Heteronymous H-reflex in temporal muscle motor units

An electric stimulation of the masseteric nerve elicits a heteronymous H-reflex in the temporal muscle. The characteristics of this reflex response were investigated by analysis of the firing probability changes of single motor units. Eleven healthy subjects participated in the experiments. The heteronymous H-reflex of the temporal muscle was electrically elicited by stimulation of the masseteric nerve at 120% of the intensity needed for the maximal masseteric M-wave. From 8 to 24 motor units were sampled from the temporal muscle of each subject. Peri-stimulus time histograms of motor unit recordings were built with a 0.5-ms bin width. The mean firing probability was calculated for the 20 ms preceding the stimulus. The firing probability was considered increased when it exceeded the mean by 3 standard deviations. Of 104 sampled motor units, 40 motor units showed a significant increase of the firing probability, which lasted 1 ms or less in 29 of them. In 12 out of 16 motor units, a significant increase of firing probability also persisted at a lower stimulation intensity (120% of the threshold needed to elicit a masseteric M wave). These data indicate that: (1) some temporal muscle motor units are modulated by afferents from the masseter muscle, (2) the heteronymous H-reflex has a monosynaptic component, and (3) there might be a more complex than just monosynaptic organization serving the heteronymous temporal H-reflex. For the latter conclusion regarding synaptic wiring, however, PSTH studies like the present one can offer only indirect evidence, and this question could be better studied in animals.     

Temporalis muscle for facial reanimation. A 13-year experience with 224 procedures

A procedure for temporalis muscle transposition was used to reanimate the paralyzed face in 219 patients. In most cases, facial paralysis had followed an operation to remove an acoustic tumor. Analysis of the results showed this procedure to be highly successful and the method of choice, alone in cases of long-standing facial paralysis or to augment the effects of facial nerve grafting or hypoglossal-facial nerve anastomosis, in reanimating the mouth. It was successful in restoring a smile to 80% of the 219 patients and provided overall improvement in mouth function in 96%. Complications occurred in 21% of patients, with the most common being infection (12% of patients). Since one of us began to use the procedure to reanimate the eye and mouth, results of temporalis muscle transposition have been improved by the following: (1) using the procedure to reanimate the mouth only; (2) performing revision surgery, most often tightening the corner of the mouth (25% of patients), as indicated; (3) transposing only the midsection of the muscle; (4) implanting a prefabricated Silastic prosthesis to fill the muscle defect; (5) when indicated, lengthening the muscle with polytef (Gore-Tex+); and (6) placing the muscle in a tunnel lateral to the superficial musculoaponeurotic system to avoid injuring the underlying facial nerve should some spontaneous recovery of facial nerve function be possible.     

Surgical pathology of parotid gland tumors

The records of 27 patients operated for parotid tumors were reviewed retrospectively. Pleomorphic adenoma was the most frequent tumor (37.1%) and required subtotal parotidectomy in all cases. Twenty percent presented permanent facial paralysis of the marginal mandibular branch. No recurrence has been observed in five years of follow-up. Warthin's tumor, found in 11.1% of patients, was removed by either superficial or subtotal parotidectomy. Parotidean cysts were observed in 7.4% and were excised by superficial parotidectomy. The malignant tumors included squamous cell carcinoma (22.2%), adenoid cystic carcinoma (14.8%), melanoma (3.7%), and renal-cell metastasis (3.7%). All were treated by total parotidectomy with conservation of the facial nerve in 67%. Twenty-five percent had postoperative facial paralysis and 33% developed Frey's syndrome. Thirty-three percent died in the next 5 years from locoregional metastases.     

