AAHS ASPN ASRM - 2013 Annual Meeting - American Association ...

ASPN Scientific Paper Presentations C
A Novel Method of Head Fixation for the Study of Rodent Facial Function
Institution where the work was prepared: Massachusetts Eye and Ear Infirmary, Boston, MA, USA
Tessa A. Hadlock, MD1; Susan Mackinnon2; James T. Heaton, PhD1; (1)Massachusetts Eye and Ear Infirmary and Harvard Medical School, (2)Washington University in St.
Louis
Inroduction:
The rodent vibrissial system offers an excellent model for the study of both sensory and motor function. Existing methods of head fixation for precise measurements
of ocular and vibrissial function are suboptimal, involving exposure of the cranium and the application of a piece of dental cement from which several
threaded rods emerge. The purpose of this study was to create a simple head fixation device that minimizes the skin – foreign body interface, therefore
improving biocompatibility, dramatically decreasing infection rates, and permitting essentially indefinite repeated measurements of facial function.
Materials / Methods:
A template was designed to fit onto the calvarium of the rat, with holes positioned on the surface of the cranium, and located laterally to avoid penetration
of sutures and dural sinuses. Then, a number of replicate devices were machined from surgical-grade commercially pure titanium. Four 250-400 g female Wistar
rats underwent placement of the head fixation plates. Briefly, a midline incision was made in the scalp, and two small incisions corresponding to the location
of the fixing posts were made. A subperiosteal plane was developed over the calvarium, the sterile plate was secured to the calvarium with 26 gauge surgical
wire sutures, and the skin was closed. Animals were handled daily for 2 weeks prior to and 2 weeks after implantation of the devices. On POD#14, animals
were removed from their cages, and the head was placed between two threaded fixation pins secured to a platform. The animals remained in the head fixed
position for a ten minute period, during which they were rewarded with chocolate drink before being released and returned to the cages. Testing proceeded
on a daily basis for the ensuing week, and then weekly for the ensuing month.
Results:
There was no breakdown of skin overlying the implanted head plate in any of the animal. There was no obvious dural penetration of the surgical wires, and
animal behavior was normal during the study period, with no gross motor or behavioral deficits.
Conclusions:
We have described a novel method of head fixation that allows precise, repetitive measurements of both ocular and vibrissial function and can be stably maintained
for months. The use of a biocompatible implant largely eliminates the tissue reaction at the skin interface, and decreases infection risk. The device permits
an unhindered view of whisker and eyelid movement, and leaves the superior surface of the cranium accessible for neurosurgical manipulation.
Small Fibers Dysfunction during Entrapment Neuropathy and after Surgical Decompression in a Rat Model
Institution where the work was prepared: Ching-Hua Hsieh, Kaohsiung, Taiwan
Ching-Hua Hsieh, MD1; Tsu-Hsiang Lu, BA1; Seng -Feng Jeng, MD2; Shun-Sheng Chen, MD, PhD1; (1)Chang Gung Memorial Hospital in Kaohsiung, (2)Chang Gung
Memorial Hospital in Kaohsiung
Purpose:
To investigate the small fibers dysfunction during entrapment neuropathy and after surgical decompression by skin biopsy with intra-epidermal nerve fibers
density (IENFD) derived from quantification of PGP 9.5 immunoreactive epidermal nerve fibers and with immunohistochemistry of sensory receptor proteins
substance P (SP) of the hindpaw skins in a established rat model of chronic nerve compression
Material and methods:
Right sciatic nerve of the experimental SD rat was wrapped around with one inner diameter 1.3 mm silastic tube as an entrapment model. Sham operation
was performed on the left sciatic nerve. As growing up of the rat, the sciatic nerve would become constricted by the tube and sustain neuropathy. Surgical
decompression as removal of the silastic tube was performed six months later. Hindpaw skins of rats in indicated times (entrapment one, three, and six months,
post decompression one and three months) were harvested for calculating IENFD and for immunohistochemistry of SP. Semisection with toluidine blue stain
of the entrapped sciatic nerves were performed to evaluate the status of the myelinated fibers. Right hindpaw skins of naïve rats were used as a control.
Result:
With progressive diminished SP-immunoreactive fibers, decrease of IENFD became more prominent in both hindpaws after entrapment one, three and six
months (control: 20.04±2.26, 19.39±2.38, 20.45±2.40; experiment: 12.12±2.12, 6.27±1.02, 1.83±0.48; sham: 13.72±2.20, 8.59±1.37, 4.56±1.07 fibers/mm).
The small fibers dysfunction was more obvious in the experimental hindpaw than in those of sham operation and naïve control. After decompression one and
three months, increased IENFD in both sides were found (control: 20.38±2.24, 18.94±2.24; experiment: 7.00±1.14, 6.97±1.40; sham: 6.41±1.16, 9.92±1.64
fibers/mm). In addition, degeneration during entrapment and regeneration after decompression of the myelinated fibers were found in the semisection examination.
Discussion:
With remarkable improvement of postoperative clinical function and electrophysiologic values, surgical decompression often helps to ameliorate some of the
pathologic change; however, conventional nerve conduction studies only detect abnormalities of large-fibre sensory nerves and offer no information regarding
the status of small-fibre neuropathy. This study provided quantified and morphologic information regarding the cutaneous small fibers deficit during
entrapment and after surgical decompression in a rat model. And it was of noted that not only the lesion side skin but also the contra-lateral side skin would
present sensory deficit.
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