Electrophysiological study of diaphragmatic myoclonus

Unraveling belly dancer's dyskinesia and other puzzling diagnostic contortions: A narrative literature review

Belly dancer's dyskinesia (BDD) is characterized by involuntary abdominal wall movements that are rhythmic, repetitive, and dyskinetic. The present study aims to review BDD's etiology, pathophysiology, and management. We searched six databases to locate existing reports on BDD published from 1990 to October 2023 in electronic form. A total of 47 articles containing 59 cases were found. The majority of the patients affected by BDD were female, accounting for 61.01% (36/59) of the cases. The mean and median ages were 49.8 (standard deviation: 21.85) and 52 years (range: 7-85), respectively. The BDD was unilateral in only 3.38% (2/59). The most commonly reported causes associated with BDD were 17 idiopathic, 11 drug-induced, 11 postsurgical procedures, 5 pregnancies, and 4 Vitamin B12 deficiencies. BDD is a diagnosis of exclusion, and other more common pathologies with similar presentation should be ruled out initially. Differential diagnostic reasoning should include diaphragmatic myoclonus, cardiac conditions, truncal dystonia, abdominal motor seizures, propriospinal myoclonus, and functional or psychiatric disorders.

Hiccup-like Contractions in Mechanically Ventilated Patients: Individualized Treatment Guided by Transpulmonary Pressure

Hiccups-like contractions, including hiccups, respiratory myoclonus, and diaphragmatic tremor, refer to involuntary, spasmodic, and inspiratory muscle contractions. They have been repeatedly described in mechanically ventilated patients, especially those with central nervous damage. Nevertheless, their effects on patient-ventilator interaction are largely unknown, and even more overlooked is their contribution to lung and diaphragm injury. We describe, for the first time, how the management of hiccup-like contractions was individualized based on esophageal and transpulmonary pressure measurements in three mechanically ventilated patients. The necessity or not of intervention was determined by the effects of these contractions on arterial blood gases, patient-ventilator synchrony, and lung stress. In addition, esophageal pressure permitted the titration of ventilator settings in a patient with hypoxemia and atelectasis secondary to hiccups and in whom sedatives failed to eliminate the contractions and muscle relaxants were contraindicated. This report highlights the importance of esophageal pressure monitoring in the clinical decision making of hiccup-like contractions in mechanically ventilated patients.

Electrophysiological assessment of respiratory function

While the traditional lung function tests are used to assess lung capacity and pulmonary function, they cannot evaluate respiratory driving function and the integrity of the conduction pathway from the central nervous system to the respiratory motor neuron in the spinal cord and to the diaphragm. The inspiratory trigger is sent from the central nervous system through the phrenic nerve and drives the diaphragm to generate inspiratory movement. Therefore, phrenic nerve stimulation and diaphragmatic electromyography are two fundamental methods to assess respiratory function. There are several useful tools to assess respiratory motor system including electrical or magnetic phrenic nerve stimulation, diaphragmatic needle electromyography, and diaphragmatic ultrasound. By these means, physicians can assess current respiratory status in different neurological diseases that affect respiratory muscles, follow-up of the severity of respiratory impairment, help to predict the chance of successfully weaning from ventilatory support, and confirm clinical diagnoses such as diaphragmatic myoclonus. Although some of these tests require special training, applying these neurophysiological assessments in clinical practice is highly recommended.

Principles of Electrophysiological Assessments for Movement Disorders

Electrophysiological studies can provide objective and quantifiable assessments of movement disorders. They are useful in the diagnosis of hyperkinetic movement disorders, particularly tremors and myoclonus. The most commonly used measures are surface electromyography (sEMG), electroencephalography (EEG) and accelerometry. Frequency and coherence analyses of sEMG signals may reveal the nature of tremors and the source of the tremors. The effects of voluntary tapping, ballistic movements and weighting of the limbs can help to distinguish between organic and functional tremors. The presence of Bereitschafts-potentials and beta-band desynchronization recorded by EEG before movement onset provide strong evidence for functional movement disorders. EMG burst durations, distributions and muscle recruitment orders may identify and classify myoclonus to cortical, subcortical or spinal origins and help in the diagnosis of functional myoclonus. Organic and functional cervical dystonia can potentially be distinguished by EMG power spectral analysis. Several reflex circuits, such as the long latency reflex, blink reflex and startle reflex, can be elicited with different types of external stimuli and are useful in the assessment of myoclonus, excessive startle and stiff person syndrome. However, limitations of the tests should be recognized, and the results should be interpreted together with clinical observations.

