Menière's disease as a manifestation of vestibular ganglionitis.

OBJECTIVE: To present morphologic evidence of viral-induced vestibular nerve pathology in Menière's Disease (MD). MATERIAL STUDIED: Twelve temporal bones (TB) from 8 patients with the clinical symptoms of MD. RESULTS: There was endolymphatic hydrops (EH) and perilymphatic fibrosis in 10 of the 12 TB from MD patients. Of the 10 TB with EH of the pars inferior, 3 also contained outpouchings in the pars superior (utricle and canals), and 3 showed apical spiral ganglion cell loss. Focal vestibular nerve axonal degeneration was observed in all but one TB. CONCLUSION: Morphologic changes in TB of patients with MD, and clinical observations in patients with recurrent vestibulopathy, support the concept that the pathologic mechanism responsible for auditory and vestibular symptoms in MD may be reactivation of a latent viral vestibular ganglionitis.

Morphologic correlates for laryngeal reinnervation.

OBJECTIVE: To describe morphologic correlates for laryngeal reinnervation. STUDY DESIGN: Review of anatomic experiments dealing with laryngeal innervation performed over a 25-year period. METHODS: Description of results from experimental studies on the cat and human laryngeal muscles and nerve supply. RESULTS: Despite separation of abductor and adductor laryngeal motor neurons in the central nervous system, the mixture of abductor and adductor axons in the recurrent laryngeal nerve indicates that selective re-innervation of an individual laryngeal muscle must be accomplished at the neuromuscular junction (NMJ) of the muscle. The optimal time for a reinnervating neural source to re-occupy vacated NMJ is at the time of denervation. If the reinnervation procedure is attempted long (>1 mo) after denervation, extraneous end plates of other neural systems must be eliminated to provide vacant NMJ. The nerve muscle pedicle (NMP) concept is an effective model for reinnervation of a laryngeal muscle provided its activity pattern is similar to that of the denervated muscle and its insertion into vacated NMJ is timely. CONCLUSION: NMP offers a logical method for selective laryngeal muscle reinnervation. Critical to the success of NMP are the physiological input to the NMP and timing of NMP implantation.

Adult spontaneous cerebrospinal fluid otorrhea: diagnosis and management.

OBJECTIVE: To describe demographic, radiologic, and surgical features in adult patients with spontaneous cerebrospinal fluid otorrhea (SCSFO). STUDIED: Review was made of office and hospital charts of 21 patients with SCSFO and 2 patients with spontaneous CSF rhinorrhea, all of which were repaired successfully from 1989 to 1998. METHOD: Radiologic examples of the structure responsible for SCSFO and rhinorrhea are used to illustrate the changes essential for diagnosis. RESULTS: The responsible lesion for SCSFO and rhinorrhea in the adult are arachnoid granulations (AG) or villi, which do not reach a venous lumen and are aberrantly distributed in areas of the anterior, middle, and posterior cranial fossae that are in proximity to the middle ear/mastoid space, ethmoid, and sphenoid sinuses. The ages of the 21 patients ranged from 38 to 83 years (mean 63 years) with all but one older than 50 years. The sex ratio was 14 women to 7 men; the CSF leak was right sided in 13 and left sided in 8 patients. Eighteen of the SCSF leaks were located in the middle cranial fossa surface of the temporal bone (TB) while two were on the posterior fossa border of the TB. The middle fossa leaks were managed by craniotomy and repair with fascia, whereas the posterior fossa defects were obliterated by adipose tissue inserted through an intact canal wall mastoidectomy. The most common radiologic finding on computerized tomography (CT) was a soft tissue mass adjacent to a tegmen bone defect. The posterior fossa AG created an erosion of cortical and trabecular bone in the mastoid compartment. Spontaneous CSF rhinorrhea in two patients also radiologically appeared as soft tissue mass adjacent to bone erosion in the sphenoid and ethmoid sinuses. These also represent aberrant AGs, which are responsible for CSF rhinorrhea in later life. CONCLUSIONS: The demographic, radiologic, and pathologic findings in this series of 21 TB and 2 paranasal sinus SCSF leaks support the concept that the responsible lesions are AGs that are aberrantly located adjacent to pneumatized parts of the skull. Because these AGs enlarge with age, they may erode through the bony confines of the TB and sinuses and present as SCSFO or rhinorrhea in middle and old age.

The pathology of facial and vestibular neuronitis.

OBJECTIVE: To measure disease of idiopathic nature in the ganglia of the human facial (FN) and vestibular nerves (VN). METHOD: One hundred horizontally sectioned human temporal bones (TB) were examined under light microscopy. The TB were sectioned at 20 microm, and every 10th section was stained with hematoxylin and eosin and mounted. The volume fractions (VF) of degenerated cells in the FN ganglion and focal axonal degeneration in the VN were measured with stereologic techniques. RESULTS: Twenty-five TB were excluded because of artifact or poor staining of the FN and VN. Fifty-one TB contained degenerated cells in the FN meatal ganglion (MG) and/or focal axonal degeneration in the VN. Thirty-one FN had degenerated cells in the MG (VF = 1% to 55%) and none in the geniculate ganglion. In 45 TB, focal axonal degeneration was found in the VN (VF = 1% to 50%; the VF was less than 15% in all but one TB). MG and VN degeneration occurred together in 25 TB. None of the cases had a history of FN paralysis, but 20 had a history of vertigo. Twenty-four TB from patients of similar ages with similar otopathologies did not reveal degeneration in the FN or VN. CONCLUSION: The FN and VN lesions in these 51 TB may be virus-induced and reflect a higher incidence of idiopathic FN and VN neuronitis than previously thought.

Evidence for laryngeal paralysis in cricoarytenoid joint arthritis.

OBJECTIVE/HYPOTHESIS: To demonstrate denervation atrophy of laryngeal muscles in a case of gout involving the cricoarytenoid joint. METHODS: The posterior cricoarytenoid (PCA) and arytenoideus (A) muscles from a 72-year-old man with extensive gout were compared with those from a normal adult larynx (age and sex unknown) using stereologic techniques for changes in muscle composition and fiber diameter. RESULTS: The PCA and A muscles in the gout specimen contained changes Indicative of muscle degeneration. In the PCA the volume fraction (VF) of intact muscle was 0.30, of degenerating muscle 0.13, and of fat 0.16. A normal PCA had a VF for intact muscle of 0.64 and 0 for degenerating muscle and fat. Similar changes were seen in the gout A muscle but were not measured. Muscle fiber diameters in the gout PCA (1,024 fibers) showed a significantly higher atrophy and hypertrophy factor than the normal PCA (1,255 fibers). The variability coefficient in the gout PCA (487) was almost double that in the normal PCA (290). Although muscle fiber diameters were not measured in the A muscle in gout, variability in fiber size was seen. CONCLUSIONS: The pattern and magnitude of muscle fiber degeneration in the PCA and A muscles from a larynx with gout fixation of the cricoarytenoid joint indicate neural degeneration. Since similar changes were not found in the thyroarytenoid (TA) and lateral cricoarytenoid (LCA), the neuropathy is selective for the posterior branch of the recurrent laryngeal nerve. This neuropathy is likely responsible for vocal cord adduction (stridor) and incomplete closure of the posterior commissure (aspiration) associated with acute cricoarytenoid arthritis. In chronic cricoarytenoid joint arthritis, ankylosis of the joint space maintains the adducted cord position.

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.

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.

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.

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.

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.

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.

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.

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.

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.