This document describes Chiari malformation, specifically Chiari type I and II. It discusses the presentation, diagnosis, and treatment of a 34-year-old female patient presenting with progressive arm weakness, shoulder pain, and headaches exacerbated by coughing. Examination found reduced sensitivity in her arms. MRI confirmed Chiari type I malformation with tonsillar herniation. The patient underwent posterior fossa decompression surgery, with improvement in symptoms at 6-month follow up. Chiari malformations cause hindbrain herniation and obstruction of CSF flow, often requiring surgery to enlarge the posterior fossa.

1. Chiari Malformation
Dr.Usman Haqqani
Resident Neurosurgery B
LRH PESHAWAR

2. Case scenerio
• A 34 year old female presents to the opd
with progressive weakness in both her
arms associated with intermittent bilateral
shoulder pain .She has not noticed any
functional impairment and is still working
normally.On further asking she admits she
has intermittent headaches over the lower
occipital area and aggravates with
coughing and sneezing.

3. examination
• On physical examination, she has no
neurologic deficits other than
• Reduced of sensitivity to hot and cold
sensation over her arms
• Numbness and tingling over arms
• Loss of muscle strength in her right
shoulder and hand which could not be
appreciated very clearly.

4. History based differential diagnosis

5. Investigation

6. Operative Intervention

7. Post op day 4

8. Review in Opd at 6 months
• Power Right arm had improved from 4/5 to
5/5.
• No occipital headaches with coughing and
straining
• No other neurological deficit

9. Introduction
• Chiari malformations are pathological
herniations of the hindbrain through the
foramen magnum and into the cervical spinal
canal.
• 1890s – Hans Chiari, pathologist described
four congenital malformations
• Majority are congenital; but can be acquired
as well  secondary CIM

10. Different subtypes..
• Chiari O
• posterior fossa appear “crowded”
• No herniation
• large syrrinx that resolve with posterior fossa
decompression

11. • Chiari I
• caudal displacement of cerebellar tonsils > 5mm below
the foramen magnum
• Sign and symptoms commonly present in adulthood.
• may or may not have syrinx but are usually associated
with syrinx
• HCP in 10-20 % cases

14. • Chiari II
• caudal migration of cerebellar vermis
• almost always occurs in patients with neural tube
defects (myelomeningocele and encephalocele)
• syrinx is common
• HCP in 90% cases

17. • Chiari III
• rare and extreme form of hindbrain hernia
• <1% occurrence
• has low occipital and high cervical sacs containing
significant portions of the cerebellum and brainstem.
• Hydrocephalus is common and severe
neurological and developmental problems present

19. • Chiari IV
• cerebellar hypoplasia or aplasia
• not a form of hindbrain hernia
• its inclusion is hence debatable

21. Chiari I Malformation
• Theory: Difficulty in rapidly equilibriating the CSF
pressure wave seen during the Valsalva maneuver
• Prolonged intracranial hypertension relative to
intraspinal compartment  downward migration of
the cerebellar tonsils  obstruction of normal CSF
flow from 4th ventricle to cervical subarachnoid
space  CIM
• Obstruction of Foramen of Magendie by
arachnoid veils or septation might also lead to the
same

22. • Conditions artificially lowering the
intraspinal pressure relative to ICP like
lumboperitoneal shunt –
iatrogenic/acquired
• Some derailment on chromosomes 9 and
15

23. Clinical Presentation
• S&S related to brainstem compression
• S&S related to cerebellar compression
• S&S related to spinal cord dysfunction
secondary to syringomyelia

26. Clinical Presentations..
• Non radicular occipital or cervical pain
• Dysesthesias in the C2 dermatome
• Neckpain and headache - exacerbated on
exertion or by coughing or sneezing (valsalva
induced)
• Non verbal children  irritability, crying, failure
to thrive, opisthotonos

27. Diagnosis
• MRI – Craniovertebral junction and entire
spinal cord
• 50-75% patients have syringomyeliasyrinx
• CT – bony abnormality; plain films for
evaluating stability issues
• Dynamic MRI (cine MRI) – for CSF flow
around the CVJ

29. Treatment
• Treatment is different for symptomatic and non
syptomatic patients
• No medical treatment
• Observation in asymptomatic patients without an
associated syrinx
• Surgery: for symptomatic patients and
asymptomatic patients with syrinx

30. Treatment
• 10% patients with CIM – associated
hydrocephalus
– CSF diversionary shunt or ETV as the
initial form of therapy
• Symptomatic ventral compression out
of proportion to dorsal compression
 ventral decompression (transoral
odontoid resection)