Respiratory difficulty with palatal, laryngeal and respiratory muscle tremor in adult-onset Alexander's disease

Sleep apnoea and respiratory difficulties are reported in adult-onset Alexander's disease (AOAD), an autosomal-dominant leukodystrophy that presents mainly with progressive ataxia. We demonstrate for the first time that the respiratory symptoms can result from association of palatal tremor with a similar tremor of laryngeal and respiratory muscles that interrupts normal inspiration and expiration.A 60-year-old woman presented with progressive ataxia, palatal tremor and breathlessness. MRI revealed medullary atrophy, bilateral T2 hyperintensities in the dentate nuclei and hypertrophic olivary degeneration (HOD). AOAD was confirmed genetically with a positive glial fibrillary acidic protein (GFAP) mutation. Electrophysiological study revealed 1.5 Hz rhythmic laryngeal and respiratory muscle activity. Her respiratory symptoms were significantly improved at night with variable positive pressure ventilation.This case illustrates that palatal tremor in AOAD, and potentially in other conditions, may be associated with treatable breathlessness due to a similar tremor of respiratory muscles.

Ultrasound as Diagnostic Tool for Diaphragmatic Myoclonus

BACKGROUND

Diaphragmatic myoclonus is a rare disorder of repetitive diaphragmatic contractions, acknowledged to be a spectrum that includes psychogenic features. Electromyography has been the diagnostic tool most commonly used in the literature.

METHODS

To test if we could perform a noninvasive technique to delineate the diaphragm as the source of abnormal movements and demonstrate distractibility and entrainability, we used B-mode ultrasound in a patient with diaphragmatic myoclonus.

RESULTS

Ultrasound imaging clearly delineated the diaphragm as the source of her abdominal movements. We were able to demonstrate entrainability of the diaphragm to hand tapping to a prescribed rhythm set by examiner.

CONCLUSION

We recommend the use of ultrasound as a noninvasive, convenient diagnostic tool for further studies of diaphragmatic myoclonus. We agree with previous findings that diaphragmatic myoclonus may be a functional movement disorder, as evidenced by distractibility and entrainability demonstrated on real-time video with ultrasonography.

Synchronous Diaphragmatic Flutter Secondary to Primary Hypoparathyroidism in a Dog

A 3 yr old, spayed, female miniature mchnauzer was presented for rhythmic, spontaneous contractions of the abdominal wall and across the costal arches. The rate of contractions coincided with the heart rate and increased during exercise. The dog was diagnosed with primary hypoparathyroidism based on low plasma ionized calcium and serum parathyroid hormone (PTH) concentrations. Fluoroscopic exam confirmed the diagnosis of a synchronous diaphragmatic flutter. Treatment of the hypocalcemia led to resolution of the diaphragmatic flutter.

Unusual focal dyskinesias

This chapter reviews focal dyskinesias that affect a restricted region of the body in isolation. Focal dyskinesias often affect body parts not commonly involved in isolation by movement disorders and are not readily classified into one of the major categories of movement disorders or peripheral nerve excitability syndromes. The clinical features and phenomenology of these "unusual focal dyskinesias" are discussed according to the region affected (ear, lip, chin, jaw, tongue, abdomen, and diaphragm (belly dancer's dyskinesias), back, scapula, and limbs). The phenomenology and origin of the unusual focal dyskinesias remain the subject of debate. Most are characterized by slow semirhythmic jerky movements at variable (usually slow) frequencies superimposed on sustained postures, consistent with dystonic movements. However, the body parts affected and pattern of occurrence (in repose rather than during action) are different to those usually seen in primary dystonia. Many of the unusual focal dyskinesias are associated with trauma and pain to the affected region, prompting the suggestion that the movements follow central sensorimotor reorganization occurring spontaneously or secondary to changes in the peripheral nervous system. In other cases, inconsistent signs and spontaneous recovery suggest a psychogenic origin.

Leeuwenhoek's disease: diaphragmatic flutter in a cardiac patient

A 15-year-old girl gave a recent history of dyspnoea and "funny turns". She had congenital aortic stenosis, previous valvotomies, a mechanical valve replacement, permanent pacemaker, atrial tachyarrhythmias, impaired ventricular function, systemic hypotension, pulmonary hypertension, and anxiety. The diagnosis of diaphragmatic flutter was delayed due to all the differential diagnoses and rarity of the condition. It was confirmed by observation, respiratory band monitoring, volume-time spirogram and fluoroscopy during an attack.

Paroxysmal nonepileptic events of childhood

The paroxysmal nonepileptic events of childhood are a group of disorders, syndromes, and phenomena that mimic true epileptic seizures. Clinical experience and a clear description of the event in question will usually lead to a correct categorization. They span in age from neonate to young adult and are apt to be the most common diagnostic challenges clinicians face regularly. The key to diagnosis is a detailed history and careful observation. Despite the large number of discrete entities enumerated herein, common principles in clinical approach are successful and described. Each entity can pose a significant clinical challenge in identification, etiologic pathophysiology, genetics, and management. A simple division is offered here separating those episodes that are associated with an altered mental status or occurring during sleep and those without an altered mental status or occurring while awake.

