Tinnitus is the subjective perception of sound without the presence of a corresponding external or internal sound source. Most tinnitus cases are related to hearing impairment but nearly 25% of all patients with tinnitus have normal hearing thresholds (Langguth et al., 2019). There are two types of tinnitus, idiopathic or primary and secondary, with idiopathic tinnitus being by far the most frequent form (Tunkel et al., 2014). Idiopathic tinnitus is in most cases associated with sensorineural hearing loss and it is well-established that tinnitus often accompanies noise-induced hearing loss and presbycusis (Haider et al., 2018). Secondary tinnitus is caused by a specific underlying cause or an identifiable organic condition, which can be either an auditory disorder, such as cerumen impaction of the external auditory canal, middle ear disease, and various cochlear and auditory nerve abnormalities, or a nonauditory disorder, such as myoclonus, vascular anomalies, and intracranial hypertension.

Usually, the patients can cope well with their tinnitus, but nearly 10% experience bothersome tinnitus (Axelsson and Ringdahl, 1989) that can be accompanied by anxiety, depression, insomnia, stress, and emotional disturbance. Tinnitus prevalence ranges from 5.1% to 42.7% according to various reports and the prevalence of bothersome tinnitus ranges from 3.0% to 30.9% (McCormack et al., 2016). Its increasing frequency among the general population has become a major daily concern for all otolaryngologists.

The lack of knowledge about the precise pathophysiological mechanism of idiopathic tinnitus limits our ability to offer an effective treatment. Various therapeutic methods have been implemented on patients with tinnitus over time including educational counselling, medications, tinnitus retraining therapy, sound masking, biofeedback therapy, acupuncture, intra-tympanic injections and various other therapies with specific devices (Langguth et al., 2019)). However, a review of medical literature indicates that results are contradictory for most of the aforementioned therapies with the inevitable consequence that most patients cannot have their condition treated effectively (Tang D et al., 2019).

In recent years, a food supplement trading as MemoVigor 2 was introduced in the Greek market for the treatment of tinnitus. This medication is also in use at several European countries and contains a combination of therapeutic ingredients, including various vitamins, acetyl-L-carnitine, Ginkgo biloba (G. biloba) and Bilberry plant extracts, trace minerals and phospholipids. Most of them have antioxidant activity and have been previously used for the treatment of tinnitus, and also for the treatment of various peripheral and central vestibular syndromes, as well as for lesions of the acoustic and the facial nerve.

There are a few recent studies in which compounds of antioxidants have been also used for the treatment of idiopathic tinnitus. Petridou et al. (Petridou et al., 2019) treated 70 patients with idiopathic tinnitus, with a multivitamin-multimineral supplement including various vitamins, phytochemicals, minerals and a-lipoic acid, in a randomized, double-blind, placebo-controlled clinical trial. The authors found tinnitus improvement in the antioxidant group in the tinnitus questionnaires and the specific measures of tinnitus perception used and concluded that antioxidant therapy seems to reduce the subjective discomfort and tinnitus intensity in tinnitus patients. More recently, Knäpper et al. (Knäpper et al., 2023) studied the effectiveness of Tinnitan Duo^®, a food supplement containing G. biloba, 5-hydroxytryptophan, magnesium, melatonin, vitamins B5 and B6, and zinc at improving tinnitus. The authors studied 29 patients who completed the study from a total of 61 patients and found that the food supplement was associated a significant improvement in tinnitus according to THI and tinnitus loudness measurements. The main limitations of this study were the small sample and the absence of a placebo group.

The objective of the present study was to evaluate the effectiveness of the MemoVigor 2 food supplement in the treatment of recent-onset idiopathic tinnitus.

This was a prospective single-centre randomized, double-blind, placebo-controlled clinical trial reviewed and approved by the Institutional Review Board of Tzaneio General Hospital of Piraeus (Ref.14549-49-05/12/2019). The research was conducted in accordance with the principles of the Helsinki Declaration of 1975 as revised in 2013 and was registered with ISRCTN (reference: ISRCTN16025480). The clinical trial of this study followed the guidelines of CONSORT (Figure 1).

The primary outcome measure was tinnitus change measured using the Tinnitus Handicap Inventory questionnaire (THI) at baseline and post-3-month. The secondary outcome measures were tinnitus severity measured using Mini Tinnitus Questionnaire (Mini-TQ) at baseline and post-3-month and tinnitometry findings including tinnitus pitch matching, tinnitus loudness matching, tinnitus minimum masking level (MML) and residual inhibition (RI) of tinnitus measured at baseline and post-3-month. Also, tinnitus perception change was estimated from the patients at the end of the study using the Patients’ Global Impression of Change (PGIC). Additionally, evaluation of hearing was also performed using audiometry at baseline and post-3-month.

Two hundred and seventy-four patients were enrolled in the study. Twelve patients did not fulfil the inclusion criteria and 22 patients refused to participate. Out of the 240 remaining patients, 120 were allocated to the intervention group and received MemoVigor 2 and 120 patients were allocated to the placebo group. Patients were recruited in one investigational centre from December 2019 to March 2023. All subjects were white/caucasian. Fourteen patients from the intervention group and 17 patients from the placebo group missed to follow-up mainly owed to hospital avoidance because of the Covid pandemic and were excluded from further study. Also, 2 and 3 patients from the two groups respectively discontinued intervention for reasons irrelevant to the study. Accordingly, 104 patients from the intervention group and 100 patients from the placebo group were available for our research (Figure 1). Patient compliance was good. The average missed tablets in the intervention group were three and in the placebo group were four. No adverse reactions were mentioned in either of the two groups.

