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Effects of age and radiation treatment on function of extrinsic tongue muscles.

Russell JA, Connor NP - Radiat Oncol (2014)

Bottom Line: Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction.Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction, and the reduction in the speed of tongue muscle contraction was exacerbated in the aged-rat tongue.This work provides a foundation for future investigations of treatments for concurrent effects of aging and radiation on muscles of the tongue and swallowing.

View Article: PubMed Central - PubMed

Affiliation: University of Wisconsin School of Medicine and Public Health, Otolaryngology Head and Neck Surgery, Madison, WI, 53706, USA. russell@surgery.wisc.edu.

ABSTRACT

Background: Radiation treatment for head and neck cancer often results in difficulty swallowing. Muscle weakness and fibrosis have been identified clinically as possible etiologies for swallowing problems following radiation. Aging may compound the effects of radiation on swallowing because radiation-induced damage to muscles and other tissues critical for the oropharyngeal swallow is overlaid on a declining sensorimotor system. However, there have been no investigations of the manner in which aging and radiation treatment effects combine to impact tongue muscles, which are critical effectors of the oropharyngeal swallow.

Methods: Thirty-seven male Fisher 344/Brown Norway rats were divided into four groups; young adults (9 month old), old (32 months old), young radiation (9 months), and old radiation (32 months old). Two fractions of 11 Gy on consecutive days was delivered by external beam radiation to the ventral side of the rat's body over the anterior portion (20 X 30 mm area) of the anterior digastric muscle. Two-way analysis of variance (ANOVA) was used to examine the effects of age and radiation and their interaction on muscle contractile properties. Post-hoc testing was completed using Fisher's least significant differences (LSD).

Results: Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction. However, radiation treatment did not lead to muscle atrophy and fibrosis formation in the GG muscle. Radiation treatment did not exacerbate atrophic changes observed with aging, or lead to additional fibrosis formation in the GG muscle from that observed in the other groups.

Conclusions: The purpose of this research was to determine the effect of radiation on muscles of the tongue and to determine whether aging altered the extent of radiation injury to tongue muscles. Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction, and the reduction in the speed of tongue muscle contraction was exacerbated in the aged-rat tongue. This work provides a foundation for future investigations of treatments for concurrent effects of aging and radiation on muscles of the tongue and swallowing.

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Related in: MedlinePlus

Maximum tetanic force. Box and whisker plot showing that (A) radiation treatment was associated with significantly (p<.001) reduced maximum tetanic tongue force during whole nerve stimulation in both age groups, and (B) that age and radiation did not have a significant effect on maximum tetanic force during medial nerve stimulation. Boxes depict the interquartile range (IQR), with a line at the median. Whiskers extend to the last observation within 1.5x the IQR. The closed circles are observations beyond 1.5x the IQR. Y = Young Adult Control; YR = Young Adult Radiated; O = Old Control, OR = Old Radiated.
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Fig4: Maximum tetanic force. Box and whisker plot showing that (A) radiation treatment was associated with significantly (p<.001) reduced maximum tetanic tongue force during whole nerve stimulation in both age groups, and (B) that age and radiation did not have a significant effect on maximum tetanic force during medial nerve stimulation. Boxes depict the interquartile range (IQR), with a line at the median. Whiskers extend to the last observation within 1.5x the IQR. The closed circles are observations beyond 1.5x the IQR. Y = Young Adult Control; YR = Young Adult Radiated; O = Old Control, OR = Old Radiated.

Mentions: Stimulation of the whole hypoglossal nerves bilaterally elicited a retrusive tongue action. Representative retrusive tetanic waveforms for young and old rats in the control and radiation condition are shown in Figure 3. Weight had a significant effect on maximum retrusive tetanic force and, therefore, the results of ANCOVA using a weight covariate are reported. There was not a significant interaction between age and radiation treatment. However, as shown in Figure 4A, there was a significant main effect for age on maximum retrusive tetanic force (F[1,32] = 7.43, p < .01). Based on the weight-adjusted means, the old adult group produced significantly less maximum retrusive tetanic force than the young adult control (p < .001). In addition, there was a significant main effect for radiation treatment with significantly reduced tetanic tension in the radiation treatment group (F[1,32] = 18.62, p < .001).Figure 3


Effects of age and radiation treatment on function of extrinsic tongue muscles.

