Fungus Ball of the Maxillary Sinus-Modern Treatment by Osteoplastic Approach and Functional Endoscopic Sinus Surgery.

PURPOSE: Functional endoscopic sinus surgery (FESS) is considered standard surgical therapy for fungus ball of the maxillary sinus. However, recent findings have indicated an odontogenic etiology, which requires simultaneous treatment of the dental origin. This study presents the authors' treatment results of fungus ball of the maxillary sinus using a combination of FESS and an endoscopically assisted osteoplastic approach through the anterior wall of the maxillary sinus, enabling simultaneous treatment of the dental origin. MATERIALS AND METHODS: A cohort of 22 patients with histopathologically confirmed fungus ball of the maxillary sinus was retrospectively analyzed. Clinical records and medical imaging data were reviewed to evaluate the etiology, clinical and radiologic findings, and postoperative outcome. RESULTS: Only 15 patients presented nonspecific clinical symptoms compatible with chronic unilateral maxillary sinusitis. Computed tomography visualized complete opacity of the maxillary sinus in 11 patients and intralesional hyperdensity in 12 patients. An odontogenic association was verified in 18 patients. Twenty-one patients underwent endoscopically assisted osteoplastic surgery through the anterior maxillary sinus wall. In 12 cases, the assumed persistent odontogenic source was treated simultaneously. Depending on the patency of the ostiomeatal complex, the accompanying chronic sinusitis was treated by FESS. CONCLUSIONS: The present data support the assumption of an odontogenic etiology of fungus ball of the maxillary sinus. Hence, surgical management requires simultaneous treatment of the fungal mass, the odontogenic origin of the disease, and the accompanying chronic sinusitis. To properly treat fungus ball, the authors present a modern treatment concept, using a minimally invasive endoscopically assisted osteoplastic approach through the anterior maxillary wall, for sufficient and necessary surgical treatment.

Estrogen and Progesterone hormone receptor expression in oral cavity cancer

BACKGROUND: Recent studies have shown an increase in the incidence of oral squamous cell carcinoma (OSCC) in younger patients. The hypothesis that tumors could be hormonally induced during pregnancy or in young female patients without the well-known risk factors alcohol or tobacco abuse seems to be plausible. MATERIAL AND METHODS: Estrogen Receptor alpha (ERá) and Progesterone Receptor (PR) expression were analyzed in normal oral mucosa (n =5), oral precursor lesions (simple hyperplasia, n = 11; squamous intraepithelial neoplasia, SIN I-III, n = 35), and OSCC specimen. OSCCs were stratified in a young female (n = 7) study cohort and older patients (n = 46). In the young female study cohort three patients (n = 3/7) developed OSCC during or shortly after pregnancy. Breast cancer tissues were used as positive control for ERá and PR expression. RESULTS: ERá expression was found in four oral precursor lesions (squamous intraepithelial neoplasia, SIN I-III, n = 4/35, 11%) and in five OSCC specimen (n = 5/46, 11%). The five ERá positive OSCC samples were older male patients. All patients within the young female study cohort were negatively stained for both ERá and PR. CONCLUSIONS: ER expression could be regarded as a seldom risk factor for OSCC. PR expression seems to be not relevant for the development of OSCC

Standardized pretreatment inflammatory laboratory markers and calculated ratios in patients with oral squamous cell carcinoma.

