Evaluating the structural properties of suprahyoid muscles and their potential for moving the hyoid

Relação da atividade elétrica dos músculos supra e infra-hióideos durante a deglutição e cefalometria

OBJETIVO: investigar a influência da postura habitual da cabeça, da posição mandibular e do osso hióide na atividade dos músculos supra e infra-hióideos durante deglutição de diferentes consistências de alimentos. MÉTODO: estudo observacional, transversal, com mulheres entre 19 e 35 anos, sem alterações miofuncionais de deglutição. A postura craniocervical, posição da mandíbula e osso hióide foram avaliados pela cefalometria. A atividade eletromiográfica dos músculos supra e infra-hióideos foi coletada durante a deglutição de água, gelatina e biscoito. RESULTADOS: amostra com 16 mulheres, média de idade 24,19±2,66 anos. No repouso, observaram-se correlações negativas/moderadas entre a atividade elétrica dos músculos supra-hióideos com as variáveis posturais NSL/CVT (posição da cabeça em relação às vértebras cervicais) e NSL/OPT (posição da cabeça em relação à coluna cervical) e positiva/moderada com o ângulo CVA (posição de flexão/extensão da cabeça). Durante a deglutição do biscoito, a atividade dos músculos infra-hióideos apresentou correlação negativa/moderada com o ângulo NSL/OPT. Constatou-se maior atividade elétrica dos músculos supra-hióideos durante a deglutição de todos os alimentos testados e, dos músculos infra-hióideos, no repouso. Os supra-hióideos foram mais ativos que os infra-hióideos durante a deglutição, entretanto, houve aumento da atividade eletromiográfica em ambos os grupos musculares durante a deglutição do biscoito, comparado com a deglutição de água e gelatina. CONCLUSÃO: a hiperextensão da cabeça repercutiu na menor atividade dos músculos supra-hióideos no repouso e, dos músculos infra-hióideos, na deglutição. A consistência do alimento influenciou na atividade elétrica dos músculos supra e infra-hióideos, havendo maior recrutamento muscular na deglutição de alimento sólido.

Kinematic effects of hyolaryngeal electrical stimulation therapy on hyoid excursion and laryngeal elevation

The purpose of this study was to assess the effect of repeated sessions of electrical stimulation therapy (EST) on the neck muscles with respect to the stimulation site by using quantitative kinematic analysis of videofluoroscopic swallowing studies (VFSS) in dysphagia patients with acquired brain injury. We analyzed 50 patients in a tertiary hospital who were randomly assigned into two different treatment groups. One group received EST on the suprahyoid muscle only (SM), and the other group received stimulation with one pair of electrodes on the suprahyoid muscle and the other pair on the infrahyoid muscle (SI). All patients received 10-15 sessions of EST over 2-3 weeks. The VFSS was carried out before and after the treatment. Temporal and spatial parameters of the hyoid excursion and laryngeal elevation during swallowing were analyzed by two-dimensional motion analysis. The SM group (n = 25) revealed a significant increase in maximal anterior hyoid excursion distance (mean ± SEM = 1.56 ± 0.52 mm, p = 0.008) and velocity (8.76 ± 3.42 mm/s, p = 0.017), but there was no significant increase laryngeal elevation. The SI group (n = 25), however, showed a significant increase in maximal superior excursion distance (2.09 ± 0.78 mm, p = 0.013) and maximal absolute excursion distance (2.20 ± 0.82 mm, p = 0.013) of laryngeal elevation, but no significant increase in hyoid excursion. There were no significant differences between the two groups with respect to changes in maximal anterior hyoid excursion distance (p = 0.130) and velocity (p = 0.254), and maximal distance of superior laryngeal elevation (p = 0.525). EST on the suprahyoid muscle induced an increase in anterior hyoid excursion, and infrahyoid stimulation caused an increase in superior laryngeal elevation. Hyolaryngeal structural movements were increased in different aspects according to the stimulation sites. Targeted electrical stimulation based on pathophysiology is necessary.

Aging-related geniohyoid muscle atrophy is related to aspiration status in healthy older adults

BACKGROUND

Age-related muscle weakness due to atrophy and fatty infiltration in orofacial muscles may be related to swallowing deficits in older adults. An important component of safe swallowing is the geniohyoid (GH) muscle, which helps elevate and stabilize the hyoid bone, thus protecting the airway. This study aimed to explore whether aging and aspiration in older adults were related to GH muscle atrophy and fatty infiltration.

METHOD

Eighty computed tomography scans of the head and neck from 40 healthy older (average age 78 years) and 40 younger adults (average age 32 years) were analyzed. Twenty aspirators and 20 nonaspirators from the 40 older adults had been identified previously. Two-dimensional views in the sagittal and coronal planes were used to measure the GH cross-sectional area and fatty infiltration.

