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Biomedical subjects

R R Gacek

Publications and source records attributed to R R Gacek.

At least 19 recordsLinked to original sources
PubMed1998

Morphological and neurochemical correlates of vestibular compensation.

Morphometric analysis of the cat's superior vestibulo-ocular neurons (SVON) 8 weeks, and 1 and 2 years following vestibular neurectomy or labyrinthectomy revealed similar changes which indicate that an excitatory mode of input to the denervated SVON is responsible for the behavioral recovery. These changes include an increased proportion of strong asymmetric synapses, somal spines surrounding the SP, increased size of and number of SP at long (> 1 year) survival periods. There is a parallel decrease < 1 year and increase > 1 year of contralateral vestibular nerve SP on SVON which matches in timing and magnitude the number of ipsilateral vestibular nerve SP after surgical ablation. These unexpected SVON are consistent with the hypothesis that neurotrophins regulate symmetry in the adult vestibular system. This hypothesis was tested in a series of 13 heterozygous brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4 (NT4) knockout mice. Following unilateral surgical labyrinthectomy the BDNF and NT4 knockout mice demonstrated no delay in behavioral recovery compared to their normal littermate controls. However, the NT3 knockout mice required twice the time to recover from balance deficits as their littermate controls. These results indicate that NT3 protein is important for normal vestibular function.

Animals↗
PubMed1998

Pseudoepitheliomatous hyperplasia versus squamous cell carcinoma of the external auditory canal.

Four case reports are presented to demonstrate the clinical and histopathologic similarity of pseudoepitheliomatous hyperplasia (PH) to squamous cell carcinoma (SCC) in the external auditory canal (EAC). In all four cases the original report of SCC on a biopsy specimen of an EAC lesion was corrected on review to PH. In one patient conservative management resulted in resolution of the EAC lesion. A second patient underwent radiation therapy and partial temporal bone resection with no SCC found in the surgical specimen. A third patient's ear canal had healed with conservative treatment and repeated biopsy revealed no malignancy. After a 6-year symptom-free interval, she developed invasive SCC with bone involvement that required surgery and radiation treatment. A fourth patient underwent a sleeve resection of the skin of the EAC that proved to be PH, and no evidence of SCC was found. A thoughtful clinical history, careful physical examination, response to conservative treatment, and close communication with the pathologist should be exercised in the evaluation of EAC lesions.

Adult↗
PubMed1998

Neurotrophin 3, not brain-derived neurotrophic factor or neurotrophin 4, knockout mice have delay in vestibular compensation after unilateral labyrinthectomy.

On the basis that neurotrophins (NTs) affect neuronal synaptic plasticity, are expressed in various cell types of the vestibular system, and exert a trophic influence on statoacoustic neurons, the authors hypothesized a role for NTs in vestibular compensation. To test this hypothesis, they performed unilateral surgical labyrinthectomy in 11 heterozygous (+/-) neurotrophin 3 (NT3) and brain-derived neurotrophic factor (BDNF) knockout mice and in two neurotrophin 4 (NT4) homozygous (-/-) knockout mice, each with a control (+/+) sibling, for a total of 26 mice. Four BDNF(+/-) and four NT3(+/-) mice with their (+/+) controls each were allowed to recover in a normal lighted room for 3, 7, 14, and 30 days following labyrinthectomy. Two BDNF(+/-) and two NT4(-/-) mice with controls were kept in total darkness for 1- and 16-day survival periods. One NT3(+/-) mouse without a control (which died in surgery) was sacrificed after 16 days in darkness. The behavior of all mice was videorecorded to monitor their recovery. Compared with normal (+/+) littermate controls, NT3(+/-) mice demonstrated a delay in compensation (8 to 10 days) in light surround, whereas NT4(-/-) mice showed only a minor delay in dark surround. Despite a 40% lower vestibular ganglion cell population in BDNF(+/-) mice compared with (+/+) controls, BDNF(+/-) mice did not reveal a detectable delay in recovery following labyrinthectomy. These findings suggest that a 50% loss of NT3 protein significantly affects vestibular recovery in adult mice. Perhaps variations in achieving vestibular compensation in humans may be partly secondary to genetically different NT3 levels in vestibular pathways.

Animals↗
PubMed1998

On the duality of the facial nerve ganglion.

