American Society for Peripheral Nerve (ASPN)
Fall 2021 Issue
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Spotlight on Sensory Reconstruction
Gregory Borschel, MD
Sensory reconstruction... we need it from head to toe! Below is just a little work ASPN members (or soon to be members) are doing to restore sensation. Can you feel it?

The eyes have it!
Providing sensory reconstruction to insensate regions is often a major patient concern, and it has become a hot topic. One form of trigeminal reconstruction, “corneal neurotization,” was pioneered by ASPN Founding Member Julia K. Terzis. Lack of corneal innervation leads to neurotrophic keratopathy, in which patients develop corneal ulcers and low vision due to corneal scarring. Transferring new axons into the cornea interrupts this otherwise intractable and inevitable march toward blindness that affects 1/2000 worldwide. -Greg Borschel

Treatment of neurotrophic keratopathy with minimally invasive corneal neurotisation: long-term clinical outcomes and evidence of corneal reinnervation

Don’t forget the lower lip… it’s critical, too!

Patrick B. Garvey, MD
Sensory Reconstruction of the Inferior Alveolar Nerve with Processed Nerve Allograft at the Time of Oncologic Mandibulectomy
Patrick B. Garvey, MD


The inferior alveolar nerve (IAN) is a distal branch of the mandibular branch of the trigeminal nerve (V3). The IAN enters the medial surface of the mandibular ramus behind the lingula and travels within the mandible, giving sensory branches to the mandibular teeth, before exiting the mandible at the mental foramen as the mental nerve. The mental nerve supplies sensation to the overlying skin of the ipsilateral chin and lower lip. The most common cause of injury to the inferior alveolar nerve is from third molar or “wisdom tooth” extraction. Injury to the IAN causes permanent numbness of the ipsilateral half of the lower lip. Oral surgeons routinely perform repair of IAN trauma with either direct repair of the nerve or interposition grafts. Recently, processed nerve allografts from cadaver sources have become commercially available and gained popularity among oral surgeons for IAN, as these biologic devices allow for repair without harvesting autograft nerve from a donor site. Studies of outcomes from the benign oral surgery literature have shown comparable outcomes for nerve repair with allograft nerve to autogenous nerve and superior outcomes compared to direct repair.[1, 2]

Similar to benign IAN injuries, oncologic mandible resections also result in permanent numbness of the ipsilateral lower lip and chin. Advanced squamous cell carcinomas that invade into the bone of the mandible usually require a segmental mandibulectomy to remove the tumor with clear margins. Until recently, little attention was paid to the permanent sensory loss that followed an oncologic mandibulectomy. However, patient reported outcomes studies measuring the impact of IAN trauma on patients’ quality of life in the benign literature have suggested that this lack of lip sensation causes significant disability for patients.[3] Furthermore, the availability of “off-the-shelf” processed nerve allografts has facilitated long-segment sensory nerve reconstruction in the midst of the labor intensive procedure of mandible reconstruction with free fibula osteocutaneous flaps.

For the past two years, we have been performing sensory reconstruction of the IAN with allograft nerves in our mandibulectomy patients at the time of free fibula flap mandible reconstruction. Despite this being our initial learning curve period when we first adopted this strategy, our results have been encouraging. We have observed lower lip sensory restoration that is comparable to what has been published in the benign literature for IAN reconstruction. Interestingly, we also found that postoperative radiation therapy did not appear to negatively affect our patients’ outcomes. The main challenges that we have encountered have related to patient selection and surgical technique. It seems that not every patient is a for IAN reconstruction. Surgeons may find that patients with prior surgery or radiation therapy, particularly when a mandibulectomy has already been performed, may not be ideal candidates for IAN reconstruction. It can be challenging to identify the cut proximal and distal nerve ends for grafting. Another pitfall that we have encountered is in the situation of leakage of saliva into the neck wound from an intraoral dehiscence of the skin island and native oral mucosa. The allograft appears to be quickly degraded by saliva, contamination, and infection.

