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Results for “Olfactory Nerve Injuries”

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PubMedDate not supplied

The immunopathology of olfactory nerve injury and hemorrhage in gerbils.

Patients with head injury may experience olfactory dysfunction. Unfortunately, little is known about changes in the olfactory neuroepithelium caused by intracranial olfactory nerve injury and hemorrhage. We performed olfactory nerve section or bulbectomy in 53 Mongolian gerbils and subjected the olfactory neuroepithelium to immunohistochemical analysis. A decrease or disappearance of the antiserum to an olfactory marker protein containing olfactory receptor neurons was evident in the sectioned group. Degeneration of the olfactory neuroepithelium contralateral to olfactory nerve injury was also noted in animals with perineural hemorrhage. These findings suggest that olfactory dysfunction may occur not only with nerve injury but also secondary to intracranial hemorrhage.

Animals↗
PubMed2006

Response of matrix metalloproteinase-9 to olfactory nerve injury.

Matrix metalloproteinases function in the remodeling of the extracellular matrix during growth and development as well as in injury and disease processes. We examined the role of matrix metalloproteinase-9 in a model of olfactory nerve injury in mice. We measured changes in matrix metalloproteinase-9 protein levels for up to 60 days following olfactory nerve transection. Matrix metalloproteinase-9 levels increased within hours after injury, peaked at day 1 and were elevated for approximately 2 weeks before returning to control levels over the 60-day time period. The increase in matrix metalloproteinase-9 was temporally associated with the degeneration of olfactory neurons that follows nerve transection and with increased gliosis. Our results demonstrate a temporal relationship between matrix metalloproteinase-9 elevation, degeneration of olfactory neurons and gliosis.

Animals↗
PubMed2003

Microglia in the olfactory bulb of rats during postnatal development and olfactory nerve injury with zinc sulfate: a lectin labeling and ultrastrucutural study.

Using isolectin (GSA I-B4) as a marker, this study examined the possible alterations of lectin-labeled membranous glycoproteins in microglial cells in the olfactory bulb of normal development and under experimentally induced degeneration. In light microscopy, several morphological types of microglial cells representing different degrees of cell differentiation were distributed in the bulb laminae. A gradient of microglial differentiation extending from the intermediate to superficial and intermediate to deep occurs in the bulb layers. The differentiation gradient and lectin labeling pattern of microglial cells in the developing bulb resembled those in other areas of the brain tissues. Differentiating microglia showed a gradual diminution of lectin staining when the nascent round cells transformed into the mature ramified cells. Microglia in the external plexiform layer of the olfactory bulb were the first to mature and the cells expressed very weak lectin reactivity. In mature or adult rats, some microglial cells showing intense lectin labeling were observed in the olfactory nerve layer, granule cell layer and subependymal layer. Ultrastructurally, lectin labeling was localized at the trans saccules of the Golgi apparatus. Microglial cells in other bulb laminae, however, exhibited a negative reaction for the isolectin at the Golgi apparatus. Following intranasal irrigation of zinc sulfate, some microglial cells in the olfactory nerve layer and glomerular layer were activated to become phagocytic cells with increased lectin labeling at their ramified processes. GSA I-B4 staining was also localized at their trans saccules of the Golgi apparatus. The lectin labeling pattern of these phagocytic cells resembled that of differentiating microglia in postnatal bulbs, suggesting that bulb microglia in the lesioned sites were activated through cell dedifferentiation into macrophages.

Animals↗
PubMedDate not supplied

Posttraumatic olfactory dysfunction: MR and clinical evaluation.

PURPOSE: To evaluate the sites of injury in patients with posttraumatic olfactory deficits and to compare damage with findings on clinical olfactory tests. METHODS: Twenty-five patients with posttraumatic olfactory dysfunction were examined by means of olfactory testing, endoscopy, and MR imaging. MR surface-coil scans through the olfactory bulbs and tracts and head-coil scans of the temporal lobes were evaluated. Quantitative and qualitative gradings of damage to the olfactory bulbs, tracts, subfrontal region, hippocampus, and temporal lobes were compared with results on tests of odor identification, detection, memory, and discrimination. RESULTS: Twelve patients were anosmic, eight had severe impairment, and five were mildly impaired. Injuries to the olfactory bulbs and tracts (88% of patients), subfrontal region (60%), and temporal lobes (32%) were found, but these did not correlate well with individual olfactory test scores. Volumetric analysis showed that patients without smell function had greater volume loss in olfactory bulbs and tracts than did those posttraumatic patients who retained some sense of smell. Qualitative and quantitative assessments of damage showed few significant correlations with olfactory tests, probably because of multifocal injuries, primary olfactory nerve damage, and the constraints of a small sample size on the detection of clinically significant differences. CONCLUSION: MR imaging shows abnormalities in patients with posttraumatic olfactory dysfunction at a very high rate (88%), predominantly in the olfactory bulbs and tracts and the inferior frontal lobes.