Analyzing the inflammatory microenvironment has become an important issue in the management of oral squamous cell carcinoma (OSCC). Pretreatment C-reactive protein (CRP) levels, leucocytes, monocytes, lymphocytes, neutrophils, basophils, eosinophils, platelets, neutrophil-to-lymphocyte ratio (NLR), derived NLR (dNLR), lymphocyte-to-monocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR) derived from the peripheral blood were analyzed. Receiver operating characteristic (ROC) curves determined a cut-off value for each parameter in 146 patients with OSCC compared with 93 controls and the results were associated with clinicopathological characteristics. CRP expression of tumors was measured by immunohistochemistry. ROC analysis determined cut-off values for CRP levels, leucocytes, monocytes, lymphocytes, neutrophils, NLR, dNLR, LMR, PLR and showed significant differences between the OSCC and control group. Compared with single laboratory tests calculated ratios were superior in measuring sensitivity and specificity of OSCC disease. NLR was significant directly associated and correlated with PLR. LMR was significant inversely associated and correlated with NLR and PLR. Immunohistochemical analysis did not show CRP expression of OSCCs. This study highlights the first analysis for cut-off values of pretreatment single laboratory tests and calculated ratios, which are strongly needed for a follow-up of cancer patients. Additionally, the calculated baselines can be used as a goal for successful immunotherapies in the future. The links between NLR, LMR, and PLR might be helpful for the clinical course (monitoring) of cancer patients and have been first described for OSCC in this study. Taken together, analyzing these data provides an additional practical guideline of further postoperative OSCC management.

Monitoring carcinogenesis in a case of oral squamous cell carcinoma using a panel of new metabolic blood biomarkers as liquid biopsies.

INTRODUCTION: One of the common malignant tumors of the head and neck worldwide with generally unfavorable prognosis is squamous cell carcinoma (OSCC) of the oral cavity. Early detection of primary, secondary, or recurrent OSCC by liquid biopsy tools is much needed. CASE PRESENTATION: Twelve blood biomarkers were used for monitoring a case of OSCC suffering from precancerous oral lichen ruber planus mucosae (OLP). After curative R0 tumor resection of primary OSCC (buccal mucosa), elevated epitope detection in monocytes (EDIM)-Apo10, EDIM-transketolase-like-1 (TKTL1), squamous cell carcinoma antigen (SCC-Ag), total serum lactate dehydrogenase (LDH), and its anaerobic isoforms (LDH-4, LDH-5) decreased to normal levels. Three and six months after surgery, transformation of suspicious mucosal lesions has been accompanied with an increase of EDIM scores, total serum LDH values, and a metabolic shift from aerobic (decrease of LDH-1, LDH-2) to anaerobic (increase of LDH-4, LDH-5) conditions. Two months later, secondary OSCC was histopathologically analyzed after tissue biopsy. Cytokeratin fraction 21-1 (CYFRA 21-1), carcinoembryonic antigen (CEA), and carbohydrate antigen 19-9 (CA19-9) were not affected during the clinical course of carcinogenesis. CONCLUSIONS: A combination strategy using a standardized panel of established (metabolic) blood biomarkers (TKTL1, LDH, LDH isoenzymes) is worth and can be recommended among others (apoptosis resistance-related Apo10, SCC-Ag) for early detection and diagnosis of primary, secondary, and recurrent OSCC. A tandem strategy utilizing (metabolic pronounced) routine liquid biopsies with imaging techniques may enhance diagnosis of OSCC in the future. Although we demonstrated the diagnostic utility of separated liquid biopsies in our previous study cohorts, further investigations in a larger patient cohort are necessary to recommend this combination strategy (EDIM blood test, LDH value, metabolic shift of LDH isoenzymes, and others, e.g., SCC-Ag or immunophenotyping) as a diagnostic tool for the addition to the OSCC staging system and as a routine procedure in the aftercare.

HPV Involvement in Head and Neck Cancers: Comprehensive Assessment of Biomarkers in 3680 Patients.

