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PubMed2003

Clinical relevance of the distance between the cochlea and the facial nerve in cochlear implantation.

HYPOTHESIS: To elucidate possible mechanisms of facial nerve costimulation after cochlear implantation that are supposed to result from the close cochlea to facial nerve contact. BACKGROUND: One of the postoperative complications of cochlear implantation is facial muscle twitching, which has preferentially been found in otosclerotic patients. It impairs hearing benefits because of deactivation of electrodes and can still not be adequately prevented. METHODS: A total of 13 temporal bones were dissected to quantify where the labyrinthine portion of the facial nerve is closest to the scala tympani, the placement site of the cochlear implantation electrode array. After the typical operative procedures to find out the number of electrodes lying closest to the facial nerve were performed, a cochlear implantation array was inserted into four specimens. The clinical records of 14 otosclerotic patients were investigated to correlate these results with the position of in vivo deactivated electrodes. RESULTS: The closest distance between the scala tympani and the nerve was only 0.33 mm (+/-0.14). On average, after insertion of 23 electrode resp. marking rings, the facial nerve was reached. This is clinically the position of most frequently deactivated electrodes to prevent postoperative facial nerve costimulation. CONCLUSIONS: These investigations support the hypothesis that a direct current spread at the site of the facial nerve crossing the cochlear basal turn is most likely the reason for postoperative facial muscle twitching facilitated in otospongiotic bone. Prevention could therefore be achieved by cochlear implantation designs and surgical techniques that take into consideration the site of closest contact.

Adult↗

PubMed1981

Recruitment patterns of motor units in speech production.

Single motor units were recorded with intramuscular electrodes in sites selected to isolate units of the mentalis muscles of two human subjects. Order of recruitment of three groups of motor units was analyzed during repetition of syllables. Within each group motor units showed variable patterns of recruitment over repeated utterances. These recruitment patterns of labial motor units and the patterns observed by Sussman et al. in a jaw opening muscle are used to illustrate issues critical to interpretation of recruitment patterns of motor units active during speech. From extant data, inferences about the size of the motor units active cannot be made; however, the variability of recruitment patterns has significance for hypotheses about the underlying mechanisms of recruitment. Discussion includes the question of the size of motor units as inferred from action potential amplitude, differences in methodology between experiments in speech and those often used to interpret them, and the extent to which it is possible to isolate motor units from a single muscle in electromyography of facial muscles.

Action Potentials↗

PubMed1985

Neuromuscular adaptation of craniofacial muscles to altered oral sensation.

Experimentally induced changes in oral sensation to the tongue altered the use of specific craniofacial muscles. An acrylic wedge was anchored to the maxillary teeth of ten adult rhesus monkeys, providing a tactile-pressure sensation to the dorsal surface of the tongue. Fifteen craniofacial and tongue muscles were studied by electromyography during the first 6 months of adaptation. The results showed that there was an overall shift in those muscles that were normally tonically active in the craniofacial region. Muscles of the suprahyoid region, the geniohyoid and digastric, as well as the platysma muscle of the face, and the lateral pterygoid muscle were tonically active in more animals after placement of the wedge. In contrast to the enhanced activity of mandibular and facial muscles that function during mandibular depression, only the anterior temporalis muscle in the superficial and deep region demonstrated more tonic activity. The superficial and deep masseter regions, as well as the medial pterygoid muscle, demonstrated no change in their EMG activity. Only the lip muscles and mentalis demonstrated increased activity, whereas the facial muscles with more vertically oriented fibers did not demonstrate any increased activity. These findings suggest that a change in the tactile stimulation to the tongue can induce a new balance in the level of activity of specific craniofacial muscles and that this altered neuromuscular pattern can remain throughout the first 6 months of adaptation.

Adaptation, Physiological↗

PubMed2007

Electrophysiological study of ephaptic axono-axonal responses in hemifacial spasm.

