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Dexter's change in appearance causes concern

When a worried owner comes to see us because something is not right with their pet, it can be really rewarding to make an accurate diagnosis, and even more so to correct the problem. We always aim to do both of these if we can. Occasionally, however, we can neither pin down the cause of the problem nor solve it, and yet the outcome is still good. Our star this week was just such a case.

Dexter is a 5 year old crossbreed dog with a lovely gentle temperament. His story begins several months ago when he was out on his usual walk in the park and deftly caught a treat in his mouth. His owner then noticed that he was mouthing the treat and drooling from one side of his mouth. This episode didn’t last long and Dexter’s owner thought no more of it at the time. But over the next few weeks she began to notice a change in Dexter’s appearance.

At first she thought she was imagining it, but soon she was convinced that his face had become ‘lopsided’, and the more she considered it, the more obvious it became. After a few weeks, although Dexter was very much his normal, happy self otherwise, he did not look right and so he came to see us.

When we examined Dexter, if we had not known there was a problem from his owner, we might have not noticed an abnormality. This was made especially tricky by the fact that he made it clear he wanted a fuss, rather than to sit still and be stared at! However, with a bit of time we could see that his face was completely asymmetrical. His right ear was lower than his left, the left side of his mouth was ‘smiling’ more and his nose appeared deviated to his left hand side. From the rest of our examination Dexter seemed in fine health. He was a fit and healthy dog, with no abnormal behaviour and no elevated temperature, no signs of pain or swelling and no other neurological changes. It was a bit of a mystery.

We suspected that Dexter had a problem with one of his cranial nerves, the group of nerves communicating between the central nervous system and the structures of the head, which could have a multitude of different causes. Because his condition had developed slowly and he was so well in himself, there was no requirement for immediate treatment. Instead, we booked Dexter in for further investigations to try to discover what might be causing his strange symptoms.

The following week, Dexter returned to stay with us for the day, which he thoroughly enjoyed as none of us could resist giving him a cuddle before we started his investigations. First we performed a thorough neurological examination, in which we work through a series of observations and tests to assess different nerve functions. This confirmed our findings from the initial consultation and also showed that Dexter’s left eye could not blink properly. From the neurological exam we concluded that Dexter had a problem with his facial nerve, which controls many of the muscles of the face. While it was difficult to be sure which side of Dexter’s face was ‘normal’ we felt it most likely that the left facial nerve was affected, due to the reduced blink reflex on that side, and that he had a spasm of the muscles supplied by the left facial nerve. So we had localised the cause of the symptoms but we still didn’t know what was causing them.

We sedated Dexter to allow further examination and discovered that his facial asymmetry resolved when he was asleep, which was interesting but still didn’t help us. We then examined his ears and the back of his mouth, to look for any inflammation, infection or mass that could be affecting the nerve as it travels through the head, but we found nothing. An x-ray of Dexter’s head looked completely normal too. As we had found no anatomical cause for the facial nerve problem we decided to send a blood sample for analysis, to rule out some hormonal conditions that cause nerve problems. Because localised nerve problems can sometimes be due to an inflammation of the nerve, known as neuritis, we sent Dexter home on a trial treatment of anti-inflammatories, to see if this resolved his problem.

One week later, with completely normal blood results and no improvement on his trial treatment, we had some decisions to make about Dexter. While we knew that facial nerve problems can sometimes happen for no reason and need no treatment, there was still the concern that we had not ruled out some potentially serious causes, such as a problem with his middle ear or a tumour. After discussion with his owner we opted to refer Dexter to a specialist centre where he would be able to undergo more advanced imaging to rule these last few conditions out.

Thankfully, the specialists found no alarming causes for Dexter’s problem and he ended up with a diagnosis of Idiopathic Facial Nerve Paresis, which is similar to the condition Bell’s Palsy in humans. The word ‘idiopathic’ is one that vets encounter on fairly frequent basis, and it can be quite a frustrating one for us, as it means that the cause is not known. However, in Dexter’s case, this was the best possible outcome – he had no nasty underlying problem and he could continue his normal life. His owner just needed to use lubricant eye drops in his affected eye while he couldn’t blink normally.

Many dogs with this problem gradually return to normal over several months, but some will always have some degree of asymmetry. We actually found Dexter’s new quirky look rather endearing and it will certainly add to his individuality if it remains. Either way, what hasn’t changed is his enthusiasm, zest for life and fantastic personality.