OBJECTIVE: The goal of this study was to determine the various anatomical and surgical relationships between the facial and hypoglossal nerves to define the required length of each for a nerve transfer, either by means of a classical hypoglossal-facial nerve anastomosis or combined with any of its variants developed to reduce tongue morbidities. METHODS: Five adult cadaver heads were bilaterally dissected in the parotid and submaxillary regions. Two clinical cases are described for illustration. RESULTS: The prebifurcation extracranial facial nerve is found 4.82 0.88 mm from the external auditory meatus, 5.31 1.50 mm from the mastoid tip, 15.65 0.85 mm from the lateral end of C1, 17.19 1.64 mm from the border of the mandible condyle, and 4.86 1.29 mm from the digastric muscle. The average lengths of the mastoid segment of the facial nerve and the prebifurcation extracranial facial nerve are 16.35 1.21 mm and 18.93 1.41 mm, respectively. The average distance from the bifurcation of the facial nerve to the hypoglossal nerve turn is 31.56 2.53 mm. For a direct hypoglossal-facial nerve anastomosis, a length of approximately 19 mm of the hypoglossal nerve is required. For the interposition nerve graft technique, a 35 mm-long graft is required. For the technique using a longitudinally dissected hypoglossal nerve, an average length of 31.56 mm is required. Exposure of the facial nerve within the mastoid process drilling technique requires 16.35 mm of drilling. CONCLUSION: This study attempts to establish the exact graft, dissection within the hypoglossal nerve, and mastoid drilling requirements for hypoglossal to facial nerve transfer.

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Facial reanimation by means of the hypoglossal nerve: anatomic comparison of different techniques.

Background: Multistage reconstructive procedures are often required to try to
restore the emotional potential of human expression in cases of facial paralysis.
In this study, the senior author’s (J.K.T.) experience with the technique of direct
nerve to muscle neurotization as a part of multistage facial reanimation procedures
is presented. Age, denervation time, etiology of the lesion, previous
reconstructive procedures, and types of muscles responsible for animation were
analyzed to make evidence-based recommendations on the indications of the
technique as well as its role and effectiveness in facial reanimation.
Methods: Retrospective review of 37 pediatric patients who underwent direct
muscle neurotization took place. The patients were divided into three groups,
depending on the region that direct neurotization was aiming to augment.
GroupAinvolved 28 patients for eye closure and blink, groupBincluded 15 patients
for smile, and group C included 19 patients for depressor augmentation.
Results: Twenty patients were female and 17 male. Patient age ranged from 1 to
16 years, with a mean age (�SD) of 9 � 2.8 years. Denervation time ranged from
3 months to 15.25 years, and the mean denervation time was 6.72 years. Electromyographic
scoring of the neurotized muscles showed an overall mean improvement
of 36 percent for eye closure, 34.25 percent for blink, 37 percent for smile
augmentation, and 30 percent for depressor function restoration.
Conclusion: Direct muscle neurotization has a valid role in pediatric facial reanimation
procedures, as it augments and promotes expressivity.

Outcomes of direct muscle neurotization in pediatric patients with facial paralysis.

Object. Although the use of multiple agents is efficacious in animal models of peripheral nerve injury, translation to clinical applications remains wanting. Previous agents used in trials in humans either engendered severe side effects or were ineffective. Because the blood—central nervous system barrier exists in nerves as it does in the brain, limited drug delivery poses a problem for translation of basic science advances into clinical applications. Convection-enhanced delivery (CED) is a promising adjunct to current therapies for peripheral nerve injury. In the present study the authors assessed the capacity of convection to ferry macromolecules across sites of nerve injury in rat and primate models, examined the functional effects of convection on the intact nerve, and investigated the possibility of delivering a macromolecule to the spinal cord via retrograde convection from a peripherally introduced catheter. Methods. The authors developed a rodent model of convective delivery to lesioned sciatic n...

Convection-enhanced delivery in intact and lesioned peripheral nerve

A patient experienced phrenic nerve paralysis after doxycycline sclerotherapy for treatment of chylous fistula at our institution. The purpose of this study is to use physiologic testing to determine whether doxycycline is capable of inducing defects in neural function. A nonrandomized, controlled trial was performed with nerve-conduction studies to determine possible deleterious effects of doxycycline sclerotherapy. Thirty-eight CD rats were used and separated into four groups. Doxycycline was applied to the sciatic nerves of rats by either topical application directly on the nerve or by intraneural injection. Nerve-conduction studies were done before surgery and at 1,7, and 21 days after surgery. The results showed a statistically significant decrement in nerve-conduction velocity and strength of transmitted impulse in those nerves injected with doxycycline solution. Complete nerve block was seen frequently. This effect was not seen with topical application of doxycycline or normal saline solution or with intraneural injection of normal saline solution. This study demonstrates that doxycycline can induce a marked decrement in neural function when applied to the subepineural layers of the sciatic nerve in the rat. Therefore doxycycline sclerotherapy should be used with great caution in situations in which it could become exposed to nerves that have sustained surgical trauma.

