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Biomedical subjects

R R Gacek

Publications and source records attributed to R R Gacek.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1992

Ultrastructural changes in contralateral superior vestibulo-ocular neurons one year after vestibular neurectomy in the cat.

Twenty contralateral superior vestibulo-ocular neurons (SVON) from 3 cats were studied morphologically one year after a right vestibular neurectomy. Eighteen SVON contained a smooth or slightly crenated nuclear membrane, a 63% loss of synaptic profiles (SP) and a 22% decrease in size compared to control SVON. Two cells contained nuclear membrane invaginations, a 40% loss of SP and a 31% size decrease compared to control SVON. The volume fractions of rough endoplasmic reticulum and ribosomes were decreased in these two cell groups but no change was noted in Golgi apparatus and mitochondria. These contralateral SVON reached a size, innervation density and content of organelles similar to ipsilateral SVON at one year following vestibular neurectomy.

Animals↗
PubMed1992

Otogenic brain abscess: the Syracuse experience.

A review is presented of five cases of otogenic brain abscesses (from among 34 cases of brain abscesses of all causes) treated during a 16-year period at a major university hospital in upstate New York. Although the morbidity and mortality rates are high for patients with brain abscess, advances in the microbial isolation methods, specificity of antimicrobial agents, and earlier diagnosis by CT scans have all contributed to an improved outcome for this dreaded disease.

Adult↗
PubMed1991

Autosomal dominant sensorineural hearing loss. Pedigrees, audiologic findings, and temporal bone findings in two kindreds.

We report the clinical and otopathologic findings in three persons from two kindreds affected with adult-onset autosomal dominant progressive sensorineural hearing loss. The primary pathologic change is a deposit of acid polymucosaccharide ground substance in the cribrose areas; in the spiral ligament, limbus, and spinal lamina of the cochlea; and in the stroma of the maculae and cristae. These deposits obstruct the channels that accommodate the dendritic nerve fibers to the auditory and vestibular sense organs. The end result is strangulation and degeneration of dendrites followed by retrograde neuronal degeneration in association with varying degrees of atrophic change in the sense organs.

Adult↗
PubMed1991

Ultrastructure of cat superior vestibular commissural neurons.

The ultrastructure of the feline superior vestibular commissural neurons (CNs) was studied after labeling by contralateral injection of horseradish peroxidase. These small spindle-shaped cells are found in clusters oriented in a rostrocaudal, dorsoventral or lateromedial direction. The CNs have a cleft nucleus, with the majority of nerve terminals contacting the CN near the emergence of polar dendrites. Polarization of the afferent synaptic profiles suggests a bidirectional nature of inputs to CNs by the vestibular nerve, contralateral CNs, and/or cerebellar systems. One type of labeled cell does not conform to this pattern, instead resembling a vestibulo-ocular neuron. Hence, it may function as a commissural and a vestibulo-ocular neuron. Characterization of different types of synapses, based on the size and eccentricity of their synaptic vesicles, indicates a continuum rather than separate populations. Volume fraction of intracellular organelles showed a larger volume fraction percent of polyribosomes in larger cells. Since this organelle is involved with protein synthesis, this finding may indicate that larger CNs have a more extensive dendritic tree.

Adaptation, Physiological↗
PubMed1991

Singular neurectomy update. II. Review of 102 cases.

During the past 18 years, 102 singular neurectomies (SN) were performed on 95 patients with chronic cupulolithiasis of the posterior canal sense organ. Bilateral sequential singular neurectomies were performed in 7 patients and unilateral singular neurectomies in 88 patients. Ninety-nine (97%) of the 102 singular neurectomies completely eliminated the positional nystagmus and vertigo produced by the involved (undermost) ear in the Hallpike maneuver. Following three singular neurectomies (3%), there was improvement but incomplete relief from the positional nystagmus. A sensorineural hearing loss caused by the singular neurectomies occurred in four patients (4%). A thorough knowledge of the surgical and histologic anatomy of the round window niche and singular canal, together with the use of local anesthesia to allow monitoring of a vestibular response to singular neurectomy are essential for effectiveness and safety.

Adult↗
PubMed1991

Ultrastructural changes in contralateral vestibulo-ocular neurons following vestibular neurectomy in the cat.

