Multiple Malformations of the Craniocervical Junction in German Spitz Adult Dog

Background: Craniocervical junction abnormalities (CJA) are described as complex congenital malformations affecting the caudal occipital region and 1st cervical vertebrae. These abnormalities often include Chiari malformations, atlanto-occipital overlapping, cervical canal stenosis, and atlantoaxial instability. There are few descriptions of these conditions in veterinary literature, despite their relevance. This report’s aim is to describe a case of complex craniocervical malformation in a dog, presenting the clinical findings, diagnostic methods, surgical treatment, and post-operative evolution, thus improving the understanding and management of such cases in veterinary practice. Case: A 4-year-old German Spitz dog, weighing 4.6 kg, was presented to a Veterinary Hospital in São Paulo State with a history of cervical hyperesthesia and non-ambulatory tetraparesis. Neurological examination revealed an absence of conscious proprioception in both thoracic and pelvic limbs, along with segmental hyperreflexia, pointing the neurolocalization of the lesion to the C1-C5 spinal segment. The dog's clinical evolution indicated further involvement of the brainstem, thalamic, and cerebellar regions. Cervical radiographs showed changes suggestive of craniocervical and vertebral malformations at C1-C2. Magnetic resonance imaging (MRI) further elucidated these findings, revealing a complex malformation causing significant compression of the medulla oblongata, atlanto-occipital overlapping, dysplasia/hypoplasia of the occipital bone, and mild cerebellar herniation, leading to partial obstruction of cerebrospinal fluid (CSF) flow. CSF cytology did not show significant abnormalities. Due to the unfavorable evolution of the patient, it was necessary to intervene surgically. The dog underwent foramen magnum decompression (FMD) with suboccipital craniectomy associated to cranioplasty using titanium mesh. Additionally, C1 laminoplasty and C1-C2 laminectomy were performed to maintain the stability of the atlanto-occipital joint and provide access to the dura mater. The dog presented a gradual and complete recovery of its motor function in the post-operative period, indicating a successful surgical treatment. Discussion: This case highlights the importance of advanced diagnostic imaging, such as MRI, in accurately identifying and assessing craniocervical junction abnormalities in dogs beyond what radiographs are able to identify. The successful surgical outcome obtained in this case shows the effectiveness of combining different surgical approaches for the management of such malformations. The foramen magnum decompression with cranioplasty, C1 laminoplasty, and C1-C2 laminectomy are great examples of fruitful combined techniques. Conservative therapies, such as pain management and the use of carbonic anhydrase inhibitors, may be satisfactory treatment options but could be insufficient for severe cases. Surgical intervention, as demonstrated, can significantly improve prognosis and quality of life by relieving compressive forces on the medulla oblongata and restoring normal CSF flow. The use of cranioplasty is particularly beneficial in reducing complications associated with scar tissue formation. This report adds valuable data to the limited veterinary literature on CJA, emphasizing the need for precise diagnosis and the advantages of the association of surgical approaches. This knowledge will ultimately improve treatment outcomes and the quality of life for animals with such abnormalities. Keywords: laminectomy, malformation, magnetic resonance, small animals, surgery.