Electrodiagnostic methods for neurogenic dysphagia¹

Abstract

Objective: Swallowing mechanisms and neurogenic dysphagia have not been systematically studied by the EMG technique. It is desirable to evaluate neurogenic dysphagia for diagnostic and possibly for therapeutic purposes using electrophysiological methods.

Results: The following methods were described: mechanical upward/downward movements of the larynx were detected using a piezoelectric sensor, while submental integrated EMG activity was recorded during dry and wet swallowing. The EMG activity of cricopharyngeal muscle of the upper oesophageal sphincter was also recorded in some normal subjects and patients. Piecemeal deglutition and the dysphagia limit were determined in all patients to detect dysphagia objectively. In this study 75 normal subjects and 177 neurological patients with various degrees of dysphagia were investigated.

Results: Voluntarily triggered oropharyngeal swallowing was commonly pathological in the majority of patients, with or without overt dysphagia. The dysphagia limit appeared to be an objective measure of the degree of dysphagia in more than 90% of patients. Pathophysiological mechanisms were different in at least three groups of patients with neurogenic dysphagia. In the group of patients with muscular disorders, laryngeal elevators were involved while the CP-sphincterwas intact. The second group included patients with the clinical signs of corticobulbar fibre involvement such as amyotrophic lateral sclerosis and pseudobulbar palsy. In these patients, there was incoordination between paretic laryngeal elevators and hyperreflexic CP-sphincter. In the third group (patients with Parkinson's disease), the swallowing reflex was delayed and prolonged.

Conclusions: EMG methods described in the present study are very useful for the diagnosis of neurogenic dysphagia, objectively and quickly. They are important to understand the physiological mechanisms for deglutition and its disorders.

Introduction

Swallowing is usually subdivided into 3 phases; an initial oral phase, a pharyngeal phase and the oesophageal phase (Logemann, 1983; Dodds et al., 1990). The oral phase is mainly under voluntary control and highly variable in many respects. The pharyngeal phase encompasses several closely co-ordinated actions that involve bolus transport from the oropharynx into the oesophagus without aspiration. The late part of the oral phase of swallowing is usually intermingled with the pharyngeal phase, therefore it may be referred to as the oropharyngeal phase of swallowing (Logemann, 1983; Bass and Morrell, 1992). During oropharyngeal swallowing or `swallowing response' (Cook, 1991; Cook, 1993) the following related events occur successively. First, the swallowing reflex is triggered by the entrance of the bolus from the oral to the pharyngeal cavity. The swallowing response or swallowing reflex can therefore be initiated voluntarily (Lazzara et al., 1986; Dodds, 1989). Once triggered, the pharyngeal phase is almost always involuntary and automatic. There are two sequences for bolus transport into the oesophagus. The first is the propulsive force on the bolus provided by the tongue and sweeping effect by pharyngeal constrictor oblique muscle (Dodds et al., 1990; Kahrilas et al., 1993; Kahrilas and Logemann, 1993). The second is the relaxation and opening of the cricopharyngeal sphincter muscle of the upper oesophageal sphincter for the bolus transport into the oesophagus, where the third phase of swallowing starts (i.e. Donner et al., 1985; Dodds et al., 1990). Oesophageal phase is completely involuntary and autonomic. Modulation of oropharyngeal swallowing and its involuntary behaviour receives major contributions from neural activity in brain-stem, cerebral cortex, extrapyramidal and limbic cortical systems (Miller, 1982, Miller, 1993; Martin and Sessle, 1993). Therefore, any disorder involving various neural structures or lower cranial nerves or their oropharyngeal striated muscles can cause neurogenic dysphagia that may lead to misdirection of the bolus into nasal, oral or laryngeal cavities (Logemann, 1983; Logemann, 1991; Logemann, 1996; Morrell, 1992).

It is essential that neurogenic dysphagia be evaluated by some diagnostic methods, because various functions of the oropharyngeal swallowing system can have different disorders which should be treated according to the causes and pathophysiologic mechanisms involved (Logemann, 1996). Videofluroscopic/cinefluoroscopic methods and manometric evaluations may be necessary in some patients with dysphagia, but these methods are expensive and time consuming. Moreover, care of neurologically impaired patients during examination is sometimes difficult. Bedside examination and clinical evaluation of swallowing cannot be accurate and clinicians may fail to identify 40–60% of aspirating patients during bedside examinations (Linden and Siebens, 1983; Logemann, 1983; Splaingard et al., 1988). Simple screening tests have recently been developed for use before further radiological and manometric evaluation in patients with dysphagia. Most of these tests rely on clinical observation and subjective evaluation while the patient drinks a cup of water (Splaingard et al., 1988; De Pippo et al., 1992; Nathadwarawala et al., 1992; Nilsson et al., 1993; Hughes and Wiles, 1996).

Until now, swallowing and its disorders have not been systematically studied by electrophysiological methods. We have recently developed convenient and simple methods to evaluate patients with overt or silent dysphagia and to demonstrate their deglutition problems objectively (Ertekin et al., 1995; Ertekin et al., 1996; Ertekin et al., 1997; Ertekin, 1996; Pehlivan et al., 1996). In this paper of the qualitative results from 75 normal adult subjects will be given. The existence of different pathophysioloqical mechanisms of dysphagia will be discussed in 177 patients having overt or suspected dysphagia.