Trigeminal neuritis: the dog with a dropped jaw
6-year-old Golden Retriever that acutely cannot close its mouth: the jaw hangs, it drools and cannot prehend food, although it swallows normally. The mouth closes manually without pain or resistance; facial sensation is preserved and there are no other deficits. It lives in Madrid and has not travelled.
What is the most likely diagnosis and appropriate management?
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A. Temporomandibular luxation: reduction under anaesthesia
With luxation the mouth cannot be closed manually, it is usually painful and the jaw deviates to one side.
B. Idiopathic trigeminal neuritis: nutritional support and hydration; it usually recovers within 2–4 weeks
Correct. Bilateral involvement of the motor mandibular branch causes the dropped jaw. Treatment is supportive: feed food balls or gruel, ensure hydration and, if needed, an oesophagostomy tube. Corticosteroids have not been shown to shorten recovery.
C. Masticatory muscle myositis: immunosuppressive prednisolone
Masticatory myositis usually presents with pain and, in the chronic phase, with inability to open the mouth (trismus) and atrophy, not with a painless dropped jaw.
D. Paralytic rabies: isolation and mandatory notification
A dropped jaw is a sign of paralytic rabies, but mainland Spain is rabies-free; it should only be considered with a history of travel, importation or contact with suspect animals, and it usually progresses rapidly.
lightbulb Key takeaway
An acute, painless dropped jaw that closes manually, with normal swallowing, is typical of idiopathic trigeminal neuritis. If it persists beyond a few weeks, or there is marked atrophy or unilateral loss of facial sensation, look for other causes (nerve sheath tumour, lymphoma).
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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.