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Activity of temporal and masseter muscles in children with a lateral forced bite.

The activity of the temporal and masseter muscles with the mandible in postural position and during chewing, maximal bite in the intercuspal position, and swallowing were recorded electromyographically in nineteen children with laterally forced bite. Of the children, aged 8-12 years, sixteen had unilateral crossbite. In all of the individuals there was lateral deviation between the retruded contact position and the intercuspal position. The magnitude of the lateral deviation was measured with a modified gnathothesiometer. The muscle activity was recorded bilaterally from the temporal muscle and from the masseter muscle. In the postural position asymmetric activity was found in the temporal muscle suggesting that the mandible in postural position was still displaced to the side of forced bite. During chewing the activity was asymmetric both in the anterior and the posterior temporal portions. This asymmetric muscle activity was interpreted as an adaptation to avoid cuspal interferences. Also in maximal bite the muscle activity was asymmetric, while the activity during swallowing was affected less than in the other functions. The swallowing activity was, however, less in children with a forced bite than in children with normal occlusion.

Child↗

Bilateral cephalhematomas in a juvenile--case report.

A 14-year-old boy presented with subperiosteal cephalhematomas in bilateral parietotemporal sites after a minor head injury. Magnetic resonance (MR) imaging showed that one of the hematomas had progressed beyond suture lines, and spread under the temporal muscle layer. Progressive enlargement of the cephalhematomas occurred despite medical and needle aspiration treatment. Surgery found that the hematoma had separated the periosteum from the skull bone surface, and the periosteum had lost the tight attachment to the suture lines. Continuous suction-drainage reduced the size of the hematomas without complications. MR imaging can identify subperiosteal cephalhematomas. The relationship of the hematoma and the temporal muscle may be the key MR imaging finding for the diagnosis of cephalhematoma. We suggest that some juvenile cephalhematomas may be a different clinical entity from those occurring in neonates.

Adolescent↗

Enhancement pattern of normal extraocular muscles in dynamic contrast-enhanced MR imaging with fat suppression.

PURPOSE: To evaluate the internal structure of normal extraocular muscles on fat-suppressed dynamic contrast-enhanced MR imaging. MATERIAL AND METHODS: Ten subjects were examined using fat-suppressed dynamic contrast-enhanced MR imaging. We evaluated the enhancement pattern (C-shaped or ring-like) of extraocular muscles and quantified the maximum ratios of enhancement (Rmax) and maximum ratios of signal increase (Vmax). We also quantified Rmax and Vmax in the central and peripheral portions of medial rectus muscles. RESULTS: In the early phase of dynamic contrast-enhanced MR imaging, a C-shaped or ring-like pattern was observed in 100% of inferior rectus, 95% of medial rectus, 55% of superior rectus, 20% of lateral rectus, and 15% of superior oblique muscles. Overall mean Rmax and Vmax values showed statistically significant differences to the temporal muscles. For the peripheral portion of medial rectus muscles, mean Rmax and Vmax values were greater than for the central portion. CONCLUSION: Using fat-suppressed dynamic contrast-enhanced MR imaging, the C-shape or ring-like internal structure of the extraocular muscles could be visualized, and were considered to reflect their structure of orbital and global layers. Potential usefulness of the fat-suppressed dynamic contrast-enhanced MR imaging for detecting pathological status is suggested.

Adipose Tissue↗

Methodological requirements for accurate measurements of brain and body temperature during global forebrain ischemia of rat.

The methodological requirements for accurate measurements of brain and body temperature during brain ischemia have been validated in Wistar rats submitted to 30 min of four-vessel occlusion. During ischemia, brains were exposed to three different temperature profiles: spontaneous cooling from 36 to 31 degrees C (n = 10), constant hypothermia at 30 degrees C (n = 19), and constant normothermia at 36 degrees C (n = 21). Direct and indirect brain temperature recordings were carried out by placing fine thermocouples (200 microns diameter) into the striate nucleus, the temporal muscle, and the epidural space. Body temperature was measured with a flexible thermocouple inserted at various depths into the rectum. Accurate measurements of body temperature required insertion of the rectal probe to a depth of at least 6 cm; lesser insertion resulted in an underestimation of up to 6 degrees C. Accurate estimates of brain temperature were obtained in all three experimental conditions by recording of the epidural temperature. The temperature in the temporal muscle, by contrast, differed from the brain temperature by up to 2 degrees C, depending upon the experimental condition and the duration of ischemia. We therefore suggest that indirect measurements of brain temperature during ischemia are carried out in the epidural space in order to avoid misinterpretations of temperature-sensitive pathological changes.

Animals↗

Tegmen tympani cerebrospinal fluid leak repair.