One of the classic features of hemifacial spasm (HFS) is spread of the blink reflex responses to muscles other than the orbicularis oculi. The pathophysiological mechanisms underlying the generation of such abnormal responses include lateral spread of activity between neighboring fibers of the facial nerve and hyperexcitability of facial motoneurons. In this report we present evidence for another mechanism that can contribute to the generation of responses in lower facial muscles resembling the R1 response of the blink reflex. In 13 HFS patients, we studied the responses induced in orbicularis oris by electrical stimuli applied at various sites between the supraorbital and zygomatic areas. We identified responses with two different components: an early and very stable component, with an onset latency ranging from 10.5 to 14.8 ms, and a more irregular longer-latency component. Displacement of the stimulation site away from the supraorbital nerve and towards the extracranial origin of the facial nerve caused a progressive shortening of response latency. These features indicate that, in our patients, the shortest latency component of the orbicularis oris response was likely generated by antidromic conduction in facial nerve motor axons followed by axono-axonal activation of the fibers innervating the lower facial muscles. Our results suggest that motor axono-axonal responses are generated by stimulation of facial nerve terminals in HFS.

Adult↗

PubMed1976

Electromyographic biofeedback for relief of tension in the facial and throat muscles of a woodwind musician.

Electromyographic (EMG) biofeedback, for the relaxation of specific throat and facial muscles, was given to a woodwind musician. The patient had a nineteen-year history of tics and high levels of tension in his throat and facial muscles. Eventurally these problems progressed to a point that interfered with his ability to perform as a professional woodwind musician. Following detoxification from alcohol and Dexamyl, and after a period of psychotherapy, EMG biofeedback relaxation training was started for the muscles specifically showing chronically high tension levels. The EMG training consisted of four phases designed to help the patient progressively lower tension and generalize these newly learned techniques to his professional life. He had a total of twenty treatments of approximately 45 minutes each. This procedure resulted in dramatic reductions in tension levels of the specific throat and facial muscles along with increased proficiency as a musician and in psychological functioning.

Adult↗

PubMed1991

Dentofacial morphology in professional opera singers.

The interaction between muscle function and bone development has been studied mainly in animals. The aim of the present investigation was to study the dentofacial skeleton in individuals with a high degree of activity of muscles associated with the facial skeleton. It was assumed that a professional singer would constitute such an individual. Lateral cephalograms of singers from the Royal Opera Choir in Stockholm were studied and compared with lateral cephalograms of a control group. Significant differences between the singers and controls were found, such as length of mandible, length of maxilla, and increased facial height. The findings could be interpreted as an association between facial muscle hyperactivity and respiratory hyperfunction and dentofacial morphology.

Adult↗

PubMed1992

Reanimation of the paralyzed face.

The challenge of reconstruction in the paralyzed face is to provide symmetry both at rest and in active expression. Although functional considerations must take precedence, the patient with unilateral facial palsy faces social stigmata that are exceptionally difficult. The best reconstructions in late paralyses fall far short of natural facial expression. Conley, one of the pioneers in facial nerve rehabilitation, reflected the frustration of dealing with limited techniques: It has been assumed by many surgeons that involuntary emotional communication is through the facial nerve, but this has never been substantiated. Indeed, emotional expression may be beyond our concept of a mere physical tract. It certainly has never been totally restored by any surgical technique that attempts to rehabilitate the face. When injury to the facial nerve is established, early nerve grafting on the ipsilateral side is the best treatment. In acoustic neuroma and other intracranial operations, the only real opportunity for grafting or repair is at the time of the procedure. If the nature of the injury is uncertain, a period of 12 months is allowed to elapse before consideration of intervention, which should be started if there is no return of function at that point. Electromyography may be of assistance in assessing minimal early return; if any early return is noted, further waiting is indicated. If there is no return at 1 year, cranial nerve XII to VII crossover will preserve facial muscle tone and permit a more measured decision-making approach. Patients with multiple cranial nerves involved may be candidates for a partial hypoglossal transfer using a nerve graft, to attempt to preserve swallowing. In selected cases, cross-facial nerve grafting to the preserved facial muscles will give excellent results and obviate the need for local or distant muscle transfers. When treating established paralysis of long duration, cross-facial nerve grafting with microneurovascular muscle transfer is the best option for symmetrical movement of the face. Temporalis and masseter muscle transfers should be reserved for the patient with intercurrent medical disease or the patient who refuses additional operations or operative sites. Static slings and other related procedures should be considered adjunctive but not primary treatment in the vast majority of cases. Although there are limitations in each of the procedures described, close cooperation between the otolaryngologist, the neurosurgeon, and the plastic surgeon can provide many patients with satisfactory rehabilitation from facial paralysis.