Adolescent↗
PubMedDate not supplied

Management of cranial nerves I through VII following skull base surgery.

Cranial nerve injuries are common with skull base surgery. While injuries to the seventh and tenth cranial nerves can be corrected to satisfactory degrees, rehabilitation of the third, fourth, and sixth nerves is possible to only a limited degree. This study stresses the management of facial paralysis following skull base surgery and is based upon the author's experiences in dealing with 38 patients who suffered such a facial paralysis. The best results of rehabilitative surgical treatment were achieved with techniques that connect the central stump to the peripheral system. The time between nerve injury and repair was the most significant determinant of the success of the surgical procedure: when the nerve was repaired within three months of the injury, the best results were obtained; when the central stump was not available or the injury was more than two years old, repair was not as satisfactory. In the latter case the procedure of choice was the 12th-7th nerve hookup. Indications and results of facial nerve grafting, cross faciofacial nerve hookups, muscle swings, free muscle implantations, and eye reanimation techniques are discussed.

Abducens Nerve Injury↗
PubMed2002

Administration of transforming growth factor-alpha enhances anatomical and behavioral recovery following olfactory nerve transection.

Although replacement of olfactory receptor neurons (ORNs) and subsequent reinnervation of the olfactory bulb occur following ORN injury, the intrinsic and extrinsic factors that contribute to the regulation of this dynamic process have not yet been fully identified. Recent research indicates that several growth factors have neurogenic effects on ORNs in vitro, and that chronic in vivo administration of either basic fibroblast growth factor, epidermal growth factor, or transforming growth factor-alpha (TGF-alpha) following chemical lesion can enhance the normal rate of ORN reinnervation of the olfactory bulb. The primary goal of the present experiments was to further assess the extent to which growth factor-related enhancements in the rate of anatomical recovery during ORN reconstitution and subsequent reinnervation of olfactory bulb are accompanied by enhancements in the rate of recovery of odor-guided behavior.A series of experiments in rats was conducted to initially characterize the time course of the anatomical and behavioral recovery normally observed following ORN reconstitution as a consequence of olfactory nerve transection, and to subsequently characterize the anatomical and behavioral effects of TGF-alpha administration on this normal rate of recovery. Consistent with a host of prior studies, olfactory nerve transection produced consistent and substantial deafferentation of olfactory bulb followed by a time-dependent anatomical recovery which was significantly enhanced by administration of TGF-alpha. The effect of TGF-alpha on functional recovery following olfactory nerve transection was also assessed using an odor-guided fear conditioning task. ORN lesioned animals receiving injections of TGF-alpha during recovery were found to display enhanced conditioned responding to an olfactory stimulus compared to untreated subjects. Further behavioral analyses suggested that this enhanced functional recovery was likely not due to non-specific effects of TGF-alpha on cognition or motor activity, but rather to enhanced olfactory input to the CNS. Future studies will likely reveal the exact mechanism of action mediating the anatomical and concomitant behavioral effects of this growth factor. Since ORNs are one of only a few populations of neurons capable of regeneration or replacement, the continued study of the cellular and molecular factors that coordinate this regenerative process may ultimately lead to the development of therapeutic strategies to promote an enhanced functional recovery following injury to other neuronal populations.

Animals↗
PubMed2002

Phantom smelling.

A case of phantom smelling (phantosmia) is described in a 28-yr.-old man who developed permanent bilateral anosmia after a serious injury to olfaction-related brain structures at the age of 25 years. The findings indicate that, even years after loss of input from olfactory receptors, the neural representation of olfactory perception can still recreate olfactory sensations without any conscious recall of them. This indicates that the neural representation of olfactory sensations remains functional and implies that neuronal activity in the olfactory organ or in other brain structures gives rise to olfactory experiences perceived as originating from the perception of original odor substances. The report suggests the intriguing possibility that the olfactory perception is not a passive process that merely reflects its normal input from the olfactory system but is continuously generated by a neural representation in the olfactory organ or in other olfaction-related brain structures, based on both genetic and sensory determinants. To the author's knowledge this is the first reported case of its kind.

Adult↗
PubMed2005

Microsurgical anatomic features of the olfactory nerve: relevance to olfaction preservation in the pterional approach.

