Fibrocartilaginous Embolism (FCE) & Acute Non-compressive Nucleus Pulposus Extrusion (ANNPE)
Background
Intervertebral discs are soft, cushion-like structures located between the bones of the spine (vertebrae). They act as shock absorbers and assist with mobility allowing the spine to bend, twist, and move while protecting the spinal cord from impact.
Each disc consists of two main parts:
- Nucleus pulposus – a soft, jelly-like centre that helps absorb shock.
- Annulus fibrosus – a tough, fibrocartilaginous outer ring that holds the nucleus in place and provides structural support.
Fibrocartilaginous embolism (FCE) is a sudden, non-progressive spinal cord disorder that occurs when a small piece of intervertebral disc material (fibrocartilage) enters a blood vessel supplying the spinal cord occluding the blood flow.
Although the exact reason why this happens is not fully understood, the resulting interruption of blood supply causes damage to the spinal cord tissue in a similar way that a “stroke’ damages the brain.
What is ANNPE?
Acute non-compressive nucleus pulposus extrusion (ANNPE) occurs when a small amount of disc material suddenly extrudes from an intervertebral disc and impacts the spinal cord. It is sometimes referred to as a ‘high-velocity low-volume’ disc extrusion.
ANNPE typically occurs when excessive force is applied to a normal disc (for example during high-impact exercise, rough play, or trauma). This force can cause a tear in the outer layer of the disc (annulus fibrosis) allowing a small amount of inner disc material (nucleus pulposus) to “burst” out and bruise the spinal cord. The bruising triggers inflammation within the spinal cord, leading to the sudden onset of neurological signs. Because the amount of extruded disc material is very small and compression of the spinal cord is minimal, surgery to decompress the spinal cord is not required.
Diagram showing the blood supply to the spinal cord. Small arteries along the spine help nourish the cord and the bones. In some cases, disc material can pass into these vessels and block blood flow, which can cause part of the spinal cord to be damaged. Herath, Tharuka Milinda, Nadiene Lutchman, May Saleh, and Leena Naidu. “Fibrocartilaginous embolism: a rare aetiology of spinal cord infarction.” BMJ Case Reports 16, no. 11 (2023): e257951.
What are the signs of FCE and ANNPE?
Both FCE and ANNPE commonly occur in young, mid-sized to large breed dogs, although they also sporadically occur in smaller breeds.
Clinical signs depend on where the spinal cord is affected and how severe the injury is. Because the spinal cord controls movement of the body, the level/location of injury (on the spinal cord) determines which limbs are affected. Some dogs may have weakness or paralysis affecting all four limbs while others may only show signs in the hind limbs. In many cases, the signs are asymmetrical, meaning one side of the body (left or right) is more affected than the other.
Many dogs develop signs suddenly during or shortly after vigorous activity. Some dogs may show signs of pain in the first 12-24 hours, but this improves quickly. After this initial period, most dogs with FCE or ANNPE are not painful.
The severity of the condition can vary between dogs. To help describe the severity of neurological dysfunction, veterinarians often assign a neurological grade which is typically classified as follows:
Grade 1 – Pain only
Grade 2 – Walking with weakness
Grade 3 – Unable to walk with voluntary movement of limbs
Grade 4 – Inability to move limbs but pain sensation is present
Grade 5 – Lack of movement and pain sensation
Transverse MRI images of a normal canine spinal cord (left), with an intervertebral disc extrusion lesion causing extradural compression (middle), and an intramedullary T2 hyperintense lesion within the spinal cord (right). The latter is consistent with an ischemic myelopathy, such as fibrocartilaginous embolic (FCE) myelopathy.
How is FCE and ANNPE diagnosed?
A careful clinical history and neurological examination can raise suspicion for FCE or ANNPE. However, a definitive diagnosis usually requires advanced imaging, with an MRI scan considered the gold standard.
MRI allows the veterinarian to differentiate non- compressive intervertebral disc injuries like FCE or ANNPE and compressive intervertebral disc disease, which would require different treatment recommendations for your pet.
What treatment options are available?
Both FCE and ANNPE are non-surgical conditions. Recovery is not guaranteed, and intensive nursing care is usually required for approximately 4 to 6 weeks, with repeated assessments during that time to monitor progress.
The mainstay of treatment is supportive care, which includes:
- Recumbent care: Provide clean, soft bedding to prevent pressure sores (decubital ulcers) and reposition your pet every 4-6 hours if they cannot move on their own.
- Bladder care: Some pets may have difficultly controlling their bladder either temporarily or permanently. Care may include manual bladder expression, placement of a urinary catheter or a cystotomy tube for long-term cases. Additionally, monitoring for signs of urinary tract infections due to incomplete bladder emptying is essential.
- Physiotherapy: Gentle exercises help reduce muscle wastage (disuse atrophy), improve circulation, and maintain mobility of limbs, joints, and muscles.
What is the prognosis?
The prognosis of FCE and ANNPE is variable and depends on severity of the spinal cord injury based on neurological grade (provided above). Preservation of pain sensation (the ability to detect painful stimuli applied to toes) is a good sign as it indicates that tracts running along the spinal cord are still able to transmit signals to the brain, improving chance of recovery.
Dogs with a mild spinal cord injury can recover quickly and regain full function including normal walking and bladder control. Dogs with a more severe spinal cord injury may still be able to recover, but recovery can take longer and the dog may have persistent neurological deficits such as urinary incontinence or wobbly/unstable walking (ataxia).
Ultimately, each case is unique, and recovery outcomes vary. Based on your pet’s presentation, clinical signs, and MRI findings, your veterinarian can give you an indication about their expected recovery.
Next steps
If you think your dog may have a spinal cord injury, please contact your regular veterinarian or one of our Pet Emergency hospitals as soon as possible.
Generally, we will arrange a consultation with one of our surgeons to assess your dog and discuss what is involved.
Recent literature
Recent literature reporting the outcomes of dogs with either of these conditions is outlined below:
Bartholemew et al. 2016 – “Clinical characteristics of canine fibrocartilaginous embolic myelopathy (FCE): a systematic review of 393 cases (1973–2013)”
• Prognosis for recovery of ambulation was good to excellent with 85% of cases regaining the ability to walk unassisted, most within 3 weeks.
• Persistent neurological deficits were common in patients that recovered ambulation (49%).
• When pain sensation was absent in the affected limbs at initial presentation, rate of recovery was lower (10%).
Togawa et al. 2024 – “Outcome in paraplegic dogs with or without pain perception due to thoracolumbar fibrocartilaginous embolic myelopathy or acute non-compressive nucleus pulposus extrusion”
• 1 of 12 deep pain negative dogs (8.3%) regained independent ambulation
• 9 of 14 deep pain positive dogs (64.3%) regained independent ambulation.
• Deep pain negative dogs had a significantly higher risk of not regaining independent ambulation compared with deep pain positive dogs.
• The absence of pain perception is a useful negative prognostic indicator in dogs with severe thoracolumbar FCE or ANNPE.
Dr Daniel Poletto
BVB DVM
Surgical Resident
If you have concerns for your pet in connection to this condition we recommend discussing it with your primary care vet in the first instance, or get in touch with our team for more information.
If you need urgent medical help, contact our 24 hour Pet Emergency team at Stafford, North Lakes, or Sunshine Coast on 1300 QLD VET (1300 753 838)