Neuromagnetic detection of the laryngeal area: Sensory-evoked fields to air-puff stimulation.

The sensory projections from the oral cavity, pharynx, and larynx are crucial in assuring safe deglutition, coughing, breathing, and voice production/speaking. Although several studies using neuroimaging techniques have demonstrated cortical activation related to pharyngeal and laryngeal functions, little is known regarding sensory projections from the laryngeal area to the somatosensory cortex. The purpose of this study was to establish the cortical activity evoked by somatic air-puff stimulation at the laryngeal mucosa using magnetoencephalography. Twelve healthy volunteers were trained to inhibit swallowing in response to air stimuli delivered to the larynx. Minimum norm estimates was performed on the laryngeal somatosensory evoked fields (LSEFs) to best differentiate the target activations from non-task-related activations. Evoked magnetic fields were recorded with acceptable reproducibility in the left hemisphere, with a peak latency of approximately 100ms in 10 subjects. Peak activation was estimated at the caudolateral region of the primary somatosensory area (S1). These results establish the ability to detect LSEFs with an acceptable reproducibility within a single subject and among subjects. These results also suggest the existence of laryngeal somatic afferent input to the caudolateral region of S1 in human. Our findings indicate that further investigation in this area is needed, and should focus on laryngeal lateralization, swallowing, and speech processing.

Videofluoroscopic assessment of pharyngeal stage delay reflects pathophysiology after brain infarction.

OBJECTIVES/HYPOTHESIS: The pathophysiology of dysphagia caused by brain infarction varies with the site of the lesion in the brain. Patients with suprabulbar lesions have demonstrated delayed triggering of pharyngeal stage including delayed laryngeal elevation. Patients with severe pharyngeal stage delay have a high risk of intractable aspiration to the lower respiratory tract. Despite this, few studies have compared the pharyngeal stage delay with the lesion site. We defined a new temporal parameter of the pharyngeal stage delay to assess laryngeal elevation delay against the bolus inflow into the pharyngeal space. This study aimed to elucidate whether this parameter of pharyngeal stage delay is clinically useful to assess the pathophysiology of brain lesions after brain infarction. STUDY DESIGN: Case-control study. METHODS: Videofluoroscopic assessment of swallowing examinations was performed from January 7, 2000 to March 29, 2011 at Kyushu University Hospital. We evaluated the pharyngeal stage delay using motion analysis on videofluoroscopic swallowing examination in patients with normal swallowing and brain infarction patients divided into pathophysiologic lesion groups. Laryngeal elevation delay time and pharyngeal delay time were analyzed. RESULTS: Significant differences in laryngeal elevation delay time were observed between each pathophysiologic lesion group. However, pharyngeal delay time remained similar among groups. Brain infarctions of corticobulbar tract and basal ganglion were significantly associated with laryngeal elevation delay time prolongation. CONCLUSIONS: Laryngeal elevation delay time with low-viscosity contrast medium is a recommended parameter to discriminate the corticobulbar tract and the basal ganglion lesion.