • Brain stem symptoms, e.g. respiratory distress, central sleep apnea, diminished fine motor skills
  • Truncal symptoms, e.g. progressive scoliosis
  • Distal neurological symptoms, e.g. ataxia, bowel/bladder incontinence

DECISION TO OPERATE BASED ON MRI

  • Enlarging Syrinx
  • Signal changes within the cord/brain stem
  • Reduced flow on cine studies
  • Progressive tonsillar herniation

SURGICAL TECHNIQUE

  • Midline sub-occipital incision
  • 2.5x2.5cm bony decompression +/- C1 laminectomy
  • Dural opening
  • Cytoreduction of cerebellar tonsils using bipolar electrocautery
  • Opening of obex
  • Closure of dura using patch (usually autologous muscular fascia)

Operative exposure of a Chiari I malformation.

SUCCESS

  • >90% of syrinxes will reduce in size after decompression 1
  • 50-90% of patients will have improvement in their pre-operative symptoms 1, 2

1 Time course of syringomyelia resolution following decompression of Chiari malformation Type I.  Wetjen NM, Hiess JD, and Oldfield EH in J Neurosurg Pediatr. 2008 Feb;1(2):118-23
2 Outcome of Chiari-associated syringomyelia after hindbrain decompression in children: analysis of 49 consecutive cases.  Attenello FI, McGirt MJ, Gathinii M et al in Neurosurgery. 2008 Jun;62(6):1307-13; discussion 1313

COMPLICATIONS

  • Bleeding/Infection
  • Failure to Improve
  • CSF leak
  • Bony regrowth
  • Age dependent

WHY IS YOUNGER MORE DIFFICULT?

Size – more difficult to get adequate bony decompression

Bony healing – greater tendency to close openings1

Greater growth – more changes in skull morphology

Associated symptoms – higher incidence of respiratory and lower cranial nerve dysfunction - Leading cause of death2

1 Re-operation for Chiari Malformations Sacco D, Scott RM in Pediatr Neurosurg. 2003 Oct;39(4):171-8.
2 Chiari Type II Malformation: Past, Present, and Future Stevenson KL in Neurosurg Focus 2004 Feb 15;16(2):E5.

Chiari Malformations By Eric Trumble, MD

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