Osteopetrosis in a young adult dog causing multiple cranial nerve deficits

A two-year-old Cocker Spaniel was presented for investigation of lethargy and cranial nerve deficits. Neurological examination revealed multiple cranial nerves deficits and haematology and serum biochemistry revealed mild anaemia. MRI of the brain revealed caudoventral cerebellar herniation and cervical syringohydromyelia, while both MRI and CT revealed hyperostosis of the calvarium and narrowing of the calvarial foramina. Radiographs demonstrated marked osteosclerosis of the skull, vertebrae, sternebrae, ribs and long bones of the limbs. Further biochemistry revealed total calcium, ionised calcium and vitamin D levels to be unremarkable. This led to a diagnosis of osteopetrosis. Osteopetrosis is an extremely rare condition in dogs, with only sporadic cases being reported previously in the literature.