Calvarial Hyperostosis Syndrome

Case example

Cheeky Calvarium

An 8-month-old, male Bulldog presented with chronic swelling of forehead and painful left auricular region.

CT findings

  • Image 1: Severe, bilateral, asymmetric thickening and hyperostosis/sclerosis of frontal, parietal and occipital bone cortices along external sagittal crest.
  • Image 2: Mild to moderate amount of smooth and columnar periosteal new bone causes mass-effect, skin-surface convexities and decrease in size of calvarium with crowding of the left cerebellar hemisphere. No evidence of mandibular involvement.
  • Image 3: Temporalis muscle vasculature is asymmetric and multifocally increased in volume. Subcutaneous thickening is also evident.
  • Image 4: Medial retropharyngeal lymph nodes are mildly enlarged and mildly heterogeneously contrast enhancing.


  • Severe idiopathic calvarial hyperostosis with secondary cerebellar crowding, muscular hyperemia and reactive medial retropharyngeal lymphadenopathy.

Take Home

  • Calvarial Hyperostosis Syndrome (CHS) mostly reported in Bullmastiffs and usually self-limiting.
  • Recent literature suggests syndrome to be separate entity to Craniomandibular Osteopathy (CMO)
  • Characterized by asymmetric, bilateral cortical thickening of dorsal aspect of calvarium with smooth periosteal proliferation and hyperemia.
  • Radiography can be sufficient. Dual-phase CT examination allows for more detailed evaluation of surrounding soft tissues, lymph nodes and calvarial extension.

More information

  • »Idiopathic hyperostosis of the calvaria in five young bullmastiffs«
    — Pastor et al.., J Am Anim Hosp Assoc (2000); 36(5):439-445
  • »Calvarial Hyperostosis syndrome in two bullmastiffs«
    — MConnell et al., Vet Radiol & Ultrasound 2006; 47(1): 72-77
  • »Calvarial hyperostosis presenting as unilateral exophthalmos in a female English Springer Spaniel«
    — Mathes et al., Vet Ophthalmology 2012; 15(4): 263-270