MRI characteristics for "phantom" scratching in canine syringomyelia

Area of Science:

• Veterinary Neurology
• Comparative Medicine
• Neuroscience

Background:

• Canine syringomyelia (SM) often presents with characteristic scratching behavior.
• This study investigates the spinal cord lesions associated with phantom scratching in dogs.
• The phenomenon resembles fictive scratching seen after spinal cord transection.

Purpose of the Study:

• To identify the specific spinal cord lesion characteristics related to phantom scratching in Cavalier King Charles spaniels with symptomatic SM and Chiari-like malformation (CM).
• To compare MRI findings between dogs with SM exhibiting phantom scratching and those without.

Main Methods:

• Retrospective analysis of medical records and MRI scans from Cavalier King Charles spaniels diagnosed with symptomatic SM and CM.
• Division of the cohort into groups with (n=19) and without (n=18) phantom scratching.
• Quantitative measurement of syrinx dimensions and qualitative assessment of syrinx extension to the superficial dorsal horn (SDH) on transverse MRI images.

Main Results:

• Phantom scratching in dogs with SM is associated with a large dorsolateral syrinx extending to the SDH in cervical spinal cord segments C3-C6.
• The estimated syrinx size in dorsal quadrants was significantly larger (2.5 to 9.5 times) in dogs with phantom scratching compared to those without.
• A statistically significant difference in syrinx size was observed (p-value = 0.009).

Conclusions:

• MRI evidence indicates that phantom scratching in SM-affected dogs is linked to a large cervical syrinx involving the SDH.
• A potential hypothesis is that damage in this cervical region influences the lumbosacral scratching central pattern generator (CPG).
• Alternative explanations for scratching should be considered if a large dorsolateral cervical syrinx with SDH involvement is not identified in SM-affected dogs.