Unbiased Quantification of the Microdissected Human Scarpa???s Ganglion Neurons

Gangliformis Intumescentia and Beyond: Antonio Scarpa and His Core Contribution to Neuroanatomy, Neurosurgery, and Otoneurosurgery

Nearly 250 years ago, Antonio Scarpa became a professor of anatomy and surgery only 2 years after he graduated from the University of Padua. The young lecturer soon became one of the most renowned anatomists in Italy and a director of the Faculty of Medicine at the University of Pavia. He worked in the fields of general surgery and ophthalmology. Several anatomic structures have been named after him, mainly Scarpa fascia and Scarpa triangle. His interest in neuroanatomy was ardent, despite being occasionally neglected. Scarpa's contributions to the fields of neurosciences have been significant. He was the first to describe the round window and the secondary tympanic membrane, and he eventually focused on the auditory and olfactory organs. Notably, the vestibular ganglion is now known as Scarpa ganglion. Scarpa's magnum opus was the book Tabulae Neurologicae, in which he described the path of several cranial nerves including the vagus nerve and innervation of the heart. Since his death in 1832, Scarpa's head has been preserved at the University History Museum of the University of Pavia. In this historical vignette, we aim to describe Antonio Scarpa's troubled life and brilliant career, focusing on his core contributions to neuroanatomy, neurosurgery, and otoneurosurgery.

Correlation between High-Resolution Computed Tomography Scan Findings and Histological Findings in Human Vestibular End Organs and Surgical Implications

BACKGROUND

Histological study of vestibular end organs has been challenging due to the difficulty in preserving their structures for histological analysis and due to their complex geometry. Recently, radiology advances have allowed to deepen the study of the membranous labyrinth.

SUMMARY

A review and analysis of surgical implications related to the anatomy of the vestibular end organ is performed. Radiological advances are key in the advancement of the knowledge of the anatomy and pathology of the vestibule. Thus, application of such knowledge in the development or improvement of surgical procedures may facilitate the development of novel techniques. Key Messages: During the last few decades, the knowledge of the anatomy of the auditory system through histology and radiology had improved. Technological advances in this field may lead to a better diagnosis and therapeutic approach of most common and important diseases affecting the inner ear.

Immunohistochemical techniques for the human inner ear

In this review, we provide a description of the recent methods used for immunohistochemical staining of the human inner ear using formalin-fixed frozen, paraffin and celloidin-embedded sections. We also show the application of these immunohistochemical methods in auditory and vestibular endorgans microdissected from the human temporal bone. We compare the advantages and disadvantages of immunohistochemistry (IHC) in the different types of embedding media. IHC in frozen and paraffin-embedded sections yields a robust immunoreactive signal. Both frozen and paraffin sections would be the best alternative in the case where celloidin-embedding technique is not available. IHC in whole endorgans yields excellent results and can be used when desiring to detect regional variations of protein expression in the sensory epithelia. One advantage of microdissection is that the tissue is processed immediately and IHC can be made within 1 week of temporal bone collection. A second advantage of microdissection is the excellent preservation of both morphology and antigenicity. Using celloidin-embedded inner ear sections, we were able to detect several antigens by IHC and immunofluorescence using antigen retrieval methods. These techniques, previously applied only in animal models, allow for the study of numerous important proteins expressed in the human temporal bone potentially opening up a new field for future human inner ear research.

Unbiased stereological estimation of the spiral ligament and stria vascularis volumes in aging and Ménière's disease using archival human temporal bones

The present study applies the unbiased stereological technique-Cavalieri principle to measure the volumes of the stria vascularis (SV) and the spiral ligament (SL) using postmortem archival human temporal bones from normal young and older subjects and subjects with Ménière's disease. Normative data was obtained from subjects without ages ranging from 15 to 84 years old who had no history of audiovestibular disease (N=25). For comparison purposes, the normative specimens were divided into three groups: group 1 (n=8) had ages ranging from 15 to 38 years old, average age=23.9; group 2 (n=8) had ages ranging from 51 to 59 years old, average age=55.1; group 3 (n=9) had ages ranging from 64 to 84 years old, average age=74.3. The average SV volume of group 3 (0.479 mm3) was significantly lower than that of group 1 (0.705 mm3) (p<0.0005) and was significantly lower than that of group 2 (0.603 mm3) (p=0.01). The average SL volume of group 3 (8.42 mm3) was significantly lower than that of group 1 (9.54 mm3) (p<0.05), but was not significantly lower than that of group 2 (8.58 mm3). Five subjects with Ménière's disease, confirmed by histopathological examination (ages ranging from 63 to 91 years old, average age=73.4), were studied. The average SV volume in Ménière's subjects (0.378 mm3) was significantly lower than age-matched controls (p<0.05). The average SL volume in Ménière's subjects (7.01 mm3) was also significantly lower than age-matched controls (p<0.05). The SV and SL volumes were unaffected by gender. The present study demonstrates for the first time the use of the unbiased stereological technique-Cavalieri principle-as a reliable and efficient method to obtain volumetric estimates of the SV and the SL by using archival human temporal bone specimens.

Estimation of the number of nerve fibers in the human vestibular endorgans using unbiased stereology and immunohistochemistry

The objective of this study was to obtain estimates of the number of nerve fibers in the human crista ampullaris and utricular macula from normal individuals using unbiased stereology and immunohistochemistry. Vestibular endorgans with the attached vestibular nerve stump were microdissected from the temporal bones. Specimens were divided into two groups. The first group (group 1, N = 8, age range, 68-98 years old, mean = 87 years) was fixed with paraformaldehyde and post-fixed with osmium tetroxide. The second group (group 2, N = 5, age range, 80-98 years old, mean = 86.6 years) was fixed with paraformaldehyde, immunoreacted with monoclonal antibodies against neurofilaments, and post-fixed with osmium tetroxide. The endorgans of both groups were embedded in resin and 2-mum thick sections were made. Estimates of the number of nerve fibers were obtained using an unbiased stereological method, the fractionator. The diameter distribution of nerve fibers was also obtained. The average number of fibers in the horizontal, posterior and superior cristae of individuals in group 1 (N = 14 cristae) was 1424+/-320 (CV = 0.22). The average percentage of small (less than 3 microm), medium (between 3 and 5 microm) and large (more than 5 microm) size fibers was 22.4%, 51.5% and 26.1%, respectively. In group 2 (N = 12), there was an average of 1792+/-99 (CV = 0.05) nerve fibers. The average percentage of small, medium and large size fibers was 22%, 51.2% and 26.8%. In the macula utricle from group 1, there was an average of 3026 nerve fibers (N = 2, ages 80 and 96 years old). There was an average 30.75% small, 56% medium and 13.2% large size fibers. In the utricular macula from group 2 (N = 3, ages 84, 92 and 96 years old), there was an average of 3715 nerve fibers. The average percentage of small, medium and large size fibers was 33.2%, 51.7% and 15.1%. The nerve fiber number in both groups is within the range of previous studies, however, the number of fibers in group 2 was significantly higher than that in group 1 (p = 0.01). This difference is likely due to increased sensitivity gained by the immunohistochemical staining of the axoplasm of nerve fibers in group 2. Results from the present study demonstrate the use of unbiased stereology and immunohistochemistry in human vestibular endorgans, as a reliable and efficient method to estimate the number of nerve fibers. These methods can be applied for studies of normal aging and pathological conditions of the vestibular periphery.