April 2008
Dr Gerhard Steenkamp

A dog is presented with inability to open its jaw for the past 2 weeks, there is no history of trauma that the owners know of.  You try to open the mouth while in the clinic but it is impossible and the patient is reluctant for you to apply any pressure to open the mouth.  During a general anaesthesia you once again fail to force the jaws apart.  You make a dorso-ventral radiograph (photo 1).  On this radiograph it is impossible to determine the extent of the mineralised tissue and therefore a CT scan is performed.  A 3D reconstruction of the CT showing the normal side (photo 2) and affected side is shown (photo 3)

Photo 1

Photo 2

Photo 3

1 What abnormalities can you see on the radiographs/CT images
2 What is your diagnosis?
3 What treatment options are available for this patient?
4 What complications can be expected with these patients post-operative?
 
Memo

1 Radiograph: There is a radiodense mass extending from the caudal mandible to just rostral to the middle of the zygomatic arch on the left.  This mass appears to have the same density of that of bone. The left TMJ is also difficult to visualise as this mass appears to be superimposed over it.

CT:  New bone formation extending from the coronoid process to the caudal zygomatic arch.

2 Temporo-mandibular joint ankylosis.  This condition is common following trauma
 to the zygomatic arch area, even if it is not obvious initially.  It may also be

present in cases of craniomandibular osteopathy where it will usually be bilateral.

3 Surgical removal of the affected bones where ankylosis is present. Partial zygomatic arch and coronoid resection.  Thereafter disarticulation of the TM joint.

4 Blinking reflex lost in ipsilateral eye due to neuropraxia of the palpebral nerve
 (NVII).

Haemorhage in potential space due to boneloss.
Re-ankylosis (especially in young patients) especially if not sufficient bone was
removed initially.