Dan Bagger-Sjöbäck

EFFECTS OF USING COMBINED TRANSPETROSAL SURGICAL APPROACHES TO TREAT PETROCLIVAL MENINGIOMAS

OBJECTIVESurgical treatment may be required for large petroclival meningiomas; however, surgery for these lesions is a major undertaking, and modern surgical approaches are still associated with considerable morbidity and recurrence rates. We analyzed our series of transpetrosally operated petroclival meningiomas to obtain detailed information regarding the surgery outcomes with respect to facial nerve effects, hearing changes, general neurological and psychosocial differences, and recurrence rates to identify opportunities for improvement. METHODSBetween 1994 and 2004, we used transpetrosal approaches to operate on 29 patients for petroclival meningiomas larger than 30 mm. All patients were analyzed in detail regarding neurological outcomes and hearing abilities after surgery. Swedish-speaking patients were contacted for a psychosocial follow-up evaluation using the short-item 36 (SF-36) form. ResultsAfter surgery, the Glasgow Outcome Score improved in 14 patients, was unchanged in 11 patients, and worsened in four patients. Facial nerve function was found to be of House-Brackmann Grade 3 or worse in six patients (including three individuals with transcochlear surgery and facial nerve rerouting). Of the 23 patients who underwent hearing-preservation surgery, serviceable hearing was preserved in 17 individuals. Nineteen Swedish patients were contacted for psychosocial evaluation. Three patients could not participate for health reasons; of the remaining 16 patients, 12 reported physical health scores that were below mean values for the general population. For patients who did not experience very serious neurological compromise, we found that unexpected painful trigeminal neuropathy and unilateral swallowing difficulties conveyed a negative influence on health. Three years after surgery, the patients reported more normalized health scores. CONCLUSIONGenerally, outcomes compared well with current reports. Outcomes can be improved, however by improving patients psychosocial support; striving to decompress, preserve, and minimize dissection of ill-defined planes of cranial nerves; and using Simpson Grade 4 gamma knife approaches when radicality is precluded. Currently, the performance of transpetrosal surgery for petroclival meningiomas is a major undertaking that significantly affects a patients health for several years; however, the approaches that we used allowed a high degree of tumor control with relatively little neurological morbidity.

Degradation of the Homogeneous Substance in the Endolymphatic Sac

The accumulation and degradation of a homogeneous precipitate in the lumen of the endolymphatic sac (ES) was studied in mice. Filling of the endolymphatic sac was induced by surgical labyrinthectomy and the sacs were studied 1-8 weeks postoperatively. The initial phase (1-2 weeks postlabyrinthectomy) was characterized by filling of the ES with the homogeneous precipitate. The number of freely floating cells in the lumen was increased after two weeks. Three weeks postoperatively the ES lumen was generally clear, with apparently no stainable material. Ultrastructural analysis of the ES showed that this clearance of the endolymphatic space resulted from degradational activity in the epithelial cells initiated in the proximal portion of the sac. Breakdown of the homogeneous substance seemed to result from cellular ingestion with concomitant lysosomal digestion. Four weeks postoperatively cell clusters were observed subepithelially and were filled with densely staining precipitate, indicating that these cells or macrophages were involved in the turnover of the homogeneous substance in the ES. The functional significance of a degradational system of this substance in the ES is discussed.

Cochlear hair cell loss in single-dose versus continuous round window administration of gentamicin

Conclusions Gentamicin-induced cochlear hair cell loss depends on local middle ear administration kinetics and the total drug dose. Single-dose gentamicin instillation in the middle ear is associated with a high variation in hair cell loss. Objective To compare the effects of single-dose and continuous round window administration of gentamicin on cochlear hair cell loss in a guinea pig model. Material and methods Two methods for drug administration to the inner ear were used. In groups of five animals, a total dose of 0.8 or 3.2 mg of gentamicin was either instilled as a single dose directly into the round window niche or administered continuously over a 1-week period using a pump–catheter system. Continuous administration was achieved by means of a posterior tympanotomy and subcutaneous placement of an osmotic pump fitted with a catheter. The tip of the catheter was fixed in the round window niche. One group of five animals served as controls and received a saline infusion. The animals were sacrificed after 1 week and hair cell loss was determined microscopically after dissection and phalloidin labelling of the basilar membrane and organ of Corti. Results Quantitation of cochlear hair cell loss revealed a dose-dependent effect of gentamicin. With both treatment modalities the higher dose induced a higher percentage of hair cell loss. There was inner and outer hair cell loss in all four groups that received gentamicin. With the single-dose instillation, hair cell loss was distributed irregularly from the round window membrane towards the cochlear apex, whereas continuous administration induced hair cell loss close to the round window membrane. Single-dose instillation induced greater hair cell loss than continuous administration at the same dose. The inter-individual variation in hair cell loss was highest following single-dose instillation.

