Perilymphatic fistula: analysis of free amino acids in middle ear microaspirates.

High-performance liquid chromatography was used to determine 19 free amino acid concentrations in perilymph, serum/plasma, and red blood cell intracellular fluid. Significant differences were found between perilymph and these fluids. Free amino acid analysis was then used to quantitatively analyze middle ear microaspirates in order to test the hypothesis that perilymph is a potential source of clear fluid in perilymphatic fistulas (PLF). Fourteen unknown samples from patients with visually identified PLF, including patients with no identifiable otic capsule defect, were studied. Six samples on amino acid pattern analysis were correlated most similarly with perilymph (rrho greater than 0.95). Four of these six samples were scored on the basis of quantitative amino acid values as similar to perilymph. However, three samples of clear fluid were more similar to serum/plasma than to perilymph on both amino acid pattern and quantitative amino acid score analysis. These results objectively suggest perilymph as a potential source of clear fluid in some patients with a diagnosis of PLF. Not all clear fluid observed in the middle ear, however, is potentially perilymph.