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Biomedical subjects

R R Gacek

Publications and source records attributed to R R Gacek.

125 records · Page 7Linked to original sources
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Neuroanatomical correlates of vestibular function.

Neuroanatomical data revealed by new neuroanatomical techniques over the past decade, have clarified the central connections of the peripheral vestibular sense organs. A knowledge of this information is important in the clinical evaluation of vestibular disorders. The reflex connections of the semicircular canals serve vestibulocerebellar, vestibulo-ocular, commisural, and vestibulospinal pathways. The central connections of the utricular macula are primarily in a descending direction to the motor neurons of the entire length of the spinal cord. These form the basif for vestibulospinal reflexes which are characteristically associated with utricular function. Additional central connections provide the basis for vestibulo-ocular responses to utricular activity. Finally, the saccule has reflex connections both to the upper spinal cord to a minor degree and to extraocular nuclei that serve vertical and oblique eye movements. The minor vestibular group Y nucleus provides a commissural reflex connection for the saccule.

Acoustic Maculae↗
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Management of vallecular pseudodiverticulum.

Vallecular pseudodiverticulum following laryngectomy may be responsible for dysphagia if large enough to compress the cervical esophagus. The pouch probably represents a defect caused by the antagonistic action of tongue and inferior constrictor muscles in laryngectomy repair. Initially, the pocket may remain limited or may form a pharyngocutaneous fistulous tract. Two laryngectomy patients who developed a large vallecular pseudodiverticulum were sufficiently symptomatic to require surgical management. An external approach was used successfully to resect the party wall between the diverticulum and the cervical esophagus.

Aged↗
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Surgical landmark for the facial nerve in the epitympanum.

The bony partition between the epitympanum and the anterior epitympanum serves as a reliable landmark for the facial nerve canal which is located at its base. The consistency of this landmark probably relates to the fact that it forms part of the fallopian canal during fetal development. This surgical landmark is useful where middle ear anatomy is obscured by disease or when a total facial nerve decompression procedure is planned.

Ear, Middle↗
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Singular neurectomy update.

The results of a poll revealed that 96 singular neurectomies have been performed by ten surgeons in this country. Eighty-eight of these (91.7%) resulted in complete relief of benign paroxysmal positional vertigo (BPPV). In seven patients (7.3%) there was a sensorineural hearing loss as a result of this procedure. The average hospital stay for patients having this procedure ranged from 2-6 days, and the return to work time ranged from 1 to 3 weeks. These results indicate that singular neurectomy is an effective selective vestibular ablation procedure for BPPV and that the risks and disability are comparable to other routine middle ear procedures. The causes for failure of this procedure to relieve positional vertigo are a) misdiagnosis of BPPV and b) failure to recognize the singular nerve in the middle ear. Knowledge of the pathophysiology of the disorder and of the anatomical variation in the location of the singular canal will reduce these causes of failure.

Ear, Inner↗
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Pathology of jugular foramen neurofibroma.

Tumors of jugular foramen may closely resemble glomus jugulare tumors clinically and radiographically. A tissue diagnosis is necessary to make a differentiation of these tumors. This conclusion is supported by the findings in a temporal bone from a patient who was diagnosed clinically as having a glomus jugulare tumor 57 years before her death at the age of 84 years. Compression of the 7th and 8th cranial nerves in the internal auditory canal and the 10th and 11th cranial nerves at the jugular foramen represents the mechanism of neural signs produced by a neurofibroma arising in the jugulare foramen. This case further demonstrates that conservative treatment of benign extradural tumors may be compatible with a long and useful life.

Adult↗
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Three-dimensional computer reconstruction of the distribution of neuromuscular junctions in the thyroarytenoid muscle.

Microinjections of botulinum toxin have recently been shown to be effective in the treatment of strabismus, and it has also been suggested that microinjections of this myoneural blocking agent might be of value in the treatment of spastic dysphonia. The success of such a microinjection technique would rely on a precise knowledge of the distribution of myoneural junctions in the thyroarytenoid muscle. In view of this potential application as well as the need for such information in reinnervation procedures, we have used computer graphics to reconstruct the three-dimensional distribution of motor end-plates in the thyroarytenoid muscle. Three cat and one human (fresh autopsy specimen) larynges were frozen and sectioned on a cryostat. Serial sections were then processed for the histochemical localization of acetylcholinesterase activity to demarcate the neuromuscular junctions. An X-Y digitizer was used to reference the position of the motor end-plates in each serial section, and the three-dimensional distribution of the neuromuscular junctions was reconstructed on a computer graphics terminal. The results are discussed in regard to their applicability to clinical treatment of spastic dysphonia and other disorders of phonation.

Animals↗
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Cupulolithiasis and posterior ampullary nerve transection.

Schuknecht's description of a degenerated otoconial mass embedded in the cupula of the posterior canal crista of the downmost ear in the Hallpike test has been termed cupulolithiasis to reflect the pathophysiology in the syndrome described by Barany. The hypothesis that the otoconial mass renders the cupula of the posterior canal gravity-sensitive has received considerable experimental and clinical support. Clinical support is provided here by the observation that complete relief of the paroxysmal positional vertigo followed transection of the posterior ampullary nerve (singular nerve) in 31 ears of 29 patients complaining of chronic cupulolithiasis. Two patients in the series exhibited bilateral cupulolithiasis and were relieved by sequential bilateral singular neurectomies. Twenty-seven patients were relieved by unilateral singular neurectomy. Although there were three instances of sensorineural hearing loss following surgery in the first 15 patients, no hearing loss has been observed following surgery in the last 16 operations. This low incidence of sensorineural hearing loss has resulted from modifications in surgical technique.