OBJECTIVE: To describe the transmastoid approach for closing cerebrospinal fluid leaks in the tegmen tympani using autologous materials (temporal muscle fascia and abdominal fat) and heterologous materials (bovine collagen), together with its advantages and disadvantages. MATERIAL AND METHODS: We present the cases of three patients who underwent closure of spontaneous cerebrospinal fluid leaks in the tegmen tympani in which we used the transmastoid approach and autologous and heterologous materials. The three patients underwent canal wall-up mastoidectomy, posterior tympanotomy, removal of the malleus head and incus and, consequently, exposure of the tegmen tympani and the cerebrospinal fluid leak. Closure was performed using temporal muscle fascia, abdominal fat and bovine collagen, fixed in place with fibrin glue. A lumbar shunt was established, as is routine. RESULTS: The cerebrospinal fluid leak was closed in all patients using the technique described, with a minimum follow-up of 14 months. CONCLUSION: The technique presented herein is an excellent option in cases of cerebrospinal fluid leakage in the tegmen tympani; it is easy to perform and results in minimal risk to patients.

Adipose Tissue↗

[A clinical study on occlusal plane in relation with orofacial morphology and stomatognathic function].

Occlusal plane is one of the important and fundamental factors that establish the mandibular position and the form of dental arch and prosthesis. The aim of this study is to investigate the morphological and functional importance of occlusal plane in relation with orofacial morphology and stomatognathic function. Cephalograms were taken and electromyograms of masseter, anterior and posterior temporal muscles were recorded during clenching, tapping and chewing movements in 30 normal young adult subjects. Mandibular movements were simultaneously recorded using Sirognathograph (Siemens, West Germany). A correlation analysis was performed to study the relationship between the occlusal plane and morphological and functional parameters. As a result, the occlusal plane angle showed; 1) close correlations with the mandibular plane angle, Camper's plane angle and palatal plane angle, 2) correlations with the duration of activity of anterior temporal muscles and the sagittal angle of chewing pathway. The results suggest that there is a close relationship between the occlusal plane and orofacial morphology. Furthermore, the morphological parameters closely related to the occlusal plane were found to affect stomatognathic function. It is concluded that the occlusal plane is the important factor which harmonizes morphology and function of the stomatognathic system.

Cephalometry↗

The function of the disco-muscular apparatus in the human temporomandibular joint.

The morphology and function of the disco-muscular apparatus of the human TMJ is a controversial subject. Connections between the muscles which move the mandible and the "disco-capsular complex" have been described in a contradictory way. The disco-muscular apparatus is also described as being more extensive than that of the M. pterygoideus alone to include to the Mm. temporalis and masseter. However, the involvement of the latter is considered to be a peripheral variation of the normal anatomy and of little, if any, functional significance. The existence of independent relationships between the deep portions of the masseter and temporal muscles and the disco-capsular apparatus of the human TMJ is rarely discussed or explained. The morphologic findings were derived from fixed and unfixed human temporomandibular joints (TMJ) of varying ages and both sexes, whereby the functional maturity of the masticatory apparatus was taken into consideration. The results of the study show that aside from fibers originating from the superior venter of the M. pterygoideus lateralis, additional muscle or connective tissue fibers from the perimysium of the M. masseter are inserted to varying extents into the disc. The same is true for the M. temporalis, which is also directly connected to the disc via muscular or fibrous elements, or indirectly via fibers from the M. masseter. The insertion of the M. pterygoideus lateralis is always in the medial portion of the Discus articularis and those of the Mm. temporalis and masseter in the middle and lateral portions of the disc respectively. It is highly probable that a direct force transfer through the Mm. temporalis and masseter to the articular disc takes place, and that these muscles contribute to the movement of the disc during jaw movement, whereas the size and form of the muscle insertions are subject to a great deal of individual variation.

Adolescent↗

Innervation of the temporalis muscle for selective electrical denervation.

Bilateral hypertrophy of the temporal muscle can give the impression of an aggressive and violent facial appearance. The authors performed closed selective denervation of the deep temporal nerve using electrocauterization. Before the procedure, precise anatomical knowledge of the deep temporal nerve is mandatory. Sixteen hemifaces of Korean cadavers were dissected. To standardize the position of the anterior division of the deep temporal nerve, we recorded the distance from six anatomical landmarks to the nerve. In 19% (3 of 16) of cadavers, one deep temporal nerve was observed, and in the remainder, two deep temporal nerves were identified. In all our specimens, a mean of three (range: 1-4) temporal branches also arose from the buccal nerve. One temporal branch arising in common with the masseteric nerve was observed in 2 of 15 of our specimens. On the infratemporal crest, the distances from the anterior division of the deep temporal nerve to the posterior division of the deep temporal nerve and to the masseter nerve were 4.7 +/- 0.9 mm (range: 3-6 mm) and 8.3 +/- 1.1 mm (range: 6-10 mm), respectively. On the superior surface of the zygomatic arch, the distance from the most concave point of the zygomatic bone (point A) to the anterior division of the deep temporal nerve was 19.4 +/- 1.2 mm (range: 18-21 mm). On the inferior surface of the zygomatic arch, the distance from the prominent point of the condylar process of the mandible to the anterior division of the deep temporal nerve was 22.3 +/- 1.6 mm (range: 22-25 mm). Great consistency in the position of the anterior division of the deep temporal nerve was shown. The results of this study could provide a basis for closed selective denervation of the anterior division of the deep temporal nerve using electrocauterization. Clinical application is needed.

