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At least 19 recordsLinked to original sources
PubMed2001

Meningiomas intrinsic to the geniculate ganglion.

Geniculate ganglion meningiomas are extremely rare lesions-only 14 cases have been reported in the literature. Two new cases of these tumors are described. On computed tomography and magnetic resonance imaging, both lesions appeared centered on the area of the geniculate ganglion, extending to the tympanic cleft and eroding the middle cranial fossa floor. The first case was treated through a middle cranial fossa approach. Because the tumor was so large in the second case, a subtotal petrosectomy was used. The authors review the literature to clarify the clinical and radiological characteristics of these tumors and their surgical treatment.

Case Reports↗
PubMed1990

[Decompression of geniculate ganglion of facial nerve].

Decompression of geniculate ganglion of facial nerve in 20 cases of facial palsy caused by temporal bone fracture, herpes zoster otitic and Bell's palsy was reported. Sixteen cases had been followed up for half to four years. Complete recovery was observed in 13 cases and partial recovery in 3 cases. Transmastoid-attical approach was used. The geniculate ganglion and the distal part of the labyrinthine segment of the facial nerve could be exposed by this approach. The authors emphasized the importance of decompression of the geniculate ganglion, because of the anatomic characteristics and the pathologic features. The indications, the surgical approach and the precautions during operation were discussed.

Adolescent↗
PubMed2007

The radiographic prevalence of geniculate ganglion dehiscence in normal and congenitally thin temporal bones.

OBJECTIVE: To determine the prevalence of a dehiscent geniculate ganglion on routine temporal bone computed tomography (CT). STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Two hundred seventy-eight consecutive temporal bone CT examinations for a total of 556 sides were reviewed. One hundred ninety-one sides were excluded. Reasons for exclusion included reconstructed coronal views, no coronal views, or a pathologic process, which involved the geniculate ganglion. Six examinations were from patients with clinical superior canal dehiscence confirmed by surgical repair or positive vestibular evoked myogenic potentials. Twenty-four scans were from patients with radiographic superior canal dehiscence confirmed by two independent readings. MAIN OUTCOME MEASURES: The incidence of geniculate ganglion dehiscence in patients with and without radiographic or clinical superior canal dehiscence. Dehiscent geniculate ganglion was defined as at least two consecutive cuts on a coronal CT showing no bone overlying the geniculate ganglion. RESULTS: The overall incidence of a dehiscent geniculate ganglion was 14.5% in the 365 sides reviewed. The incidence of a dehiscent geniculate ganglion is increased in patients with radiographic and clinical superior canal dehiscence as compared with normal patients and was significantly different by chi analysis (38.1 versus 11.4%). CONCLUSION: The presence of radiographic geniculate ganglion dehiscence is common. This finding has particular importance when the middle cranial fossa or subtemporal approach is used, as the facial nerve is more at risk especially when used to address superior canal dehiscence.

Adolescent↗
PubMedDate not supplied

Surgical anatomy of the Geniculate ganglion.

The position and the average dimensions of the geniculate ganglion have been measured with the Zeiss screw micrometer in 24 temporal bones obtained from the histological collection of the ENT department of the University of Zurich. The geniculate ganglion has been found to lie like a cup over the anterior portion of the genu of the VII nerve. Its dimensions have shown only minimal variations (standard deviation of average length, height and width less than 10%). Surgical resection of the anterior third of the genu of VII nerve has been shown to include 90% of the ganglion cells but not to endanger the motor fibres. These surgical measurements are the basis for performing a resection of the geniculate ganglion in cases of geniculate neuralgia.

Adolescent↗
PubMed1978

Electron-microscopic analysis of the mouse facial nerve near the geniculate ganglion.

An electron-microscopic analysis of the mouse facial nerve near the geniculate ganglion shows that there are, on the everage, 603 more nerve fibers in the portion of the nerve distal to the geniculate ganglion than there are in the part proximal to the ganglion. The average distal increase in the number of unmyelinated fibers is 444 and that in the myelinated fibers is 165. The somatic motor nerve fibers and the parasympathetic fibers in the mouse facial nerve may not contribute to the distal excess. It is possible that the increase in the number of unmyelinated fibers distal to the geniculate ganglion is mainly due to the presence of postganglionic sympathetic fibers in the facial trunk distal to the geniculate ganglion and the greater petrosal nerve. The distal increase in the number of myelinated fibers may be mainly contributed by the sensory fibers.

Animals↗
PubMed2004

Each sensory nerve arising from the geniculate ganglion expresses a unique fingerprint of neurotrophin and neurotrophin receptor genes.

