Is syringohydromyelia painful?

JSAP 2007

Author

Obi Veterinary Education
April 05, 2025

C. Rusbridge, H. Carruthers, M.-P. Dubé, M. Holmes, N. D. Jeffery

Background
The study investigates the relationship between syrinx dimensions and pain in Cavalier King Charles Spaniels (CKCS) with syringomyelia (SM), a condition associated with Chiari-like malformation. This malformation results in abnormal cerebrospinal fluid dynamics, leading to the formation of syrinxes in the spinal cord. The authors hypothesized that pain is associated with the size and specific involvement of the dorsal part of the spinal cord.

Methods
Magnetic resonance imaging (MRI) scans of 74 CKCS were analyzed, focusing on syrinx dimensions, their asymmetry, and their location in the spinal cord. Observers blinded to the clinical status of the dogs recorded maximum syrinx width and dorsal asymmetry. Clinical signs, particularly pain, were assessed based on owner reports and physical examination findings. Statistical analyses evaluated correlations between syrinx dimensions, their dorsal cord involvement, and the presence of pain.

Results
Of 55 dogs with syringomyelia, only 35% exhibited pain.
Maximum syrinx width was the strongest predictor of pain. Dogs with pain had wider syrinxes (mean width: 0.58 cm) compared to those without pain (mean width: 0.32 cm).
Syrinx asymmetry in the dorsal spinal cord was more common in painful cases, but its significance diminished when controlling for syrinx width.
Syrinx length correlated with pain in asymmetric syrinxes, although this was secondary to width.
Scoliosis was noted in 11% of syrinx-positive dogs, exclusively in those with wide, asymmetric syrinxes.

Limitations
Pain assessment relied on subjective owner reports, introducing potential bias.
The study population included clinically referred dogs and breeder-screened dogs, which could skew results.
Only the cervical spinal cord was examined, potentially missing relevant findings in other spinal regions.

Conclusions
The study concluded that syrinx width, particularly when located dorsally, is the most significant predictor of pain in CKCS with syringomyelia. The findings suggest neuropathic pain due to dorsal horn damage, highlighting the need for targeted therapeutic approaches focusing on dorsal horn mechanisms. This research also provides thresholds for syrinx dimensions to aid in clinical diagnosis and prognosis.

FIG 1. Mid saggittal T2-weighted magnetic resonance imaging of the brain and upper cervical spinal cord from case 52, a 4-year-old female neutered cavalier King Charles spaniels that had signs of pain from 1-7 years old. Clinical signs included yelping while scratching at the right shoulder area. This was more likely when she was excited. Note that while this syrinx is wide it is not especially long

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