31. • Most common surgical procedure: Posterior
fossa decompression
• Goal: enlarge posterior fossa to recreate
cisterna magna, thereby permitting normal flow
of CSF
• Syrinx decrease in size and does not require
direct Rx in majority after this

32. Posterior fossa decompression..
• Prone position and neck flexed
• Incision from below inion to the spinous process of
C2
• Avascular plane (nuchal ligament) b/t paraspinous
muscles followed down to bone and subperiosteal
dissection performed
• Moderate suboccipital craniectomy, width of the
foramen magnum followed by removal of posterior
arch of atlas

33. Posterior fossa decompression..
• Dura opened
• Arachnoid adhesions obstructing flow
removed and the floor of the 4th ventricle
examined
• Portion of occipital pericranium harvested
through a separate incision and duroplasty
performed

37. Posterior fossa decompression..
result
• Encouraging result in long term follow up
• Early treatment tends toward better outcomes
• ~85% patients – relief of head and neck pain esp. if valsalva
induced
• Associated syrinx decrease in size or collapse in majority
• If no improvement in symptoms and size of syrinx in 6 months
 reexploration with coagulation or resection of a cerebellar
tonsil

38. Surgical outcome
•Placement of syringosubarachnoid
shunt in cases not responding to
decompression
• Advanced symptoms – medullary dysfunction, muscle
wasting and dysesthesias in trunk or extremities –
unlikely to resolve but should not progress
• Mild to moderate scoliosis  likelihood of improvement

40. Chiari II malformation
• Caudal displacement of cerebellar vermis, lower
brainstem and fourth ventricle seen exclusively in
patients with myelomeningocele
• Numerous other anomalies associated in various
combinations
– vertical straight sinus
– large venous lakes in the tentorium
– fenestrations in falx, which is often not well formed – gyri
of left and right hemispheres interdigitate – “Chinese
lettering” on axial MRI

41. Pathophysiology..
• Similar to CIM – difficulty in equilibrating
dynamic CSF pulse pressure induced by
valsalva
• Leaking from myelomeningocele sac
lowers intraspinal pressure

42. Clinical presentation..
• Pertaining to brainstem, cerebellar and spinal cord dysfunction
• Usualy present in infancy/early childhood
• Worst outcome if symptoms appear before 3 months age
• Stridor, apnea and dysphagia resulting in aspiration  might cause
death
• Nystagmus – earliest sign of cerebellar dysfunction
• Initial spinal cord symptoms (weakness, bowel and bladder
dysfunction) – secondary to inadequate formation of the lower spinal
cord

44. Diagnosis
• MRI – cranial and spinal
• Plain dynamic cervical spine radiographs
 instability

46. Characteristic Chiari I Chiari II
Usual age of diagnosis Adults and older children Infants and young children
Clinical findings
•Headache and neck pain (worsened by cough or
Valsalva maneuver)
•Myelopathy
•Cerebellar symptoms
•Lower brainstem symptoms (eg, dysarthria,
dysphagia, downbeat nystagmus)
•Central cord symptoms (eg, hand weakness,
dissociated sensory loss, cape anesthesia)
•In infants, signs of brainstem dysfunction
predominate: swallowing/feedingdifficulties,
stridor, apnea, weak cry, nystagmus
•Weakness of extremities
Primary anatomical abnormalities
•Herniation of cerebellar tonsils through foramen
magnum, producing compression of
cervicomedullary junction
•Herniation of lower brainstem through foramen
magnum
•Cephalad course of cranial nerves
•Kinking of cervicomedullary junction
•"Beaking" of tectum
•Upward herniation of vermis through incisura
•Nearly vertical tentorium
Myelomeningocele No Always
Hydrocephalus Less than 10% of cases Very common
Syringomyelia 30-70% Common
Associated abnormalities
•Craniocervical hypermobility syndromes
•Klippel-Feil anomaly
•Hereditary connective tissue disorders and
neurofibromatosis type II
•Callosum corpus pellucidum septum of agenesis
•Hypoplasia or
•Enlargement of massa intermedia
•Heterotopias and gyral abnormalities
Shared associated abnormalities
•Basilar invagination
•Occipitalization of atlas
•Bifida of C1 posterior arch
•Foramen magnum variant anatomy
•Basilar invagination
•Occipitalization of atlas
•Bifida of C1 posterior arch
•Foramen magnum variant anatomy

47. • Thank you!!