Adult↗

The mesencephalic locomotor region is activated during the auditory startle response of the unrestrained rat.

We describe an acoustically evoked potential in the midbrain of the rat which occurred in conjunction with the auditory startle response, 'startle correlated potential'. This potential had a variable latency to the onset of the startle-eliciting acoustic stimuli, but was precisely coupled to the startle response in the electromyogram (EMG) of the temporal muscle which was simultaneously recorded. We tried to localize the source of this potential by recording evoked potentials at different recording sites in individual awake and unrestrained rats using a specially constructed microdrive. The potential may be generated in part by neurons in the region of the pedunculopontine tegmental nucleus, lying within the electrophysiologically defined mesencephalic locomotor region (MLR). We suggest, therefore, that the startle correlated potential reflects the activation of the MLR during the startle response. Timing calculations make it unlikely that the startle correlated potential is generated by a sensorimotor relay within the primary startle circuit which produced a fast startle twitch in the temporal muscle. Instead, the startle correlated potential probably reflects the involvement of the MLR in a later secondary startle response or in response modulation, e.g. habituation. In our opinion the most interesting possibility is that the MLR could be activated during a startle response to inhibit and reset the current motor program.

Acoustic Stimulation↗

Comparative electromyographic study of elevator muscles in patients with complete dentures and natural dentition.

An analysis of integrated electromyographic (IEMG) activity of masseter and anterior temporal muscles was undertaken in fifteen patients with complete dentures and eight adult subjects with natural dentition. Bipolar surface electrodes were used for IEMG recordings during maximal voluntary clenching and saliva swallowing in the inter-cuspal position. The IEMG activity of both muscles during maximal voluntary clenching was significantly lower in patients with complete dentures than in subjects with natural dentition. During saliva swallowing the activity in both muscles was similar in both groups. This may have a great clinical significance in the maintenance of the functional state of the different structures of the stomatognathic system in complete denture wearers, since the process of swallowing is a 24-h function repeated about 600-2400 times each day.

Aged↗

Influence of intense light stimulation on trigeminal and cervical pain perception thresholds.

Thirty-three migraineurs and 23 healthy controls were submitted to pressure algometry before and after light-induced discomfort was elicited by progressive light stimulation in a monoblind fashion. Pressure algometries were performed on the emergence of the supraorbital, infraorbital, mental and greater occipital nerves, and over the temporal muscles, always throughout the same sequence and from right to left. Measurements were carried out before and immediately after light stimulation and after 10 min of the second algometry. The final result for each site measured at each time-point was the mean of the three measurements. Light stimulation was carried out progressively until light-induced discomfort was reported, to a maximum of 20,000 lux. A heat-blocking glass protected patients' eyes. Migraineurs presented significant and persistent drops in pain perception thresholds after light stimulation, at all sites tested (P = 0.002 to < 0.0001). These drops were not seen in controls, in whom, conversely, a less significant increase was seen on right infraorbital and left temporal muscle sites. Our results indicate that in migraineurs, light may have a relevant role in trigeminal and cervical pain perception thresholds.

Adult↗

Exteroceptive suppression periods in jaw-closing muscles. Variability and relation to experimental pain and sustained muscle contraction.

The duration of the late exteroceptive suppression period (ES2) of temporal muscle EMG activity has been reported to be reduced in patients suffering from chronic tension-type headache. Methods of recording and analysing ES2 have varied between centers and reproducibility of results within subjects, although insufficiently studied, has generally been poor. ES2 was investigated in 30 healthy subjects, using a computerized technique of recording, rectifying and averaging the EMG signals. Hour to hour and week to week variations of ES2 durations were calculated, and the influence of pain during a cold pressor test and of sustained muscle contraction on ES2 durations was investigated. The intra-individual variation of ES2 durations was 16.0% from hour to hour and 20.7% from week to week. The inter-individual variation was 36.7%. The present method for analysis of ES2 periods proved to be reliable, as the intra-observer variation was 4.2% and the inter-observer variation 4.6%. ES2 periods were significantly shorter on the first compared to the second day of examination (p = 0.006) and during experimental pain (p = 0.0005). We recommend the use of the computerized average technique in future studies and caution against the dependence of results upon factors such as conditioning and pain.