Neurons in the geniculate ganglion, like those in other sensory ganglia, are dependent on neurotrophins for survival. Most geniculate ganglion neurons innervate taste buds in two regions of the tongue and two regions of the palate; the rest are cutaneous nerves to the skin of the ear. We investigated the expression of four neurotrophins, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and NT-4, and five neurotrophin receptors, trkA, trkB, trkC, p75, and truncated trkB (Trn-B) in single sensory neurons of the adult rat geniculate ganglion associated with the five innervation fields. For fungiform papillae, a glass pipette containing biotinylated dextran was placed over the target papilla and the tracer was iontophoresed into the target papilla. For the other target fields, Fluoro-Gold was microinjected. After 3 days, geniculate ganglia were harvested, sectioned, and treated histochemically (for biotinylated dextran) or immunohistochemically (for Fluoro-Gold) to reveal the neurons containing the tracer. Single labeled neurons were harvested from the slides and subjected to RNA amplification and RT-PCR to reveal the neurotrophin or neurotrophin receptor genes that were expressed. Neurons projecting from the geniculate ganglion to each of the five target fields had a unique expression profile of neurotrophin and neurotrophic receptor genes. Several individual neurons expressed more than one neurotrophin receptor or more than one neurotrophin gene. Although BDNF is significantly expressed in taste buds, its primary high affinity receptor, trkB, was not prominently expressed in the neurons. The results are consistent with the interpretation that at least some, perhaps most, of the trophic influence on the sensory neurons is derived from the neuronal somata, and the trophic effect is paracrine or autocrine, rather than target derived. The BDNF in the taste bud may also act in a paracrine or autocrine manner on the trkB expressed in taste buds, as shown by others.

Animals↗
PubMed2005

Selective gentamicin uptake by cytochemical subpopulations of guinea-pig geniculate ganglion cells.

Cytochemical subpopulations of geniculate ganglion (GG) cells were identified in guinea-pigs using immunohistochemistry and selective gentamicin accumulation. Two subpopulations of GG cells were evident based upon their location and immunoreactivity for peptide 19 (PEP 19), for plasma membrane Ca2+-ATPase (PMCA-ATPase), and for neurofilament proteins. Cells within the posterior part of GG were positive for PEP 19 and PMCA-ATPase, but not for 68 kD or 160 kD neurofilament proteins. Cells within the anterior part showed complementary staining properties. Cells within these populations showed differences in accumulation of gentamicin, depending upon the administration route. Cells within the posterior part showed avid accumulation of gentamicin when animals received the drug systemically. When the drug was administered directly into the middle ear, cells within the anterior part showed avid gentamicin accumulation. Immunostaining for gentamicin in both cell populations was much more extreme and remained so for longer post-administration times when compared with spiral ganglion and vestibular ganglion cells. The results suggest that cells in the anterior part of GG have little exposure to gentamicin in the serum and that perhaps they innervate the middle ear mucosa or they absorb the drug through their axons within the middle ear. In contrast, cells in the posterior part of GG have greater access to systemically administered gentamicin either directly or via their axon terminals.

Adenosine Triphosphatases↗
PubMed1983

Fine structure of the neurons of the geniculate ganglion of the cat.

The geniculate ganglion of adult cat was studied electron microscopically. The results revealed that the neuronal soma displays different cytoplasmic features and the neurons were classified into two types: light cells and dark cells. Light neurons contained individual clumps of Nissl substance distributed randomly throughout the cytoplasm, dark neurons were characterized by densely packed stacks of Nissl substance in the peripheral cytoplasm. The unipolar cell process showed several ultrastructural peculiarities which differ from multipolar nerve cell axons.

Animals↗
PubMed1982

The ultrastructure of the geniculate ganglion.

The ultrastructure of the geniculate ganglion was studied in the guinea pig and monkey. Two cytologically distinct colonies of ganglion cells were seen and identified as light and dark cells. All neurons were unmyelinated and most were unipolar, although a few bipolar cells were seen. The axons, upon leaving the cell bodies, followed convoluted courses in the vicinity of the cells bodies before becoming invested by myelin sheaths. Two types of nerve terminal were identified on the small light cells. The first type contained predominantly agranular and spherical vesicles and had synaptic contact with the cell body. The second type did not show synaptic contacts but contained many ellipsoidal vesicles. This study provided no information on the functional significance of these nerve terminals.

Animals↗
PubMed1997

Meningiomas intrinsic to the geniculate ganglion.

