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Difference between revisions of "5° Clinical case: Spontaneous Electromyographic Activity"
5° Clinical case: Spontaneous Electromyographic Activity (view source)
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'''Abstract:'''This chapter delves into the complex and often debated topic of electromyography (EMG) in resting muscles, especially in patients with Orofacial Pain (OP) and Temporomandibular Disorders (TMDs). The central question revolves around whether a muscle at rest is truly silent or exhibits motor unit activity. Several studies, including those by Zieliński et al. and Fernández-de-Las-Peñas et al., have shown that changes in electromyographic patterns of masticatory muscles may be linked to myofascial trigger points (MTrPs) and TMDs. The presence of altered EMG activity in muscles at rest could be indicative of associated pain or dysfunction in masticatory and neck-shoulder muscles. | |||
The article explores the relationship between depression and resting masticatory muscle activity, as depression is known to affect the stomatognathic system. However, a key question remains: how relevant is EMG activity in resting muscles to a patient’s psychological state? This article presents the 5th clinical case study of a 65-year-old female patient suffering from Orofacial Pain and TMD, where traditional diagnostic approaches failed to uncover the true underlying condition. Through advanced EMG techniques, including surface and needle EMG, spontaneous motor unit activity was observed, revealing the presence of "involuntary EMG activity" that likely originated from a central pacemaker, rather than muscle fiber or motor neuron damage. | |||
An experimental pharmacological study using Propofol was conducted to decouple brainstem activity from cortical control. The study's results demonstrated that the patient’s EMG activity ceased upon Propofol administration, providing evidence of a central origin of the pacemaker activity, independent of brainstem functions. This led to a final diagnosis of Focal Oromandibular Dystonia rather than TMD. | |||
The | The article concludes by emphasizing the importance of considering neurological factors, such as involuntary EMG activity driven by a central pacemaker, in diagnosing and treating OP and TMD. It advocates for a more comprehensive neuro-electrophysiological approach, integrating techniques like bilateral trigeminal motor evoked potentials (bRoot-MEPs) to better understand the functional and organic aspects of TMDs. This case underscores the potential for misdiagnosis when relying solely on traditional gnathological and EMG methods without deeper neurophysiological exploration. | ||
===Introduction === | ===Introduction === | ||
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=====Propofol===== | =====Propofol===== | ||
The effects of anesthetics produce loss of consciousness, memory, changes in spontaneous activity, attenuation of protective reflexes, loss of postural reflexes and also adverse effects such as hallucinations, euphoria and amnesia. Furthermore they may affect the level or homeostasis of neurotransmitters in the brain such as dopamine, noraepinephrine and acetylcholine (ACh).<ref>Angel A. : Central neuronal pathways and the process of anaesthesia. British Journal of Anaesthesia 1993; 71:148-163</ref> Ach was the first neurotransmitter to be described and cholinergic neurons are widely distributed in the brain. Cholinergic mechanisms are known to be important in the striatum where a balance between dopamine and ACh release ensures normal motor output,<ref>Iversen SD.: Behavioural evaluation of cholinergic drug. Life Sciences 1997; 60: 1145-1152</ref> hippocampus and frontal cortex where ACh plays an important role in the regulation of consciousness, memory etc. | The effects of anesthetics produce loss of consciousness, memory, changes in spontaneous activity, attenuation of protective reflexes, loss of postural reflexes and also adverse effects such as hallucinations, euphoria and amnesia. Furthermore they may affect the level or homeostasis of neurotransmitters in the brain such as dopamine, noraepinephrine and acetylcholine (ACh).<ref>Angel A. : [https://www.bjanaesthesia.org/article/S0007-0912(17)45772-2/pdf Central neuronal pathways and the process of anaesthesia.] British Journal of Anaesthesia 1993; 71:148-163</ref> Ach was the first neurotransmitter to be described and cholinergic neurons are widely distributed in the brain. Cholinergic mechanisms are known to be important in the striatum where a balance between dopamine and ACh release ensures normal motor output,<ref>Iversen SD.: Behavioural evaluation of cholinergic drug. Life Sciences 1997; 60: 1145-1152</ref> hippocampus and frontal cortex where ACh plays an important role in the regulation of consciousness, memory etc. | ||
