Deglutition in Myasthenia Gravis

Autoimmune Neurogenic Dysphagia

Autoimmune neurogenic dysphagia refers to manifestation of dysphagia due to autoimmune diseases affecting muscle, neuromuscular junction, nerves, roots, brainstem, or cortex. Dysphagia is either part of the evolving clinical symptomatology of an underlying neurological autoimmunity or occurs as a sole manifestation, acutely or insidiously. This opinion article reviews the autoimmune neurological causes of dysphagia, highlights clinical clues and laboratory testing that facilitate early diagnosis, especially when dysphagia is the presenting symptom, and outlines the most effective immunotherapeutic approaches. Dysphagia is common in inflammatory myopathies, most prominently in inclusion body myositis, and is frequent in myasthenia gravis, occurring early in bulbar-onset disease or during the course of progressive, generalized disease. Acute-onset dysphagia is often seen in Guillain–Barre syndrome variants and slowly progressive dysphagia in paraneoplastic neuropathies highlighted by the presence of specific autoantibodies. The most common causes of CNS autoimmune dysphagia are demyelinating and inflammatory lesions in the brainstem, occurring in patients with multiple sclerosis and neuromyelitis optica spectrum disorders. Less common, but often overlooked, is dysphagia in stiff-person syndrome especially in conjunction with cerebellar ataxia and high anti-GAD autoantibodies, and in gastrointestinal dysmotility syndromes associated with autoantibodies against the ganglionic acetyl-choline receptor. In the setting of many neurological autoimmunities, acute-onset or progressive dysphagia is a potentially treatable condition, requiring increased awareness for prompt diagnosis and early immunotherapy initiation.

Reliability and main findings of the flexible endoscopic evaluation of swallowing-Tensilon test in patients with myasthenia gravis and dysphagia

BACKGROUND AND PURPOSE

Diagnosis of pharyngeal dysphagia caused by myasthenia gravis (MG) based on clinical examination alone is often challenging. Flexible endoscopic evaluation of swallowing (FEES) combined with Tensilon (edrophonium) application, referred to as the FEES-Tensilon test, was developed to improve diagnostic accuracy and to detect the main symptoms of pharyngeal dysphagia in MG. Here we investigated inter- and intra-rater reliability of the FEES-Tensilon test and analyzed the main endoscopic findings.

METHODS

Four experienced raters reviewed a total of 20 FEES-Tensilon test videos in randomized order. Residue severity was graded at four different pharyngeal spaces before and after Tensilon administration. All interpretations were performed twice per rater, 4 weeks apart (a total of 160 scorings). Intra-rater test-retest reliability and inter-rater reliability levels were calculated.

RESULTS

The most frequent FEES findings in patients with MG before Tensilon application were prominent residues of semi-solids spread all over the hypopharynx in varying locations. The reliability level of the interpretation of the FEES-Tensilon test was excellent regardless of the rater's profession or years of experience with FEES. All four raters showed high inter- and intra-reliability levels in interpreting the FEES-Tensilon test based on residue clearance (kappa = 0.922, 0.981). The degree of residue normalization in the vallecular space after Tensilon application showed the highest inter- and intra-rater reliability level (kappa = 0.863, 0.957) followed by the epiglottis (kappa = 0.813, 0.946) and pyriform sinuses (kappa = 0.836, 0.929).

CONCLUSION

Interpretation of the FEES-Tensilon test based on residue severity and degree of Tensilon clearance, especially in the vallecular space, is consistent and reliable.

Fiberoptic endoscopic evaluation of swallowing with simultaneous Tensilon application in diagnosis and therapy of myasthenia gravis

BACKGROUND

Dysphagia is a common symptom in myasthenia gravis (MG). Clinical examination alone fails to detect and grade myasthenic dysphagia sufficiently. For a more precise examination of swallowing function in myasthenia gravis additional technical tools are necessary.

OBJECTIVE

To investigate the diagnostic and therapeutic impact of fiberoptic endoscopic evaluation of swallowing with simultaneous Tensilon application (FEES-Tensilon Test) in myasthenia gravis.

METHODS

FEES-Tensilon Test was performed following a standardized protocol. Four severely affected patients with dysphagia as their leading symptom were examined. Dysphagia was characterized by five salient endoscopic findings: leakage, delayed swallowing reflex, penetration, aspiration and residues. If a normalisation or at least an improvement of swallowing function occurred shortly after Tensilon administration the FEES-Tensilon Test was rated as being positive.

RESULTS

In three patients the FEES-Tensilon Test successfully detected MG-related dysphagia. In one patient with dysphagia caused by oculopharyngeal muscular dystrophy the FEES-Tensilon Test was truly negative. Beside an early diagnosis of MG-related dysphagia, the FEES-Tensilon Test was useful in the differentiation between myasthenic and cholinergic crisis and in guiding treatment decisions. In all patients the FEES-Tensilon Test was superior to clinical evaluation of dysphagia. No severe side effect occurred while performing the FEES-Tensilon Test.

CONCLUSION

The FEES-Tensilon Test is a suitable tool in the diagnosis and therapy of myasthenia gravis with pharyngeal muscles weakness.

