PCA Muscle Research Articles

Local vital reaction following injuries of the neck

Sixty-one cases of hemorrhaging of the laryngeal muscles are reported among 86 deaths due to compression of the neck (strangulation by ligature and/or with the hands, blunt force); the results of histological examinations of these cases (laryngeal muscles; hemorrhaging of the cervical muscles and tongue in numerous cases) are discussed, as well as 55 comparative cases (natural, violent death) with regard to vital changes from the hemorrhaging aspect. Although sanguineous infiltration of the laryngeal muscles can occur after death (prone position), it differs macroscopically and in some cases also microscopically from the vital type: extensive bleeding on the inside of the larynx or dorsally above the larynx (PCA muscle), possible combined with histologically detectable ruptures of muscle cells, must be viewed as the result of laryngeal compression suffered when still alive. No clear-cut evidence of emigration or infiltration of leukocytes was found in the cases of immediately fatal strangulation, but there was occasional evidence (6 cases) when protracted maltreatment had taken place. Although there was no clear correlation with age, sex, type of impact, cause of death, or amount of laryngeal bleeding, in 25 of the 61 cases leukocytes were sometimes detectable in enormous amounts within the extravasation; the ratio exceeded that to be expected from the composition of the blood. Findings of this nature have also been made in cases of vital bleeding in other violent or natural deaths; they are not a cell reaction in the proper sense but, when distinctly marked, a vital event--at least in the laryngeal region. These findings can support the assumption of the amount of hemorrhaging in deaths in which the survival time was inadequate for a leukocyte emigration. In 20 cases such findings were combined with localized leucocytosis, which is regarded as an early vital reaction.

Neuromuscular junctions of the posterior cricoarytenoid muscle in the human adult, human fetus and cat. Histochemical and electron microscopic study.

The motor end plate of the posterior cricoarytenoid muscle (PCA muscle) in the human adult, human fetus and cat was examined by using electron microscopy and histochemical methods. In the present study, we observed the single-type motor end plate and en plaque type neuromuscular junction. At the neuromuscular junction of the fetal PCA muscle, the primary synaptic cleft, the basement membrane and the postsynaptic density could already be observed; however, there was no secondary synaptic cleft. Histochemically, the subneural apparatus was filled with electron-dense products, indicating acetylcholinesterase (AChE) activity. The primary and secondary synaptic clefts in the adult PCA muscle were well developed and intense AChE activity was present. The appearance of the neuromuscular junction and its localization of AChE activity was similar to that in the cat PCA muscle.

Evoked response in the posterior cricoarytenoid to stimulation of the ipsilateral vagus.

As no complete study has been made of reflex response to stimulation of ipsilateral vagus in regard to extramedullary respiratory control system, the authors have tried to clarify the influence of the stimulation of the vagus on the ipsilateral posterior cricoarytenoid muscle (PCA).Reflex responses in the recurrent laryngeal nerve and motor action potentials of the PCA elicited by stimulation of the ipsilateral vagus were compared with those elicited by stimulation of the internal branch of the superior laryngeal nerve.The latent periods in the case of stimulation of the vagus were much longer and reflex discharges in tonic fibers were not noticeable. In addition, reflex inhibition of spontaneous respiratory activity of the PCA was not re-markable. Decrease in activity of the PCA muscle, which is usually caused by inflation of the lung, was caused by the low frequency of central vagal stimu-lation. On the other hand, high frequency of central vagal stimulation caused increase in activity of this muscle. It is known that forced hyperinflation by introducing excessive amount of air results in increased inspiratory activity (Head's paradoxcal reflex). So it seems most likely that these high frequency of vagal stimulation are equivalent to mechanical inflation by excessive amount of air.Based upon the facts mentioned above, it can be said that reflex response in the PCA elicited by vagal stimulation may not take part in laryngeal reflex closure, but may take part in respiratory control system to regulate the activity of the PCA muscle. The PCA muscle, hence, can be firmly considered to be one of the respiratory muscle from the viewpoint of extramedullary respiratory control system.

On the significance of posterior crico-arytenoid muscle hemorrhage

Sixteen cases of gross fresh PCA muscle hemorrhages were collected from a series of 1500 medicolegal autopsies consecutively performed by the authors, an incidence of about 1%. These hemorrhages occurred in cases of deaths resulting from a variety of causes, including natural disease, physical agents and drugs. In none of the cases was there any evidence of external trauma to the neck. In two cases endotracheal intubation had been performed; however, the lack of injury to the tissues between the tube and the muscles probably rules this factor out. In over 50% of the cases, PCA muscle hemorrhages were found in association with “asphyxial” petechial hemorrhages. A consideration of our findings and a study of the literature points out that before considering any individual case of PCA muscle hemorrhages as resulting from direct trauma, additional evidence is needed.