Randomized testing of taste discrimination in a case of congenital aglossia

AimsIsolated Congenital Aglossia (ICA) is a rare syndrome where an individual is born without a tongue. A few anecdotal reports have identified taste as a sensation experienced by the person with congenital aglossia (PWCA). To date no systematic investigations have been reported. This study aimed to systematically determine gustatory function in a PWCA.MethodsThe current study utilized a randomized, double-blinded, controlled trial that tested the five basic tastes: sweet (sucrose), sour (acetic acid), salty (sodium chloride), bitter (caffeine), and umami (monosodium glutamate, MSG) in a 44 year old female PWCA. Five concentration levels (three for salty) were tested in triplicate for each stimulus. A nose clip was used to exclude contribution by olfactory detection. Contingency tables were constructed to determine relationships between identification accuracy and stimulus or concentration level.ResultsThe sweet (17.1 g/L), salty (0.58 g/L), and bitter (0.02 g/L) stimuli were detected at comparable concentrations to those reported in non-randomized trials, while sour (0.02 g/L) was detected at a lower concentration. The most common substitution was salty for umami (n = 7). Identification accuracy was significantly associated with taste stimuli χ2 = 12.634, p = 0.013. Concentration level was significantly associated with identification accuracy only for salty, χ2 = 9.000, p = 0.011.ConclusionThis study has demonstrated the perception of different tastes in a PWCA. This is the first known report of umami being identified as a unique taste in a PWCA. Variations in threshold taste concentrations compared to normal individuals indicate certain gustatory dysfunction.