Brachial plexus avulsion in the cat: Horner and panniculus reflex
1-year-old cat hit by a car 3 days ago. It drags its right thoracic limb and bears weight on the dorsum of the paw. Radiographs show no fractures.
| Parameter | Result | Reference |
|---|---|---|
| Right thoracic withdrawal reflex | Absent; flaccid tone | Normal |
| Nociception, right thoracic digits | Absent | Present |
| Panniculus reflex | Absent on the right side | Present bilaterally |
| Right eye | Miosis and third eyelid protrusion | Normal |
Which statement is correct?
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A. It is a right C1-C5 spinal cord lesion
A C1-C5 lesion causes upper motor neuron signs (normal or increased reflexes) and also affects the pelvic limb. Here there is a single flaccid, areflexic limb.
B. It is an isolated radial nerve injury from humeral trauma
The radial nerve explains knuckling, but not the absent flexion, the absent panniculus reflex or Horner syndrome.
C. It is an avulsion of the brachial plexus roots (C6-T2), with a poor prognosis because nociception is absent
Correct. Lower motor neuron monoplegia, Horner syndrome (sympathetic roots T1-T3) and an absent panniculus on the affected side (lateral thoracic nerve, C8-T1) indicate avulsion of the caudal roots. Without nociception in the digits, functional recovery is unlikely.
D. It is an upper motor neuron lesion from head trauma
Head trauma does not cause flaccidity and areflexia of a single limb, and the mental status is normal.
lightbulb Key takeaway
The panniculus contracts on both sides even when only one is stimulated: if it is absent on one side whichever side is stimulated, the lesion is efferent (C8-T1). With avulsion and no nociception, watch for self-mutilation and dragging ulcers; if there is no improvement within weeks, amputation is a reasonable option.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.