Chiari Malformations
Family of disorders characterised by anomalies cranio-cervical junction and downward displacement of the cerebellar contents. Divided into 4 types:
- Chiari Type I
- Tonsillar herniation >5mm below the foramen magnum
- No associated brainstem herniation or supratentorial anomalies
- Low frequency of hydrocephalus
- Often diagnosed in adulthood or adolescence
- Chiari Type II (Arnold-Chiari Malformation)
- Caudal herniation of the vermis, brainstem, and 4th ventricle
- Associated with:
- Myelomengingocele
- Brain anomalies
- Hydrocephalus
- Syringomyelia
- Usually diagnosed prenatally or at birth
- Chiari Type III
- Occipital encephalocele
Containing dysmorphic cerebellar and brainstem tissues. - High mortality in infancy
Due to respiratory failure.
- Occipital encephalocele
- Chiari Type IV
- Hypoplastic or aplastic cerebellum
Epidemiology and Risk Factors
Pathophysiology
Aetiology
Clinical Manifestations
May be asymptomatic.
Clinical features include:
- Cranial nerve palsies
- Syringomyelia
- Myelopathy
- Cerebellar symptoms
- Neck pain
- Occipital headache
Diagnostic Approach and DDx
Diagnosis is based upon imaging alone.
Investigations
Imaging:
- CT
- MRI
Management
Medical management focuses on:
- Respiratory failure
- Feeding difficulties
- Neurogenic bowel
- Neurogenic bladder
Surgery:
- Aims to decompress cranio-cervical junction and restore normal CSF flow across the foramen magnum
Anaesthetic Considerations
- A
- Atlanto-axial instability
- D
- ICP
Hydrocephalus. - Myelomeningocele
May lead to:- Hypovolaemia
Losses from defect. - Infection
- Heat loss
- Hypovolaemia
- ICP