Jaw Jerk Reflex

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Hercules C. Karkazis - One of the best experts on this subject based on the ideXlab platform.

  • Age and Ageing 1998; 27: 689-695 © 1998, British Geriatrics Society Jaw Reflexes in healthy old people
    2014
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis
    Abstract:

    Objective: to investigate variations in the masseteric myotatic Reflex (Jaw-Jerk) and the silent period from the 5th to the 9th decades of life. Subjects and methods: electromyographic data were recorded from the masseter muscle of the preferred chewing side by surface electrodes, using a computerized recording and analysis system. Chin taps were applied with a neurologist's hammer during mandibular rest and at 40 % intercuspal clenching in 30 healthy people aged from 49 to 87 years. The influence of age, gender and silent period type were analysed by multiple regression analysis (P< 0.05). Results: even in the very old subjects all Reflexes were elicited, at least once. However, with increasing age the overall occurrence of the Jaw-Jerk Reflex at rest (%) and its amplitude, at rest and at clench, were reduced, while its latency at rest was significantly increased (P s 0.05). No age effects were recorded in most parameters of the Jaw-Jerk Reflex at clench and in the silent period. Women showed a tendency for reduced latencies of the Jaw-Jerk and the early silent period and increased silent period duration (P — 0.05). They also had a steeper decline in myotatic Reflex activity, particularly at rest. Conclusion: simple masseteric Reflex activity is maintained until very old age, particularly when elicited during contraction of the Jaw elevators

  • Jaw Reflexes in healthy old people
    Age and ageing, 1998
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis
    Abstract:

    Objective: to investigate variations in the masseteric myotatic Reflex (Jaw-Jerk) and the silent period from the 5th to the 9th decades of life. Subjects and methods: electromyographic data were recorded from the masseter muscle of the preferred chewing side by surface electrodes, using a computerized recording and analysis system. Chin taps were applied with a neurologist's hammer during mandibular rest and at 40% intercuspal clenching in 30 healthy people aged from 49 to 87 years. The influence of age, gender and silent period type were analysed by multiple regression analysis (P< 0.05). Results: even in the very old subjects all Reflexes were elicited, at least once. However, with increasing age the overall occurrence of the Jaw-Jerk Reflex at rest (%) and its amplitude, at rest and at clench, were reduced, while its latency at rest was significantly increased (P s 0.05). No age effects were recorded in most parameters of the JawJerk Reflex at clench and in the silent period. Women showed a tendency for reduced latencies of the Jaw-Jerk and the early silent period and increased silent period duration (P — 0.05). They also had a steeper decline in myotatic Reflex activity, particularly at rest. Conclusion: simple masseteric Reflex activity is maintained until very old age, particularly when elicited during contraction of the Jaw elevators.

  • the masseteric Jaw Jerk Reflex in older dentate subjects and edentulous denture wearers
    Gerodontology, 1995
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis, P.-a. Molivdas
    Abstract:

    The aim of the present study was to investigate any variations in the Jaw-Jerk Reflex in edentulous subjects wearing complete dentures, compared to an age and sex-matched dentate group. The Reflex was elicited by chin taps in 22 older dentate subjects with mean age 61.3 years and in 22 denture wearers with mean age 63.1 years. Surface electromyographic recordings were obtained from the masseter muscle of the preferred chewing side during mandibular rest and at moderate clenching (40% of the individual maximum clenching masseteric EMG activity). A Jaw-Jerk Reflex was recorded in all subjects at least once, and its occurrence during clenching was reduced compared to rest. The occurrence of the Reflex was however increased in the denture wearers in both experimental conditions, while minor differences were observed in the values for latency, duration and amplitude between the two dental status groups. These results suggest that under the present experimental conditions the periodontal ligament receptors might inhibit Reflex activity. Multiple sensory interactions are expected in denture wearing. However a particular source of sensory feedback is provided by the stimulation of mucosal receptors from the acrylic denture base. Since the occurrence of the Jaw-Jerk at clench in the denture wearers was also reduced compared to the rest experiments, a potential inhibitory effect of the mucosal receptors can be speculated. According to the findings in the present study the loss of teeth and the rehabilitation with complete dentures do not severely disrupt the Reflex activity investigated.