BACKGROUND: We conducted a large international study to estimate fractions of head and neck cancers (HNCs) attributable to human papillomavirus (HPV-AFs) using six HPV-related biomarkers of viral detection, transcription, and cellular transformation. METHODS: Formalin-fixed, paraffin-embedded cancer tissues of the oral cavity (OC), pharynx, and larynx were collected from pathology archives in 29 countries. All samples were subject to histopathological evaluation, DNA quality control, and HPV-DNA detection. Samples containing HPV-DNA were further subject to HPV E6*I mRNA detection and to p16(INK4a), pRb, p53, and Cyclin D1 immunohistochemistry. Final estimates of HPV-AFs were based on HPV-DNA, HPV E6*I mRNA, and/or p16(INK4a) results. RESULTS: A total of 3680 samples yielded valid results: 1374 pharyngeal, 1264 OC, and 1042 laryngeal cancers. HPV-AF estimates based on positivity for HPV-DNA, and for either HPV E6*I mRNA or p16(INK4a), were 22.4%, 4.4%, and 3.5% for cancers of the oropharynx, OC, and larynx, respectively, and 18.5%, 3.0%, and 1.5% when requiring simultaneous positivity for all three markers. HPV16 was largely the most common type. Estimates of HPV-AF in the oropharynx were highest in South America, Central and Eastern Europe, and Northern Europe, and lowest in Southern Europe. Women showed higher HPV-AFs than men for cancers of the oropharynx in Europe and for the larynx in Central-South America. CONCLUSIONS: HPV contribution to HNCs is substantial but highly heterogeneous by cancer site, region, and sex. This study, the largest exploring HPV attribution in HNCs, confirms the important role of HPVs in oropharyngeal cancer and drastically downplays the previously reported involvement of HPVs in the other HNCs.

Immunophenotyping of patients with oral squamous cell carcinoma in peripheral blood and associated tumor tissue.

The immune system is important for elimination of cancer cells. Tumors including oral squamous cell carcinoma (OSCC) are capable of escaping detection by host immune cells through apoptotic depletion of tumor-infiltrating lymphocytes (TILs). Circulating peripheral blood lymphocytes (PBLs) and corresponding TILs of tumor specimen were evaluated before and after curative tumor resection (n = 30) compared with PBLs of controls (n = 87). PBLs were characterized for the total number of T cells (CD3(+)), T helper cells (Th, CD3(+)/CD4(+)), regulatory T cells (Treg, CD4(+)/CD25(+)/CD127(low)), cytotoxic T cells (Tc, CD3(+)/CD8(+)), activated T cells (CD3(+)/HLA-DR(+)), and natural killer (NK) cells (CD3(-)/CD16(+)/CD56(+)). In tumor tissue, the prevalence of CD3(+), CD4(+), and CD8(+) TILs was assessed using immunohistochemistry, whereas the incidence of apoptosis was assessed using terminal deoxynucleotidyl transferase deoxyuridinetriphosphate nick-end labeling (TUNEL) assay. In PBLs of pretreated OSCC patients, a highly significant decrease in total number of T cells (p = 0.0001), Th cells (p < 0.0001), Treg cells (p < 0.0001), Tc cells (p < 0.0001), and NK cells (p = 0.0037) were found compared with controls. Decreased PBLs of OSCC patients were correlated with decreased numbers of corresponding TILs, which were associated with increased detection of apoptosis in the tumor tissue. Compared with the controls, the total number of T cells remained unchanged after surgery but the total number of NK cells significantly increased. Standardized immunophenotyping of OSCC may help to identify patients likely to benefit from cancer immunotherapy strategies and/or chemoradiation. Finally, future attempts to enhance an effective tumor-reactive immune response by immunotherapy or vaccination should be made by promoting tumor-specific Th and/or Tc cell/NK cell responses.

Glutaminolysis and carcinogenesis of oral squamous cell carcinoma.