Propofol is thought to potentiate the inhibitory effect of GABAA receptors and to have a different action from barbiturates or benzodiazepines. An elegant study<ref>Kikuchi T, Wang Y, Sato K, Okumura F.: In vivo effects of propofol on aceylcholine release from the fronatl cortex, hippocampus and striatum studied by intracerebral microdialysis in freely moving rats</ref> carried out through intracerebral microdialysis in mice demonstrated that propofol, with doses of 50 mg/kg, decreased the release of ACh from the frontal cortex by 85%, by 72% by the hippocampus and by 19% by the striatum. | Propofol is thought to potentiate the inhibitory effect of GABAA receptors and to have a different action from barbiturates or benzodiazepines. An elegant study<ref>Kikuchi T, Wang Y, Sato K, Okumura F.: [https://www.bjanaesthesia.org/article/S0007-0912(17)40431-4/pdf In vivo effects of propofol on aceylcholine release from the fronatl cortex, hippocampus and striatum studied by intracerebral microdialysis in freely moving rats]Br J Anaesth. 1998 May;80(5):644-8. doi: 10.1093/bja/80.5.644.</ref> carried out through intracerebral microdialysis in mice demonstrated that propofol, with doses of 50 mg/kg, decreased the release of ACh from the frontal cortex by 85%, by 72% by the hippocampus and by 19% by the striatum. | ||
=====Blink reflex===== | =====Blink reflex===== | ||
The blink is a reflex that is evoked by hitting the eyebrow region on one side of the forehead. Electrophysiologically it is possible to evoke it by applying an electrical stimulus on the eyebrow arch in correspondence with the supraorbital foramen. The responses are recorded through two surface electrodes positioned on the orbicularis oculi muscle on each side and the motor potentials can be mainly represented by two events, namely the ipsilateral R1 response to stimulation and the bilateral R2. These responses represent a monosynaptic and polysynaptic circuitry for R1 and R2 respectively. The R1 response was considered to follow a trigeminal pathway in the pons while the R2 via a pathway adjacent the reticular formation reaches the facial nuclei.<ref>Ongerboer de Visser BW, Kuypers HG (1978): Late blink reflex changes in lateral medullary lesions. An electrophysiological and neuro-anatomical study of Wallenberg's syndrome. ''Brain'' '''101''': 285-294. </ref><ref>Ongerboer de Visser BW (1983b): Comparative study of corneal and blink reflex latencies in patients with segmental or with cerebral lesions. In: Desmedt JE , editor. ''Advances in neurology''. New York: Raven Press. p 757-772.</ref><ref>Ongerboer de Visser BW (1983b): Comparative study of corneal and blink reflex latencies in patients with segmental or with cerebral lesions. In: Desmedt JE , editor. ''Advances in neurology''. New York: Raven Press. p 757-772.</ref> | The blink is a reflex that is evoked by hitting the eyebrow region on one side of the forehead. Electrophysiologically it is possible to evoke it by applying an electrical stimulus on the eyebrow arch in correspondence with the supraorbital foramen. The responses are recorded through two surface electrodes positioned on the orbicularis oculi muscle on each side and the motor potentials can be mainly represented by two events, namely the ipsilateral R1 response to stimulation and the bilateral R2. These responses represent a monosynaptic and polysynaptic circuitry for R1 and R2 respectively. The R1 response was considered to follow a trigeminal pathway in the pons while the R2 via a pathway adjacent the reticular formation reaches the facial nuclei.<ref>Ongerboer de Visser BW, Kuypers HG (1978): Late blink reflex changes in lateral medullary lesions. An electrophysiological and neuro-anatomical study of Wallenberg's syndrome. ''Brain'' '''101''': 285-294. </ref><ref>Ongerboer de Visser BW (1983b): Comparative study of corneal and blink reflex latencies in patients with segmental or with cerebral lesions. In: Desmedt JE , editor. ''Advances in neurology''. New York: Raven Press. p 757-772.</ref><ref>Ongerboer de Visser BW (1983b): Comparative study of corneal and blink reflex latencies in patients with segmental or with cerebral lesions. In: Desmedt JE , editor. ''Advances in neurology''. New York: Raven Press. p 757-772.</ref> | ||
The main neural circuitry of the blink reflex is located in the brainstem but recent work, using functional magnetic resonance imaging (fMRI), has demonstrated that two main areas in the posterior lobe of the cerebellar hemisphere, mainly on the side ipsilateral to the stimulation, are activated during the blink reflexes in humans.<ref>Dimitrova A, Weber J, Maschke M, Elles HG, Kolb FP, Forsting M, Diener HC, Timmann D. Eyeblink-related areas in human cerebellum as shown by fMRI. Hum Brain Mapp. 2002 Oct;17(2):100-15.</ref> | The main neural circuitry of the blink reflex is located in the brainstem but recent work, using functional magnetic resonance imaging (fMRI), has demonstrated that two main areas in the posterior lobe of the cerebellar hemisphere, mainly on the side ipsilateral to the stimulation, are activated during the blink reflexes in humans.<ref>Dimitrova A, Weber J, Maschke M, Elles HG, Kolb FP, Forsting M, Diener HC, Timmann D. [https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/12353244/ Eyeblink-related areas in human cerebellum as shown by fMRI.] Hum Brain Mapp. 2002 Oct;17(2):100-15.</ref> | ||
====Experimental procedure==== | ====Experimental procedure==== | ||