Wilson's disease presenting with an unusual cough

A 26-year-old man developed an unusual repetitive, nonproductive cough. Extensive pulmonary and otolaryngology investigations failed to disclose a cause. It was only after he developed additional neurological manifestations ultimately leading to the diagnosis of Wilson's disease (WD) that a neurological basis for the cough was suspected. Features of the cough suggest it was a form of respiratory dyskinesia, a previously unreported presentation of WD.

Distal spinal and bulbar muscular atrophy caused by dynactin mutation

Impaired axonal transport has been postulated to play a role in the pathophysiology of multiple neurodegenerative disorders. In this report, we describe the results of clinical and neuropathological studies in a family with an inherited form of motor neuron disease caused by mutation in the p150Glued subunit of dynactin, a microtubule motor protein essential for retrograde axonal transport. Affected family members had a distinct clinical phenotype characterized by early bilateral vocal fold paralysis affecting the adductor and abductor laryngeal muscles. They later experienced weakness and atrophy in the face, hands, and distal legs. The extremity involvement was greater in the hands than in the legs, and it had a particular predilection for the thenar muscles. No clinical or electrophysiological sensory abnormality existed; however, skin biopsy results showed morphological abnormalities of epidermal nerve fibers. An autopsy study of one patient showed motor neuron degeneration and axonal loss in the ventral horn of the spinal cord and hypoglossal nucleus of the medulla. Immunohistochemistry showed abnormal inclusions of dynactin and dynein in motor neurons. This mutation of dynactin, a ubiquitously expressed protein, causes a unique pattern of motor neuron degeneration that is associated with the accumulation of dynein and dynactin in neuronal inclusions.

EMG-interference pattern analysis

The EMG interference pattern, built up of single motor unit action potentials, may be analyzed subjectively, or objectively by computer aided, quantitative methods, like counting of zero-crossings, counting of spikes, amplitude measurements, integration of the area under the curve, decomposition techniques, power spectrum analysis and turn/amplitude analysis. Since the shape of the interference pattern of healthy muscles is dependent on age, sex, force, muscle, temperature, fatigue, fitness level, recording site and surrounding tissue, electrode type, sensitivity, filters, sampling frequency and threshold level, all methods of analyzing the IP have to be standardized. Quantitative methods of analyzing the EMG interference pattern may be used for monitoring botulinum toxin therapy of dystonia and spasticity, quantifying spontaneous activity, assessment of chronic muscle pain, neuro-urological and proctological function, and diagnosing neuromuscular disorders. For diagnostic purposes, the methods favored are those that use needle electrodes and do not require measurement or monitoring of muscle force. The most well-evaluated methods are those using turn/amplitude analysis, like the cloud methods and the peak-ratio analysis. Peak-ratio analysis has the advantage that reference limits are easy to obtain and that its utility is well established and confirmed by several investigations. Overall, automatic methods of EMG interference pattern analysis are powerful tools for diagnostic and non-diagnostic purposes.

The utility of interference pattern analysis

The interference pattern of the electrical activity of muscle can be quantified by amplitude measurements, different spike counting methods, and power spectrum analyses. Interference pattern analysis (IPA) methods are used to describe the degree of activation of different muscles, muscle fatigue, occupational work, muscles in chronic pain syndromes, disused muscle, and dystonic muscle treated with botulinum toxin. In patients with neuromuscular disorders, the turns/amplitude analysis is useful for diagnosis. High diagnostic yields can be obtained without force measurements, for example, by using the amplitude as an indicator of force (the peak ratio method) or plotting the amplitude against the turns (cloud analysis). The diagnostic possibilities of the power spectrum analysis and the motor unit firing rate obtained by decomposition techniques are still unclear.

Bulbar myoclonus without palatal myoclonus. A hypothesis on pathophysiology

A 40-year-old woman with myoclonic contractions bilaterally in the infrahyoid neck muscles, especially in the left cricothyroid muscle, was presented and successfully treated with botulinum toxin injections. The patient had a wide, aberrant vessel curving into the left dorsolateral reticular formation of the medulla oblongata. Based on our observations, we propose that symptomatic bulbar and palatal myoclonus is caused by pathology in the dorsolateral reticular formation, and not by inferior olivary dysfunction as is currently thought.

Novel measurement for automated interference pattern analysis of the diaphragm

The automated interference pattern analysis for limb muscles was modified to take into account the unique features of the needle EMG of the diaphragm. The modification was successful in recording more accurately the number of small and large segments and the activity levels with inspiratory effort. "Clouds" were generated in ten healthy subjects. The techniques may prove useful in electrophysiological investigations.