Spinal Dysraphism

Spinal dysraphism comprises several congenital anomalies characterized by a defect in the closure of the neural tube during the early stages of embryonic development. This disorder hinders the proper development of the tissues of the central nervous system.

Symptoms

Clinical signs of spinal dysraphism usually manifest between four and six weeks of age, evidenced by abnormal mobility. Some animals exhibit a characteristic `bunny hopping` gait (simultaneous movement of the pelvic limbs), proprioception problems, scoliosis, limb weakness, postural disturbances and abnormal spinal reflexes. In addition, unusual streaks of hair along the back and curled tails are observed. Despite these symptoms, it is important to note that this disorder does not worsen over time, and affected dogs usually lead a normal life.

Disease Management

There are no specific preventive measures or treatments for this condition. Dogs with mild symptoms generally lead a normal life. The treatment approach is primarily symptomatic, focusing on pain control. In addition, physical therapy may be considered to improve muscle mobility and make adaptations to the environment as needed.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

During gestational development, the neural tube forms as the precursor structure of the central nervous system, which includes the brain and spinal cord. Any defect in this fundamental structure can have significant consequences for neurodevelopment, such as spinal dysraphism or myelodysplasia. The NKX2-8 gene, belonging to a family of genes that regulate anatomical patterns during embryogenesis, is specifically expressed in the developing neural tube. In the study by Safra et al. (2013), a variant was described in the Braco De Weimar breed consisting of the change from G to AA (c.449delinsTT) in exon 2 of the NKX2-8 gene. This change introduces an early stop codon that is predicted to result in a truncated protein. In this same study, it is proposed that the mutation is unique to the Braco de Weimar breed, not shared with other dog breeds.

Most affected breeds

Weimar Braque

Bibliography

Safra N, Bassuk AG, Ferguson PJ, et al. Genome-wide association mapping in dogs enables identification of the homeobox gene, NKX2-8, as a genetic component of neural tube defects in humans. PLoS Genet. 2013;9(7):e1003646.