OBJECTIVE: To present the clinical, surgical and histopathological manifestations of meningioma intrinsic to the geniculate ganglion. STUDY DESIGN: Retrospective study of outcome. SETTING: Three private tertiary and one university (otology/neurotology) referral centers. PATIENTS: Six patients with cranial nerve VII paresis underwent magnetic resonance imaging and/or high-resolution computed tomography for subsequently histologically proven intrinsic meningioma of the geniculate ganglion. An additional six cases were identified in the literature. Most patients were female and ranged in age from 5 to 40 years. INTERVENTION: Total tumor removal via middle fossa and mastoid exposures followed by cable graft VII-VII neuroanastomosis. MAIN OUTCOME MEASURE: Meningioma can occur intrinsic to the geniculate ganglion and produces gradual VIIth nerve paresis as its first symptom. Other sites of predilection may occur extrinsically within the temporal bone or along intracranial venous sinuses at sites of arachnoid villi. RESULTS: Hearing was maintained in each patient, and postoperative House-Brackmann grade III-V facial nerve function was achieved. CONCLUSIONS: Intrinsic meningiomas of the geniculate ganglion rarely occur. However, this entity should be included in the differential diagnosis of a slowly progressive VIIth nerve paresis, especially in young females. Surgical removal and cable graft VII-VII neuroanastomosis is the treatment of choice. Long-term follow-up should be maintained because of the potential for von Recklinghausen's disease.

Adolescent↗
PubMed2005

Hemangiomas of the geniculate ganglion.

OBJECTIVE: To describe the presentation, evaluation, and management of patients with geniculate ganglion hemangioma. STUDY DESIGN: Retrospective case review. SETTING: Tertiary-care academic medical center. PATIENTS: Six patients with hemangiomas of the geniculate ganglion, evaluated and managed at a single institution. INTERVENTION: All patients underwent imaging and follow-up, with five of the patients undergoing operative intervention. MAIN OUTCOME MEASURES: Tumor size and extent, facial nerve and hearing function, histopathologic findings, and complications are discussed as a function of observation versus microsurgical excision. RESULTS: Six patients with ossifying hemangiomas of the geniculate ganglion were evaluated at a single institution over a 10-year period. These patients underwent operative intervention when their facial nerve function began to decline. Hearing was preserved in five of the six cases. Resection and grafting of the facial nerve was required in five of six cases. Two of the six cases were found to have histologic evidence of facial nerve infiltration on pathologic examination. CONCLUSION: The majority of these tumors infiltrated the facial nerve and could not be completely removed without excision of the nerve itself. Based on this experience, it would seem reasonable to defer surgical excision until facial nerve function has declined to grade 3 or worse. Whether earlier subtotal excision would result in better outcomes or not remains unanswered. This study presents several complicated scenarios that illustrate the difficulty of clinical decision-making in this disease. Associated clinical dilemmas and controversies are discussed.

Adult↗
PubMed2004

Rat gustatory neurons in the geniculate ganglion express glutamate receptor subunits.

Taste receptor cells are innervated by primary gustatory neurons that relay sensory information to the central nervous system. The transmitter(s) at synapses between taste receptor cells and primary afferent fibers is (are) not yet known. By analogy with other sensory organs, glutamate might a transmitter in taste buds. We examined the presence of AMPA and NMDA receptor subunits in rat gustatory primary neurons in the ganglion that innervates the anterior tongue (geniculate ganglion). AMPA and NMDA type subunits were immunohistochemically detected with antibodies against GluR1, GluR2, GluR2/3, GluR4 and NR1 subunits. Gustatory neurons were specifically identified by retrograde tracing with fluorogold from injections made into the anterior portion of the tongue. Most gustatory neurons in the geniculate ganglion were strongly immunoreactive for GluR2/3 (68%), GluR4 (78%) or NR1 (71%). GluR1 was seen in few cells (16%). We further examined if glutamate receptors were present in the peripheral terminals of primary gustatory neurons in taste buds. Many axonal varicosities in fungiform and vallate taste buds were immunoreactive for GluR2/3 but not for NR1. We conclude that gustatory neurons express glutamate receptors and that glutamate receptors of the AMPA type are likely targeted to synapses within taste buds.

Animals↗
PubMed1992

Geniculate ganglion: anatomic study with surgical implications.