Glutaminolysis is a crucial factor for tumor metabolism in the carcinogenesis of several tumors but has not been clarified for oral squamous cell carcinoma (OSCC) yet. Expression of glutaminolysis-related solute carrier family 1, member 5 (SLC1A5)/neutral amino acid transporter (ASCT2), glutaminase (GLS), and glutamate dehydrogenase (GLDH) was analyzed in normal oral mucosa (n = 5), oral precursor lesions (simple hyperplasia, n = 11; squamous intraepithelial neoplasia, SIN I-III, n = 35), and OSCC specimen (n = 42) by immunohistochemistry. SLC1A5/ASCT2 and GLS were significantly overexpressed in the carcinogenesis of OSCC compared with normal tissue, while GLDH was weakly detected. Compared with SIN I-III SLC1A5/ASCT2 and GLS expression were significantly increased in OSCC. GLDH expression did not significantly differ from SIN I-III compared with OSCC. This study shows the first evidence of glutaminolysis-related SLC1A5/ASCT2, GLS, and GLDH expression in OSCC. The very weak GLDH expression indicates that glutamine metabolism is rather related to nucleotide or protein/hexosamine biosynthesis or to the function as an antioxidant (glutathione) than to energy production or generation of lactate through entering the tricarboxylic acid cycle. Overcoming glutaminolysis by targeting c-Myc oncogene (e.g. by natural compounds) and thereby cross-activation of mammalian target of rapamycin complex 1 or SLC1A5/ASCT2, GLS inhibitors may be a useful strategy to sensitize cancer cells to common OSCC cancer therapies.

Evaluation of a biomarker based blood test for monitoring surgical resection of oral squamous cell carcinomas.

INTRODUCTION: The potential use of determination of biomarkers in blood for the monitoring of surgical removal of oral squamous cell carcinomas (OSCC) was evaluated using the epitope detection in monocytes (EDIM) technology. MATERIALS AND METHODS: In tumor specimen, elevated Apo10 and transketolase-like 1 (TKTL1) expression was analyzed by immunohistochemistry. Apo10 and TKTL1 biomarkers have been used prospectively for EDIM blood test in patients with primary and/or recurrent OSCC (n = 92) before surgery and after curative tumor resection (n = 45). RESULTS: There were highly significant (p < 0.0001) correlations found between EDIM blood scores and the tissue expression of both biomarkers measured by immunohistochemistry (Apo10: n = 89/92, 97%; TKTL1: n = 90/92, 98%). EDIMApo10 and EDIM-TKTL1 scores were positive in 92% (EDIM-Apo10: n = 85/92) and 93% (EDIM-TKTL1: n = 86/92), respectively, in patients with OSCC before surgery. The combined score EDIM-Apo10/EDIM-TKTL1 increased significantly the detection rate of tumors to 97% (n = 89/92). After surgery, the EDIM-TKTL1 and EDIMApo10 scores significantly decreased in 75.6 and 86.7% of the patients (p < 0.0001), respectively, in the aftercare. CONCLUSIONS: The correlation of TKTL1 and Apo10 immunohistochemistry with the blood test results indicates that the EDIM blood test could serve as a non-invasive diagnostic tool (liquid biopsy) to assess surgical removal of OSCC by determination of two biomarkers. CLINICAL RELEVANCE: This is the first study that has been demonstrated a reliable and successful monitoring of OSCC cancer patients by a blood test. The specific and significant decrease of EDIM-TKTL1 and EDIM-Apo10 scores after surgery could serve as a new tool for monitoring surgical removal of OSCC.

Serum vitamin D levels of patients with oral squamous cell carcinoma (OSCC) and expression of vitamin D receptor in oral precancerous lesions and OSCC

BACKGROUND: Resistance to programmed cell death (apoptosis) is a crucial factor for the carcinogenesis of oral squamous cell carcinoma (OSCC). Vitamin D (calcitriol) may overcome apoptosis resistance in tumor cells of OSCC. Vitamin D receptor (VDR) expression in oral precancerous lesions of OSCC has not been analyzed and serum vitamin D level seems to be a predictor of cancer development. MATERIAL AND METHODS: Expression of VDR was analyzed in normal oral mucosa (n=5), oral precursor lesions(simple hyperplasia, n=11; squamous intraepithelial neoplasia, SIN I-III, n=35), and OSCC specimen (n=42) by immunohistochemistry (IHC). Moreover, serum vitamin D levels were measured by 25(OH)D3 (calcidiol) in patients with OSCC (n=42) and correlated with IHC results. RESULTS: Expression of VDR was significantly increased in precancerous and OSCC compared with normal tissue. Compared with SIN I-III lesions VDR expression significantly decreased in OSCC. Severe vitamin D deficiency was detected in our OSCC patient cohort but there was no significant correlation analyzed between serum vitamin D levels and corresponding immunohistochemically detected VDR expression in OSCC. CONCLUSIONS: Our survey provides the first evidence of VDR expression in precancerous lesions of OSCC. Apoptosis induction of VDR+ cells in oral precancerous lesions and OSCC by natural vitamin D or synthetic vitamin D compounds could be useful for chemoprevention. Moreover, systemically and/or locally applied, these compounds may act as sensitizers for apoptosis mediated by radio-, and chemotherapy treatment in OSCC