OBJECTIVE: The pterional approach represents the standard approach for most lesions of the anterior and middle cranial fossa. It requires some degree of frontal lobe retraction, which may result in temporary or permanent damage of olfaction because of nerve avulsion or mechanical compression. The purpose of this study, based on microanatomic dissection of human cadaveric specimens, was to review the microsurgical anatomic features of the nerve and suggest operative nuances that may contribute to reducing the rate of postoperative olfactory dysfunction. METHODS: Twenty olfactory nerves and tracts were examined in 10 human cadaveric heads obtained from three fresh and seven formalin-fixed adult cadavers. A standard pterional craniotomy was performed. The olfactory nerve was dissected from its arachnoidal envelopes and then mobilized for an average length of 30 mm (range, 25-35 mm). RESULTS: The possible retraction of the frontal lobe was 10 to 15 mm. More retraction invariably resulted in nerve disruption. CONCLUSION: The standard sylvian and basal cistern opening may be insufficient to guarantee preservation of olfactory function. Early identification and arachnoidal dissection of the nerve may reduce the rate of olfaction compromise. The opening of the subarachnoidal space should be performed in a proximal-to-distal manner to allow early visualization of the olfactory bulb and its dissection. The arachnoidal dissection should be performed with sharp instruments, avoiding any traction on the posterior portion of the olfactory tract. Any direct retractor compression should also be avoided to spare the microvasculature lying on the dorsal surface of the nerve.

Cadaver↗
PubMed1992

[Evaluation of the surgical results of the interhemispheric approach in comparison with the pterional approach for anterior communicating artery aneurysms].

From 1986 to 1990, 77 cases of ruptured anterior communicating artery (Aco) aneurysms have been operated on through an interhemispheric approach or a pterional approach. In this study, we mainly investigated the following factors: surgical outcome, surgical complications, degree of evacuation of subarachnoid clot, and frequency of symptomatic vasospasm. The difference of outcome between the two surgical groups was not statistically significant. Each operating method had characteristic surgical complications. Pterional approach had a tendency to complicate premature rupture, sacrifice small vessels around the aneurysm, and to result in Korsakoff syndrome and inadequate clipping. Interhemispheric approach was apt to complicate cerebral contusion, bilateral olfactory nerve injury and hemorrhagic infarction due to sacrifice of the bridging veins. The pterional approach could evacuate more of the subarachnoid clot than could the interhemispheric approach, but there was no significant difference in frequency of symptomatic vasospasm depending on which method was used.

Adult↗
PubMed1976

Techniques to prevent olfactory nerve reconstitution in the pigeon.

Transectioned olfactory nerves in birds can reestablish structural and functional connections with the olfactory bulbs in comparatively short time spans, thereby hampering long-range studies of avian olfaction and behavior. Accordingly, techniques are described that are suitable for impeding the reconstitution of the olfactory nerve after its transection in the pigeon. These involve the use of inexpensive and easily obtainable materials including cotton pellets, glass beads, and polyethylene tubing.

Animals↗
PubMed1998

Skull-base trauma: neurosurgical perspective.

Trauma to the cranial base can complicate craniofacial injuries and lead to significant neurological morbidity, related to brain and/or cranial nerve injury. The optimal management involves a multidisciplinary effort. This article provides the neurosurgeon's perspective in management of such trauma using a 5-year retrospective analysis of patients sustaining skull-base trauma. The salient features of anterior and middle skull-base (temporal bone) trauma are summarized, and the importance of frontal basilar trauma as well as brain injury is evident. With these injuries, all cranial nerves (except 9 to 12) are at risk; the olfactory nerve and the facial nerve are the first and second, respectively, to sustain injuries. This retrospective analysis provides a better understanding of cranial base trauma and its management. It emphasizes the multifaceted nature of such trauma and the need to recognize anterior skull-base complications, including cerebrospinal fluid leak and brain injury.

Adult↗
PubMed2002

Neural regeneration and the peripheral olfactory system.

The peripheral olfactory system is able to recover after injury, i.e., the olfactory epithelium reconstitutes, the olfactory nerve regenerates, and the olfactory bulb is reinnervated, with a facility that is unique within the mammalian nervous system. Cell renewal in the epithelium is directed to replace neurons when they die in normal animals and does so at an accelerated pace after damage to the olfactory nerve. Neurogenesis persists because neuron-competent progenitor cells, including transit amplifying and immediate neuronal precursors, are maintained within the population of globose basal cells. Notwithstanding events in the neuron-depleted epithelium, the death of both non-neuronal cells and neurons directs multipotent globose basal cell progenitors, to give rise individually to sustentacular cells and horizontal basal cells as well as neurons. Multiple growth factors, including TGF-alpha, FGF2, BMPs, and TGF-betas, are likely to be central in regulating choice points in epitheliopoiesis. Reinnervation of the bulb is rapid and robust. When the nerve is left undisturbed, i.e., by lesioning the epithelium directly, the projection of the reconstituted epithelium onto the bulb is restored to near-normal with respect to rhinotopy and in the targeting of odorant receptor-defined neuronal classes to small clusters of glomeruli in the bulb. However, at its ultimate level, i.e., the convergence of axons expressing the same odorant receptor onto one or a few glomeruli, specificity is not restored unless a substantial number of fibers of the same type are spared. Rather, odorant receptor-defined subclasses of neurons innervate an excessive number of glomeruli in the rough vicinity of their original glomerular targets.

