fMRI of Swallowing in Pediatric Subjects

It is widely accepted with regard to cognitive functions such as vision and speech that children have certain "critical periods of learning" where these functions are cortically integrated. This project aims to use functional magnetic resonance imaging (fMRI) to test the hypothesis that a critical period exists for the development of the neurological infrastructure of the swallowing mechanism, and that if the act of swallowing and feeding is altered or restricted during this period, subsequent "cortical" dysphagia (difficulty swallowing) will ensue.

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Dysphagia comprises a broad spectrum of pathologies that can involve the nervous system or the aerodigestive tract. A child who has a structural cause for dysphagia, such as a tracheoesophageal fistula producing aspiration, often develops subsequent dysphagia when he is deprived of oral alimentation for a period of time prior to surgical repair.

We are using fMRI of children during swallowing to visualize differences in the cortical representation of swallowing in normal children and patients with pathologic changes in the swallowing mechanism. Normal children and a precisely defined cohort of children with abnormal swallowing mechanisms producing dysphagia will be imaged, and cortical activation patterns in the two groups will be compared.

Another goal of this project is to define the age range and duration of the critical period for learning normal swallowing reflexes in children who have been deprived of the ability to feed orally for varying periods of time. FMRI of swallowing will be performed on these children both prior to surgery and post-operatively at periodic intervals over a three to five year period.

Specialized fMRI methods, which are immune to the inevitable head motions associated with swallowing, are being developed for this project. Voice prompts of "swallow" and "rest" are alternately played over the MRI gradient system at 9 second intervals. Four seconds after each prompt, a dataset is acquired in a period of 3 seconds. The delay is chosen in order to maximize the contrast between resting and active datasets, since the peak hemodynamic response occurs at approximately 5-6 seconds after the onset of activation. Using the MRI gradient system in order to produce the prompts, rather than an external sound system, allows precise synchronization of the imaging sequence with the voice prompts.