Serum vitamin D levels of patients with oral squamous cell carcinoma (OSCC) and expression of vitamin D receptor in oral precancerous lesions and OSCC.

BACKGROUND: Resistance to programmed cell death (apoptosis) is a crucial factor for the carcinogenesis of oral squamous cell carcinoma (OSCC). Vitamin D (calcitriol) may overcome apoptosis resistance in tumor cells of OSCC. Vitamin D receptor (VDR) expression in oral precancerous lesions of OSCC has not been analyzed and serum vitamin D level seems to be a predictor of cancer development. MATERIAL AND METHODS: Expression of VDR was analyzed in normal oral mucosa (n=5), oral precursor lesions (simple hyperplasia, n=11; squamous intraepithelial neoplasia, SIN I-III, n=35), and OSCC specimen (n=42) by immunohistochemistry (IHC). Moreover, serum vitamin D levels were measured by 25(OH)D3 (calcidiol) in patients with OSCC (n=42) and correlated with IHC results. RESULTS: Expression of VDR was significantly increased in precancerous and OSCC compared with normal tissue. Compared with SIN I-III lesions VDR expression significantly decreased in OSCC. Severe vitamin D deficiency was detected in our OSCC patient cohort but there was no significant correlation analyzed between serum vitamin D levels and corresponding immunohistochemically detected VDR expression in OSCC. CONCLUSIONS: Our survey provides the first evidence of VDR expression in precancerous lesions of OSCC. Apoptosis induction of VDR+ cells in oral precancerous lesions and OSCC by natural vitamin D or synthetic vitamin D compounds could be useful for chemoprevention. Moreover, systemically and/or locally applied, these compounds may act as sensitizers for apoptosis mediated by radio-, and chemotherapy treatment in OSCC.

Apoptosis resistance-related ABCB5 and DNaseX (Apo10) expression in oral carcinogenesis.

BACKGROUND: Apoptosis resistance is a crucial factor for the carcinogenesis of oral squamous cell carcinoma (OSCC). METHODS: Expression of apoptosis resistance-related ATP-binding cassette (ABC) transporter ABCB5 [subfamily B (MDR/TAP) member 5] and DNaseX (Apo10) were analyzed in normal oral mucosa (n = 5), oral precursor lesions (simple hyperplasia, n = 11; squamous intraepithelial neoplasia, SIN I-III, n = 35), and OSCC specimen (n = 42) by immunohistochemistry. RESULTS: Expression of ABCB5 and Apo10 were significantly increased in the carcinogenesis of OSCC compared with normal tissue. Compared with SIN I-III, ABCB5 expression was significantly decreased in OSCC. Apo10 expression did not significantly differ from OSCC compared with SIN I-III. CONCLUSIONS: This study provides the first evidence of the expression of ABCB5 and Apo10 in the multi-step carcinogenesis of OSCC. Overcoming drug resistance of ABCB5+ and Apo10+ cells in precursor lesions and tumors by natural compounds may act as sensitizers for apoptosis or could be useful for chemoprevention.

Association of cancer metabolism-related proteins with oral carcinogenesis - indications for chemoprevention and metabolic sensitizing of oral squamous cell carcinoma?