Twenty contralateral superior vestibular vestibulo-ocular neurons (SVON) from 4 cats were studied morphologically 8 weeks after a right vestibular neurectomy. Nine SVON demonstrated a 35% loss of somal synaptic profiles (SP), normal nuclear and cytoplasmic size, but a slight decrease in organelles responsible for protein synthesis (rough endoplasmic reticulum and polyribosomes). Eleven SVON showed an 82% loss of SP, decrease in cell and nuclear size, and significant reduction in rough endoplasmic reticulum (RER) and polyribosomes. These transneuronal SVON changes are presumed to be the result of commissural pathway degeneration caused by the vestibular neurectomy.

Animals↗
PubMed1990

Neck dissection injury of a brachial plexus anatomical variant.

We describe an unusual brachial plexus anatomical variant that renders it vulnerable to injury in radical or modified neck dissection. It is represented by a looping redundant course of the most cephalad cervical division contribution to the brachial plexus. Unless recognized during development of the inferior surgical plane by blunt dissection techniques, injury to this portion of the brachial plexus may occur. An awareness of this infrequent variation in brachial plexus anatomy should be maintained.

Aged↗
PubMed1990

Ultrastructural changes with age in the human superior laryngeal nerve.

Electron-microscopic morphometric techniques were used to examine age-related changes in postmortem human superior laryngeal nerves obtained at autopsy (young adult, aged 20 to 30 years; old, 60 years and over). A statistically significant age-related loss of myelinated nerve fibers was detected (old, 7032 +/- 1572; young, 10,179 +/- 1969), representing a 31% decrease. Much of this loss occurred selectively in small myelinated fibers (1 to 2 microns) where there was an extensive (67%) and significant age-related fiber loss. A corresponding analysis of axonal diameter of myelinated nerve fibers similarly showed an extensive (67%) and statistically significant decrease in myelinated fibers with small axonal diameters (0 to 0.5 microns) in the old age group compared with the young adult age group. These findings may represent a significant histomorphologic correlate to the observed age-related sensorimotor dysfunction of the upper aerodigestive tract common in the elderly.

Adult↗
PubMed1990

Arachnoid granulation cerebrospinal fluid otorrhea.

A case report and review of the temporal bone (TB) collection in the Department of Otolaryngology at SUNY Health Science Center in Syracuse demonstrated the occurrence of arachnoid granulations (AGs) in the posterior fossa surface of the TB and their role in cerebrospinal fluid (CSF) otorrhea. A large AG responsible for CSF otorrhea in a 64-year-old man was excised with soft tissue repair of the dural defect. Sixteen of 188 TBs (8.5%) in the collection contained 24 AGs ranging in size from 0.07 to 80.65 mm3. Nine AGs (37%) were small (less than 1 mm3) and did not demonstrate enlargement. Twelve (50%) were of intermediate size (2.50 to 9.32 mm3), and three (13%) were large (49.82 to 80.65 mm3). The intermediate and large AGs were associated with bone erosion and a high incidence of communication with a pneumatized mastoid complex (serous otitis media or meningitis). These findings suggest that AGs of sufficient size to produce bone erosion are the primary responsible lesions in adult-onset spontaneous CSF otorrhea.

Aged↗
PubMed1990

Age-related changes in the neuromuscular junctions in the human posterior cricoarytenoid muscles: a quantitative study.

The posterior cricoarytenoid muscle is unique histochemically, ultrastructurally, and functionally. It has been suggested that the posterior cricoarytenoid muscle undergoes early aging. Aging in peripheral nerves has been reported to resemble a "dying back" neuropathy in that the most severe and earliest age-related changes occur at the most distal levels of the nerve fibers. The lengths and terminal axonal branching of neuromuscular junctions in 17 human posterior cricoarytenoid muscles aged 4 days to 95 years were determined. Both neuromuscular junction lengths and the numbers of axonal terminal branches in the very young group differed significantly from values in two older groups. In contrast to results reported for some other muscles, there was no significant age-related change in these parameters in the posterior cricoarytenoid muscle during adult life. This difference may be related to the repetitive contraction of the posterior cricoarytenoid muscle.

Acetylcholinesterase↗