However, for the majority of our patients with uneventful postoperative recoveries, sensory outcomes have been good, and the patients have been pleased with the procedure. Since the IAN is completely resected with the mandibulectomy specimen, our patients experienced several months of complete ipsilateral lip numbness, as has been the case for patients without IAN reconstruction. It has been tremendously rewarding for our surgeons to witness our patients’ enthusiasm when their sensation does begin to return. Indeed, whereas for the first few months of the patients’ recovery, they are entirely concerned with the appearance of their lower face contour, intelligibility of their speech, and ability to chew and eat certain foods, around five or six months after surgery their attention turns almost entirely to their sensory recovery. And, qualitatively, the difference in the patients’ moods has been apparent to us in comparison to the mandibulectomy patients who did not undergo sensory reconstruction.

References
  1. Zuniga JR. Sensory outcomes after reconstruction of lingual and inferior alveolar nerve discontinuities using processed nerve allograft - a case series. J Oral Maxillofac Surg, 2015. 73: p. 734-744.
  2. Zuniga JR, Williams F, Petrisor D. A Case-and-Control, Multisite, Positive Controlled, Prospective Study of the Safety and Effectiveness of Immediate Inferior Alveolar Nerve Processed Nerve Allograft Reconstruction With Ablation of the Mandible for Benign Pathology. J Oral Maxillofac Surg, 2017. 75(12): p. 2669-2681.
  3. Leung YY, McGrath C, Cheung LK. Trigeminal neurosensory deficit and patient reported outcome measures: the effect on quality of life. PLoS One, 2013. 8(10): p. e77391.
Anne Peled, MD
Ziv Peled, MD
A breast just isn’t complete without sensation…
The past several decades have seen remarkable advancements in the treatment of breast cancer from an oncologic standpoint, as well as in aesthetic and reconstructive outcomes. However, following mastectomy, most women report poor, if any, sensation in their breasts. Anticipated loss of sensation can be a huge barrier for women considering mastectomy and has associated long-term negative physical and psychological impact on breast cancer survivors and previvors.

Over the past several decades, techniques for neurotization of flaps in autologous reconstruction have evolved and allowed many women the opportunity to have restoration of sensation following mastectomy. However, as the vast majority of breast reconstructions performed in the US are implant-based, extending the option of sensation preservation and restoration for all types of reconstruction is essential. In the past few years, we have developed a surgical procedure designed to optimize sensation in the setting of mastectomy and immediate, implant-based reconstruction. Our initial study published in 2019 described high rates of preserved two-point discrimination in the NAC following lateral intercostal nerve preservation and/or nerve reconstruction with allograft. At this point, we have performed over 150 such procedures and continue to refine our surgical technique. These refinements have allowed the use of shorter allografts due to the ability to preserve greater lengths of native intercostal nerves, which expands the option of nerve reconstruction to patients undergoing reconstruction with larger implant sizes. We have also been able to utilize autografts from accessory intercostal nerves in a greater number of cases, thus reducing the utilization of cadaveric allografts. Even with more rigorous outcome metrics (e.g. quantitative pressure threshold testing & Breast-Q questionnaires), over 65% of our patients are reporting some or a lot of sensation in their nipples and over 90% are reporting some or a lot of sensation in their breasts overall. Upon further questioning, many of these same women report that their breasts still play an important role in intimacy post-operatively and that in the course of their daily lives, they don’t feel much different than they did pre-operatively. As reconstructive surgeons, being able to restore not only breast appearance, but also sensation is incredibly exciting and we look forward to the time when sensation-preserving approaches will become more widely adopted and hopefully available for all patients undergoing mastectomy. -Ziv and Anne Peled

Nerve Allografting for Sensory Innervation Following Immediate Implant Breast Reconstruction

See a comprehensive list of ASPN member publications on the ASPN Member Publications webpage.
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