  • The masseteric JawJerk Reflex in older dentate subjects and edentulous denture wearers
    Gerodontology, 1995
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis, P.-a. Molivdas
    Abstract:

    The aim of the present study was to investigate any variations in the Jaw-Jerk Reflex in edentulous subjects wearing complete dentures, compared to an age and sex-matched dentate group. The Reflex was elicited by chin taps in 22 older dentate subjects with mean age 61.3 years and in 22 denture wearers with mean age 63.1 years. Surface electromyographic recordings were obtained from the masseter muscle of the preferred chewing side during mandibular rest and at moderate clenching (40% of the individual maximum clenching masseteric EMG activity). A Jaw-Jerk Reflex was recorded in all subjects at least once, and its occurrence during clenching was reduced compared to rest. The occurrence of the Reflex was however increased in the denture wearers in both experimental conditions, while minor differences were observed in the values for latency, duration and amplitude between the two dental status groups. These results suggest that under the present experimental conditions the periodontal ligament receptors might inhibit Reflex activity. Multiple sensory interactions are expected in denture wearing. However a particular source of sensory feedback is provided by the stimulation of mucosal receptors from the acrylic denture base. Since the occurrence of the Jaw-Jerk at clench in the denture wearers was also reduced compared to the rest experiments, a potential inhibitory effect of the mucosal receptors can be speculated. According to the findings in the present study the loss of teeth and the rehabilitation with complete dentures do not severely disrupt the Reflex activity investigated.

  • The influence of gender on the masseter electromyographic Jaw-Jerk Reflex in young human subjects
    Journal of oral rehabilitation, 1994
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis
    Abstract:

    Summary 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 (6.14ms, 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 (6.86ms) and females (6.73ms). It was concluded that sex variation should be taken into consideration in the interpretation of the Jaw-Jerk Reflex.

Anastassia E. Kossioni - One of the best experts on this subject based on the ideXlab platform.

  • Age and Ageing 1998; 27: 689-695 © 1998, British Geriatrics Society Jaw Reflexes in healthy old people
    2014
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis
    Abstract:

    Objective: to investigate variations in the masseteric myotatic Reflex (Jaw-Jerk) and the silent period from the 5th to the 9th decades of life. Subjects and methods: electromyographic data were recorded from the masseter muscle of the preferred chewing side by surface electrodes, using a computerized recording and analysis system. Chin taps were applied with a neurologist's hammer during mandibular rest and at 40 % intercuspal clenching in 30 healthy people aged from 49 to 87 years. The influence of age, gender and silent period type were analysed by multiple regression analysis (P< 0.05). Results: even in the very old subjects all Reflexes were elicited, at least once. However, with increasing age the overall occurrence of the Jaw-Jerk Reflex at rest (%) and its amplitude, at rest and at clench, were reduced, while its latency at rest was significantly increased (P s 0.05). No age effects were recorded in most parameters of the Jaw-Jerk Reflex at clench and in the silent period. Women showed a tendency for reduced latencies of the Jaw-Jerk and the early silent period and increased silent period duration (P — 0.05). They also had a steeper decline in myotatic Reflex activity, particularly at rest. Conclusion: simple masseteric Reflex activity is maintained until very old age, particularly when elicited during contraction of the Jaw elevators

  • Jaw Reflexes in healthy old people
    Age and ageing, 1998
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis
    Abstract:

    Objective: to investigate variations in the masseteric myotatic Reflex (Jaw-Jerk) and the silent period from the 5th to the 9th decades of life. Subjects and methods: electromyographic data were recorded from the masseter muscle of the preferred chewing side by surface electrodes, using a computerized recording and analysis system. Chin taps were applied with a neurologist's hammer during mandibular rest and at 40% intercuspal clenching in 30 healthy people aged from 49 to 87 years. The influence of age, gender and silent period type were analysed by multiple regression analysis (P< 0.05). Results: even in the very old subjects all Reflexes were elicited, at least once. However, with increasing age the overall occurrence of the Jaw-Jerk Reflex at rest (%) and its amplitude, at rest and at clench, were reduced, while its latency at rest was significantly increased (P s 0.05). No age effects were recorded in most parameters of the JawJerk Reflex at clench and in the silent period. Women showed a tendency for reduced latencies of the Jaw-Jerk and the early silent period and increased silent period duration (P — 0.05). They also had a steeper decline in myotatic Reflex activity, particularly at rest. Conclusion: simple masseteric Reflex activity is maintained until very old age, particularly when elicited during contraction of the Jaw elevators.

  • the masseteric Jaw Jerk Reflex in older dentate subjects and edentulous denture wearers
    Gerodontology, 1995
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis, P.-a. Molivdas
    Abstract:

    The aim of the present study was to investigate any variations in the Jaw-Jerk Reflex in edentulous subjects wearing complete dentures, compared to an age and sex-matched dentate group. The Reflex was elicited by chin taps in 22 older dentate subjects with mean age 61.3 years and in 22 denture wearers with mean age 63.1 years. Surface electromyographic recordings were obtained from the masseter muscle of the preferred chewing side during mandibular rest and at moderate clenching (40% of the individual maximum clenching masseteric EMG activity). A Jaw-Jerk Reflex was recorded in all subjects at least once, and its occurrence during clenching was reduced compared to rest. The occurrence of the Reflex was however increased in the denture wearers in both experimental conditions, while minor differences were observed in the values for latency, duration and amplitude between the two dental status groups. These results suggest that under the present experimental conditions the periodontal ligament receptors might inhibit Reflex activity. Multiple sensory interactions are expected in denture wearing. However a particular source of sensory feedback is provided by the stimulation of mucosal receptors from the acrylic denture base. Since the occurrence of the Jaw-Jerk at clench in the denture wearers was also reduced compared to the rest experiments, a potential inhibitory effect of the mucosal receptors can be speculated. According to the findings in the present study the loss of teeth and the rehabilitation with complete dentures do not severely disrupt the Reflex activity investigated.

  • The masseteric JawJerk Reflex in older dentate subjects and edentulous denture wearers
    Gerodontology, 1995
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis, P.-a. Molivdas
    Abstract:

    The aim of the present study was to investigate any variations in the Jaw-Jerk Reflex in edentulous subjects wearing complete dentures, compared to an age and sex-matched dentate group. The Reflex was elicited by chin taps in 22 older dentate subjects with mean age 61.3 years and in 22 denture wearers with mean age 63.1 years. Surface electromyographic recordings were obtained from the masseter muscle of the preferred chewing side during mandibular rest and at moderate clenching (40% of the individual maximum clenching masseteric EMG activity). A Jaw-Jerk Reflex was recorded in all subjects at least once, and its occurrence during clenching was reduced compared to rest. The occurrence of the Reflex was however increased in the denture wearers in both experimental conditions, while minor differences were observed in the values for latency, duration and amplitude between the two dental status groups. These results suggest that under the present experimental conditions the periodontal ligament receptors might inhibit Reflex activity. Multiple sensory interactions are expected in denture wearing. However a particular source of sensory feedback is provided by the stimulation of mucosal receptors from the acrylic denture base. Since the occurrence of the Jaw-Jerk at clench in the denture wearers was also reduced compared to the rest experiments, a potential inhibitory effect of the mucosal receptors can be speculated. According to the findings in the present study the loss of teeth and the rehabilitation with complete dentures do not severely disrupt the Reflex activity investigated.

  • The influence of gender on the masseter electromyographic Jaw-Jerk Reflex in young human subjects
    Journal of oral rehabilitation, 1994
    Co-Authors: Anastassia E. Kossioni, Hercules C. Karkazis
    Abstract:

    Summary 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 (6.14ms, 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 (6.86ms) and females (6.73ms). It was concluded that sex variation should be taken into consideration in the interpretation of the Jaw-Jerk Reflex.

