Chiari Malformations in Cats

Chiari malformations spur the development of syringomyelia, which occurs following obstruction of cerebrospinal fluid. This condition is typically rare in cats, most commonly affecting certain canine breeds. Among cats, Persians have a higher predisposition for developing Chiari malformations.

Chiari malformations are characterized by fluid-filled cavities within the spinal cord, most often near the skull. These congenital malformations obstruct the hole at the base of the skull, known as the foramen magnum, disrupting the flow of cerebrospinal fluid throughout the spinal cord. Chiari malformations are more common in pets that have a too-large brain for a too-small skull.

Chiari malformations are a serious and painful condition that may be life-threatening for your cat. If you notice any of the following symptoms, seek veterinary attention immediately:

• Scratching around the head and neck
• Face rubbing
• Signs of pain
• Behavioural changes
• Excessive meowing
• Hesitancy in jumping
• Scoliosis
• Weakness
• Muscle deterioration
• Pelvic and limb weakness
• Confusion and/or disorientation
• Loss of balance
• Seizures

The causes of Chiari malformations in cats are not fully understood. The disease is typically considered congenital, or inherited at birth. This is due to an incongruity between skull and brain size. The condition is more commonly seen in small canine breeds such as the King Charles spaniel. It is less often diagnosed in cats, but tends to affect Persian cats in particular.

There are other suspected causes of Chiari malformations that are linked to other obstructions of the cerebrospinal fluid, including:

• Tumors
• Arachnoid cysts
• Spina bifida
• Spinal dysraphism
• Inflammatory disease
• Trauma
• Feline infectious peritonitis

Your vet will make a tentative diagnosis based on presentation of symptoms as well as age and breed information. Be sure to inform your vet of the extent and duration of your cat’s symptoms. Your vet will make a definitive diagnosis by taking an MRI. Radiographic images, CT scans, and/or ultrasounds of the spine may also be taken to rule out other spinal diseases as a cause of Chiari malformations.

Treatment methods will vary depending on the severity of the condition. However, most treatment methods for Chiari malformations are not entirely curative. The primary objective of treatment is to relieve your pet’s pain and reduce symptoms.

Surgery is one treatment option, particularly for pets experiencing pain, and will involve two procedures: foramen magnum decompression and dorsal laminectomy of C1, the first vertebrae in the spine. The veterinary surgeon will first remove a portion of the supraoccipital bone, which is one of the main bones connecting the spine and the skull, and the first vertebrae. This is done to establish a pathway for the cerebrospinal fluid. A muscle graft or titanium mesh plate may be applied over the foramen magnum to prevent the formation of scar tissue.

Medications will usually be prescribed in conjunction with surgery, although for some cases, medication alone may be sufficient in reducing clinical signs. Prescribed medications generally include pain medication, corticosteroids, and other drugs that reduce production of cerebrospinal fluid.

Your vet will be able to advise you on a treatment method based on your cat’s specific needs as well as your personal and financial preferences. In some cases, the condition may be treated with oral medications at first, but may require surgical treatment if the disease progresses or does not respond to pain medication.

Recovery and prognosis will depend on the severity of the condition and the success of the treatment method. Always follow your vet’s post-treatment and/or post-operative instructions carefully. Always administer any prescribed medications as instructed. Do not allow your cat to irritate the surgery site.

Cats are generally hospitalized following surgery until pain can be managed with oral analgesics. Recovery time following surgery may range from one to four weeks. Ensure your cat has a warm, safe place to rest during the recovery period and that their activity is limited. Surgical treatment is successful in 80 percent of cases, with up to 45 percent of cases never reporting recurrence. Note that, with Chiari malformations, “phantom scratching” of the neck, head, or ears may continue to occur even after surgical treatment. 

There is a chance that the malformations will recur even with surgical treatment and medical management. Scar tissue is often the cause of recurrence, as it may cause recompression of the brain. This is why muscle grafts or the insertion of a titanium mesh plate are generally recommended as part of surgical treatment.

Your vet will schedule a follow-up appointment in order to take a CT scan to monitor healing and progress and to establish whether or not continuation of oral medications is required. If the condition seems to have recurred, or if your cat is still experiencing pain while taking pain medications, contact your vet immediately.