Neuronal nicotinic receptor operates slow Ca2+ mobilization at mouse muscle endplate

The authors describe the anatomical characteristics of the levator labii superioris muscle by dissection in cadavers. PURPOSE: We describe the characteristics of these muscle, the details and relations, hopefully contributing to the study of muscle of the face. METHODS: Twenty faces of cadavers were dissected. The following features were studied: origin, insertion, length, width, thickness, relations, innervation and blood supply. RESULTS: In all cases the muscle originated from the inferior orbital margin. Two insertions were observed: via lateral fibers, superficial to the orbicularis oris muscle and via deep fibers than form part of the raphe at the corner of the mouth (70%); via superficial fibers to the orbicularis oris muscle (30%). The average of the length was 24.66 mm and the average of the thickness was 3.57mm. The width at its insertion was 11.2mm, and at the origin was 15.96mm. The levator labii superioris muscle was found to be anterior to the levator anguli oris; it was posterior to the distal portion of the zygomaticus minor (90%) and posterior to the mid portion of the zygomaticus minor (10%). The innervation was from the inferior branch of the zygomatic nerve (facial nerve) and from the infraorbital nerve (trigeminal nerve). The inferior portion of the muscle is supplied by branches of the angular artery and the superior part from branches of the infraorbital artery.     

The influence of gender on the masseter electromyographic jaw-jerk reflex in young human subjects

The purpose of this study was to investigate the effect of gender on the masseteric jaw-jerk reflex, evoked in a sample of nine male and nine female young subjects. Electromyographic jaw-jerk recordings elicited by chin-taps in the relaxed masseter muscle of the preferred chewing side, were obtained using a computerized recording and analysis system. In both groups, a jaw-jerk reflex was recorded in 95.56% out of the total number of chin-taps. The mean latency was significantly shorter in the females (5.75 ms) than in the males (6.14 ms, P = 0.0045), while the amplitude of the reflex was significantly higher in the females (P = 0.0005). No significant differences were found in the mean duration between males (6.86 ms) and females (6.73 ms). It was concluded that sex variation should be taken into consideration in the interpretation of the jaw-jerk reflex.     

Surgical anatomy of the internal thoracic artery

BACKGROUND: The internal thoracic artery (ITA) has become increasingly important in coronary artery bypass grafting due to the excellent long-term results. This study reviews its anatomic characteristics. METHODS: The ITAs of 100 cadavers were examined and their origin, relation to the phrenic nerve, presence of lateral costal branch; origin of pericardiacophrenic arteries, length, level and type of ITA termination, relation with the transverse muscle of thorax, collateral parietal branches, and distance between the ITA and sternal margins were studied. RESULTS: The ITA was present in all cases, originating directly from the subclavian artery or from a common trunk with other arteries. Its length was 20.4 cm on average, and the most frequent level of termination was at the sixth intercostal space, existing as a bifurcation in 93% and as a trifurcation in 7%. The pericardiacophrenic artery originated from the ITA in 89%. The lateral costal branch was present in 15% of the cases. The ITA was covered by the transverse muscle of the thorax for 7.5 cm (average) and was crossed anteriorly by the phrenic nerve in 70.0%. CONCLUSIONS: Information provided by this study may contribute to knowledge of its anatomic characteristics and in turn help prevent complications in ITA dissections.     

One-stage transfer of the latissimus dorsi muscle for reanimation of a paralyzed face: a new alternative

The two-stage method combining neurovascular free-muscle transfer with cross-face nerve grafting is now a widely accepted procedure for dynamic smile reconstruction in cases with long established unilateral facial paralysis. Although the results are promising, the two operations, about 1 year apart, exert an economic burden on the patients and require a lengthy period before obtaining results. Sequelae such as hypoesthesia, paresthesia, and conspicuous scar on the donor leg for harvesting a sural nerve graft also cannot be disregarded. To overcome such drawbacks of the two-stage method, we report a refined technique utilizing one-stage microvascular free transfer of the latissimus dorsi muscle. Its thoracodorsal nerve is crossed through the upper lip and sutured to the contralateral intact facial nerve branches. Reinnervation of the transferred muscle is established at a mean of 7 months postoperatively, which is faster than that of the two-stage method. In our present series with 24 patients, 21 patients (more than 87 percent) believed that their results were excellent or satisfactory, which also compares well with the results of the two-stage method combining free-muscle transfer with cross-face nerve graft.     