F. Bosman - One of the best experts on this subject based on the ideXlab platform.

  • Jaw-Jerk Reflex activity in relation to various clenching tasks in man
    Experimental Brain Research, 1993
    Co-Authors: F. Lobbezoo, R. Buchner, H. W. Glas, A. Bilt, F. Bosman
    Abstract:

    In order to investigate whether the mandibular stretch (Jaw-Jerk) Reflex is modulated in a task-dependent manner, Jaw-Jerk Reflexes were elicited in eight subjects during clenching with unilateral and bilateral tooth support, respectively. The Reflexes were examined in the electromyographic (EMG) activity recorded by means of surface electrodes and were elicited by means of small transient Jaw displacements at a constant value of 80 μm. Low levels of background EMG were applied ranging from 1 to 30% maximal voluntary contraction (MVC) as controlled by means of visual feedback. Linear relationships were observed between Reflex amplitude and level of background EMG. The slope in these relationships served as a measure of Reflex gain. For the masseter as well as the anterior temporal muscles, the Reflex gain, averaged over both sides, was larger during clenching with unilateral tooth support than with bilateral tooth support ( P < 0.05). Furthermore, the gain was larger on the side without tooth support during unilateral clenching and larger on the side without visual feedback of elevator muscle activity during bilateral clenching. It can be concluded that the Jaw-Jerk Reflex is modulated to subserve the stabilization of the mandible, with the Reflex sensitivity being larger the more that alternative stabilizing factors such as mechanical tooth contact, visual feedback and feedback from periodontal pressure receptors around the teeth are lacking. The Reflex modulation may be of functional importance in stabilizing the mandible during its movement in the chewing process, as the food is predominantly placed unilaterally between the antagonistic teeth during individual chewing cycles.

  • Gain and threshold of the Jaw-Jerk Reflex in man during isometric contraction
    Experimental Brain Research, 1993
    Co-Authors: F. Lobbezoo, R. Buchner, H. W. Glas, A. Bilt, F. Bosman
    Abstract:

    The control of mandibular posture has been related to the activity of the anterior temporal muscles, whereas the masseter muscles have been viewed mainly as force producers. However, these groups of muscles, especially in the deep layers, are highly endowed with muscle spindles, so that a difference in function should imply a difference in the Reflex sensitivity. By studying the Jaw-Jerk Reflex by means of bipolar surface electromyogram, the Reflex sensitivity was determined from relationships between Reflex amplitude and Jaw displacement from both groups of muscles in eight subjects. At a constant level of background muscle activity, and hence with a constant excitability of the alpha motoneurons, the Reflex sensitivity can be determined from these relationships in terms of gain and threshold. In order to account for differences in thickness of the soft tissues overlying the various muscles studied, the Reflex amplitude was normalized with respect to the level of maximal voluntary contraction (MVC). In experiments where the inter-electrode distance was 18 mm over both groups of muscles, the Reflex gain of the anterior temporal muscles was larger than that of the masseter muscles ( P < 0.05). The threshold value did not differ significantly from zero for either group of muscles. Normalization of the Reflex amplitude with respect to MVC can be carried out correctly only if the Reflexly activated muscle fibres are distributed uniformly within the muscle. In order to gain an insight into this distribution, control experiments were performed with three subjects in which the inter-electrode distance was varied, thus influencing the depth in the muscle from which active muscle fibres were recorded. The Reflex gain of the masseter muscle with an inter-electrode distance of 22 mm, which records from deeper layers of the muscle as well as superficial ones, was larger than with a distance of 11 mm ( P < 0.01–0.10 in the various subjects). No such differences were found for the anterior temporal muscle. It was concluded that the afferents of the spindles in the Jaw-elevator muscles do not project uniformly upon the motoneurons, but involve mainly fibres in the deeper layers of the muscle. The difference in gain found between the masseter and the anterior temporal muscles with the same inter-electrode distance of 18 mm is likely to be due to a larger distance of the Reflexly activated muscle fibres in the masseter muscle with respect to the electrodes rather than to a difference in Reflex sensitivity between the muscles. Hence, the masseter as well as the anterior temporal muscles could be involved in mandibular stabilization.