Russell JA, Connor NP - Radiat Oncol (2014)

Maximum tetanic force. Box and whisker plot showing that (A) radiation treatment was associated with significantly (p<.001) reduced maximum tetanic tongue force during whole nerve stimulation in both age groups, and (B) that age and radiation did not have a significant effect on maximum tetanic force during medial nerve stimulation. Boxes depict the interquartile range (IQR), with a line at the median. Whiskers extend to the last observation within 1.5x the IQR. The closed circles are observations beyond 1.5x the IQR. Y = Young Adult Control; YR = Young Adult Radiated; O = Old Control, OR = Old Radiated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4269095&req=5

Fig4: Maximum tetanic force. Box and whisker plot showing that (A) radiation treatment was associated with significantly (p<.001) reduced maximum tetanic tongue force during whole nerve stimulation in both age groups, and (B) that age and radiation did not have a significant effect on maximum tetanic force during medial nerve stimulation. Boxes depict the interquartile range (IQR), with a line at the median. Whiskers extend to the last observation within 1.5x the IQR. The closed circles are observations beyond 1.5x the IQR. Y = Young Adult Control; YR = Young Adult Radiated; O = Old Control, OR = Old Radiated.
Mentions: Stimulation of the whole hypoglossal nerves bilaterally elicited a retrusive tongue action. Representative retrusive tetanic waveforms for young and old rats in the control and radiation condition are shown in Figure 3. Weight had a significant effect on maximum retrusive tetanic force and, therefore, the results of ANCOVA using a weight covariate are reported. There was not a significant interaction between age and radiation treatment. However, as shown in Figure 4A, there was a significant main effect for age on maximum retrusive tetanic force (F[1,32] = 7.43, p < .01). Based on the weight-adjusted means, the old adult group produced significantly less maximum retrusive tetanic force than the young adult control (p < .001). In addition, there was a significant main effect for radiation treatment with significantly reduced tetanic tension in the radiation treatment group (F[1,32] = 18.62, p < .001).Figure 3

Bottom Line: Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction.Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction, and the reduction in the speed of tongue muscle contraction was exacerbated in the aged-rat tongue.This work provides a foundation for future investigations of treatments for concurrent effects of aging and radiation on muscles of the tongue and swallowing.

View Article: PubMed Central - PubMed

Affiliation: University of Wisconsin School of Medicine and Public Health, Otolaryngology Head and Neck Surgery, Madison, WI, 53706, USA. russell@surgery.wisc.edu.

ABSTRACT

Background: Radiation treatment for head and neck cancer often results in difficulty swallowing. Muscle weakness and fibrosis have been identified clinically as possible etiologies for swallowing problems following radiation. Aging may compound the effects of radiation on swallowing because radiation-induced damage to muscles and other tissues critical for the oropharyngeal swallow is overlaid on a declining sensorimotor system. However, there have been no investigations of the manner in which aging and radiation treatment effects combine to impact tongue muscles, which are critical effectors of the oropharyngeal swallow.

Methods: Thirty-seven male Fisher 344/Brown Norway rats were divided into four groups; young adults (9 month old), old (32 months old), young radiation (9 months), and old radiation (32 months old). Two fractions of 11 Gy on consecutive days was delivered by external beam radiation to the ventral side of the rat's body over the anterior portion (20 X 30 mm area) of the anterior digastric muscle. Two-way analysis of variance (ANOVA) was used to examine the effects of age and radiation and their interaction on muscle contractile properties. Post-hoc testing was completed using Fisher's least significant differences (LSD).

Results: Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction. However, radiation treatment did not lead to muscle atrophy and fibrosis formation in the GG muscle. Radiation treatment did not exacerbate atrophic changes observed with aging, or lead to additional fibrosis formation in the GG muscle from that observed in the other groups.

Conclusions: The purpose of this research was to determine the effect of radiation on muscles of the tongue and to determine whether aging altered the extent of radiation injury to tongue muscles. Radiation was associated with a significant decrease in tongue force production and reduced speed of tongue muscle contraction, and the reduction in the speed of tongue muscle contraction was exacerbated in the aged-rat tongue. This work provides a foundation for future investigations of treatments for concurrent effects of aging and radiation on muscles of the tongue and swallowing.

Show MeSH
Related in: MedlinePlus