Adult↗
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Histochemical study of posterior cricoarytenoid muscle reinnervation by a nerve-muscle pedicle in the cat.

Reinnervation of the posterior cricoarytenoid (PCA) muscle with a nerve-muscle pedicle (NMP) has been proposed for patients with bilateral abductor vocal cord paralysis. Since its success has been controversial, a glycogen depletion histochemical technique was used to examine reinnervation. An ansa cervicalis NMP was implanted into the denervated PCA in nine cats. Eight months later, vocal cord activity was evaluated. The NMP nerve was stimulated extensively in seven cats (experimental group). Optical densities of NMP-supplied PCA muscle fibers from experimental and control groups were compared to detect differences in glycogen content. The results demonstrated quantitative evidence of reinnervation in two experimental animals. Electrical stimulation of the NMP produced abduction in one of these two animals, but was never observed during spontaneous respiration or airway occlusion. These observations indicate that reinnervation can occur but abduction requires electrical stimulation. The NMP technique may be more successful with an electrical pacer.

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

Vestibulo-ocular (VO) neurons in the superior vestibular nucleus were labeled retrogradely with horseradish peroxidase and studied quantitatively using electron microscopy to determine the morphologic correlates of vestibular compensation. Eleven VO neurons from three normal cats were compared to 26 VO neurons in four animals killed 8 weeks after vestibular neurectomy and 13 VO cells from two animals killed 1 year after vestibular neurectomy. The results demonstrated a marked reduction (74%) in the number of synaptic profiles (SPs) on the VO cell soma in both experimental groups. Synaptic vesicles in the remaining SPs on VO neurons were fewer, smaller, and rounder than vesicles in control animals. The residual SPs also were associated with more asymmetric synapses. The experimental VO neuron showed a significant decrease in soma and organelles associated with protein synthesis.

Animals↗
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Evaluation and management of primary petrous apex cholesteatoma.

Primary cholesteatoma of the petrous apex is an uncommon congenital lesion that is suspected clinically by such indirect methods of examination as conventional and tomographic radiology, computerized axial tomographic scan, and angiography. If these indirect methods indicate a petrous apex lesion, the area should be investigated by biopsy through the sphenoid, middle fossa, or translabyrinthine routes. Tumor extension, sphenoid pneumatization, and normal labyrinthine function are factors that determine the surgical approach. Once a diagnostic surgical procedure confirms the presence of an epidermoid cyst at the petrous apex, permanent fistulization through the sphenoid or the middle ear is recommended as definitive management.

Angiography↗
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Commissural projections of the superior vestibular nucleus in the rat.

Wheatgerm agglutinin horseradish peroxidase (WGA-HRP) injections confined to the superior vesicular nucleus (SVN) of six Fischer 344 rats labeled commissural vestibular neurons (CVN) in central and ventral portions of contralateral SVN and Group Y nucleus (Grp Y). When the injection included medial vestibular nucleus (MVN) and Grp Y, labeling was similar with additional labeling in contralateral ventrolateral MVN. A dried pledget of WGA-HRP placed in a midline IV ventricle lesion (N = 4), bilaterally labeled SVN and Grp Y (MVN could not be assessed) CVN. While Grp Y CVN are significantly smaller (138.8 +/- 64.7 microns2) than the CVN in the SVN (177.9 +/- 73.9 microns2) or MVN (196.2 +/- 61.9 microns2), cellular eccentricity (shape) is similar in all three nuclei (0.80, 0.77, SVN, MVN, Grp Y).

Analysis of Variance↗
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Localization of adductor and abductor motor nerve fibers to the larynx.

Knowledge of the location of motor nerve fibers to the adductor and abductor muscles of the larynx may be useful in the diagnosis and treatment of innervation disorders in this organ. Anterograde degeneration and retrograde tracer anatomical techniques have demonstrated the central and peripheral positions of these two groups of motor nerve fibers in the cat. Traditional nerve fibers degeneration methods applied following intracranial transection of the vagus nerve rootlets indicated that: 1) Most of the fibers in the recurrent laryngeal nerve (RLN) are motor; 2) Almost all of these motor fibers leave the brain stem in the most rostral rootlet(s) of the vagus nerve; and 3) Motor fibers to the larynx form a discrete bundle within the trunk of the vagus nerve before forming the RLN. A tracer (horseradish peroxidase) of retrograde axoplasmic flow in motor neurons has been employed to demonstrate: 1) Dorsoventral division of the adductor and abductor neurons in the nucleus ambiguus; and 2) Diffuse arrangement of both adductor and abductor nerve fibers in the vagus nerve but collection of these fibers into abductor and adductor halves of the RLN prior to entering the larynx. These findings dispel theories of differential cord paralysis (Semon's law) based on a vulnerable position of abductor fibers at the periphery of the RLN. Furthermore, the diffuse arrangement of these fiber groups explains the usually mixed functional results obtained following reimplantation of the RLN into a laryngeal muscle.

Animals↗