  • Electromyographic parameters related to clenching level and Jaw-Jerk Reflex in patients with a simple type of myogenous cranio-mandibular disorder.
    Journal of oral rehabilitation, 1992
    Co-Authors: R. Buchner, H.w. Van Der Glas, J.e.i.g. Brouwers, F. Bosman
    Abstract:

    A discriminant analysis has been applied on several electromyographic (EMG) parameters of the masseter and the anterior temporal muscles, related to clenching and the Jaw-Jerk Reflex, to characterize Jaw muscle function of patients with craniomandibular disorder (CMD) with respect to controls. The subject samples, matched for age, consisted of 20 females with myogenous CMD, and 20 symptom-free females. The Jaw-Jerk Reflex was elicited by a downward-directed mandibular load, transmitted by a bite-fork causing a similar occlusion and bite-rise as a splint. The patients differed mainly from the controls by smaller maximum EMG activity in both muscle groups (P less than 0.05 with the bite-fork inserted). This finding was related to a smaller muscle strength as the EMG level did not improve with pain-free Jaw muscles after therapy using a relaxation splint. Discriminating factors of secondary importance were an enhanced bilateral asymmetry in the muscle activity of the patients, and in the Reflex amplitude normalized for background EMG activity. In all subject samples, the activity of the anterior temporal muscles decreased with respect to the masseter muscles when the bite-fork was inserted (P less than 0.05-0.001). The therapeutic effect of a relaxation splint may, in part, be related to a relief of the temporal muscles.

R. Buchner - One of the best experts on this subject based on the ideXlab platform.

  • Sensitivity of the Jaw-Jerk Reflex in patients with myogenous temporomandibular disorder
    Archives of oral biology, 1996
    Co-Authors: Frank Lobbezoo, H.w. Van Der Glas, A. Van Der Bilt, R. Buchner, Frits Bosman
    Abstract:

    Changes in the activity of human Jaw-elevator muscles related to the mandibular stretch (Jaw-Jerk) Reflex could be involved in the aetiology of temporomandibular disorders (TMD). In order to investigate whether there are differences in the sensitivity of the Jaw-Jerk Reflex between myogenous TMD patients (n = 10) and gender- and age-matched controls (n = 10), Jaw-Jerk Reflexes were elicited under standardized conditions. By measuring the Reflex with bipolar surface electromyography (EMG), Reflex sensitivity was determined from relations between Reflex amplitude and Jaw displacement from the masseter and the anterior temporalis muscles. Reflex amplitude and background EMG activity were normalized with respect to the maximal voluntary contraction (MVC) to correct for differences in the thickness of soft tissues overlying the muscle or in electrode placement. In addition to normalization with respect to MVC, for the patients, normalization was also applied with respect to a MVC that was scaled by multiplying values by the ratio of the mean MVC of controls to the mean MVC of patients. At a constant level of background EMG activity, the Reflex sensitivity can be determined from the slope (Reflex gain) and x-intercept (Reflex threshold) of the Reflex amplitude-Jaw displacement relation. No significant differences between patients and controls were found for the gain or threshold values of either the masseter or the anterior temporalis muscles with a univariate analysis of variance. It is concluded that Jaw-Jerk Reflex sensitivity is not significantly changed in myogenous TMD patients. Therefore, the fusimotor system probably does not play a part in the perpetuating myogenous TMD.

