Achondroplasia

Findings

Frontal bossing is noted in the calvarium. There is mild narrowing of the foramen magnum. The ventricles and sulci are prominent. There is no mass effect or midline shift. There is no abnormal extra-axial fluid collection. No areas of abnormal attenuation are noted.

Differential diagnosis for frontal bossing and small foramen magnum:
- Achondroplasia
- Thanatophoric dysplasia
- Achondrogenesis
- Camptomelic dysplasia
- Pseudoachondroplasia
- Metatrophic dysplasia
- Hypochondroplasia


Diagnosis: Achondroplasia (skull findings)


Key points

Achondroplasia is a short-stature skeletal dysplasia caused by mutation of fibroblast growth factor receptor-3 gene
Usually not recognized until children > 2 years old
Calvaria enlarged with frontal bossing, megalencephaly
Skull base small with narrow foramen magnum
Narrow jugular foramina may cause hydrocephalus via venous hypertension
Thoraco-lumbar gibbus or kyphosis in infancy
Cervicomedullary decompression surgery in 17%
Short petrous carotid canals
Mastoids under pneumatized
Mid-face hypoplasia, dental crowding
Urgent to treat cranio-cervical junction stenosis to prevent sudden death
Normal lifespan and intelligence