Experimental Study Of The Mechanism For The Presence Of The Horner Syndrome In Obstetric Brachial Plexus Palsy (OBBP)

Objectives To identify whether the Horner syndrome absolutely indicates the early exploration of brachial plexus in obstetric bracial plexus palsy (OBBP), the different mechanism of the anatomical basis that the Horner syndrome occurs was investigated between OBBP and adult brachial plexus injury.Methods Six newborn (twelve sides) and six adult (twelve sides) cadavers were bilaterally dissected to observed the neural connection between the sympathetic ganglions and C5-T1 nerve roots, which form the brachial plexus. 2. In 2 fresh newborn and 2 fresh adult cadavers, the distribution of Acetylcholinesterase (AChE) positive neurons in C5-T1 segments of spinal cords was observed. Furthermore, the distribution of neuronal Nitric Oxide Synthase (nNOS), which is the marker of sympathetic preganglionic neurons, was investigated using immunohistochemical staining method in C5-T1 segments of spinal cords and nerve roots.Results 1. In ten sides of twelve sides (83.3%) of the newborns, there were white rami communicates running from the nerve roots of C7, C8 and Tl to stellate ganglions; in the other three sides (16.7%), the rami communicates originated from the roots of C8 and Tl. In contrast, the rami communicates could only be seen in the nerve roots of C8 and Tl in adults. 2. In both newborns and adults, the AChE and nNOS positive neurons similarly distributed in intermediolateral nucleus (IML) of Tl segments of spinal cords. In newborns, however, the nNOS positive neural fibers were observed in C7, C8 and Tl ventral roots whereas it can only be seen in C8 and Tl ventral roots of adults.Conculsion In newborns, there were sympathetic preganglionic fibers in the nerve root of C7, whose avulsion may partly be relative to the occurring of Hornersyndrome in OBPP. Therefore, the Horner syndrome may not be usually considered as the absolute indication for early explorarion of brachial plexus in OBPP.Part 2 The establishment of animal models for the study of the different mechanisms that the Horner syndrome occurs following the brachial plexus injury between the rats at different agesObsjectives To simulate the clinical symptom of Horner syndrome caused by obstetrical brachial plexus palsy and adult brachial plexus injury, the animal models of young and adult rats were respectively established with Horner syndrome following various type of brachial plexus injury, which provide the theoretic bases for further experiment in vivo.Methods 1. To observe the anatomical relationship among the sympathetic ganglions , white ramis and the nerve roots which consist brachial plexus, the cervical sympathetic nerves were dissected in four specific pathogen free Sprague-Dawley 14-day-old rats (called as yound group as followed) and four adult rats. 2. Fifty six young rats and fifty six adult rats are randomly devided into seven groups according to the different operation on right sides as follows: avulsion of C7 root, avulsion of C8 root , avulsion of Tl root, avulsion of C7-C8 roots, avulsion of C8-T1 roots, the division of the caudal inter-ganglionic branches of superior cervical ganglion and the resection of caudal inter-ganglionic branches of stellate ganglion. After the intervention, the presence of Horner syndrome on rats were observed. Also the positive ratios were compared between the different groups.Results 1. Through the anatomical study of the cervical sympathetic ganglion, the existence of white communicating ramis originated from C7 and C8 and Tl roots is confirmed while no communicating branches from superior cervical ganglion and middle cervical ganglion has been observed. 2. Six of the eight fourteen-day-old rats (75%) in the C7-C8 roots avulsed group had developed a positive Horner syndrome, while only two adult rats in the C8-T1 roots avulsed group showed Horner syndrome. The positive ratios of Horner syndrome in the above-mentioned group were significantly different between young and adult rats (p<0.05). However, in the groupswhich had undergone the mere avulsion of C7 or C8 root, there is no significant difference in the positive ratios of Horner syndrome between the young and adult rats.Conclusion After the injury of brachial plexus, the development of the Horner syndrome in the rats at various age level follows a similar way to that in human beings, that is, the avulsion of C7 root is probably also involved in the Horner syndrome in young rats, which leads to the conclusion that the rat is an ideal animal for the further investigating of the different mechanisms that the Homer syndrome occurs between infants and adults.Part 3 The experimental study of the difference of thepreganglionic neuron's distribution innervating superior cervicalganglion in spinal cord and its mechanism between rats at differentagesObjectives To further illuminate the morphological bases of the different mechanism that the presence of Homer syndrome in obstetrical brachial plexus palsy and adult brachial plexus injury through animal model, the distribution of preganglionic neurons innervating superior cervical ganglion in the spinal cord of rats were investigated at different ages.Methods Twenty four seven-day-old Sprague-Dawley rats, twenty four fourteen- day-old SD rats and twenty four adult SD rats are respectively devided into 4 groups at random as following: C7 root intact group—the roots of C8 and Tl were avulsed and the caudal inter-ganglionic branches of stellate ganglion were resected on right side; C8 root intact group—the roots of C7 and Tl were avulsed and the caudal inter-ganglionic branches of stellate ganglion were resected on right side; Tl root intact group—the roots of C7 and C8 were avulsed and the caudal inter-ganglionic branches of stellate ganglion were resected on right side; T2 root intact—the roots of C7 and C8,as well as Tl were avulsed on right side. After operation on each group , the retrograde tracer Fluorogold (FG) was injected into superior cervical ganglions on both sides. 