Chiari Malformations

FACTS

Chiari
What Herniates
Brainstem/4V position
Define
Comments
0
nothing
normal
< 5mm tonsillar herniation but with crowded posterior fossa and large syringes that resolve with decompression
1
tonsils > 5mm
normal
Tonsils below foramen magnum > 5mm
brainstem normal position
+/- syrinx
#1 most common
Etiology: congenitally small p fossa or acquired high pressure from above cerebellum or low pressure below cerebellum
1.5
tonsils > 5mm (like CM1)
herniated (like CM2)
caudal tonsillar displacement ~ CM1 but brainstem/4th ventricle are low (~CM2)
NOT associated with neural tube defects
2
vermis + brainstem
herniated
vermis + myelo/encepalocele
#2 most common
Usually accompanied by open myelomeningocele
3
foramen magnum encephalocele
foramen magnum encephalocele
- hydro common
- very severe neurodev deficits
4
none
normal
Hypoplasia/aplasia of cerebellum
- not really applicable

HPI

  • Occipito-cervical headaches: pain at neck/occiput worse w/ Valsalva (cough/laugh/straining)
    • babies: irritability/grabbing while pooping
  • Bulbar Symptoms
  • Brainstem and cranial nerve compression (children)
    • CN 3/6: extra-ocular paresis
    • CN 9-11: downbeat nystagmus (medullary), gagging, sleep apnea, dysphagia, poor feeding, FTT, asp pna, stridor/hoarseness (rare)
    • CN 12: tongue atrophy
    • 🚩 NOTE: Chiari 2 patients especially p/w life-threatening apnea (breath-holding spells), inspiratory stridor, dysphagia, bradycardia
  • Myelopathy (if syrinx)
  • Cerebellar syndromes (rare)

PHYSICAL EXAM

universal cranial and spine exam
  • walk patient and evaluate gait
  • evaluate for scoliosis in pediatric patients (associated with syrinx)
  • Babies: reflexes, tone, stridor/apnea

IMAGING

  • MRI pan-spine without contrast:
    • syringomyelia co-occurs in ~30% of Chiari 1 malformations and can be in C/T/L spine
  • MRI brain (FAST or full)
    • with CISS sequences or CINE if available
  • CT head venogram: consider to evaluate location of occipital sinus in relation to your. craniectomy
  • CT cervical spine: consider for preop planning

A/P

Admit for surgery if
  • central apnea / abnormal respirations, rapidly progressive myelopathy, new CN deficits
Outpatient workup
  • Apnea testing
  • speech language pathology for swallowing evaluation
  • Outpatient apnea testing
  • Optho eval as indicated for hydro concerns
Outpatient surgery
  • posterior fossa decompression (SOC + C1 lami) +/- duraplasty if there is significant crowding at foramen magnum, or a syrinx.
 
Figure 1: peg-like extension of tonsils ~1.5cm below foramen magnum
Figure 1: peg-like extension of tonsils ~1.5cm below foramen magnum
 
Figure 2: elongated, pointed cerebellar tonsils w/ hydro (corpus callosum thinning)
Figure 2: elongated, pointed cerebellar tonsils w/ hydro (corpus callosum thinning)