Control of esophageal motor function

The neurobiology of swallowing and dysphagia

The neurobiological study of swallowing and its dysfunction, defined as dysphagia, has evolved over two centuries beginning with electrical stimulation applied directly to the central nervous system, and then followed by systematic investigations that have used lesioning, transmagnetic stimulation, magnetoencephalography, and functional magnetic resonance imaging. The field has evolved from mapping the central neural pathway and peripheral nerves, to defining the importance of specific regions of the lower brain stem in terms of interneurons that provide sequential control for multiple muscles in the most complex reflex elicited by the nervous system, the pharyngeal phase of swallowing. The field is now emerging into defining how the higher cortical regions interact with this brain stem control and is providing a broader perspective of how the intact nervous system functions to control the three phases of swallowing (i.e., oral, pharyngeal, and esophageal). Much of the present interest focuses on how to retrain a damaged nervous system using a variety of stimulus techniques, which follow fundamentals in rehabilitation of the nervous system.

A comparative study of esophageal and anorectal motility in myotonic dystrophy

Myotonic dystrophy may be associated with visceral abnormalities involving smooth muscle, the pathogenesis of which is not clear. Our aim was to evaluate the involvement of smooth and striated muscles at both ends of the gastrointestinal tract. Esophageal and anorectal manometric studies were performed in 13 patients and healthy controls. There was a correlation between: (1) the resting pressure in the upper esophageal sphincter and in the lower anal canal, (2) the amplitude and the coordination of contraction primary waves in the proximal and in the distal esophagus, and (3) the resting pressure in the higher anal canal and in the lower one. These results suggest that both ends of the gastrointestinal tract are disturbed in a similar fashion, both quantitatively and qualitatively and that there is a relationship between smooth and striated visceral muscle involvement in myotonic dystrophy.

Autonomic nerve dysfunction in patients with bolus-specific esophageal dysmotility

The pathogenetic mechanisms causing esophageal dysmotility is not well understood. We examined 13 patients with solid bolus dysphagia in a radiologic barium study including the swallowing of a 14-mm tablet. In all 13 patients the tablet was caught in the proximal or midesophagus. In 8 patients, the entrapment was associated with symptoms (Group 1) whereas in 5 patients (Group 2), no symptoms were reported. All 13 patients together with a control group of 56 healthy, nondysphagic subjects were tested for autonomic nerve function. Autonomic nerve function tests included registration of electrocardiographic R-R interval variation during deep breathing test (E/I ratio), a test of parasympathetic, vagal, nerve function. The results showed that the E/I ratio was significantly lower in patients with symptoms of bolus-specific esophageal dysmotility (-2,19 [1.76]) (median [interquartile range]) compared with patients without symptoms (0.05 [2, 87], p = 0.0192) and controls (-0.25 [1.26], p = 0.0009). In conclusion, symptomatic bolus-specific esophageal dysmotility is associated with vagal nerve dysfunction.