Trigeminal neuropathy in two horses following trauma to the infraorbital and mental nerves

This case series describes two cases of a head injury resulting in a traumatic neuropathy of the infraorbital nerve and the mental nerve, respectively. Both cases presented with head-shaking behaviour and assumed facial dysaesthesia. This is a cause of head-shaking not previously described in horses. One horse (Case 1) had a small wound at the level of the infraorbital foramen and was diagnosed with a bony fragment adjacent to the infraorbital nerve using computed tomography (CT) and ultrasonography. Treatment consisted of surgical removal of the fragment, systemic anti-inflammatories and multimodal analgesia. The second case (Case 2) was diagnosed with a nondisplaced comminuted fracture of the right hemi-mandible using CT. The fracture line, along with multiple small fragments, was overlying the mental nerve as the nerve exits the mental foramen. The horse was treated with multimodal analgesia, and the fracture healed without requiring stabilisation. Clinical signs took several months to resolve in both cases. There were no reported signs of dysaesthesia or head-shaking 6 months (Case 1) and 4 months (Case 2) following diagnosis. Long-term follow-up is still required to assess these horses. Traumatic neuropathy should be considered as a differential diagnosis in horses presenting with head-shaking behaviour