Article reprinted with permission of DVM360 –September 06, 2018. DVM360 MAGAZINE is a copyrighted publication of Advanstar Communications inc. All rights reserved NEUROLOGY Salivation Abnormalities of Neurogenic Origin Max presented with unilateral temporalis muscle atrophy but also with changes to his saliva. Let’s investigate what's behind it. By Rachel B. Song, VMD, MS, DACVIM (Neurology), Eric N. Glass, MS, DVM, DACVIM (Neurology), Marc Kent, DVM, DACVIM It’s Monday morning. You walk into the office, back from a long weekend. You run through the list of the day’s appointments and see that one of your favorite patients, Max, is on the day’s schedule with the chief complaint being that the “head looks funny. ”Later that day, you enter the exam room and ask, “What’s going on with Max today?” His owner replies, “Well, doc, the left side of his head completely sunk in overnight!” You take one look at Max’s head and your heart sinks—you quickly recognize that the left temporalis and masseter muscles have atrophied completely. Without the muscles, the left zygomatic arch is clearly visible to the naked eye. The left eye also has become enophthalmic with an accumulation of mucoid discharge and third eyelid elevation (Figure 1). Additionally, enophthalmos of the left eye and secondary third eyelid elevation have resulted from atrophy of the pterygoid muscles. (All photos courtesy of Drs. Rachel B. Song, Eric N. Glass and Marc Kent). When you turn Max’s head to examine the right side, you see how well-muscled his head is on the unaffected side. He’s still able to close his eyelids when you perform the palpebral reflex and the menace response. You remember that to close the eyelids, cranial nerve VII (the facial nerve) has to be functioning normally. Likewise, all the other cranial nerves appear to have normal function on your examination. When you do an oral exam on Max, you see an accumulation of thick, foamy saliva in the vet360 Issue 04 | SEPTEMBER 2018 | 20 Figure 1: Max has unilateral dysfunction of the mandibular branch of cranial nerve V (trigeminal). Atrophy of the temporalis muscle (large arrow) is evident. Loss of the masseter and temporalis muscles makes the zygomatic arch more clearly defined (arrowhead).