Neurotoxic Effects of Doxycycline Sclerotherapy

✓ Electrophysiological studies were used to evaluate neurological recovery in 14 rhesus monkeys with different nerve lesion lengths and graft lengths. After exposure of both sciatic nerves in each animal, baseline evoked nerve action potentials, muscle action potentials, and muscle strength values were determined for the posterior tibial nerves. Each nerve was then crushed over a measured distance. Three weeks later, the crushed segments were resected and the defects repaired with sural nerve grafts. In seven animals, 20-mm resection sites were repaired by 4 × 20-mm grafts in one leg and by 4 × 40-mm grafts contralaterally. In the other seven animals, the lengths of resection sites were 10 mm in one leg and 30 mm contralaterally; both nerve defects in these animals were repaired by 4 × 30-mm grafts. Electrophysiological studies were repeated at one interval of either 4, 7, or 12 months after repair. Postoperative electrophysiological values were compared to baseline values and described by the mean values...

Electrophysiological studies of various graft lengths and lesion lengths in repair of nerve gaps in primates

This experiment evaluated the electrical and histologic differences between two groups of rats, one of which underwent same-length bilateral resection of posterior tibial nerves prior to being repaired with grafts of different lengths, while the other group underwent different-length resections with same-length graft repair. In this rat model, 18 animals were used and divided into two groups. The first group of animals underwent bilateral resection of 8-mm segments of posterior tibial nerve. To repair these nerves, one leg received two 8-mm sural nerve grafts (Group A), while the other leg received two 16-mm sural nerve grafts (Group B). The second group of rats underwent posterior tibial nerve resections of 8 mm and 16 mm, respectively. The leg with the 8 mm of posterior tibial nerve resected, received two side-by-side 16-mm sural nerve grafts (Group C); the other leg with 16 mm resected, received two 16-mm sural nerve grafts (Group D). Electrophysiologic comparison of nerve conduction velocity for Groups A and B showed a significant difference (p less than 0.05), as did the same comparison for Groups C and D (p less than 0.05). Histologic studies showed that Groups A and D had marked extrafascicular escape of the regenerating nerve axons, disorganizational growth of minifascicles, and loss of integrity of the donor fascicles, while Groups B and C had very minimal extrafascicular escape of regenerating axons.(ABSTRACT TRUNCATED AT 250 WORDS)

Initial evaluation of variable graft lengths and lesion lengths in the repair of nerve gaps.

Background Gastrointestinal (GI) symptoms impact quality of life and increase health care utilization after liver transplantation (LTx). Esophagogastroduodenoscopy (EGD) is commonly used to investigate these symptoms. Aims The aim of this study was to investigate the diagnostic yield and utilization of EGD after LTx for common GI symptoms. Methods This single-center retrospective cohort study was conducted at a large liver transplant center and included all adults who underwent EGD within the first year after receiving LTx between January 1, 2015, and December 31, 2016. Biliary procedures were excluded. Results Of 437 patients who underwent LTx during the study period, 64 (15%) underwent EGD for the evaluation of GI symptoms within the first year of transplantation. After applying exclusion criteria, 57 (13%) cases were analyzed. GI hemorrhage (hematemesis/melena) was the most common reason (4%; n=18) for evaluation with EGD followed by nausea/anorexia (3%; n=12). Symptoms were investigated with EGD, including epigastric/abdominal pain (2%; n=9), dysphagia/odynophagia (2%; n=8), anemia (1%; n=5), diarrhea (1%; n=4), and heartburn (0.2%; n=1). The diagnostic yield of EGD was highest with GI hemorrhage (83%) followed by dysphagia/odynophagia (75%). EGD diagnostic yield was lower for the other symptoms, ranging from 0% to 25%. Conclusions EGD was commonly utilized within the first year of LTx, with the highest diagnostic yields for GI hemorrhage and dysphagia/odynophagia. Because of the low diagnostic yield of EGD for other symptoms, we recommend a careful selection of patients for EGD following LTx.

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Sean E Connolly

Papers

Initial evaluation of variable graft lengths and lesion lengths in the repair of nerve gaps.

The Utilization and Diagnostic Yield of Upper Endoscopy for Evaluation of Gastrointestinal Symptoms Within the First Year After Liver Transplantation.