Endolymphatic Canal Research Articles

Difficulties in Differentiation of Endolymphatic Sac Tumor That Extends Into Pontocerebellar Angle from Metastatic Tumors

Endolymphatic Sac Tumor is a local aggressive tumor that grows slowly, associated with Von-Hippel-Lindau disease and originated from endolymphatic canal. A 64-year-old male patient with VHL disease admitted to the neurosurgery department of our hospital and presented pain behind the ear and loss of sensation on the cheek. Cranial magnetic resonance imaging revealed an aggressive tumor located in the middle ear and left acoustic canal and extending to the pontocerebellar angle that eroded the mastoid and temporal bones. Histopathological examination of the lesion revealed a simple cuboidal epithelium forming glandular and papillary structures. The patient diagnosed with endolymphatic sac tumor as the presence of the morphological findings, positive staining with immunohistochemical markers such as Vimentin, NSE, EMA, PAX8, Cytokeratin 7. Our case showed neuroectodermal origin, which is even rare for von Hippel-Lindau disease, and has been discussed with histopathological findings and differential diagnosis.

Transection and occlusion of lateral semicircular canal in guinea pigs.

Audiologic and histopathologic examinations were made after occlusion of the lateral semicircular canal in eight guinea pigs. The lateral semicircular canal was drilled out, and then the canal lumens were plugged with muscle pieces. After a serial recording of auditory brain stem responses for 2 months, histologic specimens of the temporal bones were prepared in the lateral semicircular canal plane. One animal developed profound hearing loss due to suppurative labyrinthitis. The other seven animals showed no significant threshold elevation during this period. Histopathologic examination revealed that the bone defect on the lateral canal was replaced with newly formed bone; the perilymphatic and endolymphatic spaces maintained their compartmentalization; and the membranous endolymphatic canal healed to form complete blind ducts. These findings suggest that proper management of the injured semicircular canal is important for maintenance of postoperative hearing.

A hydroelastic model of macromechanics in the endolymphatic vestibular canal

A hydroelastic model describing the mechanics of the human semicircular canal is presented that extends previous work to address the influence of the shape of the labyrinth and the interaction between the endolymph and the cupula. The analysis is based extensively on the three-dimensional geometry and structure of the system and exploits the slender toroidal geometry to obtain an asymptotic solution describing the velocity distribution of the endolymph, the pressure distribution and the deflection of the cupula. All parameters appearing in the model are explicitly defined in terms of physical properties and the geometry. Results for the structure of an infant human endolymphatic canal agree well with experimental measurements of the end-organ velocity gain and phase over the entire physiological range of angular head frequencies. From 0.09 to 1.5 Hz the mechanical response relative to head velocity is essentially constant and the end-organ acts as an angular velocity transducer. Below 0.09 Hz the velocity gain is diminished and above 1.5 Hz the velocity gain is enhanced. For a 1 rad sinusoidal rotation of the head, the analysis predicts an average cupula displacement for the infant canal of approximately 8 × 10−5 cm at 0.09 Hz and 2 × 10−3 cm at 2.0 Hz.

Effect on Cochlear Potentials of Lateral Semicircular Canal Destruction

Recording of the cochlear potentials was successfully performed during experimental labyrinthectomy in the guinea pig and in three patients with acoustic neuromas during translabyrinthine removal of the tumors. In the guinea pig, complete interruption of the duct of the lateral semicircular canal including the endolymphatic canal caused little change in the endocochlear DC potential of the first cochlear turn and input-output function curve of the N1 component of the compound action potential elicited by 8-kHz tone bursts. Further drilling of the vestibular labyrinth in the guinea pig caused decline of these potentials when the vestibular was opened. In patients with acoustic neuromas, the interruption of the duct of the lateral semicircular canal hardly altered the N1 input-output function curve and N1 input-latency function curve during the 1-hour observation period. Consistent preservation of cochlear function even after interruption of lateral semicircular canals suggests the possibility of partial surgical labryrinthectomy with preservation of hearing for lesions involving semicircular canals.

Alterations of CAP audiogram by increased endolymphatic pressure and its relation to hydrops

Most current theories regarding the inner ear pathology of Menières disease assume that there is an augmentation of the endolymphatic pressure due to the presence of hydrops. In this study normal hearing pigmented guinea pigs were employed to investigate the effect of increased endolymphatic pressure on the compound action potential (CAP) audiogram. All animals were implanted with an electrode on the round window and the CAP audiogram was determined prior to further surgery. The endolymphatic canal was then visualised by a posterior fossa intra-dural surgical approach. A hole was pierced in the canal and a cannula inserted. The CAP audiogram was again determined before, and at frequent intervals after, the application of hydrostatic pressure (0.5–1 cm Hg). A similar sequence of CAP sensitivity losses was observed within 2 h for 0.5 cm Hg or 15 min for 1 cm Hg. There was at first a very high frequency loss, followed by a very low frequency loss and finally a mid frequency sensitivity loss rendered the audiogram flat and lying around 50 dB sound pressure level. Given that the first characteristic index for experimental hydrops is a low frequency loss the present data suggest that an increase in endolymphatic pressure, as in these experiments, is likely to be a rather late pathological feature of hydrops. Indeed we have shown that a high frequency loss develops at a second phase during the evolution of hydrops.