The effect of unilateral partial facial paralysis and muscle ablation on craniofacial growth and development: an experimental study in the rabbit

The effect of unilateral partial facial nerve ablation and unilateral partial midface muscle ablation on craniofacial growth and development was investigated. New Zealand White rabbits (12 days old) were randomly assigned to three experimental groups: control group, to study normal craniofacial growth and development (n = 15); nerve ablation group, surgically induced unilateral paralysis of the buccal branches of the facial nerve (n = 15); and muscle ablation group, surgical unilateral ablation of the facial muscles innervated by the buccal branches of the facial nerve (n = 12). All animals were operated on at the age of 12 days; follow-up evaluations were performed at the ages of 2 months and 6 months. The age of 2 months represents the endpoint of the prepubertal craniofacial growth and development. At the age of 6 months, the animals are fully grown; therefore, the time period between 2 and 6 months is regarded as the pubertal growth period. Computerized dorsoventral roentgencephalometric (measurement of distances and angles) and computer tomographic (three-dimensional volumetric measurements) investigations were performed at both ages. Additional dry skull measurements were performed to determine more precisely the bone segments involved in the craniofacial growth alterations studied. The obtained results indicated the following. Unilateral partial facial paralysis involving the midface resulted in growth alterations analogous to those seen after unilateral total facial paralysis. The growth alterations were not to be seen as a growth restriction (reduction in bony volume) but as growth misdirections (alterations in shape). Major growth alterations were present in those regions closely related to the facial musculature, namely the nasal, maxillary, and premaxillary regions, resulting in a snout deviation toward the operated side. The growth alterations occurred during prepuberty and remained rather stable during puberty. Morphologic signs of muscle denervation were related to the craniofacial growth disturbances. The growth alterations after unilateral partial facial paralysis were mainly biomechanically induced, as they were analogous to those observed after unilateral midfacial muscle ablation. The fact that after unilateral midfacial muscle ablation at the age of 6 months the severity of the alterations had increased was attributed to the scar formation inherent to the surgical procedure.     

Gains and losses of the XII-VII component of the "baby-sitter" procedure: a morphometric analysis

The classic hypoglossal transfer to the facial nerve is invariably followed by complications caused by tongue atrophy. In 1984, Terzis introduced the "baby-sitter" procedure which involved a formal cross-facial procedure, in addition to partial neurectomy of the hypoglossal nerve, and an end-to-side coaptation with the ipsilateral facial nerve. This reported study provides, for the first time, quantification of the number of hypoglossal motor fibers needed to successfully restore eye sphincter function, using an end-to-side coaptation with preservation of the tongue. Thirty adult Sprague-Dawley rats were divided into six groups: control, denervated, perineurial window, 20 percent partial neurectomy (PN), 40 percent PN, and 80 percent PN. The procedure involves interposing a nerve graft (saphenous) between the partially severed XII nerve and the upper zygomatic branch of the facial nerve. Evaluation of the behavioral data (blink reflex) revealed good-to-superb return of the blinking mechanism in the 40 percent group, without significant tongue atrophy. Electrophysiologic data in the 40 percent neurectomy group demonstrated superiority to the other groups. Quantitative axonal morphometry of the coaptation sites and graft, as well as motor end-plates of the orbicularis oculi muscle and tongue showed the 40 percent partial neurectomy group to be the optimal group.     

Regional muscle flap-plasty and adjuvant measures for rehabilitation of the paralyzed face

BACKGROUND: The loss of facial nerve activity reduces the quality of life in regard to functional disturbances and to the appearance of the patient. As far as possible a reconstruction of the facial nerve should be advocated. Only this procedure allows the natural variety of differentiated facial expression. If reconstruction of the facial nerve is not indicated or turns out to be unsatisfactory, a dynamic muscle transposition should be considered. PATIENTS AND METHODS: The patient records of the ENT-Departments in Fulda for the period from 1988 to 1995 and in M?nchengladbach from 1993 to 1995 were reviewed to survey the experience of secondary plastic rehabilitation of the paralysed face. Our special interest focussed on the oral region with dynamic muscle transfer. The techniques leading to rehabilitation of the lid region were included in this study. RESULTS: Transfer of the temporalis muscle was performed 12 times and a masseter muscle flap 4 times to rehabilitate the oral region. Static rehabilitation (canthoplasty, tarsorrhaphy) of the lid was performed 8 times, implantation of a gold weight in the upper lid 5 times and dynamic rehabilitation of the lid region with a temporalis muscle transposition once. CONCLUSIONS: Rehabilitation of the oral region is best managed with a temporalis muscle flap because of its favourable vector of tension and its broad, flat form. Masseter muscle transposition is particularly indicated if a temporalis muscle transfer is not possible or if resection of the facial nerve because of malignancy of the parotid gland has to be performed and nerve reconstruction is not advisable.     