Facial Muscles↗

PubMed1994

Characterization of human oro-facial and masticatory muscles with respect to fibre types, myosins and capillaries. Morphological, enzyme-histochemical, immuno-histochemical and biochemical investigations.

This study provides a comparative characterization of four human oro-facial muscles, one masticatory muscle (the masseter) and two limb muscles, with respect to muscle fibre types, myosin isoforms and capillary supply. Enzyme-histochemical methods were used to evaluate the myofibrillar ATPase fibre type composition. Immuno-histochemical techniques were used to determine the expression of myosin heavy chain (MHC) isoforms in the different fibre types. The contents of MHCs and myosin light chains (MLC) in different muscles were analysed with electrophoretic methods. In addition, the capillary bed of the muscles was evaluated using both enzyme- and immuno-histochemical techniques. The fibre type compositions of the oro-facial and masseter muscles were found to be qualitatively and quantitatively different from each other and from those of limb muscles. In general, the oro-facial muscles contained a predominance of unusually high oxidative type II fibres, with a staining reaction for ATPase in between that of type IIA and type IIB fibres, termed type IIAB. In fact, one of the oro-facial muscles, the zygomatic minor, showed the highest type II fibre proportion ever reported in humans. This fibre type pattern is in contrast to that of the masseter muscle, which contains a majority of type I fibres, small diameter low oxidative type IIB fibres and a significant proportion of ATPase-intermediately stained fibres, termed IM, and IIC. Inter- and intra-muscular variability in fibre size and shape was considerable in both the oro-facial and masseter muscles. The oro-facial muscles were devoid of muscle spindles. The immuno-histochemical and biochemical analyses showed a characteristic myosin composition of each muscle. Notably, the results indicated the presence of a previously undetected fast MHC isoform in the oro-facial muscles, tentatively termed "fast F". The masseter contained unusual myosin isoforms, such as fetal and alpha-cardiac MHCs, and unique combinations of MHC isoforms which were not found in the limb or oro-facial muscles. The type IM and IIC fibres co-expressed slow and fast A MHCs in the oro-facial and limb muscles, but slow and a "fast B like" MHC in the masseter. Individual fibres in the oro-facial and limb muscles contained one or two MHC isoforms, whereas individual fibres in the masseter co-expressed up to four different MHC isoforms. On the basis of their pattern of expression of MHC isoforms, up to five fibre types could be distinguished in the oro-facial and limb muscles and eight in the masseter.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphatases↗

PubMed2003

Axonal misdirection as contributing factor to aberrant reinnervation of muscles after facial nerve suture in cats.