Adult↗

Correlation between autoregressive moving-average model parameters of electromyogram of human jaw closing muscles and maximum clenching time at intercuspal position.

During maximum clenching in the intercuspal position, surface electromyograms of left masseter and anterior temporal muscles were sampled in 16 healthy subjects with natural dentitions to establish a four-order, autoregressive (AR) moving-average (MA) model of the myoelectrical signals. The correlation coefficients and the linear regression between the model parameters and the clenching time were calculated. The model parameters had the positive or the negative correlation, and AR model parameters had the higher correlation than MA model parameters. The model parameters relate to muscular fatigue and the slope of the regressive equation relates to the endurance time of the isometric contraction.

Adult↗

Functional reconstruction after facial paralysis: a survey.

The attempt to achieve symmetrical harmonious facial expression represents a complex surgical challenge, necessitating an individualized approach. Clinical investigations and laboratory experiments have demonstrated how to better reconstruct a "smile." In long-standing deformities, ipsilateral or crossfacial nerve grafting followed by functional muscle transfer in a 2-stage procedure seems to give the most acceptable results; however, hypoglossal-facial anastomosis and dynamic muscle techniques such as temporal muscle transposition and others can result in adequate functional reconstruction. The development of these techniques with special emphasis on those made during the last 10 years is discussed and compared with our own experiences.

Facial Expression↗

TMJ symptoms and referred pain patterns.

The purpose of this study was to determine the relationship between TMJ symptoms, (muscle tenderness, joint noise, deviant jaw opening and closing patterns, and limited jaw opening), and a history of referred pain patterns (earaches, headaches, neck pain, and sinus problems). A questionnaire was completed by 100 subjects regarding histories of the previously mentioned problems. The researcher then examined the subject's TMJs, and their symptoms were recorded as being present or absent. The following relationships were found to be significant: Headaches and lateral pterygoid muscle tenderness, Earache and medial pterygoid muscle tenderness, Neck pain and one or more tender muscles, Sinus problems and one or more tender muscles, Sinus problems and temporal muscle tenderness, Sinus problems and medial pterygoid muscle tenderness. However, r values for the above relationships were between 0.22 and 0.3 indicating that the relationships were not strong. It appears that some normal patients already have patterns of masticatory muscle tenderness and associated referred pain patterns prior to seeking treatment for acute TMJ symptoms.

Adult↗

A clinical diagnosis of diurnal (non-sleep) bruxism in denture wearers.

The purpose of this study was to establish a clinical method for diagnosing diurnal bruxism in denture wearers by recording masseter and anterior temporal electromyograph (EMG) activity. Seven suspected bruxists and five normal patients who wore complete dentures and/or distal extension base removable partial dentures were selected for participation. EMG activity in both the masseter and the anterior temporal muscles was recorded bilaterally during silent reading (10 min), maximal voluntary clenching (MVC), tapping in centric occlusion, lateral movements, chewing and swallowing. No significant differences of EMG activity were found between the groups during tapping, lateral movement, chewing and swallowing (P> 0.05). However, during 10 min of silent reading, a significant difference was found between the groups when comparing masseter muscle activity (P < 0.05). A threshold of 10% of MVC of at least 3-s duration was used to define an individual bruxism event. When the muscle activity recorded during silent reading was further analysed using these criteria, the control group displayed no bruxing activity while the suspected bruxist group displayed a mean frequency of six bruxism events (range 2-10). It was concluded that: (a) masseter muscle activity recorded during 10 min of silent reading showed significant difference between the groups; (b) the criteria selected in this study for the detection of sleep bruxism can also be used to assess diurnal bruxism; and (c) it is possible to diagnose diurnal bruxism in denture wearers by measuring the masseter EMG activity during 10 min of silent reading.

Aged↗

Silent period and jaw jerk reflex in patients with osseointegrated oral implant bridges.

The silent period in the masseter and in the anterior portion of the temporal muscle during tooth tapping, the rate of tooth tapping and the jaw jerk reflex evoked by a tap on the chin were compared in individuals with oral implant bridges and with natural teeth. Thirteen women with osseointegrated oral implant bridges in one or both jaws, aged 42-59 years, were compared with 10 women, aged 42-64 years, with natural teeth. There was no difference between women, aged 42-64 years, with natural teeth. There was no difference between women with implant bridges and those with natural teeth in tooth tapping rate or in the occurrence, latency or duration of the jaw jerk reflex. A silent period during tooth tapping was found in 12 of the 13 women with implant bridges. The latency of the silent period was the same as in the subjects with natural teeth but the duration tended to be somewhat longer. The jaw jerk and the silent period were the same in individuals with implants in both jaws as in the whole implant group. It is therefore concluded that periodontal or mucous membrane receptors cannot be solely responsible for the silent period.

Adult↗