The membranous labyrinth and its innervation inChaetodon trifasciatus (Pisces, Teleostei, Chaetodontidae)

In the butterflyfishChaetodon trifasciatus, the labyrinth is characterized by its elevated form and especially the size of the vertical canals, the almost circular form of the horizontal canal and its posterior opening not directly in the utriculus but in the common pillar of the two vertical canals. There is an almost complete separation between utriculus and sacculus which are only linked by a virtual pore. The lagena, which is medially situated to the posterior part of the sacculus, is separated from it by an incomplete vertical wall. There are two maculae neglectae, the anterior macula being situated in the pore separating utriculus from sacculus and filling this pore, the posterior in a gutter of the floor of the utriculus. A long and narrow endolymphatic canal, originating from the sacculus close to the communication with the utriculus, follows the common pillar of the two vertical canals and widens into an endolymphatic sac at the top of the membranous labyrinth. The innervation of the labyrinth is made by the acoustic ganglion, which is connected to the brain by two roots and elongated into three parts: the anterior part innervates the anterior and horizontal cristae and the utricular and saccular maculae; the middle part innervates the macula sacculae and the macula neglecta 1; the posterior part innervates the macula neglecta II, the macula lagenae and the posterior crista. The important size of the vertical canals and the almost circular form of the horizontal canal may reflect very precise locomotory aptitudes.

Asymmetry of evoked rotatory nystagmus in the guinea pig after experimental induction of endolymphatic hydrops.

We have previously shown by chronic implantation of round window electrodes, that after the experimental induction of endolymphatic hydrops by surgical blockade of the endolymphatic canal, in the guinea pig, there is a low/mid-frequency fluctuant hearing loss, followed by a very high frequency loss and after a few months the audiogram is flat. This evolution reproduces exactly that observed in Meniere's patients. The aim of this study was to investigate the evolution of one aspect of vestibular function in parallel with audiogram changes. The nystagmic responses in the dark were tested every month during the 4 months which followed hydrops induction. There was considerable variation in the number of evoked saccades for different control animals and even between different recordings for the same control animal. However, in general, the number of saccades to right and left rotation was symmetrical for control animals, whereas for hydropic animals there was a period, within the first 2 months post-operation, when there was a reduction of saccades to the left (operated side) with sometimes an increase to the right. This asymmetry which occurred in the period of fluctuant hearing losses did not however appear synchronized with audiogram fluctuations. The nystagmic responses tended to become symmetrical over the 4 months post-operation. Oral administration of glycerol to animals whose nystagmus was asymmetric brought the vestibular response towards symmetry in 50% of the cases. Although episodes of vertigo, as known in Meniere's disease, were never observed in operated guinea pigs, these data indicate that they have some functional vestibular disturbance.

A theoretical and comparative study of the functional dependence of the semicircular canal upon its physical dimensions

It has long been known that, in contrast to the range of variation of body dimensions, the semicircular canals of different animals are approximately similar in size. In the present study, measurements of the internal radius ( r ) and radius of curvature ( R ) of the endolymphatic canal were made in 87 species, comprising 46 mammals, 17 birds, 17 fishes and 7 reptiles, using specimens, and photographic records of specimens, already available. Using the principles of dynamical similarity, theoretical arguments are adduced which predict that if Steinhausen’s (1933) interpretation of semicircular canal function is correct there should be very slow increases, systematic but discreet, of r and R with body mass ( m ). The results of the measurements largely confirmed the theoretical prediction, the actual relations obtained for all species together being: log 10 100 r 2 = 0·0945 (±0·0549) log 10 m +0·2519 and log 10 100 R = 0·0761 (±0·0402) log 10 m + 2·3797 (where r and R are measured in mm and m in kg), similar relations being obtained for each class examined. It is shown that the observed changes in r and R can to a large extent account respectively for the changes in canal sensitivity and the time constant of cupular return which the theory suggests should be called for by changes in animal shape and body mass.

PRESENT STATUS OF DIAGNOSIS AND MANAGEMENT OF MENIERE'S SYNDROME

<h3>PATHOLOGY</h3> Ménière's syndrome, according to recent studies, is due to an acute increase of fluid within the internal ear, particularly within the endolymphatic canal of the inferior part of the internal ear.¹These changes will be called "hydrolabyrinth" to emphasize the similarity to hydrocephalus. As in hydrocephalus, probably more than one mechanism can produce hydrolabyrinth. The source and the chemical nature of the excess fluid is not known. Many investigators believe that the increase of fluid is due to hypersecretion and perhaps delayed resorption of endolymph. I²have advanced the opinion that the fluid escapes from dilated and permeable blood vessels. Hydrolabyrinth may resolve without injury to the internal ear. If the attacks are severe or prolonged, however, two permanent and final changes will eventually result, namely: (1) a fixed dilatation of a smaller or a greater part of the inferior portion of the internal ear, which I³described although

ANATOMY AND PHYSIOLOGY OF THE EAR

This review of the literature dealing 1 with progress made in studies of the anatomic and physiologic relations of the ear does not cover all the available bibliographic material. We have utilized abstracts whenever possible, and translations were made when the articles were of such importance as to warrant the effort. The number of articles reviewed, therefore, is not great, but, in our opinion, is adequate to summarize the present day view. ANATOMIC AND HISTOLOGIC RELATIONS OF THE LABYRINTH Bast 2 introduced the name utriculo-endolymphatic valve to designate a highly cellular connective tissue flap lined by columnar epithelium which guards the utricular opening into the endolymphatic canal. The valve is described as a fold of the posterior wall of the utricle and the endolymphatic canal at the point of junction of the two structures. Serial sections of twenty-five human fetal ears formed the basis for the study. Bast suggested that the position