Synonyms:
Arnold Chiari malformation
Chiari I malforamation:
Diagnosis:
MRI
Clinical features:
- May be asymptomatic (usually this is the case)
- In some cases can be associated with headaches and transient brainstem dysfunction
Findings on Investigations:
MRI:
- Low lying cerebellar tonsils extending below the foramen magnum
Treatment:
Usually no treatment
Medications for headache (but avoid overuse)
In some cases consider surgical decompression
Chiari II malformation:
Diagnosis:
By imaging. Chiari 1 malformation features as well as spinal cord syrinx
Prenatal diagnosis:
- Ultrasound
Findings on Investigations:
MRI, Foramen magnum MRI, sagittal:
- Tonsillar herniation: Cerebellar tonsils extending >3-5mm into the foramen magnum
- +/-associated syringomyelia
Pathology:
- a spinal meningomyelocoele +crowding of the hindbrain i.e. Small posterior fossa
- Herniation of the cerebellar vermis through the foramen magnum.
- Aqueductal stenosis or forking of the aquduct.
- Distortion of the brainstem e.g. beaking of the tectum, Z shaped or kinked medulla,
- Distortion of the spinal cord e.g. hydromyelia, diplomyelia
- +hydrocephalus
Microscopically: disorganised Purkinje and granule cell layer in the displaced vermis
Treatment:
Shunt insertion
Consider surgical decompression