Effect of the menstrual cycle on gallbladder fasting volume and postprandial emptying in nulliparous young females

In order to determine the value of a reconstructive procedure in the peripheral nerve, experimental studies often evaluate the number and the diameter of myelinated nerve fibers as a parameter for the quality of regeneration. This study addresses the correlation between the number of fibers in a peripheral motor nerve after microsurgical reconstruction and the functional result, expressed as the force of the reinnervated muscle. In a total number of 24 sheep, the motor branch to the rectus femoris muscle was severed. The muscle was reinnervated either by direct neurorrhaphy or by nerve grafting, performed in three different ways (free grafting to the ipsilateral muscle, free grafting to the contralateral muscle, vascularized grafting to the ipsilateral muscle). In the final experiments, the muscle force in the reinnervated muscle was determined by supramaximal electrical stimulation. Number and diameter of myelinated nerve fibers were evaluated by computer-assisted morphometric analysis. Regression analysis of morphometric data and the muscle forces was calculated. No correlation was found between fiber numbers in the nerve graft and the maximal force. However, a positive correlation between the number of myelinated fibers in the motor branch distal to the site of coaptation and the functional result was observed in some cases. The diameter of myelinated fibers had no influence on the functional outcome.     

The anatomy of the platysma muscle

Platysma muscle was studied in 50 cadavers. The principal anatomic variation concerned the medical fibers. In 75 percent of the cases, the fascicles are separate in the suprahyoid region but interlace with those of the opposite side, 1 to 2 cm below the chin. In 15 percent, the fascicles come together at the level of the thyroid cartilage, like a single muscle in the suprahyoid region. In 10 percent of the cadavers, the fibers were separate, but inserted in the subcutaneous muscles of the chin without decussating. The posterosuperior fibers of the platysma always pass behind the angle of the jaw and over important structures, the most significant being the mandibular branch of the facial nerve.     

Surgical treatment of facial nerve involvement caused by leprosy

Complete and partial nerve paralysis can result from leprosy. The latter is more prevalent and results in lagophthalmos and corneal hypoesthesia. The former is characterized by loss of facial expression, deviation of the face to the nonparalyzed side, difficulty in chewing, and drooling, in addition to lagophthalmos and corneal hypoesthesia. Affected patients are at risk to develop blindness, as well as suffering social and economic deprivation because of the effects of facial nerve paralysis. Prevention of blindness and amelioration of the latter were successfully achieved by muscle transfer procedures, temporalis transfer to the eyelid, and masseter transfer to the mouth and nasolabial fold in small, minimally equipped hospitals in Africa.     

The importance of sodium pyruvate in assessing damage produced by hydrogen peroxide

