Syringomyelia and Chiari-Like Malformation

What is syringomyelia and Chiari-like malformation?

Syringomyelia describes fluid-filled cavities that develop within the spinal cord, causing an abnormal sensation in affected dogs. The underlying issue is Chiari-like malformation (CLM). CLM represents a mismatch between the size of the brain, which is too big, and the space within the skull, which is too small. This leads to crowding of the back part of the brain and the brainstem and subsequent obstruction of the flow of the cerebrospinal fluid that bathes the brain and spinal cord. The most common sign is altered sensation, typically at the back of the head and the neck, which may progress to pain.

Which breeds are predisposed to this condition?

Several breeds have been identified with CLM, including:

• Cavalier King Charles Spaniel
• Brussels Griffon
• Maltese
• Yorkshire Terrier
• Chihuahua
• Pitbull Terrier (unusual because this is not a toy breed)

What are the clinical signs associated with CLM?

Dogs that develop CLM, and subsequent syringomyelia, will often develop withdrawn behavior. This may reflect a change in their mental activity or simple anticipation of pain upon being handled. They may cry out when jumping or running, defecating (due to the increased pressure inside the skull with the abdominal press to pass a stool), or when they are picked up. They may exhibit intermittent pain, particularly at night. Affected dogs may also seem sensitive when touched near the shoulder, ear, back of the neck, or breastbone. Some dogs with CLM try to scratch themselves while walking, often without any apparent stimulus. Scratching or pain may result from touch, movement, excitement, or wearing a collar. Affected dogs also may rub their faces incessantly.

Are there specific diagnostic tests for CLM and syringomyelia?

Now that magnetic resonance imaging (MRI) is readily available, the deformity associated with CLM may be demonstrated. MRI may help to predict the expected severity of clinical signs. Radiographs (X-rays) are generally not very useful for diagnosing CLM.

How are CLM and syringomyelia treated?

The focus of treatment for CLM and subsequent syringomyelia is pain relief. There are several medical options available, but most patients benefit from medication that targets the nervous system and nerve-associated pain (e.g., gabapentin). Medical acupuncture may be an effective adjunctive treatment. Other medications may also be attempted to reduce cerebrospinal fluid (CSF) production. These may include diuretics, such as furosemide, or antacids, such as omeprazole. Corticosteroids may also be used to reduce inflammation.

A surgical procedure can decompress the rear of the skull of severely affected dogs, but surgery has a very high failure rate. About half of the dogs treated surgically will decline by two and two and a half years post-op.

Dogs with CLM and syringomyelia should have the efficacy of their pain management regularly assessed (every one to three months), as their symptoms may progress over time.

Should I restrict my dog’s activity?

There is no need to restrict your dog’s activity, though removing his collar may help prevent symptoms. Raising his food and water dishes to elbow height helps to keep his neck in a neutral position. It is impossible to predict the progression of this disorder.

Some dogs remain stable for years, while others become completely debilitated within months of their first symptoms. Your dog’s response to therapy will provide insight into how he can accommodate CLM and syringomyelia.