There's been ongoing reports of some people thinking their dog has 'mild' SM because it 'only' scratches and shows no other signs of the condition (no 'obvious' pain).

For some time, leading researchers have argued the opposite -- that when a dog reaches the point of scratching, that already means it is experiencing significant discomfort and that there is no such thing as 'just' scratching. This is reflected in the pain assessment forms that some researchers have developed which places dogs that scratch daily into the higher pain category.

To put it another way -- human Chiari/SM sufferers say the single most debilitating aspect of this condition is severe headaches. Having a headache does not mean you as a person would flinch when touched or show other 'outward' signs of pain. For a dog that has a severe pain in its head -- scratching is probably going to be one way in which they react.

I have always felt strongly that thinking scratching is a 'mild' sign of SM is delusional.

This extract from the UK Kennel Club/British Vet Association CMSM testing scheme document -- agreed by several of the leading experts in CMSM -- highlights this and I think it important for us to understand (and indicates why CM alone can be so debilitating fore some dogs). My underlining:

What is CM? What is SM?
CM stands for Chiari-like malformation, which is characterised by a defect in the development of the skull causing the hind-part of the brain to herniate or protrude from the opening at the rear of the skull. This can place pressure on the spinal cord and alter the flow of cerebrospinal fluid (CSF) along the small space in the centre of the spinal cord, which is called the central canal. As a result, a fluid-filled cavity may develop within the spinal cord, called a syrinx. The presence of one or more syrinxes in the spinal cord is the condition termed syringomyelia (SM).

Although some dogs with mild CM with or without SM can seem completely normal, some will experience pain and may be unwilling or unable to exercise and may be sensitive to touch especially around the neck and shoulders and back. Severe cases with syringomyelia may display a characteristic scratching of the shoulder, neck and/or head and have neurological signs such as wobbliness and muscular weakness. Some dogs may ‘air scratch’ without making contact with the body.
I fear a lot of dogs don't get any, or adequate, treatment at all for CMSM because they 'only' scratch. Leading researchers think scratching is a sign of a more severe form that is giving significant discomfort to the dog.

Just something to think about.