OBJECTIVES: The external striated urethral sphincter (rhabdosphincter) is a tubular muscle sleeve that extends from the prostato-membranous urethra and perineal membrane to the bladder neck. The male rhabdosphincter neuroanatomy remains unclear, and a better understanding of its innervation may provide insight into potential modifications of radical pelvic surgery to improve urinary continence. METHODS: Fresh cadaveric dissections of 12 male hemipelves were undertaken to investigate the neuroanatomy of the urinary rhabdosphincter. RESULTS: Neuroanatomic courses of the nerve supply to the rhabdosphincter revealed that, in the perineum, the perineal nerve (a terminal branch of the pudendal nerve) provided branches directly to the bulbospongiosus muscle and the urinary rhabdosphincter. In the pelvis, the course of the pelvic nerve was as follows: (1) arising from the inferior hypogastric plexus, it had a weblike course beneath the muscle fascia of the levator ani muscle; (2) traveling posterolateral to the rectum, it gave many branches that perforated into the lateral rectum; and (3) at the level of the prostatic apex, still beneath the levator ani muscle fascia (superior fascia), it sent multiple direct branches to the inferolateral aspect of urinary rhabdosphincter. The pudendal nerve traversed the pelvis in the pudendal canal, and, before leaving the pelvis to enter the perineum, it gave an intrapelvic branch that courses with the pelvic nerve to innervate the rhabdosphincter. CONCLUSIONS: Our understanding of the neuroanatomy of what may be the continence nerves has been improved by fresh cadaveric dissection. The rhabdosphincter receives nerve fibers from the pelvic nerve and dual innervation from an intrapelvic branch and a perineal branch of the pudendal nerve. Better understanding of these anatomic findings may have potential surgical significance with respect to improvement in postoperative urinary continence.     

Chronic electrical stimulation of the facial nerve causes signs of facial nucleus hyperactivity

The proximal segment of the facial nerve in rats was stimulated electrically daily for a duration of 2-10 min. After 4-8 weeks of such stimulation, 12 of 18 rats developed abnormal muscle responses that could be demonstrated by recording the electromyographic response from lower face muscles (the mentalis muscle) while the temporal branch of the facial nerve was being stimulated electrically. This abnormal electromyographic response consists of activity that appears in the latency range 6.5-15 ms. In addition, these chronically stimulated rats developed signs of facial synkinesis on the side that had been chronically stimulated. This could be demonstrated by recording electromyographic activity when the blink reflex was being elicited by electrical stimulation of the ophthalmic nerve. Rats in which electrodes had been implanted but which had not been stimulated did not develop any abnormal electromyographic activity. The abnormal electromyographic activity that could be recorded in rats that had been stimulated chronically could not be recorded 4-8 weeks after the stimulation had been terminated. We interpret these results to indicate that chronic electrical stimulation of the facial nerve can render the facial motonucleus hyperactive, and that the signs of this hyperactivity (abnormal muscle response and synkinesis) are similar to those typically seen in patients with hemifacial spasm. We thus presume that these results support the hypothesis that it is the irritation of the facial nerve from a compressing blood vessel that causes the facial nucleus to become hyperactive in patients with hemifacial spasm.     

The innervation of the human posterior cricoarytenoid muscle: evidence for at least two neuromuscular compartments

Recent work has demonstrated that the dog posterior cricoarytenoid (PCA) muscle is composed of three neuromuscular compartments: a vertical, an oblique, and a horizontal. In this study, the human PCA muscle was examined for evidence of neural compartments. Fifteen human PCA muscles were processed by Sihler's stain, which renders the muscle translucent while counterstaining the nerve supply. The results clearly show that in all specimens the nerve supply of the human PCA muscle is separated into at least two main branches: one supplies the horizontal compartment and a second further subdivides to innervate both the vertical and oblique compartments. In 10 of the specimens, these nerve branches arose as separate branches from the recurrent laryngeal nerve. In all specimens, the nerve branch to the horizontal compartment was either combined or connected with the nerve branch to the interarytenoid muscle. The results suggest that the different compartments of the PCA muscle have distinct functions. In addition, the strong connections with the interarytenoid nerve complicate reinnervation procedures to reanimate a paralyzed or transplanted larynx.     