  • Jaw-Jerk Reflex activity in relation to various clenching tasks in man
    Experimental Brain Research, 1993
    Co-Authors: F. Lobbezoo, R. Buchner, H. W. Glas, A. Bilt, F. Bosman
    Abstract:

    In order to investigate whether the mandibular stretch (Jaw-Jerk) Reflex is modulated in a task-dependent manner, Jaw-Jerk Reflexes were elicited in eight subjects during clenching with unilateral and bilateral tooth support, respectively. The Reflexes were examined in the electromyographic (EMG) activity recorded by means of surface electrodes and were elicited by means of small transient Jaw displacements at a constant value of 80 μm. Low levels of background EMG were applied ranging from 1 to 30% maximal voluntary contraction (MVC) as controlled by means of visual feedback. Linear relationships were observed between Reflex amplitude and level of background EMG. The slope in these relationships served as a measure of Reflex gain. For the masseter as well as the anterior temporal muscles, the Reflex gain, averaged over both sides, was larger during clenching with unilateral tooth support than with bilateral tooth support ( P < 0.05). Furthermore, the gain was larger on the side without tooth support during unilateral clenching and larger on the side without visual feedback of elevator muscle activity during bilateral clenching. It can be concluded that the Jaw-Jerk Reflex is modulated to subserve the stabilization of the mandible, with the Reflex sensitivity being larger the more that alternative stabilizing factors such as mechanical tooth contact, visual feedback and feedback from periodontal pressure receptors around the teeth are lacking. The Reflex modulation may be of functional importance in stabilizing the mandible during its movement in the chewing process, as the food is predominantly placed unilaterally between the antagonistic teeth during individual chewing cycles.

  • Gain and threshold of the Jaw-Jerk Reflex in man during isometric contraction
    Experimental Brain Research, 1993
    Co-Authors: F. Lobbezoo, R. Buchner, H. W. Glas, A. Bilt, F. Bosman
    Abstract:

    The control of mandibular posture has been related to the activity of the anterior temporal muscles, whereas the masseter muscles have been viewed mainly as force producers. However, these groups of muscles, especially in the deep layers, are highly endowed with muscle spindles, so that a difference in function should imply a difference in the Reflex sensitivity. By studying the Jaw-Jerk Reflex by means of bipolar surface electromyogram, the Reflex sensitivity was determined from relationships between Reflex amplitude and Jaw displacement from both groups of muscles in eight subjects. At a constant level of background muscle activity, and hence with a constant excitability of the alpha motoneurons, the Reflex sensitivity can be determined from these relationships in terms of gain and threshold. In order to account for differences in thickness of the soft tissues overlying the various muscles studied, the Reflex amplitude was normalized with respect to the level of maximal voluntary contraction (MVC). In experiments where the inter-electrode distance was 18 mm over both groups of muscles, the Reflex gain of the anterior temporal muscles was larger than that of the masseter muscles ( P < 0.05). The threshold value did not differ significantly from zero for either group of muscles. Normalization of the Reflex amplitude with respect to MVC can be carried out correctly only if the Reflexly activated muscle fibres are distributed uniformly within the muscle. In order to gain an insight into this distribution, control experiments were performed with three subjects in which the inter-electrode distance was varied, thus influencing the depth in the muscle from which active muscle fibres were recorded. The Reflex gain of the masseter muscle with an inter-electrode distance of 22 mm, which records from deeper layers of the muscle as well as superficial ones, was larger than with a distance of 11 mm ( P < 0.01–0.10 in the various subjects). No such differences were found for the anterior temporal muscle. It was concluded that the afferents of the spindles in the Jaw-elevator muscles do not project uniformly upon the motoneurons, but involve mainly fibres in the deeper layers of the muscle. The difference in gain found between the masseter and the anterior temporal muscles with the same inter-electrode distance of 18 mm is likely to be due to a larger distance of the Reflexly activated muscle fibres in the masseter muscle with respect to the electrodes rather than to a difference in Reflex sensitivity between the muscles. Hence, the masseter as well as the anterior temporal muscles could be involved in mandibular stabilization.

