A rare anatomic variation of the chorda tympani.

The chorda tympani is an important anatomical structure in the tympanic cavity. It may have some anatomic variations. Its anatomic variations are of interest in certain otologic surgical procedures. There are limited reports in the literature about the variations of the chorda tympani. A 49-year-old female patient was refered to our clinic because of conductive hearing loss and tympanic membran perforation in the right ear. During the tympanoplasty surgery, when the tympanomastoid flap was elevated, the chorda tympani was seen between flap and bone as a non-described anatomic variation. This article present a non-described anatomic variation of the chorda tympani.

A Rare Case of Bifurcated Chorda Tympani.

Preservation of the chorda tympani is important in middle ear surgery to prevent dysgeusia postoperatively. However, determining the exact course of the chorda tympani before surgery is not always possible, especially in cases with accompanying malformations. In this report, we presented an extremely rare case of bifurcation of the chorda tympani in a 15-year-old male patient. We performed tympanoplasty for a middle ear malformation with conductive hearing loss. During the operation, we noticed and carefully preserved the bifurcated chorda tympani. The patient did not develop dysgeusia postoperatively. Appropriate handling and understanding of the anomalous chorda tympani preserved the patient's sense of taste and hence quality of life.

Dystonin deficiency reduces taste buds and fungiform papillae in the anterior part of the tongue.

The anterior part of the tongue was examined in wild type and dystonia musculorum mice to assess the effect of dystonin loss on fungiform papillae. In the mutant mouse, the density of fungiform papillae and their taste buds was severely decreased when compared to wild type littermates (papilla, 67% reduction; taste bud, 77% reduction). The mutation also reduced the size of these papillae (17% reduction) and taste buds (29% reduction). In addition, immunohistochemical analysis demonstrated that the dystonin mutation reduced the number of PGP 9.5 and calbindin D28k-containing nerve fibers in fungiform papillae. These data together suggest that dystonin is required for the innervation and development of fungiform papillae and taste buds.

Bony sheathed chorda tympani: a unique case of incudomalleolar fixation.

OBJECTIVE: To describe a unilateral conductive hearing loss caused by restriction of the movements of malleus and incus due to chorda tympani in a bony sheath. PATIENT: A 23-year-old man with a stable mild conductive hearing loss in the left ear and mild sensorineural hearing loss in the right ear. INTERVENTION: An exploratory tympanotomy was performed. MAIN OUTCOME MEASURE: Immobility of the ossicles due to a bony structure, which was found to be chorda tympani encircled in a bony sheath. Ossicular system regained its mobility with the severance of the chorda tympani. RESULTS: Hearing was improved both subjectively and audiographically. CONCLUSION: This is the second case of chorda tympani with a bony sheath and the first case of this pathologic finding affecting both malleus and incus. Bony sheathed chorda tympani is considered to be a congenital anomaly of the chorda tympani that causes incudomalleolar fixation and behaves as posterior bony bars.

Histopathological basis of hearing impairment in Wolf-Hirschhorn syndrome.

OBJECTIVES/HYPOTHESIS: To perform histological examination of temporal bones acquired from an infant with Wolf-Hirschhorn syndrome with an emphasis on identifying abnormalities that might be responsible for hearing impairment in this disorder. STUDY DESIGN: Retrospective case review. METHODS: Temporal bones were taken at autopsy from a 10-month-old infant with Wolf-Hirschhorn syndrome. The right-side temporal bone was studied by microdissection. The middle ear was examined, and the inner ear sensory organs dissected for study by light microscopy. The left-side temporal bone was embedded in celloidin, and sections were cut for microscopic examination. RESULTS: Chronic otitis media was observed in both ears. Inflammation, effusion, and adhesions were present in the middle ear space. The malleus was malformed, and the chorda tympani nerve was found to pass through the bone of the malleus bilaterally. There was an area of sharply defined outer hair cell loss in the lower basal turn of the right-side organ of Corti, and defects were noted in the bone of the apical osseous spiral lamina in both cochleae. CONCLUSION: In addition to the presence of otitis media, the likelihood of congenital abnormalities of the middle and inner ear should be considered in the assessment of patients with Wolf-Hirschhorn syndrome with hearing impairment.

The facial nerve in congenital middle ear malformations.