BACKGROUND: Tumor metabolism is a crucial factor for the carcinogenesis of oral squamous cell carcinoma (OSCC). METHODS: Expression of IGF-R1, glycolysis-related proteins (GLUT-1, HK 2, PFK-1, LDHA, TKTL1), mitochondrial enzymes (SDHA, SDHB, ATP synthase) were analyzed in normal oral mucosa (n = 5), oral precursor lesions (simple hyperplasia, n = 11; squamous intraepithelial neoplasia, SIN I-III, n = 35), and OSCC specimen (n = 42) by immunohistochemistry and real-time polymerase chain reaction (qPCR) analysis in OSCC cell lines. Metabolism-related proteins were correlated with proliferation activity (Ki-67) and apoptotic properties (TUNEL assay) in OSCC. Specificity of antibodies was confirmed by western blotting in cancer cell lines. RESULTS: Expression of IGF-R1, glycolysis-related proteins (GLUT-1, HK 2, LDHA, TKTL1), and mitochondrial enzymes (SDHA, SDHB, ATP synthase) were significantly increased in the carcinogenesis of OSCC. Metabolic active regions of OSCC were strongly correlated with proliferating cancer (Ki-67+) cells without detection of apoptosis (TUNEL assay). CONCLUSIONS: This study provides the first evidence of the expression of IGF-R1, glycolysis-related proteins GLUT-1, HK 2, PFK-1, LDHA, and TKTL1, as well as mitochondrial enzymes SDHA, SDHB, and ATP synthase in the multi-step carcinogenesis of OSCC. Both, hypoxia-related glucose metabolism and mitochondrial oxidative phosphorylation characteristics are associated with the carcinogenesis of OSCC. Acidosis and OXPHOS may drive a metabolic shift towards the pentose phosphate pathway (PPP). Therefore, inhibition of the PPP, glycolysis, and targeted anti-mitochondrial therapies (ROS generation) by natural compounds or synthetic vitamin derivatives may act as sensitizer for apoptosis in cancer cells mediated by adjuvant therapies in OSCC.

A biomarker based detection and characterization of carcinomas exploiting two fundamental biophysical mechanisms in mammalian cells.

BACKGROUND: Biomarkers allowing the characterization of malignancy and therapy response of oral squamous cell carcinomas (OSCC) or other types of carcinomas are still outstanding. The biochemical suicide molecule endonuclease DNaseX (DNaseI-like 1) has been used to identify the Apo10 protein epitope that marks tumor cells with abnormal apoptosis and proliferation. The transketolase-like protein 1 (TKTL1) represents the enzymatic basis for an anaerobic glucose metabolism even in the presence of oxygen (aerobic glycolysis/Warburg effect), which is concomitant with a more malignant phenotype due to invasive growth/metastasis and resistance to radical and apoptosis inducing therapies. METHODS: Expression of Apo10 and TKTL1 was analysed retrospectively in OSCC specimen (n = 161) by immunohistochemistry. Both markers represent independent markers for poor survival. Furthermore Apo10 and TKTL1 have been used prospectively for epitope detection in monocytes (EDIM)-blood test in patients with OSCC (n = 50), breast cancer (n = 48), prostate cancer (n = 115), and blood donors/controls (n = 74). RESULTS: Positive Apo10 and TKTL1 expression were associated with recurrence of the tumor. Multivariate analysis demonstrated Apo10 and TKTL1 expression as an independent prognostic factor for reduced tumor-specific survival. Apo10+/TKTL1+ subgroup showed the worst disease-free survival rate in OSCC.EDIM-Apo10 and EDIM-TKTL1 blood tests allowed a sensitive and specific detection of patients with OSCC, breast cancer and prostate cancer before surgery and in after care. A combined score of Apo10+/TKTL1+ led to a sensitivity of 95.8% and a specificity of 97.3% for the detection of carcinomas independent of the tumor entity. CONCLUSIONS: The combined detection of two independent fundamental biophysical processes by the two biomarkers Apo10 and TKTL1 allows a sensitive and specific detection of neoplasia in a noninvasive and cost-effective way. Further prospective trials are warranted to validate this new concept for the diagnosis of neoplasia and tumor recurrence.