Femoral nerve transfer for treatment of brachial plexus root avulsion

Femoral nerve transfer to the muscular branches of the thenar and hypothenar muscles was performed to determine its protective effect on the hand intrinsic muscles. Seven cases of brachial plexus root avulsion treated from May of 1989 to October of 1991 were involved. The femoral nerve transfer to the muscular branches of the thenar and hypothenar muscles was done at the same stage of multiple neurotization. The muscular branches derived from the femoral nerve were isolated and coapted with the thenar muscle branch of the median nerve and the deep branch of the ulnar nerve. A groin flap was harvested simultaneously to form a skin-tube pedicle that covered the nerve bridge. At the second stage, when regeneration of the median and ulnar nerves was found to reach as far as the level of the wrist, the femoral nerve was divided and the muscular branches of the thenar and hypothenar muscles were anastomosed with the regenerated median and ulnar nerves. All the cases were followed up for more than 6 years. Six months after femoral nerve transfer, muscle power of the interosseous muscles and adductor pollicis recovered to MRC3, whereas that of the abductor pollicis brevis recovered to MRC1 to 2. Five cases underwent second-stage transfer. Four to five years of follow-up revealed that the muscle power of the interosseous muscles and adductor pollicis was MRC2 in one case, MRC1 in three cases, and MRC0 in one case. As for the donor area, muscle power of the quadriceps femoris reduced to M3 to 4 within 1 month after femoral nerve transfer and recovered to normal at 3 months. In conclusion, femoral nerve transfer to the muscular branches of the thenar and hypothenar muscles has some protective effect on the hand intrinsic muscles. The outcome of the second stage, however, is not satisfactory.     

Botulinum toxin injection effective for post-peripheral facial nerve palsy synkinesis]

Facial synkinesis is an involuntary activation of muscles innervated by the zygomatic or mandibular branch of the facial nerve in conjunction with voluntary activation of the other branch. It appears frequently after recovery from peripheral facial nerve paralysis. We report 10 patients with facial synkinesis following Bell's palsy with a mean duration of synkinesis of 7 +/- 4 years before treatment with periorbital injections of Botulinum toxin type A. 9 had marked subjective and objective improvement starting a few days after injection and lasting 4-9 months. The results suggest a useful treatment option for post-Bell's palsy facial synkinesis with Botulinum toxin type A.     

The qualification of different free muscle transplants to reconstruct mimic function: an experimental study in rabbits

With the scutuloauricularis muscle, we developed a new model for experimental free transplantation of mimic muscles in the rabbit and studied the qualification of different muscles for free functional grafting into the position of the facial muscle, which is to be replaced. Forty adult female white New Zealand rabbits were distributed to four groups of 10 rabbits each. In group 1, the operative techniques of the new transplantation models were developed in the scutuloauricularis muscle, the pectoralis descendens muscle, and a comparable part of the rectus femoris muscle. In group 2, the scutuloauricularis muscle was transplanted orthotopically with microneurovascular anastomoses on the left side; in group 3, the pectoralis descendens muscle was transplanted into the position of the scutuloauricularis after its removal; and with the animals in group 4, a piece of the rectus femoris muscle was transplanted into the position of the mimic muscle after its removal. In all muscle transplants, the neurovascular supply was reestablished microsurgically by end-to-end anastomoses to the superficial temporal vessels and direct nerve coaptation to the facial nerve branches supplying originally the scutuloauricularis muscle. Nine months after transplantation, force measurements were performed in all transplanted muscles and the scutuloauricularis muscles of the control side. Cross-sections stained for ATPase after alkaline preincubation at pH 10.4 were used for computer-assisted planimetry of the muscle fibers. The orthotopically transplanted scutuloauricularis muscles reached with 2.84 (+/-1.04) N for maximal tetanic tension on the average 87.7 (+/-32.1) percent of that of the control scutuloauricularis muscles, the pectoralis descendens muscles with 4.25 (+/-2.15) N on the average 188.7 (+/-100.7) percent of that of the controls, and the pieces of rectus femoris muscles 6.62 (+/-2.16) N or 185.3 (+/-45.4) percent of that of the controls. All three muscles were identified as fast contracting muscles before and after transplantation. By transplantation, the content of type II muscle fibers changed from 58.2 to 68.0 percent in the scutuloauricularis muscle, from 62.4 to 74.4 percent in the musculus pectoralis descendens, and from 92.5 to 82.8 percent in the rectus femoris muscle. For the first time, an experimental model for free transplantation of mimic muscles was developed and functionally assessed. The most important result of this study was the fact that the double-sized muscle grafts developed twice the force of the control scutuloauricularis muscles, although reinnervated by the original muscle nerve branch. This result underlines the usefulness of overdimensioning during clinical muscle transplantation. It was also shown that parts of big muscles can be grafted with results similar to those experienced with complete smaller muscles.