CONDITION
Chiari-Like Malformation
Chiari-like malformation describes a structural mismatch between the back of the skull and the brain tissue it contains. In affected dogs, part of the hindbrain—the cerebellum—sits lower than usual or extends through the opening at the base of the skull, and the flow of fluid around the brain and spinal cord can be disrupted. This is seen most often in Cavalier King Charles Spaniels and some other small breeds, and many dogs with the malformation never develop signs. Owners may notice scratching at the neck or ears—sometimes without the paw making contact with the skin—or sensitivity when the dog is touched around the head, neck, or shoulders. Some dogs vocalise when picked up, avoid wearing a collar, or seem uncomfortable during activity or rest. In a proportion of cases, the disrupted fluid flow leads to fluid-filled pockets forming within the spinal cord itself, a condition called syringomyelia, and signs tend to relate to the location and size of these pockets. This page explores what may be observed, what is happening within the skull and spine, how the malformation and any associated changes are investigated with imaging, and the medical and surgical approaches that exist. The presence of the malformation does not always mean intervention is needed, and the course varies widely between individuals.
Why this matters now
Chiari-like malformation is a congenital condition, meaning the structural mismatch is present from birth, though signs may not appear until later in life. Many affected dogs begin to show signs between six months and four years of age, though some remain asymptomatic throughout their lives. The condition is seen most frequently in Cavalier King Charles Spaniels, where breeding studies suggest a high prevalence within the population, and is also recognised in other small, brachycephalic breeds including Griffon Bruxellois, King Charles Spaniels, and occasionally Chihuahuas and Yorkshire Terriers. The presence of the malformation does not reliably predict whether or when clinical signs will develop in an individual dog.
The course varies widely. Some dogs with the malformation remain comfortable and free of signs for their entire lives, while others develop mild intermittent discomfort that fluctuates over months or years. In cases where syringomyelia develops—fluid-filled cavities within the spinal cord—signs may appear gradually and worsen over time, or plateau for extended periods. The size and location of fluid pockets, when present, tend to influence the nature and severity of signs, and progression is unpredictable in any individual.
Signals & patterns
Early signals
Phantom scratching
The dog makes scratching motions near the neck, shoulder, or ear without the paw making contact with the skin, often while walking or when touched in those areas. This behaviour can appear similar to attempting to relieve an itch that cannot be reached, and may occur intermittently or in response to specific triggers such as excitement or collar pressure.
Sensitivity around the head and neck
The dog may flinch, pull away, or vocalise when touched lightly around the ears, back of the head, neck, or shoulders. This sensitivity can be inconsistent, present on some occasions but not others, and owners may initially attribute it to a sore spot or minor injury.
Reluctance to wear a collar
A dog that previously tolerated a collar may begin to resist having one put on, scratch at it persistently, or show signs of discomfort when the collar is in place. Switching to a harness sometimes reduces visible discomfort, though this does not address the underlying cause.
Vocalisation when handled
The dog may yelp, whimper, or cry out when picked up, particularly if pressure is applied around the chest, neck, or shoulders. This response can be unpredictable, occurring on some occasions but not others, and may be mistaken for anxiety or a musculoskeletal issue.
Rubbing or pressing the head
Some dogs rub the side or back of the head against furniture, the floor, or the owner's body, or press the head into corners. This behaviour may reflect discomfort or altered sensation in the head or upper neck, and can appear similar to seeking relief from pressure or pain.
Later signals
Weakness or altered gait
The dog may develop a subtle unsteadiness, stiffness, or asymmetry in the way the limbs move, often affecting the forelimbs first. In some cases, one limb may appear weaker or less coordinated than the others, and these changes can be mistaken for arthritis or a soft-tissue injury.
Progressive neck or spinal pain
Discomfort may become more consistent or pronounced, with the dog showing reluctance to lower the head to eat or drink, difficulty navigating stairs, or a hunched posture. Pain may worsen with activity or certain head positions, and the dog may seek out soft surfaces or avoid movement.
Scoliosis or postural changes
In a proportion of cases, particularly where syringomyelia is present, the spine may develop a sideways curvature (scoliosis) visible when the dog is viewed from above or behind. This reflects asymmetric pressure or neurological effects within the spinal cord, and may be accompanied by altered weight distribution or gait.