Dexamethasone levels and base-to-apex concentration gradients in the scala tympani perilymph after intracochlear delivery in the guinea pig.

HYPOTHESIS: To determine whether intracochlearly applied dexamethasone will lead to better control of drug levels, higher peak concentrations, and lower base-to-apex concentration gradients in the scala tympani (ST) of the guinea pig than after intratympanic (round window [RW]) application. BACKGROUND: Local application of drugs to the RW results in substantial variation of intracochlear drug levels and significant base-to-apex concentration gradients in ST. METHODS: Two microliters of dexamethasone-phosphate (10 mg/ml) were injected into ST either through the RW membrane, which was covered with 1% sodium hyaluronate gel or through a cochleostomy with a fluid tight seal of the micropipette. Perilymph was sequentially sampled from the apex at a single time point for each animal, at 20, 80, or 200 min after the injection ended. Results were mathematically interpreted by means of an established computer model and compared with previous experiments performed by our group with the same experimental techniques but using intratympanic applications. RESULTS: Single intracochlear injections of 20 minutes resulted in approximately 10 times higher peak concentrations (on average) than 2 to 3 hours of intratympanic application to the RW niche. Intracochlear drug levels were less variable and could be measured for over 220 minutes. Concentration gradients along the scala tympani were less pronounced. The remaining variability in intracochlear drug levels was attributable to perilymph and drug leak from the injection site. CONCLUSION: With significantly higher, less variable drug levels and smaller base-to-apex concentration gradients, intracochlear applications have advantages to intratympanic injections. For further development of this technique, it is of importance to control leaks of perilymph and drug from the injection site and to evaluate its clinical feasibility and associated risks.

Dexamethasone concentration gradients along scala tympani after application to the round window membrane.

HYPOTHESIS: Local application of dexamethasone-21-dihydrogen-phosphate (Dex-P) to the round window (RW) membrane of guinea pigs produces a substantial basal-apical concentration gradient in scala tympani (ST) perilymph. BACKGROUND: In recent years, intratympanically applied glucocorticoids are increasingly being used for the treatment of inner ear disease. Although measurements of intracochlear concentrations after RW application exist, there is limited information on the distribution of these drugs in the inner ear fluids. It has been predicted from computer simulations that substantial concentration gradients will occur after RW application, with lower concentrations expected in apical turns. Concentration gradients of other substances along the cochlea have recently been confirmed using a sequential apical sampling method to obtain perilymph. METHODS: Dexamethasone-21-dihydrogen-phosphate (10 mg/ml) was administered to the RW membrane of guinea pigs (n = 9) in vivo for 2 to 3 hours. Perilymph was then collected using a protocol in which 10 samples, each of approximately 1 mul, were taken sequentially from the cochlear apex into capillary tubes. Dexamethasone-21-dihydrogen-phosphate concentration of the samples was analyzed by high-performance liquid chromatography. Interpretation of sample data using a finite element model allowed the longitudinal gradients of Dex-P in ST to be quantified. RESULTS: The Dex-P content of the first sample in each experiment (dominated by perilymph from apical regions) was substantially lower than that of the third and fourth sample (dominated by basal turn perilymph). These findings qualitatively demonstrated the existence of a concentration gradient along ST. After detailed analysis of the measured sample concentrations using an established finite element computer model, the mean basal-apical concentration gradient was estimated to be 17,000. Both absolute concentrations of Dex-P in ST and the basal-apical gradients were found to vary substantially. CONCLUSION: The existence of substantial basal-apical concentration gradients of Dex-P in ST perilymph were demonstrated experimentally. If the variability in peak concentration and gradient is also present under clinical conditions, this may contribute to the heterogeneity of outcome that is observed after intratympanic application of glucocorticoids for various inner ear diseases.