  • Bilateral asymmetries in the Jaw-Jerk Reflex activity in man
    Archives of oral biology, 1993
    Co-Authors: Frank Lobbezoo, H.w. Van Der Glas, A. Van Der Bilt, R. Buchner, Frits Bosman
    Abstract:

    Abstract In order to investigate whether there are bilateral differences in the sensitivity of the mandibular stretch (Jaw-Jerk) Reflex between patients with a myogenous craniomandibular dysfunction (CMD) and healthy controls free from signs and symptoms of CMD, Jaw-Jerk Reflexes were elicited under standardized conditions in two groups of 10 gender- and age-matched subjects. The Reflexes were recorded bilaterally from the masseter and the anterior temporal muscles by means of bipolar surface electromyogram (EMG). Reflex amplitudes at a mandibular displacement of exactly 80 μm and at a background muscle activity of exactly 12% maximum voluntary contraction were determined from relations between Reflex amplitude and Jaw displacement. These were obtained at a visually controlled, constant clenching level. For both groups, comparisons were made between Reflex amplitudes from the right- and the left-hand side. In CMD patients with predominantly unilateral Jaw muscle pain, comparisons were also made between the pain and non-pain sides. Although significant side asymmetries were found in many individuals, no significant differences were found among bilateral asymmetries in Reflex sensitivity between patients and controls. No influence of pain side on the asymmetries was found. It was concluded that neuromuscular factors do not cause significant bilateral differences in the sensitivity of the Jaw-Jerk Reflex between patients with myogenous CMD and controls. In a control experiment, in which eight healthy control subjects participated, the influence of a possible asymmetry in Jaw displacement on the Reflex sensitivity was evaluated. To achieve this, Reflexes were elicited not only by means of a bilaterally imposed mandibular load, but also by means of loading via a unilateral bite-fork, so that an equal, constant Jaw displacement could be imposed successively on both sides of the mandible. As no significant differences were found in bilateral asymmetries in Reflex sensitivity between unilateral and bilateral mandibular loading, the influence of a possible asymmetrical Jaw displacement on side asymmetries in the Jaw-Jerk Reflex sensitivity is negligible in our experimental model.

  • Electromyographic parameters related to clenching level and Jaw-Jerk Reflex in patients with a simple type of myogenous cranio-mandibular disorder.
    Journal of oral rehabilitation, 1992
    Co-Authors: R. Buchner, H.w. Van Der Glas, J.e.i.g. Brouwers, F. Bosman
    Abstract:

    A discriminant analysis has been applied on several electromyographic (EMG) parameters of the masseter and the anterior temporal muscles, related to clenching and the Jaw-Jerk Reflex, to characterize Jaw muscle function of patients with craniomandibular disorder (CMD) with respect to controls. The subject samples, matched for age, consisted of 20 females with myogenous CMD, and 20 symptom-free females. The Jaw-Jerk Reflex was elicited by a downward-directed mandibular load, transmitted by a bite-fork causing a similar occlusion and bite-rise as a splint. The patients differed mainly from the controls by smaller maximum EMG activity in both muscle groups (P less than 0.05 with the bite-fork inserted). This finding was related to a smaller muscle strength as the EMG level did not improve with pain-free Jaw muscles after therapy using a relaxation splint. Discriminating factors of secondary importance were an enhanced bilateral asymmetry in the muscle activity of the patients, and in the Reflex amplitude normalized for background EMG activity. In all subject samples, the activity of the anterior temporal muscles decreased with respect to the masseter muscles when the bite-fork was inserted (P less than 0.05-0.001). The therapeutic effect of a relaxation splint may, in part, be related to a relief of the temporal muscles.

Giacomo Chessa - One of the best experts on this subject based on the ideXlab platform.

  • A relationship between bruxism and orofacial-dystonia? A trigeminal electrophysiological approach in a case report of pineal cavernoma
    Behavioral and Brain Functions, 2013
    Co-Authors: Gianni Frisardi, Cesare Iani, Gianfranco Sau, Flavio Frisardi, Carlo Leornadis, Aurea Lumbau, Paolo Enrico, Donatella Sirca, Enrico Maria Staderini, Giacomo Chessa
    Abstract:

    Background In some clinical cases, bruxism may be correlated to central nervous system hyperexcitability, suggesting that bruxism may represent a subclinical form of dystonia. To examine this hypothesis, we performed an electrophysiological evaluation of the excitability of the trigeminal nervous system in a patient affected by pineal cavernoma with pain symptoms in the orofacial region and pronounced bruxism. Methods Electrophysiological studies included bilateral electrical transcranial stimulation of the trigeminal roots, analysis of the Jaw Jerk Reflex, recovery cycle of masseter inhibitory Reflex, and a magnetic resonance imaging study of the brain. Results The neuromuscular responses of the left- and right-side bilateral trigeminal motor potentials showed a high degree of symmetry in latency (1.92 ms and 1.96 ms, respectively) and amplitude (11 mV and 11.4 mV, respectively), whereas the Jaw Jerk Reflex amplitude of the right and left masseters was 5.1 mV and 8.9 mV, respectively. The test stimulus for the recovery cycle of masseter inhibitory Reflex evoked both silent periods at an interstimulus interval of 150 ms. The duration of the second silent period evoked by the test stimulus was 61 ms and 54 ms on the right and left masseters, respectively, which was greater than that evoked by the conditioning stimulus (39 ms and 35 ms, respectively). Conclusions We found evidence of activation and peripheral sensitization of the nociceptive fibers, the primary and secondary nociceptive neurons in the central nervous system, and the endogenous pain control systems (including both the inhibitory and facilitatory processes), in the tested subject. These data suggest that bruxism and central orofacial pain can coexist, but are two independent symptoms, which may explain why numerous experimental and clinical studies fail to reach unequivocal conclusions.

  • Trigeminal Electrophysiology: a 2 × 2 matrix model for differential diagnosis between temporomandibular disorders and orofacial pain
    BMC Musculoskeletal Disorders, 2010
    Co-Authors: Gianni Frisardi, Gianfranco Sau, Giacomo Chessa, Flavio Frisardi
    Abstract:

    Background Pain due to temporomandibular disorders (TMDs) often has the same clinical symptoms and signs as other types of orofacial pain (OP). The possible presence of serious neurological and/or systemic organic pathologies makes differential diagnosis difficult, especially in early disease stages. In the present study, we performed a qualitative and quantitative electrophysiological evaluation of the neuromuscular responses of the trigeminal nervous system. Using the Jaw Jerk Reflex (JJ) and the motor evoked potentials of the trigeminal roots (_bR-MEPs) tests, we investigated the functional and organic responses of healthy subjects (control group) and patients with TMD symptoms (TMD group). Method Thirty-three patients with temporomandibular disorder (TMD) symptoms and 36 control subjects underwent two electromyographic (EMG) tests: the Jaw Jerk Reflex test and the motor evoked potentials of the trigeminal roots test using bilateral electrical transcranial stimulation. The mean, standard deviation, median, minimum, and maximum values were computed for the EMG absolute values. The ratio between the EMG values obtained on each side was always computed with the reference side as the numerator. For the TMD group, this side was identified as the painful side (pain side), while for the control group this was taken as the non-preferred masticatory side (non-preferred side). The 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles were also calculated. Results Analysis of the ratios (expressed as percentages) between the values obtained on both sides revealed a high degree of symmetry in the _bR-MEPs ^% in the control (0.93 ± 0.12%) and TMD (0.91 ± 0.22%) groups. This symmetry indicated organic integrity of the trigeminal root motor fibers and correct electrode arrangement. A degree of asymmetry of the Jaw Jerk's amplitude between sides (_ipJJ%), when the mandible was kept in the intercuspal position, was found in the TMD group (0.24% ± 0.14%) with a statistically significant difference in relation to the control group (0.61% ± 0.2%). This asymmetry seemed to be primarily due to a failure to facilitate the Reflex on the painful side in intercuspal position. Conclusions In this 2 × 2 matrix diagnostic model, three different types of headache may be identified: 1) those due to organic pathologies directly and indirectly involving the trigeminal nervous system denoted as "Organic Damage"; 2) those in TMD patients; 3) other types of orofacial pain in subjects who could erroneously be considered healthy, denoted as Orofacial Pain "OP". This category of patient should be considered at risk, as organic neurological pathologies could be present and yet not directly affect the trigeminal system, at least in the early stages of the disease.