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A 16 week old, female intact, miniature Australian Shepherd was presented to the neurology department for adverse reaction/pain in response to her head being touched which had been occurring for several weeks.

She was otherwise a normal playful puppy. On presentation, neurological examination was normal but she resisted dorsal head elevation and would yelp with direct head palpation and when she yawned.



T2w transverse

T2w sagittal

Transverse GRE and T2w

T1w pre- and post-contrast

There is diffuse, severe, smooth, low T1, heterogenous T2/FLAIR, and heterogenous contrast enhancing thickening of the dorsal calvarial bones (frontal lobe, parietal, and occipital) estimated up to 1.2 cm in thickness in the mid parietal region. Mild contrast-enhancing meningeal thickening of the dorsal aspect of the right cerebrum is noted. Asymmetric enhancement of the right calvarial bones is noted when compared to the left, with adjacent contrast-enhancing soft tissue swelling. No distinct abscess is identified. Severe contrast-enhancing mucosal thickening of the frontal sinuses is noted.
Tonsillomegaly and bilateral mandibular/medial retropharyngeal lymph node enlargement is typical for this young patient.

Imaging diagnoses:

● Severe dorsal calvarial osseous thickening with heterogeneous enhancement of the right parietal/occipital bones and adjacent soft tissue swelling

● Right cerebral meningeal inflammation


● The skull changes are typical for calvarial hyperostosis, typically self-limiting and noninfectious in origin

● The meningitis is likely inflammatory in origin

● Calvarial hyperostosis syndrome (CHS) is a rare, non-neoplastic, proliferative bone disease affecting the flat bones of the skull in young dogs.

● CHS is a canine hyperostotic disorder clinically resembling canine craniomandibular osteopathy (CMO) and is histologically indistinguishable from CMO.

● Genetic mutation is the presumed etiology with different gene mutations identified between the affected breeds.

● The lesions are initially painful, but self-limiting with skeletal maturity.

●Clinical signs reported with CHS include painful bony swelling of the skull, lymphadenopathy, eosinophilia, and pyrexia.

● Treatment is aimed at relieving pain.



Letko A, Leuthard F, Jagannathan V, Corlazzoli D, Matiasek K, Schweizer D, Hytönen MK, Lohi H, Leeb T, Drögemüller C. Whole Genome Sequencing Indicates Heterogeneity of Hyperostotic Disorders in Dogs. Genes. 2020; 11(2):163.

McConnell JF, Hayes A, Platt SR, Smith KC. Calvarial hyperostosis syndrome in two bullmastiffs. Vet Radiol Ultrasound. 2006 Jan-Feb;47(1):72-7. doi: 10.1111/j.1740-8261.2005.00108.x. PMID: 16429988.

RLAT radiograph of the skull, taken after the MRI

VD radiographs of the skull