A Randomized Controlled HD-tDCS Trial: Effects on Tinnitus Severity and Cognition

The Tinnitus Functional Index (TFI) is a self-reported questionnaire, consisting of 25 questions, assessing the impact of tinnitus on patients' daily lives. The patient answers each question on a Likert scale ranging from 0 to 10. Questions 1 and 3 are expressed in percentages, and the Likert scale ranges from 0% to 100% (they are transformed to a 0-10 scale). The total score is then calculated as the mean of all questions multiplied by 10 to express this as a number between 0 and 100. In addition to the total score, the score of eight subscales can be determined. The subscales are the following: intrusiveness, reduced sense of control, cognitive interference, sleep disturbance, auditory difficulties attributed to tinnitus, interference with relaxation, reduced quality of life and emotional distress. A decrease of 13 points on the scale is considered as a clinical relevant difference.

The Dutch validated version of the TQ is used to differentiate between emotional and cognitive distress, auditory difficulties, and self-experienced intrusiveness caused by the tinnitus. The total score can range from 0 to 84, assigning a subject to a distress category: slight (score = 0 - 30, grade 1), moderate (score = 31 - 46, grade 2), severe (score = 47 - 59, grade 3) and very severe (score = 60 - 84, grade 4).

The SSQ12 is a short form of the Speech, Spatial and Qualities of Hearing scale. It is developed for use in clinical research and rehabilitation settings to measure a range of hearing disabilities across several domains such as speech in noise, speech in quiet, localization, distance and movement, segregation and listening effort. Responders rate their ability to do or experience the situation described in each question by marking a 1-10 scale (1 = not at all, 10 = perfectly). Scores of all 12 questions are averaged to obtain a global SSQ-12 score.

To detect states of depression and anxiety the Hospital Anxiety and Depression Scale (HADS) is used. This self-assessment questionnaire consists of seven items in the subscale 'depression' and seven items in the subscale 'anxiety' and distinguishes clearly between both emotional disorders. The HADS serves as a screening tool for depression and anxiety. Scores of 7 or less on each subscale indicate non-cases. Scores of 8-10 are borderline abnormal (borderline case), while scores of 11-21 are abnormal (case).

The patient scores the mean and maximum loudness of their tinnitus on a scale of 0 (absence of tinnitus) to 10 (as loud as possible, cannot be any louder).

The HQ is a 14-item questionnaire that surveys a patient's hypersensitivity to sound. The 14 questions assess three dimensions (attentional, social, and emotional). The answer categories are: "no" (score of 0 points), "yes, a little" (1 point), "yes, quite a lot" (2 points), and "yes, a lot" (3 points). A total score of 28 or more indicates clinically significant hyperacusis.

The Health Utilities Index (HUI) is a family of generic health profiles and preference-based systems for the purposes of measuring health status, reporting health-related quality-of-life (QOL), and producing utility scores. The HUI comprises a 15-item questionnaire. The resulting total health-related QOL score ranges from 0.00 (dead) to 1.00 (perfect health).

The BFI2 comprises 60 statements to which subjects can assign a score ranging from 1 ('Disagree strongly') to 5 ('Agree strongly'). Each question belongs to one of the following 'Big Five' personality domains: Extraversion, Agreeableness, Conscientiousness, Negative Emotionality, and Open-Mindedness. For each domain, scores can vary from 12 to 60.