Sleep disturbance or restlessness
Dogs with progressive or more severe signs may struggle to settle comfortably, shift position frequently during rest, or vocalise when lying down. Discomfort may be worse at night or after periods of inactivity, and the dog may appear fatigued despite reduced activity levels.
Click to read about the biological mechanisms
How this is usually investigated
Investigation typically begins with a detailed history—noting the nature, frequency, and progression of any signs—and observation of the dog at rest and in movement. The malformation itself cannot be confirmed without imaging of the skull and cervical spine, and a general neurological examination may reveal sensitivity around the neck or subtle changes in gait or posture, though many affected dogs show no abnormalities on routine physical assessment. When the history and examination suggest Chiari-like malformation or syringomyelia, imaging is used to visualise the structures involved and to assess the degree of cerebellar herniation and the presence or absence of fluid accumulation within the spinal cord.
Physical examination
Magnetic resonance imaging (MRI)
Computed tomography (CT)
Options & trade-offs
Management is typically individualised and may combine medical approaches, environmental modification, and in some cases neurosurgical intervention. The aim is to reduce discomfort and maintain quality of life, and the approach chosen tends to reflect the severity and pattern of signs, the presence or absence of syringomyelia, the dog's response to initial measures, and the practical considerations that apply to each household. Not all affected dogs require treatment, and some remain comfortable for extended periods with minimal or no intervention.
Medical management
Medications are often used to reduce neuropathic pain and, in some cases, to attempt reduction of cerebrospinal fluid production. Gabapentin and pregabalin are commonly prescribed for nerve-related pain and may provide relief in dogs showing discomfort, scratching, or sensitivity to touch; sedation or unsteadiness can occur, particularly during dose adjustment. Drugs that aim to reduce fluid production include acetazolamide, a carbonic anhydrase inhibitor and diuretic, and omeprazole, a proton pump inhibitor thought to act on enzymes in the choroid plexus, though evidence supporting a meaningful reduction in cerebrospinal fluid production with either drug in dogs remains limited, and reported benefit is based largely on observed clinical response rather than confirmed physiological effect. Corticosteroids are sometimes used for short periods to reduce inflammation around the spinal cord, though prolonged use carries well-recognised side effects.
Trade-offs: Medical management does not alter the underlying malformation or resolve syringomyelia, and its effect is on symptom control rather than disease modification. Response varies widely between individuals, and some dogs show meaningful improvement in comfort whilst others derive little benefit. Medication may be required long-term, and tolerance, side effects, or diminishing effectiveness can develop over time.
Foramen magnum decompression surgery
Surgical decompression involves removing a portion of the occipital bone at the skull base to enlarge the foramen magnum and relieve compression of the cerebellum and obstruction to cerebrospinal fluid flow. In some techniques, a patch or mesh is used to cover the defect and expand the dural membrane surrounding the brain. Reported outcomes vary; studies have documented improvement in clinical signs in a proportion of dogs, though progression of syringomyelia may continue in some cases and a minority of dogs require reoperation.
Trade-offs: Surgery carries the risks associated with general anaesthesia and intracranial procedures, including infection, bleeding, and neurological deterioration. Post-operative pain and a period of restricted activity are typical. Surgery does not reverse syringomyelia that has already formed, and imaging changes may persist or worsen despite clinical improvement. It is generally considered when medical management has not provided adequate relief or when signs are severe, though not all dogs are suitable candidates. Access to specialist neurosurgical centres and the associated costs are practical considerations.
Environmental and activity modification
Adjustments to the dog's environment and routine can reduce triggers for discomfort. These may include using a harness instead of a collar to avoid pressure on the neck, raising food and water bowls to reduce sustained neck flexion during feeding and drinking, providing supportive bedding, limiting high-impact activity or jumping, and managing situations that provoke scratching or vocalisation. Some owners find that maintaining a stable temperature and avoiding sudden changes in routine or handling reduces the frequency of episodes.
Trade-offs: Modification alone does not address the underlying pathology and may be insufficient in dogs with moderate to severe signs or progressive syringomyelia. Its role is typically supportive, used alongside other measures. The degree of benefit depends on the individual dog's triggers and the extent to which these can be identified and managed within the constraints of daily life.