Videofluoroscopic assessment of swallowing function in patients with myasthenia gravis

Swallowing function in myasthenia gravis (MG) was investigated by videofluoroscopy (VF). A total of 23 VF examinations were performed on 11 MG patients at various time points over the exacerbation and remission stages of disease. The assessment parameters on VF examination are set as follows: bolus transport from the mouth to the pharynx, bolus holding in the oral cavity, velopharyngeal seal, tongue base movement, pharyngeal constriction, laryngeal elevation, upper esophageal sphincter (UES) opening, and bolus stasis at the pyriform sinus (PS). Aspiration was also assessed on VF examination. Aspiration was seen in 34.8%, and half of these cases involved silent aspiration. Three of four cases that showed silent aspiration went on to experience aspiration pneumonia during the follow-up term. By Spearman's rank correlation, disturbance of laryngeal elevation was significantly correlated with aspiration (p=0.001), and incomplete UES opening was not significantly, but tended to be, correlated with aspiration (p=0.067). Although other parameters in the oral and pharyngeal phase on VF examination, such as bolus transport from the oral cavity to the pharynx, pharyngeal constriction, or stasis at the PS, were remarkably disturbed (in more than 50% of the examinations), those parameters were not good indicators for aspiration. When a disturbance of laryngeal elevation is found at a bedside clinical test, we recommend performing precise swallowing evaluation, such as VF, Fiberoptic Endoscopic Evaluation of Swallowing (FEES), and/or scintigraphic assessment of swallowing, for MG patients, to detect silent aspiration.

Neurology and the gastrointestinal system

Both achalasia and Hirchsprung's disease arise from defects of innervation of the oesophagus and distal large bowel respectively. Their consequences are confined to disorders of motility in the relevant part of the gastrointestinal tract. Many neurogenic and primary muscle disorders are associated with abnormalities of gut motility. Stroke, even when unilateral, is commonly associated with dysphagia. Transcranial magnetoelectric stimulation has established that the pharyngeal phase of swallowing tends to receive its innervation principally from one hemisphere. In many neurological disorders, dysphagia is only one part of the clinical picture but in some--for example, the Chiari malformation--dysphagia may be the sole or major feature. Disturbances of small and large bowel motility, when seen in neurogenic disorders, are associated with autonomic neuropathy and are particularly common in diabetes mellitus. Primary muscle disorders can lead to dysphagia (for example, with polymyositis or oculopharyngeal dystrophy) or defects of large bowel motility (for example, with Duchenne's muscular dystrophy). Primary gut disorders particularly associated with neurological disease include pernicious anaemia, nicotinamide and thiamine deficiencies, selective vitamin E deficiency, and coeliac disease. Inflammatory bowel disease is associated with thromboembolic complications which may include the CNS, inflammatory muscle disease, and abnormalities on MRI of the brain of uncertain relevance. Whipple's disease is a rare condition which sometimes is largely or entirely confined to the CNS. In such cases, a particular neurological presentation can indicate the diagnosis.

Dysphagia in elderly men with myasthenia gravis

Eight elderly men whose primary symptoms of myasthenia gravis were decreased speech and swallowing ability were seen for speech pathology evaluations and videofluoroscopic swallow studies. All patients had fatigable flaccid dysarthria and greater than expected pharyngeal phase dysphagia on videofluoroscopy; eight had decreased pharyngeal motility as demonstrated by residual material in the valleculae and pyriform sinuses bilaterally; seven had episodes of laryngeal penetration secondary to overflow of residual material; and five experienced silent aspiration despite gag reflexes and the ability to cough to command. Five patients required feeding tubes because their dysphagia responded poorly to treatment. Videofluoroscopic swallow studies revealed a common swallowing profile with pharyngeal phase dysphagia greater than expected from patient symptoms. Dysphagia did not improve at the same rate as other manifestations of myasthenia gravis.

Neurogenic dysphagia: what is the cause when the cause is not obvious?

The potential causes of neurogenic oropharyngeal dysphagia in cases in which the underlying neurologic disorder is not readily apparent are discussed. The most common basis for unexplained neurogenic dysphagia may be cerebrovascular disease in the form of either confluent periventricular infarcts or small, discrete brainstem stroke, which may be invisible by magnetic resonance imaging. The diagnosis of occult stroke causing pharyngeal dysphagia should not be overlooked, because this diagnosis carries important treatment implications. Motor neuron disease producing bulbar palsy, pseudobulbar palsy, or a combination of the two can present as gradually progressive dysphagia and dysarthria with little if any limb involvement. Myopathies, especially polymyositis, and myasthenia gravis are potentially treatable disorders that must be considered. A variety of medications may cause or exacerbate neurogenic dysphagia. Psychiatric disorders can masquerade as swallowing apraxia. The basis for unexplained neurogenic dysphagia can best be elucidated by methodical evaluation including careful history, neurologic examination, videofluoroscopy of swallowing, blood studies (CBC, chemistry panel, creatine kinase, B12, thyroid screening, and anti-acetylcholine receptor antibodies), electromyography, and magnetic resonance imaging (MRI) of the brain, plus additional procedures such as lumbar puncture and muscle biopsy as indicated. Little is known about aging and neurogenic dysphagia, specifically the relative contributions of natural age-related changes in the oropharynx and of diseases of the elderly, including periventricular MRI abnormalities, in producing dysphagia symptoms and videofluoroscopic abnormalities in this population.