Abstract Whereas basic features of post-axotomy muscle reinnervation have been extensively studied in rats, little is known about axonal regrowth and pathfinding in cats. To address the question, adult cats were subjected to facial-facial anastomosis (FFA). First group served to establish optimal parameters for labeling of the zygomatic and buccal facial branches with 1,1'dioctadecyl-3,3,3,'3'-tetramethylindo-carbocyanine perchlorate (DiI) and Fast Blue (FB) placed onto respective transected nerves. The second group of animals underwent identical bilateral labeling 3 months after transection and suture of the right facial nerve. This group served to establish the number of motoneurons, which had branched after surgery and projected into both facial branches. On control side, DiI application onto zygomatico-orbital branch labeled 3883 +/- 598 (mean +/- S.D.) perikarya were confined to the dorsal and intermediate facial subnuclei, meanwhile an application of FB onto the buccal branch labeled 1617 +/- 552 perikarya in the lateral and ventrolateral subnuclei. There were no double-labeled cells. Three months after FFA all retrogradely labeled motoneurons were scattered throughout the entire facial nucleus. To establish the proportion of perikarya, that re-grew multiple axonal branches into both nerves, double-labeled (FB + DiI) motoneurons were counted from digital images. The zygomatico-orbital nerve contained 3311 +/- 430 DiI-labeled whereas the buccal nerve 1500 +/- 442 FB-labeled motoneurons. The occurrence of 311 +/- 103 double-labeled perikarya (DiI+FB) suggested that approximately 6% of all retrogradely labeled motoneurons branched axons into both nerves. I conclude that malfunctioning axonal pathfinding rather than deviant reinnervation contributed to poor recovery of function after FFA in the cat.

Animals↗

PubMed1977

The organization of the facial nucleus of the brush-tailed possum (Trichosurus vulpecula).

The facial nucleus of the brush-tailed possum has been studied using Nissl staining and the horseradish peroxidase (HRP) retrograde tracing technique. In Nissl stained sections the nucleus is seen to comprise five distinct subnuclei. Injections of HRP into individual facial muscle groups have shown that these subnuclei reflect the peripheral innervation pattern of efferents from this nucleus. Although in most cases, injection of HRP into a single facial muscle group resulted in the labelling of neurons in more than one facial subnucleus, the following subnuclei were most completely labelled subsequent to intramuscular injection of HRP: the dorsal intermediate subnucleus was labelled with HRP reaction product following injection of m. auricularis anterior; the middle intermediate subnucleus was labelled following injection of the muscle underlying the malar vibrissae; the ventral intermediate subnucleus was labelled following injection of the m. mentalis; the medial subnucleus was labelled following injection of the m. auricularis posterior; the lateral subnucleus was labelled following injection of the m. nasolabialis with HRP. In general there is a mediolateral representation in the facial nucleus of neurons innervating facial muscle groups which are found in anteroposterior succession along the head of the animal. Muscle groups found in dorsoventral succession on the animal are represented dorsoventrally in the facial nucleus.

Animals↗

PubMedDate not supplied

Motor fibre organization in the intratemporal portion of cat and rat facial nerve studied with the horseradish peroxidase technique.

The intra-axonal transport of horseradish peroxidase (HRP) was used to label fibres in the intratemporal facial nerve portion (ITFN) in the rat and cat. HRP was applied to the proximal cut end of facial nerve branches innervating different facial muscles. Following appropriate survival periods, the animals were fixed by perfusion. The ITFN was processed histochemically for demonstration of intra-axonal HRP, using tetramethylbenzidine as substrate. The distribution of labelled fibres was analyzed in serial longitudinal sections and in photographic transverse-like reconstructions from three selected levels. HRP-labelled fibres from all examined motor branches were found to be diffusely distributed almost throughout the entire ITFN, leaving only a narrow zone free of label. By applying HRP to the chorda tympani nerve, it was shown that this zoe harbours fibres of this nerve. The findings support the conclusion that the motor fibres to the facial muscles are diffusely organized in the ITFN.

Animals↗

PubMed2005

Glial cell-line derived neurotrophic factor-dependent fusimotor neuron survival during development.

Glial cell-line derived neurotrophic factor (GDNF) is a potent survival factor for motor neurons. Previous studies have shown that some motor neurons depend upon GDNF during development but this GDNF-dependent motor neuron subpopulation has not been characterized. We examined GDNF expression patterns in muscle and the impact of altered GDNF expression on the development of subtypes of motor neurons. In GDNF hemizygous mice, motor neuron innervation to muscle spindle stretch receptors (fusimotor neuron innervation) was decreased, whereas in transgenic mice that overexpress GDNF in muscle, fusimotor innervation to muscle spindles was increased. Facial motor neurons, which do not contain fusimotor neurons, were not changed in number when GDNF was over expressed by facial muscles during their development. Taken together, these data indicate that fusimotor neurons depend upon GDNF for survival during development. Since the fraction of cervical and lumbar motor neurons lost in GDNF-deficient mice at birth closely approximates the size of the fusimotor neuron pool, these data suggest that motor neuron loss in GDNF-deficient mice may be primarily of fusimotor neuron origin.