Monitoring without active intervention
In dogs with the malformation confirmed on imaging but no detectable signs, or in those with mild, stable signs that do not affect quality of life, observation without treatment is a recognised approach. This may involve periodic reassessment of comfort and function, with treatment introduced if and when signs develop or worsen. Some dogs remain asymptomatic or mildly affected throughout their lives without requiring medical or surgical intervention.
Trade-offs: Monitoring requires attentiveness to subtle changes in behaviour, comfort, or mobility, and the threshold for intervention will vary between owners and clinicians. Syringomyelia may develop or progress silently, and the absence of overt signs does not guarantee that the condition is static. Repeat imaging is sometimes used to assess progression, though the decision to image and the interval between scans are not standardised and depend on clinical judgement.
Common misconceptions
"All Cavalier King Charles Spaniels with Chiari-like malformation on imaging will eventually develop symptoms."
The presence of the malformation, even when accompanied by small syringes visible on MRI, does not reliably predict whether or when clinical signs will appear. A proportion of dogs with imaging findings remain comfortable and asymptomatic for their entire lives, whilst others develop signs that may be mild, intermittent, or stable over long periods. Progression is variable and cannot be determined from imaging alone.
"Surgery will cure syringomyelia and resolve all clinical signs."
Foramen magnum decompression aims to improve cerebrospinal fluid flow and reduce further progression, but it does not reverse established syringomyelia or guarantee resolution of signs. Some dogs show marked improvement in comfort and behaviour, whilst others experience more modest benefit or continued progression despite surgery. The outcome is individual, and realistic expectations are part of informed decision-making.
"Phantom scratching always means the dog is in pain."
Phantom scratching is thought to relate to abnormal nerve signalling associated with syringomyelia in the cervical spinal cord, and it can occur in dogs that otherwise appear comfortable and show no other signs of distress. The relationship between this behaviour and the subjective experience of pain is not fully understood, and some dogs exhibit scratching intermittently or in specific contexts without other evidence of discomfort. It is one observable sign among several, rather than a definitive indicator of pain severity.
Related conditions
Degenerative Myelopathy
Degenerative myelopathy is a progressive spinal cord disease that can share some clinical signs with advanced syringomyelia secondary to Chiari-like malformation, particularly progressive hindlimb weakness and loss of coordination. However, degenerative myelopathy typically presents without pain and with different patterns of sensory change—primarily proprioceptive deficits rather than the neck and shoulder sensitivity often seen with Chiari-like malformation.
Episodic Falling Syndrome
Episodic falling syndrome is another inherited neurological condition seen almost exclusively in Cavalier King Charles Spaniels, the same breed most commonly affected by Chiari-like malformation. The two conditions can sometimes occur in the same individual, and while episodic falling involves episodes of muscle stiffness during excitement rather than the persistent pain or neurological deficits of syringomyelia, both reflect the breed's particular genetic vulnerabilities.
Brain Tumours
Brain tumours can occasionally present with head and neck pain or behaviour changes that may superficially resemble Chiari-like malformation, particularly when the tumour affects the hindbrain region. Advanced imaging is typically needed to distinguish structural malformation from space-occupying masses, and the two processes require very different approaches.
Epilepsy in Dogs
Epilepsy can occur in dogs with Chiari-like malformation and syringomyelia, and some studies have noted a higher prevalence of seizures in affected Cavalier King Charles Spaniels. While the exact relationship remains unclear, the structural changes in the brain and disrupted fluid dynamics may, in some cases, lower the threshold for seizure activity.
Discospondylitis
Discospondylitis—an infection of the intervertebral discs and adjacent vertebrae—can produce spinal pain, reluctance to move, and neurological signs that may initially be mistaken for pain associated with syringomyelia. The two conditions require different imaging features and treatments, and careful evaluation of the spine is needed to distinguish infection from fluid-filled cavities within the cord.
Understanding what has been observed in your own dog, and how this relates to the imaging findings if these are available, can help in discussions about whether active management is appropriate now or whether observation remains a workable approach. The balance between intervention and watchful monitoring shifts over time, and revisiting the picture periodically—particularly if signs change or new behaviours emerge—can clarify whether the current approach continues to suit your dog's needs. Pain and mobility are interconnected, and this condition sits within a broader context of how discomfort, movement, and quality of life are assessed and supported.
Last reviewed: 13 September 2026 · Dr Alastair Greenway MRCVS