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An adequate answer to this question was given by a study by Adour KK<ref>Adour KK. Acute temporomandibular joint pain-dysfunction syndrome: neuro-otologic and electromyographic study. Am J Otolaryngol. 1981 May;2(2):114-22. doi: 10.1016/s0196-0709(81)80028-2.PMID: 7270801</ref> through a prospective study using neuro-otological examination and electromyography. Seven consecutive patients with cardinal symptoms of temporomandibular joint pain syndrome (pain, tenderness, clicking, and limitation of jaw movement) were evaluated within one week of the onset of their acute symptoms. Three others with chronic symptoms were tested for comparison with acute cases. All seven patients with the acute condition had asymptomatic hypoesthesia of all three divisions of the trigeminal nerve and decreased action potential of the volitional muscles in the masseter and temporal muscles. At the end of three weeks the hypesthesia resolved in all seven patients and the muscle action potential returned to normal in six of the seven. EMG testing of the single patient with persistent reduced muscle action potentials and three patients with chronic symptoms showed fibrillation, reduced polyphasic regeneration potentials, and spontaneous fasciculations with clinical atrophy and spasm of the affected masseter and temporal muscles. Other acute cranial nerve findings included unilateral glossopharyngeal and second cervical nerve hypoesthesia, motor paralysis of the superior laryngeal branch of the vagus nerve, and increased facial nerve latency. These findings suggest a neuromuscular, rather than a psychophysiological, organic cause of temporomandibular joint pain syndrome. | An adequate answer to this question was given by a study by Adour KK<ref>Adour KK. Acute temporomandibular joint pain-dysfunction syndrome: neuro-otologic and electromyographic study. Am J Otolaryngol. 1981 May;2(2):114-22. doi: 10.1016/s0196-0709(81)80028-2.PMID: 7270801</ref> through a prospective study using neuro-otological examination and electromyography. Seven consecutive patients with cardinal symptoms of temporomandibular joint pain syndrome (pain, tenderness, clicking, and limitation of jaw movement) were evaluated within one week of the onset of their acute symptoms. Three others with chronic symptoms were tested for comparison with acute cases. All seven patients with the acute condition had asymptomatic hypoesthesia of all three divisions of the trigeminal nerve and decreased action potential of the volitional muscles in the masseter and temporal muscles. At the end of three weeks the hypesthesia resolved in all seven patients and the muscle action potential returned to normal in six of the seven. EMG testing of the single patient with persistent reduced muscle action potentials and three patients with chronic symptoms showed fibrillation, reduced polyphasic regeneration potentials, and spontaneous fasciculations with clinical atrophy and spasm of the affected masseter and temporal muscles. Other acute cranial nerve findings included unilateral glossopharyngeal and second cervical nerve hypoesthesia, motor paralysis of the superior laryngeal branch of the vagus nerve, and increased facial nerve latency. These findings suggest a neuromuscular, rather than a psychophysiological, organic cause of temporomandibular joint pain syndrome. | ||
Contrary to this assertion that sees an organic neuromotor disturbance at the basis of a clinical situation of TMDs, there is the opinion that the influence of the unilateral posterior crossbite on the variations of spontaneous muscle activity in the mandibular rest position and in maximum voluntary contraction is significant and confirmed by Woźniak K et al.<ref name=":0">Woźniak K, Szyszka-Sommerfeld L, Lichota D. The electrical activity of the temporal and masseter muscles in patients with TMD and unilateral posterior crossbite. Biomed Res Int. 2015;2015:259372. doi: 10.1155/2015/259372. Epub 2015 Mar 26.PMID: 25883948 </ref> | Contrary to this assertion that sees an organic neuromotor disturbance at the basis of a clinical situation of TMDs, there is the opinion that the influence of the unilateral posterior crossbite on the variations of spontaneous muscle activity in the mandibular rest position and in maximum voluntary contraction is significant and confirmed by Woźniak K et al.<ref name=":0">Woźniak K, Szyszka-Sommerfeld L, Lichota D. [https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/25883948/ The electrical activity of the temporal and masseter muscles in patients with TMD and unilateral posterior crossbite]. Biomed Res Int. 2015;2015:259372. doi: 10.1155/2015/259372. Epub 2015 Mar 26.PMID: 25883948 </ref> | ||
Having already clarified, albeit not in depth, the terminological, clinical and scientific difficulty in understanding phenomena that represent an alteration of the trigeminal Central Nervous System in EMG activity at rest, we can only suggest more attention in planning experiments of this type. For example Woźniak K et al.<ref name=":0" /> reaches these conclusions by analyzing the asymmetry between sides of the EMG activity at rest and at maximum will to contract (MVC) and the algorithm used is the following:<math>As=\frac{\textstyle \sum_{i=1}^N |R_i-L_i|\displaystyle}{\textstyle \sum_{i=1}^N |R_i+L_i|\displaystyle} | Having already clarified, albeit not in depth, the terminological, clinical and scientific difficulty in understanding phenomena that represent an alteration of the trigeminal Central Nervous System in EMG activity at rest, we can only suggest more attention in planning experiments of this type. For example Woźniak K et al.<ref name=":0" /> reaches these conclusions by analyzing the asymmetry between sides of the EMG activity at rest and at maximum will to contract (MVC) and the algorithm used is the following:<math>As=\frac{\textstyle \sum_{i=1}^N |R_i-L_i|\displaystyle}{\textstyle \sum_{i=1}^N |R_i+L_i|\displaystyle} | ||