The geniculate ganglion and adjacent segments of the facial nerve were dissected in 11 human temporal bones to study the extent and distribution of ganglion cells. A histologic basis for the use of geniculate ganglionectomy as the treatment for geniculate neuralgia was sought. In 9 of 11 specimens (81.8%), the ganglion cell bodies appeared to be aggregated at the apex of the genu close to the origin of the greater superficial petrosal nerve. The mean ratio of the width of the ganglion cell cluster to the width of the facial nerve trunk at the level of the genu was 0.4. In two specimens, significant anatomic variation was present. One specimen showed extension of cell bodies into the labyrinthine segment of the facial nerve; another specimen showed a single ganglion cell in the region of the genu. These findings lead us to postulate that geniculate ganglionectomy may be ineffective as the sole treatment for certain cases of geniculate neuralgia, and that nervus intermedius section may also be required to achieve a more complete deafferentation.

Facial Nerve↗
PubMed2002

Expression of activating transcription factor 3 and growth-associated protein 43 in the rat geniculate ganglion neurons after chorda tympani injury.

The purpose of this study was to evaluate the degree of damage in the geniculate ganglion and its target organ as a result of chorda tympani (CT) injury. We performed unilateral transection of the rat CT and examined expression of the activating transcription factor 3 (ATF3), a neuronal injury marker, and the growth-associated protein 43 (GAP-43), a regeneration-associated molecule. The mean proportion of ATF3-immunoreactive (ir) neurons in the geniculate ganglion was approximately 32% at 3 days after CT injury, but these neurons were never detected in the naive ganglion. Using in situ hybridization, the mean percentage of GAP-43 mRNA-labeled neurons (signal : noise ratio > or = 10) was observed to have increased significantly to approximately 60% for 1-7 days after CT injury, while that in the naive ganglion was < 15%. The results of morphological studies using scanning electron microscopy and immunohistochemistry indicated that atrophic change and reduction of protein gene-product 9.5-ir fibers in the denervated papillae, mainly in the intragemmal region, were observed after CT injury. Increase in GAP-43 mRNA, suggesting CT axonal regeneration, may have a role in recovery from taste disorders. However, this regenerative process may be involved in abnormal activity in the axotomized neurons or the adjacent intact neurons and so one must not disregard the existence of injured geniculate ganglions when considering the treatment of diseases that cause CT injury.

Activating Transcription Factor 3↗
PubMedDate not supplied

Labyrinthine segment and geniculate ganglion of facial nerve in fetal and adult human temporal bones.

The later stages of development (15-40 weeks in utero) of the geniculate ganglion and labyrinthine segment of the facial nerve in the human fetus demonstrate minimal neuronal growth. The vascular supply is well established. The major changes occur in the perineural ossification pattern. The canal of the labyrinthine facial nerve segment ossifies first via the petrous apex and periotic capsule. The narrowest portion of the canal is at the geniculate ganglion in the earlier stages and at the fundus of the internal auditory canal at term. The geniculate ganglion area ossifies by means of two bony plates. The medial plate is a derivate of the periosteal growth of the petrous apex and the lateral plate is an extension of membranous bone from the squama. The major relationships to the middle ear do not change. The hiatus of the facial canal diminishes in size during gestation, but remains patent at birth.

Adult↗
PubMed2000

Biophysical properties and responses to glutamate receptor agonists of identified subpopulations of rat geniculate ganglion neurons.

The goal of the current study was to evaluate the electrophysiological properties and responses to glutamate receptor agonists of rat geniculate ganglion (GG) neurons innervating the tongue. Subpopulations of GG neurons were labeled by injecting Fluoro-Gold (FG) or True Blue chloride into the anterior tongue and soft palate (AT and SP neurons) and applying FG crystals to the posterior auricular branch of the facial nerve (PA neurons). Three to 12 days later, the GG neurons were acutely isolated and patch clamped. Although many biophysical properties of the AT, SP and PA neurons were similar, significant differences were found among these groups in properties related to cell excitability. For example, the average amount of current necessary to elicit an action potential was 61 pA in AT neurons (n=55), 90 pA in SP neurons (n=41) and 189 pA in PA neurons (n=35, P<0.001). In addition, AT neurons tended to fire significantly more action potentials during depolarization as well as following hyperpolarizing pulses than SP or PA neuron types. Most GG neurons responded to application of glutamate receptor agonists. The neurons responded with a depolarization accompanied by a reduction in input resistance. These results suggest that subpopulations of neurons in the geniculate ganglion have distinct biophysical properties and express functional glutamate receptors. The differing biophysical properties of GG neurons is possibly related to their functional heterogeneity and glutaminergic neurotransmission may function in the processing of gustatory, and other sensory information, within the geniculate ganglion and its projections.

Action Potentials↗
PubMed1995

Alterations in geniculate ganglion proteins following fungiform receptor damage.