48-72 hours later, the distribution of FG-labelled neurons in spinal cord were observed and the ratios of labelled neurons in the experimental side to thecontrol side were calculated respectively. The apoptosis of the FG-labelled neurons was identified by terminal deoxynucleotidyl transferase biotin-14-UTP nick end labeling (TUNEL) method, and the number of apoptotic neurons were counted in order to calculate the apoptotic ratio.Results In control side, FG-labelled neurons are located at C8 to T5 segments of spinal cords, most of which were observed in Tl and T2 segments. In group of C7 root intact, the number of labelled neurons in seven was 240±72, with a ratio of 15.64±4.82%, comparing to that of control side; in fourteen -day-old rats, the number was 191±64 with a ratio of 13.64±6.95%, comparing to that of control side; in adult rats, however, the labelled neurons can hardly be observed, whose number was 11 ±5, with a ratio of 0.91 ±0.45% comparing to that of control side. The ratio of labelled neurons in experiment sides to control sides between infant rats and adult group shewed a significant statistic difference (p<0.01), while the difference between seven-day-old rats and fourteen-day-old rats was not significant. The ratio of the labelled neurons in other groups that mentioned above did not show any significant difference. Apoptosis detection shewed the existence of apoptosis at various degree in the FG-labelled neurons in infant rats. Among the seven-day-old rats, the preganglionic sympathetic neurons shewed the highest level of apoptosis in the C7 intact group with an ratio of 3.1%±0.9%, while that in the C8 intact group, Tl intact group and T2 intact group was respectively 0.7%±0.4%,0.4%±0.3% and 0.3%±0.3 %. Similarly, among the fourteen-day-old rats, the labeled neurons in the C7 intact group also shewed the highest level of apoptosis with the ratio of 1.9% ±0.8%; in the C8 intact group ,T1 intact group and T2 intact group the ratio was respectively 0.3% ±0.3%, 0.3%±0.1%> 0.2%±0.1%. In the adult rats, however, no apoptosis neuron had been observed.Conclusion The study show the evidence that in infant rats, some sympathetic preganglionic neurons send out preganglionic fibres innervating the superior cervical ganglion through the C7 roots, which gradually vanish in the way of apoptosis during the course of postnatal development. It could be considered as the morphologic base of the specialty that the Horner syndrome present in obstetric brachial plexus palsy.Objectives In order to identify the mechanism that the C7 nerve root is more prone to avulsion in obstetric brachial plexus palsy (OBPP) comparing to that in adult brachial plexus injury, the anatomical feature of brachial plexus roots were investigated.Methods 1. Six newborn (twelve sides) and six adult (twelve sides) cadavers were bilaterally dissected to observe the intraspinal and extraspinal morphological features of the C5-T1 nerve roots, which form the brachial plexus. The following data were recorded: the cranial angle of nerve roots with cords, the cranial angle of anterior branches with cords, length of the ventral root emerging zone, length of the ventral roots, number of ventral rootlets. 2. In 4 newborn and 4 adult cadavers, the complex of nerve roots-attachment-transverse process were bilaterally resected and the biomechanical test was performed to examine the failure load of the complex. 3. In 6 fresh newborn cadavers, the C5-T1 nerve roots were histologically analyzed using hematoxylin and Mallory trichrome staining to observe the connection between nerve roots and their surrounding tissue.Results 1. In newborns, the nerve roots emerged at a relative horizontal angle when compared with adults. Therefore, the cranial angle of C7 nerve roots with cords in newborns were smaller than that of the anterior branches, whereas the trend is reverse in adults. In newborns, the primary protective attachment of C5-C7 nerve roots was semiconic posterosuperior ligaments, which were composed of collagen fibers. 2. The failure load of the attachment around the C5, C6 and C7 nerve roots were respectively 6.47± 1.12N, 6.23+ 1.21N and 5.03 + 1.05N. The failure load of the attachment around the C5 and C6 nerve roots were larger than that around the C7 nerve roots. The difference were statistically significant (P value are 0.019 and 0.046 respectively). 3. The collagen composition of this ligament around C7 nerve roots, however, was smaller than that of the ligament around C5 and C6 nerve roots. The difference was statistically significant (P<0.05). Furthermore, the semiconic posterosuperior ligaments around the C5 and C6 nerve roots were reinforced by Sharpey fibers at its insertion to the transverse process. Sharpey fibers were hardly seen at the ligament around the C7 nerve roots.Conclusion The higher incidence of C7 avulsion injury in OBPP may be...