OBJECTIVES: Describe quantitatively the number of ganglion cells in the geniculate (G) and meatal (M) segments of the human facial nerve. STUDY DESIGN: One hundred human temporal bone specimens that were sectioned horizontally and stained with hematoxylin and eosin were selected from a temporal bone collection on the basis of minimal artifact and absence of pathology involving the facial nerve. METHODS: Cells with a nucleolus in all sections through the facial nerve were projected on tracing paper with a camera lucida and counted manually. A modified Abercrombie technique was employed to compute total cells in the G and M segments. RESULTS: Ages of patients ranged from 1 month to 92 years; the male-to-female ratio was 56:44. The total number of cells in individual temporal bones ranged from 589 to 4183 (mean, 2162 cells). The range of cells in the G ganglion was from 66 to 4017 (mean, 1713 cells); in the M ganglion the number ranged from 0 to 2764 (mean, 448 cells). There was no correlation of total ganglion cell number to age or sex. The majority of cells were found in the G ganglion in 88% of temporal bones. In 8% temporal bones the majority of cells were in the M ganglion and in 4% the M and G ganglions contained an equal number of cells. CONCLUSIONS: The facial nerve sensory ganglion consists of two components: G and M. The G ganglion outnumbers the M component in the majority of temporal bones (88%). The M ganglion was equal to or greater in number than the G ganglion in 12% of temporal bones.

Adolescent↗
PubMed1998

Fiber grouping in the feline vestibular nerve before and after labyrinthectomy.

The vestibular nerve is composed of fibers with a wide spectrum of diameters. The fibers of largest diameter are known to innervate the type I hair cells of the cristae, while the small-diameter fibers innervate the type II hair cells. Midsized fibers (dimorphic fibers) represent neurons that innervate both type I and type II hair cells. Reports by others have commented on the tendency for clustering of fibers with like diameters. Rigorous statistical proof for or against clustering has not yet been presented. The explanation for this is, in part, the mathematic complexity of analyzing clustering in a system composed of three elements. We report a new method for analysis of fiber clustering and apply this method to large-, medium-, and small-diameter fibers in the feline vestibular nerve. The fiber grouping in the caudal and rostral ends of the vestibular nerves of six normal animals is compared to that in similar areas of the nerves of five animals 12 to 17 months after unilateral labyrinthectomy. No statistically significant clustering of fiber types was found in the rostral portion of either the control or the labyrinthectomized animals. In the caudal portion of the control nerves, clustering of the large fibers was demonstrated (p < .005, chi2 test). This clustering was not demonstrated after labyrinthectomy. An explanation of these findings is discussed. The method used in this study to analyze fiber clustering may be applicable to other nerve systems of greater complexity.

Animals↗
PubMed1998

Anatomy and significance of the subarachnoid space in the fallopian canal.

OBJECTIVE: To describe the anatomic variations of the subarachnoid space (SAS) in the facial nerve canal from human temporal bone specimens. BACKGROUND: The SAS in the facial canal usually is assumed to terminate in the petrosal segment of the canal. This temporal bone study indicates that in 12% of temporal bones the SAS extends laterally into or beyond the tympanic segment of the facial canal. METHODS: Histologic sections through the petrosal and tympanic segments of the facial canal were examined by light microscopy in 1 fetal (30 weeks) and 163 adult human temporal bones. The arachnoidal membrane of the SAS was judged to fall into three types according to its lateral extension in the fallopian canal. RESULTS: One hundred forty-four (88%) of the adult temporal bones contained an SAS limited to the petrosal fallopian canal (type I). Thirteen temporal bones (8%) demonstrated an SAS that extended into the tympanic or geniculate portions of the facial nerve (type II). There were six temporal bones (4%) in which the SAS extended lateral to the tympanic facial nerve or into a separate bony compartment (type III). CONCLUSIONS: Most (88%) temporal bones contain an SAS that is limited to the petrosal fallopian canal. In 12% of temporal bones, however, the SAS may extend laterally in the fallopian canal and present clinically as an asymptomatic enlargement of the canal by computed tomography or as cerebrospinal fluid otorrhea.

Adolescent↗
PubMed1997

Transneuronal down regulation of vestibulo-ocular neurons following vestibular ablation.

Unilateral ablation of vestibular input causes lasting morphological changes bilaterally in superior vestibulo-ocular neurons (SVON). The present study was performed to see if these changes in SVON are more pronounced after bilateral vestibular neurectomy. Twenty-three SVON from both vestibular nuclei of 2 cats sacrificed 8 weeks after bilateral ablation were examined utilizing morphometric ultrastructural techniques. There was a significantly greater somal atrophy, loss of synaptic profiles, rough endoplasmic reticulum and polyribosomes compared to unilateral neurectomy. These changes indicate a down regulation that is proportional to the level of deafferentation and may account for functional deficits seen in the vestibulo-ocular reflex after peripheral ablation.

Animals↗
PubMed1997

Morphologic changes in the vestibular nerves and nuclei after labyrinthectomy in the cat: a case for the neurotrophin hypothesis in vestibular compensation.

