MAGNETIC RESONANCE NEUROGRAPHY FOR TRIGEMINAL NEUROPATHIES

This article brings up an important point in the proper diagnosis of nerve injuries involving branches of the trigeminal nerves. That point is that MRI (magnetic resonance imaging) can be very helpful in diagnosing the problem and verifying the potential location of the problem. (J Oral Maxillofac Surg 76:725-736, 2018)

This article brought out a specific area of interest for me and that is the diagnosis and treatment of neuropathies of the lingual nerve after third molar surgery. I have been fortunate that this has been an extremely rare complication in our practice and, at the time of this writing, when it has occurred, we have never had a problem with a permanent injury such as permanent pain or numbness. I recognize that it could happen tomorrow – but we use a technique in how we approach teeth, and with the use of cone beam scanning as a pre-op study for more complicated cases, we have experienced a low complication rate.

We do however, get referred cases for treatment where other practitioners have treated a patient with a resultant nerve injury and they come to us for evaluation for repair. The first point is that early diagnosis and treatment give the best chance at resolving a nerve injury – so do not put off care waiting for the problem to resolve. There are definitely exceptions to this – such as a partial numbness or a light “tingling”. But if there is a complete numbness on the side of the tongue and it is getting past 3 months post-treatment, an MRI and surgical evaluation should be considered.

The second point is that the approach to the lingual nerve is critical. Many surgeons will make an incision back by the third molar region to access that area. There is a much easier and much better way and that is to approach the area much like one would approach the removal of exostoses – that is an incision along the back teeth and a releasing incision extending across the third molar area to the lateral aspect. A full thickness flap is then made to expose the tongue side of the jaw bone. In most cases, you will find an area where the bone is disrupted in the area of the previous surgery and the tissues along with the nerve are “pulled into” the third molar healing defect. Teasing these tissues out, and “releasing” scare tissue bands, and placing a surgical barrier graft over the bone defect will often times relieve the problem. If it is found that the nerve is severed you can try to approximate the ends, however it has never been my experience that the nerve has been cut and it is my opinion that the prognosis for repair in that case would be poor.

The third point is that if at the time of MRI and evaluation that the nerve is noted to be cut, then a microneurosurgical consult should be sought out. Going back to the beginning of this discussion, the MRI can be helpful in determining the location and the extent of these types of injuries.