Feasibility of using neuromuscular stimulation to improve swallowing following chemo-radiation for head and neck cancer

I am a licensed Speech Pathologist in the third year of my doctoral program in Communication Sciences and Disorders at James Madison University. I applied for a summer internship position to further my research skills in one of the best laboratories in the country. This experience would not only inform me about post-doctoral fellowships and research careers, but also provide research training that would be immediately applicable in my dissertation. I was thrilled to be selected for this internship and to work with the Laryngeal and Speech Section (LSS) research group of NINDS, with Dr. Christy Ludlow as the Primary Investigator.

My summer project is "Feasibility of using neuromuscular stimulation to improve swallowing following chemo-radiation for head and neck cancer." This project is an analysis of the data of the initial three subjects of a current feasibility protocol. Dr. Ludlow's group is investigating the effects, of electrical (both surface and intramuscular) stimulation on the swallowing mechanism in those with neurological deficits (i.e., strokes, brain injury). This project was aimed at determining whether intramuscular stimulation can augment swallowing to increase airway protection in this population. However, it was unknown if this stimulation could affect swallowing muscles in those with chronic dysphagia (i.e., inability to swallow) resulting from chemo-radiation. Incidence of aspiration in those who have undergone chemo-radiation therapy for cancer of the head and neck is estimated between 68-81%, with many of those requiring feeding tube dependence for chronic dysphagia. The muscle fibrosis and neuropathy resulting from chemo-radiation are significant, but occur at a peripheral level. Since there is no central neurological damage, it was unknown whether electrical stimulation could produce laryngeal movement in this population. This knowledge and experience precipitated the feasibility study that I am currently working on.

Hooked wire electrodes are placed bilaterally in the mylohyoid, geniohyoid, and thyrohyoid of subjects who are then stimulated under videofluoroscopy. They are initially stimulated at rest with different muscle combinations in an effort to determine which stimulation grouping produces movement most functional for swallowing. Once that is determined, a baseline swallow is collected, and then that muscle group is stimulated during an actual swallow.

My primary role this summer has been to perform kinematic data analysis of the videofluoroscopic images to determine the physiologic changes that occur with stimulation. The digital videofluoroscopic image is captured on a recording device and converted to an AVI file. Using Peak Motus software, I have been marking specific anatomical points on each frame of these captured trials. I place a mark on C2 and C4 of the spine, the hyoid, and a subglottic point (reflecting laryngeal movement). The spine markings create a stable y-axis against which hyoid and laryngeal movement can be measured. I can then determine the coordinates for the points and individual structures. This allows me to measure change in direction and amplitude of the structures during stimulated trials compared with rest conditions. I have marked this data for three patients, with approximately 12 trials each, ranging from 400-1000 frames per trial. These points will then be analyzed to determine: (1) if stimulation produces movement, (2) the amount of movement resulting from stimulation, and (3) if this movement generates any functional improvement in the swallow. My poster presentation will solely focus on questions 1 and 2, but the marked data will later be analyzed to ascertain functional changes.

This experience has been invaluable for me. I have learned the importance of: interdisciplinary expertise, communication and shared skills across group members, being a good lab-mate, precision with data collection, and always keeping your research questions clearly in mind. I have also grown in my understanding of: consenting subjects, intramuscular stimulation, manometry, fiberoptic endoscopy, and the scientific process. Utilization of grand rounds lectures, the writing seminar, and journal clubs with associated labs has also been of immense benefit to me.

These few months quickly taught me many things about research that I had not yet been exposed to. These skills and understandings help set the foundation of my research career and I know that I am a better researcher as a direct result of my summer internship at NIH.