Morphological changes in the vestibular nerves and superior vestibulocular neurons (SVON) after unilateral labyrinthectomy in cats revealed a progressive loss of axons in the ipsilateral vestibular nerve (35%) and synaptic profiles (SP) on ipsilateral SVON (60%) up to a 1-year survival period. Although the ipsilateral vestibular nerve showed further degeneration (45%) at 2 years post ablation, the number of SP on ipsilateral SVON increased to 60% of normal (40% loss). These SP likely represent sprouting from crossing commissural or cerebellar pathways. Contralateral vestibular nerves at 1 and 2 years post ablation revealed normal numbers and size spectrum, but the number of SP contacting the contralateral SVON at 8 weeks, 1 and 2 years paralleled the levels of SP found on ipsilateral SVON. The symmetry in adjustment of SP on the SVON of both sides of the brainstem after ablation may be explained by the neurotrophin hypothesis.

Adaptation, Physiological↗
PubMed1996

Comparison of labyrinthectomy and vestibular neurectomy in the control of vertigo.

One hundred twenty-six patients who were treated with labyrinthectomy (81 patients) or vestibular neurectomy (45) between the years 1979 and 1994 were reviewed. The cause for vertigo in 124 of the 126 patients was Meniere's disease (89 patients), labyrinthitis (15), delayed endolymphatic hydrops (8), vestibular neuritis (7), and failed labyrinthectomy (5). In the remaining 2 patients, a normal labyrinth was sacrificed to fistulize a petrous apex cyst. Both procedures were equally effective in relieving vertigo (labyrinthectomy 98.8%; neurectomy 97.8%), but the length of hospitalization, length of disability before return to work, and cost were twice as great with vestibular neurectomy than with labyrinthectomy. More patients exhibited prolonged ataxia following neurectomy (5 patients) than after labyrinthectomy (2). Vestibular neurectomy was associated with several complications: reversible facial paresis (15 patients), meningitis (1), cerebrospinal fluid leak (1), and epidural hematoma (1). Labyrinthectomy was complicated by postoperative hyponatremia in 1 patient. Selective vestibular neurectomy preserved hearing in 32 (82%) of 39 patients. Criteria for recommending either ablation procedure are discussed. The incidence of sequential involvement of the contralateral ear was 1.5%.

Aged↗
PubMed1996

Cricoarytenoid joint mobility after chronic vocal cord paralysis.

Eleven whole organ laryngeal specimens (10 human and 1 dog) with a history of long-standing (6 months to 17 years) paralysis were studied histopathologically for changes in the cricoarytenoid (CA) joints and the intrinsic laryngeal musculature. In 9 cases the paralysis was unilateral and in 2 bilateral. No evidence of CA joint ankylosis (fibrous/osseous obliteration of joint space or degeneration of articular surfaces) was seen in the specimens. The absence of CA joint ankylosis permits the efficacy of thyroplasty medialization procedures.

Aged↗
PubMed1996

Morphologic changes in contralateral superior vestibulo-ocular neurons following labyrinthectomy in the cat.

Ultrastructural changes were measured in 22 contralateral superior vestibulo-ocular neurons (SVONs) from four cats painlessly sacrificed at 8 weeks and 25 contralateral SVONs from four cats sacrificed at 1 year following unilateral labyrinthectomy. The SVONs at 8 weeks showed a 43% decrease in somal size, a 34% loss in rough endoplasmic reticulum (RER), a 48% loss of ribosomes, and a 47% decrease in the number of synaptic profiles (SPs) contacting the soma. At 1 year the SVONs had a 31% decrease in size, a 43% decrease in RER, a 50% loss of ribosomes, and a 71% decrease in SPs. Synaptic vesicles (SVs) in both groups of SVONs showed no change in size or shape compared to control SVs. These findings resemble the contralateral SVON changes that occur following excision of the vestibular ganglion.

Animals↗
PubMed1995

Ultrastructural changes in superior vestibular commissural neurons following vestibular neurectomy in the cat.

The ultrastructural changes of the feline superior vestibular commissural neurons (CNs) were quantitatively assessed 8 weeks following ipsilateral vestibular neurectomy. Results indicated a slight degeneration of synaptic profiles (SPs; 25%) representing the primary vestibular afferent input onto CN soma. The synaptic vesicles of the remaining SPs, which likely originate from the cerebellum and the contralateral CNs, were smaller and rounder, suggesting a transition from an inhibitory to an excitatory mode of response. The SP loss had little impact on the CNs' capacity for protein synthesis and structural maintenance, since there was no change in the volume fraction of intracellular organelles. These data suggest that CNs do not degenerate and are likely functional after vestibular compensation. These findings support the role of the commissural pathway in vestibular compensation as proposed by Galiana et al, which is based on the assumption that the intervestibular commissural connections remain intact following vestibular neurectomy.