The two most common anomalies of the facial nerve encountered in patients with a congenital malformation of the middle ear are displacement of the nerve and lack of a bony cover, two conditions that place the nerve at risk of being injured by the unwary surgeon. Malformations of the stapes are often found in association with facial nerve anomalies and may range from underdevelopment to complete absence. A congenital absence of the oval window is not uncommon. The position of the facial nerve in relation to the location and maturation of the ossicles will determine the method of ossicular chain repair. Creation of a new oval window by drilling may require the surgeon to purposely displace the facial nerve to ensure a more direct alignment of the prosthesis with the vestibule. Any part of the incus or malleus may be contoured by drilling to accommodate the loop end of the wire-piston prosthesis. An aberrant course of the facial nerve was found in 13/54 (24%) ears having a congenital malformation of the middle ear. All 54 ears had a patent external ear canal and an identifiable tympanic membrane. Patients with atresia or stenosis of the external ear canal were specifically excluded from this study.

Anatomic variations and anomalies involving the facial canal.

Congenital bony dehiscences in the facial canal result from incomplete closure during development and are observed in approximately 55% of temporal bones. Anomalies involving the facial canal frequently are encountered in malformations of the temporal bone. These anomalies include aberrations of the course of one or all of the segments of the canal; abnormal relation to the oval and round window; bifurcations and trifurcations of the nerve; and associations with dysplasia of the stapes, oval window, external ear canal, and auricle. Rarely, the facial nerve may be hypoplastic or totally absent. Two abnormal vessels occasionally may accompany the facial nerve in the Fallopian canal: a persistent stapedial artery and a persistent lateral capital vein.

Temporal bone pathology in congenital anomalies of the oval window and the facial nerve.

Temporal bones of six infants with congenital ear anomalies were examined for abnormalities of the oval window and facial nerve. These temporal bones were classified into two groups according to the degree of malformation: group A, those with atresia or absence of the oval window; and, group B, those with hypoplasia of the stapes and annular ligament. Group A, consisting of five ears, were associated with severe middle ear anomalies such as the abnormal course of the facial nerve and absence of the stapes. In group B, consisting of seven ears, the stapes were present and the facial nerve presented minor anomalies such as obtuse angulation at the first genu, central migration of the geniculate ganglion cells, ectopic muscles and a wide bony dehiscence of the facial canal around the oval window. Probable origin of the anomalies in group A could mainly be due to maldevelopment of the facial nerve during an earlier embryonal period while that of group B could have developed after the ninth week of the fetal period and are mostly localized along the second branchial arch.

[Malformations of chorda tympani nerve].

OBJECTIVE: To analyze the characteristics of anomalies of chorda tympani nerve. METHOD: Chorda tympani nerve and its adjacent structure were investigated during microsurgery in 667 cases of congenitally malformed external-middle ear. RESULT: Anomalies of chorda tympani nerve were found in 433 cases (64.91%). In the group of isolated middle ear malformation of chorda tympani nerve was 16/147 (10.88%); in the group of stenosis of external auditory canal 22/95 (23.15%); and in the group of atresia 394/394 (100%). In 385 cases (97.7%) chorda nerve were not discovered during operations; It were situated at atresia plate (far from malleoincudal interspace) in 9 cases (2.28%). Different feature were found such as: elongation of chorda tympani posterior canaliculus, high or low position, reduplication of chorda tympani nerve, significant low position of chorda tympani nerve in the atresia plate. CONCLUSION: Malformation of chorda tympani nerve is related to the embryologic development of the facial nerve, ossicle, oval window et. It is imparative to identify and to protect the ectopic chorda tympani nerve during operation early.

Lingual deficits in neurotrophin double knockout mice.

Brain-derived neurotrophic factor (BDNF) and Neurotrophin 3 (NT-3) are members of the neurotrophin family and are expressed in the developing and adult tongue papillae. BDNF null-mutated mice exhibit specific impairments related to innervation and development of the gustatory system while NT-3 null mice have deficits in their lingual somatosensory innervation. To further evaluate the functional specificity of these neurotrophins in the peripheral gustatory system, we generated double BDNF/NT-3 knockout mice and compared the phenotype to BDNF(-/-) and wild-type mice. Taste papillae morphology was severely distorted in BDNF(-/-) xNT-3(-/-) mice compared to single BDNF(-/-) and wild-type mice. The deficits were found throughout the tongue and all gustatory papillae. There was a significant loss of fungiform papillae and the papillae were smaller in size compared to BDNF(-/-) and wild-type mice. Circumvallate papillae in the double knockouts were smaller and did not contain any intraepithelial nerve fibers. BDNF(-/-) xNT-3(-/-) mice exhibited additive losses in both somatosensory and gustatory innervation indicating that BDNF and NT-3 exert specific roles in the innervation of the tongue. However, the additional loss of fungiform papillae and taste buds in BDNF(-/-) xNT-3(-/-) mice compared to single BDNF knockout mice indicate a synergistic functional role for both BDNF-dependent gustatory and NT-3-dependent somatosensory innervations in taste bud and taste papillae innervation and development.