Animals↗

PubMed1986

Electromyographic analysis of the ingestion and rejection of sapid stimuli in the rat.

Previous behavior studies (Grill & Norgren, 1978) demonstrated that gustatory stimuli produce stereotyped orofacial movements that constitute the observable concomitants of ingestion and rejection. For further clarification of the relation between these orofacial movements (the buccal phase of ingestion) and the act of swallowing (the pharyngeal phase), electromyographic responses to intraoral sapid stimulation were recorded from a subset of orofacial and pharyngeal muscles in a freely moving chronic preparation. Activity in a jaw opening muscle (anterior digastric), a facial muscle (zygomatic), tongue protruder (genioglossus), tongue retractor (styloglossus), and a pharyngeal constrictor used in swallowing (thyropharyngeus) differentiated between ingestive sequences to water (W), sucrose (S), and NaCl (N) and a rejection response elicited by quinine monohydrochloride (Q). Ingestion responses to W, S, and N consisted of rhythmic alterations between genioglossus and styloglossus activity (intraoral licks) accompanied by episodic bursts of pharyngeal constrictor activity (swallowing). Both bout duration and the number of swallows increased at higher concentrations of S and N. In contrast, Q stimulation elicited a rejection response, characterized by several licks and followed by long duration contractions of the zygomatic and anterior digastric muscles (gapes). During gapes, styloglossus activity rather than genioglossus activity was simultaneous with that of the anterior digastric. At higher concentrations of Q, the latency to gape decreased and the latency to swallow increased. The earliest components of the response to S, N, or Q were virtually indistinguishable from one another, results suggesting that tactile (fluid) stimulation initiates the ingestive sequence and that gustatory stimuli modulate this ongoing activity.

Animals↗

PubMed1999

Our experience with the use of the temporal muscle in facial surgery.

The authors present their experience with the use of the temporal muscle in reconstruction of defects after exenteration of the orbit, palate, filling of the spaces after extirpation of extensive tumours in the infratemporal area and area of the anterior cranial fossa. They operated a total of 25 patients where they used part of the temporal muscle or the whole muscle. None of the operated patients, although two had a ligature of the external carotid artery, developed necrosis or inflammatory complications during incorporation of the transferred muscle. The procedure can be considered a reliable method in the reconstruction of the face and cranial base.

Adolescent↗

PubMed1992

Management of facial synkinesis with Clostridium botulinum toxin injection.

Associated movements after facial paralysis (synkinesis), due to unphysiological co-innervation of the facial muscles, often complicates the rehabilitation of patients following facial palsy. Clostridium botulinum toxin is a neurotoxin that interferes with the release of acetylcholine from motor nerve end plates, causing skeletal muscular paralysis. This paper concentrates on its clinical use in treating synkinesis affecting orbicularis oculi function and documents the results of treatment in 4 patients. Control of synkinesis, achieved in all 4 patients, was effective within a few days and lasted for 4-6 months. 2 patients developed transient diplopia and ptosis shortly after injection. However, no lasting complications or systemic side-effects were noted. All patients reported a significant improvement in their symptoms and reinjection at 7 months was carried out successfully.

Botulinum Toxins↗

PubMed1978

Bell palsy: muscle reeducation by electromyograph feedback.

