TL;DR: Sudden loss of use in a cat's back legs accompanied by cold paws is likely a life-threatening Feline Aortic Thromboembolism (Saddle Thrombus) that requires immediate emergency veterinary intervention.
Why has my cat suddenly lost the use of its back legs?
When a cat suddenly loses the use of their back legs and the paws feel cold to the touch, it is most commonly a condition known as Feline Aortic Thromboembolism (FATE), or a 'Saddle Thrombus.' This occurs when a blood clot, often originating from the heart, travels through the aorta and lodges at the junction where blood flow splits to the two hind legs. This blockages cuts off vital oxygen and blood supply to the limbs, causing sudden paralysis and intense pain.
Is sudden hind leg paralysis in my cat a medical emergency?
- Urgency Level: High. This is considered one of the most painful and time-sensitive emergencies in feline medicine.
- Immediate Action Required: If your cat is vocalizing, panting, or dragging their hind end, you must transport them to an emergency veterinary hospital immediately.
- Risk of Delay: Do not wait for an appointment or try to provide home care, as the lack of blood flow can cause permanent tissue damage.
- Professional Care: The underlying heart condition requires professional stabilization and intensive pain management that cannot be provided at home.
How can a photo or video help the veterinary team triage my cat?
- Visual Triage: Providing a clear photo or short video of your cat's posture and paw pad color while you are in transit helps the triage team prepare for your arrival.
- Checking Pad Color: In many cases of Saddle Thrombus, the paw pads appear bluish, pale, or purple rather than the healthy pink color.
- Pre-arrival Preparation: Seeing these signs allows veterinary staff to prepare oxygen, pain relief, and diagnostic equipment before you even walk through the door, saving precious minutes for your pet's treatment.
Clinical Context (Merck Veterinary Manual)
Arterial thromboembolism, often secondary to underlying conditions like cardiomyopathy, hyperthyroidism, or congenital heart disease, can result in pain and paresis or lower motor neuron paralysis of the hindlimbs. Clinical signs include reduced or absent arterial pulses (femoral or pedal) in the affected limbs, which are cooler than normal, and firm, swollen gastrocnemius muscles. The cat may still be able to move the legs above the stifles, and the tail is commonly unaffected. Diagnosis is based on clinical signs, physical examination findings, and Doppler blood flow readings of the hindlimbs; ultrasound can also be used to identify the thromboembolus. Pathologic changes are present distal to the level of the middle to lower thigh and are characterized as focal muscle necrosis and degeneration of the central portions of the sciatic nerve and its branches.
Chapter: Cardiology
Source: The Merck Veterinary Manual, 11th Edition (Page 1245)