Previous anatomical studies in rat have shown that damage produced to fungiform receptors of the anterior tongue at postnatal age 2 (P2) alters the growth and ramification of primary gustatory axons in the rostral nucleus of the solitary tract (NST). Studies employing artificial rearing (AR) procedures, which functionally deprive rat pups of orochemical stimulation during critical periods of postnatal life, produce similar alterations in the development of primary gustatory axons in the NST. Therefore, orochemical stimulation during rat's early postnatal life is necessary for normal development of primary gustatory axons in the rostral NST. One hypothesis concerning receptor-damage effects and AR effects is that receptor damage during critical periods of development may alter the regulation (i.e. transcription/translation) and/or distribution (i.e. transport) of proteins in geniculate ganglion neurons, thereby affecting growth of primary gustatory axons in the rostral NST. Specific aims of the present experiments were to comprehensively examine electrophoretic profiles of geniculate ganglion proteins following P2 receptor damage and late (> P40) receptor damage. Results show that concentrations of particular geniculate ganglion proteins are differentially altered following P2 receptor damage and late receptor damage, and that early receptor damage and late receptor damage produces distinct effects on the electrophoretic profiles of particular classes of proteins. Between the ages of P7-P38, P2 receptor damage lowers ganglion concentration of an acidic membrane glycoprotein designated as A1, with an apparent M(r) of 64-67 kDa and a pI of 4.8-5.2 P2 receptor damage also lowers ganglion concentrations of GAP-43. P2 receptor damage produces transient decreases in ganglion concentrations of NF-160, NF-200, and 8 additional acidic proteins. Three of these proteins may correspond to peripheral nerve sheath proteins analyzed in previous studies of the sciatic nerve, and one of these proteins may correspond to a 24 kDa growth-associated protein characterized in regenerating optic nerve. The time-course for changes observed in ganglion proteins following P2 damage was consistent with that observed for normal anatomical development of primary gustatory axons in both the lingual epithelium and NST. Receptor damage produced at P40 and later yielded different patterns of changes in geniculate ganglion proteins. Late receptor damage produced a transient increase in ganglion concentrations of NF-160, NF-200, GAP-43 and four additional acidic proteins within the 29-57 kDa M(r) range. Late receptor damage also produced a transient decrease in the concentrations of protein A1 and a 30 kDa protein that was not affected by P2 damage. Therefore, proteins that were preferentially affected by P2 damage may be involved in the regulation of initial axonal growth within the lingual epithelium and NST, as opposed to the structural repair or maintenance of extant axons. Relationships between normal anatomical development in peripheral and central components of primary gustatory axons are discussed in relation to availability of particular cytoskeletal and growth-associated proteins.

Animals↗
PubMed2003

Embryonic geniculate ganglion neurons in culture have neurotrophin-specific electrophysiological properties.

Geniculate ganglion neurons provide a major source of innervation to mammalian taste organs, including taste buds in the soft palate and in fungiform papillae on the anterior two thirds of the tongue. In and around the fungiform papillae, before taste buds form, neurotrophin mRNAs are expressed in selective spatial and temporal patterns. We hypothesized that neurotrophins would affect electrophysiological properties in embryonic geniculate neurons. Ganglia were explanted from rats at gestational day 16, when growing neurites have entered the papilla core, and maintained in culture with added brain-derived neurotrophic factor (BDNF), neurotrophin 4 (NT4), nerve growth factor (NGF) or neurotrophin 3 (NT3). Neuron survival with BDNF or NT4 was about 80%, whereas with NGF or NT3 less than 15% of neurons survived over 6 days in culture. Whole cell recordings from neurons in ganglion explants with each neurotrophin condition demonstrated distinctive neurophysiological properties related to specific neurotrophins. Geniculate neurons cultured with either BDNF or NT4 had similar passive-membrane and action potential properties, but these characteristics were significantly different from those of neurons cultured with NGF or NT3. NGF-maintained neurons had features of increased excitability including a higher resting membrane potential and a lower current threshold for the action potential. About 70% of neurons produced repetitive action potentials at threshold. Furthermore, compared with neurons cultured with other neurotrophins, a decreased proportion had an inflection on the falling phase of the action potential. NT3-maintained neurons had action potentials that were of relatively large amplitude and short duration, with steep rising and falling slopes. In addition, about 20% responded with a repetitive train of action potentials at threshold. In contrast, with BDNF or NT4 repetitive action potential trains were not observed. The data demonstrate different neurophysiological properties in developing geniculate ganglion neurons maintained with specific neurotrophins. Therefore, we suggest that neurotrophins might influence acquisition of distinctive neurophysiological properties in embryonic geniculate neurons that are fundamental to the formation of peripheral taste circuits and a functioning taste system.

Action Potentials↗