The present case study investigated the efficacy of feedback in restoring muscle control to facial muscles which had been affected by Bell palsy. The subject, a woman, was provided an analog tone as feedback for modifying the muscle activity on the paralyzed (right) side of her face to match that of her nonaffected (left) side. The results showed a statistically significant shift in muscle activity in masseter, zygomaticus, and orbicularis oculi muscles. Post-treatment levels closely approximated the nonaffected side, and resulted in more normal facial characteristics with respect to jaw position and symmetry of smiling. Bidirectional control of the zygomaticus was also demonstrated.

Adult↗

PubMed1983

Evoked responses in normal and diseased muscle with particular reference to twitch potentiation.

The compound muscle action potential and isometric twitch tension evoked by single and repetitive electrical stimuli are indicators of the number of motor units activated and of the contractile properties of the muscle. The action potentials and mechanical responses were recorded in proximal and distal muscles in patients with myasthenia gravis and myopathy and compared with findings in normal subjects. In normal muscle, at low rates of stimulation (2-3 s-1) the decrement was at most 5% in the action potential and 15-24% in the twitch tension. Tetanic stimuli (50 s-1) were unsuitable for diagnostic purposes because of movement artefact. In patients with myasthenia gravis, the incidence and size of the decrement of evoked responses were greater in the platysma than in the elbow flexors and the adductor pollicis (ADP) muscles. The 2-3 times greater post-tetanic facilitation (PTF) of the action potential in the platysma than in extremity muscles also indicates a more severe functional block in facial muscle. The PTF is an indicator of recruitment of blocked fibres. The maximal decrement was grossly related to the titre of antibodies against the acetylcholine receptor. To reveal failure of neuromuscular transmission in patients with myasthenia gravis without a decrement, a small dose of d-tubocurarine (0.2 mg in 30 ml of saline) was injected i.v. in the upper arm in a regional curare test. The sensitivity was greater in patients with myasthenia gravis than in controls and in patients with myopathy. Potentiation of twitch tension reflects contractile properties. In normal muscle twitch potentiation in the staircase (1-3 s-1, 100 s in duration) and after tetanus (50 s-1, 1.5 s in duration) was 2-3 times greater in the platysma than in the elbow flexors and ADP, presumably related to the greater proportion of fast-twitch fibers in facial muscle. The amplitude of the action potential and the twitch tension varied proportionally with the number of fibers activated and the difference in the decrements of the action potential and the twitch during the staircase in some patients with myasthenia gravis showed that the staircase phenomenon was diminished suggesting abnormalities in the excitation-contraction coupling. The diminution of the staircase and post-tetanic potentiation (PTP) in myopathy also indicates impairment of the excitation-contraction coupling. In rats with severe chronic myasthenia gravis, the staircase and PTP were decreased even when the failing neuromuscular transmission was circumvented by applying direct stimuli to the extensor digitorum longus muscle (EDL).

Action Potentials↗

PubMed1997

Facial neuromuscular retraining for oral synkinesis.

The purpose of this paper is to describe the outcome of facial neuromuscular retraining for brow to oral and ocular to oral synkinesis in individuals with facial nerve disorders. Fourteen patients with unilateral facial nerve disorders and oral synkinesis who were enrolled in physical therapy for retraining were studied. Synkinesis was measured with quantitative video facial position analysis prior to the initiation of physical therapy and at regular intervals during retraining. Retraining included surface electromyographic biofeedback-assisted specific strategies for facial muscle reeducation and a home exercise program of specific facial movements. Twelve of 13 patients with brow to oral synkinesis and 12 of 14 patients with ocular to oral synkinesis reduced their synkinesis with retraining. Patients with a 1-year on greater duration of a facial neuromuscular disorder (excluding patients with unusually marked changes) demonstrated a significant decrease in brow to oral synkinesis and in ocular to oral synkinesis; there was a mean percentage decline in abnormal movement of 60.5 percent (SD = 26.48) and 30.1 percent (SD = 62.57), respectively. We conclude that brow to oral and ocular to oral synkineses associated with partial recovery from facial paralysis were reduced with facial neuromuscular retraining for individuals with facial nerve disorders.

Adult↗