Animals↗
PubMed2000

Post-traumatic olfactory dysfunction.

OBJECTIVES: This study demonstrates histopathologic and immunocytochemical changes in the olfactory bulb of a patient with post-traumatic olfactory dysfunction. These results are analyzed in light of current understanding of the pathophysiology of anosmia and dysosmia following head trauma. Emphasis is placed on potential mechanisms of human regeneration and recovery. STUDY DESIGN: The current study documents the history of a patient with the initial complaint of complete anosmia following minor head trauma. Two months after the injury the patient developed persistent, severe dysosmia with debilitating weight loss. Neurosurgical treatment, including removal of the olfactory bulbs and tracts, resulted in permanent resolution of dysosmia. METHODS: Histopathologic and immunocytochemical analysis of the olfactory bulbs was undertaken and compared with age-matched control tissue. RESULTS: Pathological analysis of the olfactory bulb revealed a marked reduction in the number of nerve processes with few intact olfactory glomeruli compared with an age-matched control. Specific immunohistochemical staining for the olfactory neuron-specific protein OMP, however, demonstrated the presence of intact axonal projections between the olfactory mucosa and the bulb. CONCLUSIONS: These results support the hypothesis that post-traumatic anosmia involves, at least in part, damage to peripheral olfactory nerve fibers with histological changes in the olfactory bulb. Potential mechanisms for the development of post-traumatic dysosmia are also discussed.

Adult↗
PubMedDate not supplied

The risk of olfactory disturbance from conchal plate injury during ethmoidectomy.

BACKGROUND: Even though the olfactory function usually is improved or unchanged after ethmoidectomy, some patients complain of olfactory disturbance, which may be caused by direct injury to the olfactory nerves. However, the detailed anatomic pathway of the olfactory nerves that leave the olfactory mucosa and after going through the cribriform plate insert into the olfactory bulb is uncertain. In the studies of lateral nasal wall, we referred to the thin bone that connects the middle, superior, and supreme turbinates to the skull base as the "conchal plate." We undertook this study to determine the anatomic relation between the conchal plate and the olfactory nerve. METHODS: Ten midsagittal sections from adult cadaver head specimens were used for gross anatomy and the midportion of the conchal plate was taken and fixed in 10% formalin. The microscopic structures of the conchal plate were observed after hematoxylin and eosin staining. RESULTS: The olfactory nerves originated from the olfactory mucosa lining the middle and superior turbinates and ran upward within the bone of the conchal plate. These results suggest that the olfactory nerve may be injured inadvertently in the conchal plate during ethmoidectomy and that this injury is likely to be one of the possible causes of olfactory disturbance. CONCLUSION: We propose a possibility that injury to the conchal plate can affect olfactory function. Therefore, care should be taken to avoid damage to the conchal plate during ethmoidectomy.

Adult↗
PubMed2002

[Objective test of smell with cognitive potentials].

BACKGROUND: An objective smelling test is indicated for a reliable assessment of olfactory disorders. Usually olfactory evoked potentials (OEP) are registered. But the technique of this measurement is complicated and the generation of the OEP depends on the respiration of the subject. Alternatively, the contingent negative variation (CNV) can be used in the diagnosis of anosmia and parosmia, requiring only a simple olfactory stimulator. SUBJECTS AND METHOD: OEP and CNV were derived from 25 adults with normal smelling and from 16 patients with anosmia after head injury. First, the "direct" CNV was registered when the subjects expected a tone following a smell stimulus after 1.5 s. Using two different odors in a random order, the tone only followed one of them, so the "selective" CNV was scored. RESULTS: In both tests a distinct CNV was found in 21 and 23 normal smelling subjects, respectively. OEPs were absent in 4.3 % of this control group. No patient with anosmia showed an OEP or a CNV. The amplitudes of the "selective" CNV are significantly higher than those of the "direct" CNV. No gender dependency was found. CONCLUSION: The results show that an objective olfactometry can be realized by registration of CNV. Contrary to the measurement of OEP which depend on the physical parameters of olfactory stimuli, CNV correlates well with the cognitive identification of odor.

Adult↗