Human endolymphatic sac: possible mechanisms of pressure regulation.

The ultrastructure of the normal human endolymphatic sac (ES) has been observed by transmission electron microscopy (TEM). The role of the epithelium, the various regions of the subepithelial space and the general anatomy of the ES in pressure regulation were morphologically studied to generate testable hypotheses of human ES function. Light microscopic (LM) and TEM evidence of pressure regulatory mechanisms by endolymph resorption, mechanical factors, and secretory activity are presented. These mechanisms may be useful in designing experimental studies of the ES, and in interpretation of retrospective LM and TEM studies of patients with Menières disease.

Selected pathological findings in the human cochlea.

Out of a material of 45 patients with known audiograms where the inner ears had been fixed with an aldehyde within 7 h after death, 4 cases were chosen for detailed morphological examination. The general findings in the ageing human cochlea are presented as well as the findings in the 4 specific cases.

Effects of ototoxic diuretics (loop diuretics) on the endolymphatic sac

The acute and chronic effects of treatment with ethacrynic acid (EA) and furosemide (FU) on the structure of the murine endolymphatic sac were studied by means of light and transmission electron microscopy. The animals were treated with loop diuretics in doses which are known to cause morphological alterations of the stria vascularis and a significant reduction of the endocochlear potential. A single intravenous injection of either EA or FU resulted in immediate morphological changes such as an increase in cytoplasmic contents of endoplasmic reticulum and more prominent Golgi structures of the light cells. These cells developed membrane-bound granules and a smooth tubular network in the apical cytoplasm. These findings together with the appearance of a precipitate on the luminal aspect of the cell membrane suggested secretory activity. Ten days after daily intraperitoneal injections with loop diuretics in subtoxic doses, the epithelial cytoarchitecture of the endolymphatic sac was altered, with pronounced veiling of the light cells by the dark cells. It is concluded that the changes in the endolymphatic sac epithelium after treatment with ototoxic diuretics may not be a result of a primary toxic effect on the sac per se, but rather be secondary to alterations in fluid and ion homeostasis in the rest of the inner ear.

Cytochemical Identification of Secreted Carbohydrates in the Endolymphatic Sac

Carbohydrate complexes were investigated in the murine endolymphatic sac by means of histochemical techniques in normal untreated animals as well as after ethacrynic acid treatment. The light epithelial cells were classified into three different types: normal, granular and vacuolar. The granular and vacuolar cells were believed to secrete glycoproteins and/or proteoglycans, the presence of which was closely correlated with the component of the precipitate in the lumen of the endolymphatic sac. This finding suggested that the light cells not only absorb endolymph but may also be involved with secretory activity. Such a dual modality in function may have several important implications, since it suggests that the endolymphatic sac has both absorptive and secretory functions.

Uptake of radioactive sulphur in the endolymphatic sac. An autoradiographic study.

Autoradiographic uptake of labelled sulphur (S35) in the endolymphatic sac was analysed after performing surgical labyrinthectomy and after systemic administration of glycerol and ethacrynic acid. Accumulation of radioactive substance was observed after surgical labyrinthectomy and associated with a deposition of stainable substance in the endolymphatic sac lumen. Increased activity was noted in the epithelial layer after administration of ethacrynic acid, whereas glycerol did not increase radioactivity in the endolymphatic sac despite the deposition of stainable substance therein. This fact was believed to depend on a too short time interval between the injection and the sacrifice of the animals, as well as a weaker concentration of the sulphated compound within the endolymphatic sac. The results suggest that the endolymphatic sac may secrete sulphur-containing substances presumably associated with a deposition of a stainable substance in the endolymphatic sac.

Freeze-fracture study of the vestibular hair cell surface during development

SummaryThe ciliary arrangement and external surface of the vestibular receptor cell were studied in their immature stages. In the first stages, immature stereocilia are similar to the microvilli of the adjacent supporting cells. Later, when the cilia grow, a geometric arrangement of the stereocilia occurs, while the peripheral microvilli disappear. The size of the hair cell apex increases. The biggest and more bulbous cells correspond to type I hair cells, but in the newborn cat it is difficult to distinguish accurately type II flat hair cells from immature hair cells.

Ultrastructural Localization of Carbonic Anhydrase and Its Possible Role in the Endolymphatic Sac

Carbonic anhydrase was detected histochemically in the guinea pig endolymphatic sac. The enzyme reaction was positive in both light and dark epithelial cells. In the former, the reaction product was found in the cytoplasm, especially around the intracytoplasmic vesicles and vacuoles. Reaction product was found in the basolateral infoldings as well. The dark epithelial cells also displayed carbonic anhydrase activity in the cytoplasm as well as in the lysosome-like bodies. It is suggested that this enzyme may be involved in (1) ionic or fluid regulation of the endolymph, (2) otoconia metabolism, and (3) phagocytotic activities.