Animals↗
PubMed1995

Morphologic changes in superior vestibulo-ocular neurons and vestibular nerve following labyrinthectomy in the cat.

Morphologic changes in ipsilateral superior vestibulo-ocular neurons (SVON) and the vestibular nerve were measured in 4 cats 8 weeks after labyrinthectomy and 4 cats 1 year after labyrinthectomy. There is a 20% decrease in SVON size and 30% decrease in rough endoplasmic reticulum and ribosomes with no change in the volume fractions of Golgi apparatus or mitochondria. In the central nervous system degeneration of the vestibular nerve terminals ipsilateral to the labyrinthectomy was represented by a 25% loss of synaptic profiles (SP) on SVON at 8 weeks and 57% loss of SP at 1 year after labyrinthectomy. There was no significant loss of fiber number in the vestibular nerve at 8 weeks post lesion but a 35% loss of fibers primarily of the large size at 1 year post lesion.

Animals↗
PubMed1995

Technique and results of singular neurectomy for the management of benign paroxysmal positional vertigo.

One hundred thirty-seven patients with chronic disabling paroxysmal positional vertigo were treated surgically with singular neurectomy (SN) during the years 1972-1994. One hundred forty-six SN were performed on these patients. One hundred twenty-eight patients underwent unilateral SN while 9 patients underwent bilateral sequential SN. The patients ranged in age from 25 to 86 years with a mean of 57 years and a female to male ratio of 92: 45. One hundred thirty-eight patients (94%) experienced complete relief of vertigo following SN. Three patients (2%) experienced partial relief of positional vertigo following SN and 5 patients failed to have any improvement of symptoms following SN (4%). A partial sensorineural occurred following SN in 4 patients (3%) in this series. The results indicate that SN is a safe and effective surgical treatment for chronic disabling BPV caused by the posterior semicircular canal.

Adult↗
PubMed1994

Singular neurectomy in the management of paroxysmal positional vertigo.

Paroxysmal positional vertigo is one of the common causes of episodic vertigo seen in neurotologic practice. It is thought to be caused by high specific gravity deposits in the cupula (cupulolithiasis) or membranous posterior semicircular canal (canalithesis) as a result of trauma, aging, viral insult, or surgical insult to the inner ear. The vast majority (90%) of patients undergo spontaneous resolution or cure by positioning maneuvers designed to dislodge the otoconial debris. The very small number of patients with disabling chronic paroxysmal positional vertigo (more than 1 year duration) can be effectively relieved of the positional vertigo (95%) by selective transection of the nerve supply to the posterior canal sense organ (singular neurectomy) through a tympanotomy approach using local anesthesia. The risk of sensorineural hearing loss is 3%.

Adult↗
PubMed1992

Evaluation and management of temporal bone arachnoid granulations.

The diagnosis and evaluation of temporal bone arachnoid granulations (AGs) is based on characteristic bone defects in the posterior or middle fossa surfaces of the temporal bone in adult patients with persistent serous otitis media or septic meningitis following acute otitis media. The cerebrospinal communication caused by AGs should be repaired by a middle fossa craniotomy (middle fossa AGs) or an intact canal wall mastoidectomy (posterior fossa AGs) to preserve normal sound transmission. In adult patients with chronic mastoiditis, the dural defect of an AG may permit intracranial extension of the chronic inflammatory process. This rare extension of disease should be considered in patients who have chronic ear inflammation and severe pain or signs of intracranial disease.

Adolescent↗
PubMed1992

Quantitative ultrastructural study of cat abducens interneurons.

Abducens interneurons project to the medial rectus subdivision of the contralateral oculomotor nucleus and have a role in the mediation of horizontal conjugate gaze. Two types of interneurons have been reported based on shape (fusiform and circular) and differences in organelles. In this study, 41 abducens interneurons from three young adult cats were examined in the transmission electron microscope and were classified, on the basis of eccentricity (e), as circular (e less than 0.82; N = 18) or fusiform (e greater than or equal to 0.82; N = 23). The volume fraction of nucleus, nucleolus, mitochondria, rough endoplasmic reticulum, polyribosomes, and Golgi complex and the number of synaptic profiles per 100 microns of membrane were determined. Although there is a qualitative difference in these cell types, statistical analyses indicate no significant differences in organelle content, mean area, number of synaptic profiles per 100 microns of membrane, or diameter. While the differences in shape may possibly indicate different functional groups, this notion is not supported by the variables examined or by physiological studies.

Abducens Nerve↗