RESULTS

GH cross-sectional area was larger in men than in women (p < .05). Decreased cross-sectional area was associated with aging (p < .05), and cross-sectional area was significantly smaller in aspirators compared with nonaspirators, but only among the older men (p < .01). Increasing fatty infiltration was associated with aging in the middle (p < .05) and posterior (p < .01) portions of the GH muscle. There was no significant difference in fatty infiltration of the GH muscle among aspirators and nonaspirators.

CONCLUSION

GH muscle atrophy was associated with aging and aspiration. Fatty infiltration in the GH muscle was increased with aging but not related to aspiration status. These findings suggest that GH muscle atrophy may be a component of decreased swallowing safety and aspiration in older adults and warrants further investigation.

Regional variation in geniohyoid muscle strain during suckling in the infant pig

The geniohyoid muscle (GH) is a critical suprahyoid muscle in most mammalian oropharyngeal motor activities. We used sonomicrometry to evaluate regional strain (i.e., changes in length) in the muscle origin, belly, and insertion during suckling in infant pigs, and compared the results to existing information on strain heterogeneity in the hyoid musculature. We tested the hypothesis that during rhythmic activity, the GH shows regional variation in muscle strain. We used sonomicrometry transducer pairs to divide the muscle into three regions from anterior to posterior. The results showed differences in strain among the regions within a feeding cycle; however, no region consistently shortened or lengthened over the course of a cycle. Moreover, regional strain patterns were not correlated with timing of the suck cycles, neither (1) relative to a swallow cycle (before or after) nor (2) to the time in feeding sequence (early or late). We also found a tight relationship between muscle activity and muscle strain, however, the relative timing of muscle activity and muscle strain was different in some muscle regions and between individuals. A dissection of the C1 innervations of the geniohyoid showed that there are between one and three branches entering the muscle, possibly explaining the variation seen in regional activity and strain. In combination, our findings suggest that regional heterogeneity in muscle strain during patterned suckling behavior functions to stabilize the hyoid bone, whereas the predictable regional strain differences in reflexive behaviors may be necessary for faster and higher amplitude movements of the hyoid bone.

Structural analysis of muscles elevating the hyolaryngeal complex

A critical event of pharyngeal swallowing is the elevation of the hyolaryngeal complex to open the upper esophageal sphincter. Current swallowing theory assigns this function to the submental and thyrohyoid muscles. However, the attachments of the long pharyngeal muscles indicate that they could contribute to this function, yet their role is uninvestigated in humans. In addition, there is evidence the posterior digastric and stylohyoid contribute to hyoid elevation. A cadaver model was used to document the structural properties of muscles. These properties were used to model muscle groups as force vectors and analyze their potential for hyolaryngeal elevation. Vector magnitude was determined using physiological cross-sectional areas (PCSAs) of muscles calculated from structural properties of muscle taken from 12 hemisected cadaver specimens. Vector direction (lines of action) was calculated from the three-dimensional coordinates of muscle attachment sites. Unit force vectors in the superior direction of submental, suprahyoid (which includes the submental muscles), long pharyngeal, and thyrohyoid muscles were derived and compared by an analysis of variance (ANOVA) to document each muscle's potential contribution to hyolaryngeal elevation. An ANOVA with Tukey HSD post hoc analysis of unit force vectors showed no statistically significant difference between the submental (0.92 ± 0.24 cm(2)) and long pharyngeal (0.73 ± 0.20 cm(2)) muscles. Both demonstrated greater potential to elevate the hyolaryngeal complex than the thyrohyoid (0.49 ± 0.18 cm(2)), with P < 0.01 and P < 0.05, respectively. The suprahyoid muscles (1.52 ± 0.35 cm(2)) demonstrated the greatest potential to elevate the hyolaryngeal complex: greater than both the long pharyngeal muscles (P < 0.01) and the thyrohyoid (P < 0.01). The submental and thyrohyoid muscles by convention are thought to elevate the hyolaryngeal complex. This study demonstrates that structurally the long pharyngeal muscles have similar potential to contribute to this critical function, with the suprahyoid muscles having the greatest potential. If verified by functional data, these findings would amend current swallowing theory.

Tongue-pressure and hyoid movement timing in healthy liquid swallowing

It was hypothesized that tongue-palate pressure generation might directly facilitate hyoid movement in swallowing through the anatomical connections of the extrinsic tongue muscles. If true, non-invasive measures of tongue-palate pressure timing might serve as a proxy measure of hyoid excursion. The timing relationships between events in the tongue-palate pressure and hyoid movement profiles during water and nectar-thick liquid swallowing in healthy adults were explored. Concurrent intra-oral manometry and submental B-mode midsagittal ultrasound were recorded. It was determined that there is no obligate sequence in the onsets, or offsets, of tongue-palate pressures and hyoid excursion. Timing lags (either of hyoid movement lagging tongue-palate pressures or vice versa) fell within 0.5 s, on average. It is concluded that tongue-palate pressure generation and hyoid movement are separate phenomena in the swallowing sequence and that non-invasive measures of tongue-pressure timing cannot be used reliably as proxy measures of hyoid movement timing.