Both treatment groups were similar concerning demographics and baseline characteristics presented in Table 2. The mean age was 57.7 years (SD = 11.7) for the intervention group and 56.3 years (SD = 11.5) for the placebo group. Hearing loss, history of noise exposure, tinnitus laterality, continuity, stability, description and severity were similar in the intervention and the placebo group. In 10 patients from the intervention group and 12 patients of the placebo group MRI of the internal auditory canal/cerebellopontine angle was performed with negative results.

Our randomized, double-blind, placebo-controlled, prospective study was carefully designed to assess the effect of the use of MemoVigor 2, a food supplement that combines several therapeutic ingredients, in a group of patients with idiopathic tinnitus divided into an intervention group and a placebo group. To evaluate changes in tinnitus we used audiometric measures, specific measures of tinnitus perception and tinnitus questionnaires. Audiometric results were similar in the two groups, both in the initial testing session and in the post-3-month session, probably because of the short time that elapsed between the two measurements. We found that all tinnitus measures, including tinnitus pitch, loudness at tinnitus pitch, loudness at 1 kHz, MML and RI, improved significantly in the intervention group. Most of these measures improved in the placebo group too, but to a lesser degree. MML and RI improved only in the intervention group and not in the placebo group. To evaluate tinnitus-related discomfort we used two tinnitus questionnaires, the widely used THI which measures the impact of tinnitus on patient’s quality of life, and the Mini-TQ, a reliable tool for rapid and reliable assessment of subjective tinnitus distress. Both questionnaire scores diminished significantly in both groups, but the degree of decrease was greater in the intervention group. Finally, the participants reported the tinnitus outcome after treatment using the PGIC score which differed significantly between the two groups, with greater improvement observed in the intervention group.

We selected patients with subjective tinnitus of recent onset ≤12 months. According to the Clinical Practice Guideline for Tinnitus of the American Academy of Otolaryngology-Head and Neck Surgery (Tunkel et al., 2014), the period to distinguish between recent onset and persistent tinnitus is 6 months. However, we studied patients with tinnitus duration up to 12 months, to minimize the phenomenon of spontaneous improvement or resolution that is common in sufferers within the first 6 months of the disease, so that we could evaluate if there is a certain therapeutic value of the food supplement studied. Additionally, research data exist (Carpenter-Thompson et al., 2015) that there are functional differences in neural correlates of tinnitus in adults, based on the amount of time for which they have experienced tinnitus. Patients with tinnitus lasting less than 1 year associate posterior cingulate and insula with emotional reaction to tinnitus, whereas patients having tinnitus longer than 1 year recruit more frontal regions of the brain to better control their emotional response. We did not study patients with persistent tinnitus over 1 year, because many psychological aspects interfere and some studies suggest that tinnitus may worsen depression, generalized anxiety, and the quality of life, while others have found that tinnitus improves over time spontaneously and there appears to be habituation in a sizeable percentage of patients over a prolonged period (Phillips et al., 2018; Han et al., 2021). Accordingly, the therapeutic value of MemoVigor 2 might be not quite clear, since various psychological and social aspects of tinnitus can severely affect the patients.

To evaluate a possible effect of spontaneous remission of tinnitus in our subjects we divided the intervention and the control group into two subgroups, with tinnitus duration 0-6 months and 7-12 months, and compared their results. In the intervention group, THI and Mini-TQ scores were marginally lower in the first group, implying a possible effect of spontaneous improvement during the first 6 months to several patients. In the two subgroups of the placebo-treated subjects, mean values were somewhat lower in the first group but did not reach statistical significance. We found similar results in the evaluation of the PGIC score. Accordingly, the role of tinnitus spontaneous remission in our subjects is not quite clear but is probably small. We can also hypothesize that MemoVigor 2 is more effective if administered during the first months of the disease, since later various psychological factors could interfere negatively.

In the diagnostic evaluation of tinnitus, we used both specific measures of tinnitus perception, such as tinnitus pitch and loudness, and questionnaires, since the overall impact of tinnitus is not only influenced by the characteristics of the tinnitus but also by the psychological reactions of each tinnitus sufferer. Both sets of testing are necessary and complementary because the perceptual aspects of tinnitus do not always explain the subjectively perceived severity of the symptom (Langguth et al., 2019). Tinnitus questionnaires are appropriate tools for evaluating the patient’s reaction to tinnitus. We selected the THI and the Mini-TQ because both are standardized, reliable and have been widely used, having also validated versions in the Greek language (Panagiotopoulos et al., 2015; Papitsi et al., 2020).

Among several treatment modalities which have been implemented in patients with tinnitus, pharmacotherapy has a prominent place. It seems that tinnitus can be pharmacologically assessed and treated as evidenced by the transient dose-dependent reduction of tinnitus in up to 70% of patients after intravenous application of lidocaine (Israel et al., 1982; Kleinjung and Langguth, 2021). Unfortunately, lidocaine is only effective when applied intravenously and its effect is short-lasting. Although there are no specific pharmacological compounds that have been approved for the treatment of chronic tinnitus, a large variety of drugs approved for other indications have been investigated for the treatment of tinnitus, mostly with little evidence of greater benefit than harm. These drugs include various antianxiety, anaesthetics, antiarrhythmics, anticonvulsants, antidepressants, prostaglandins, antihistamines, muscle relaxants, calcium channel blockers, diuretics, glutamate receptor antagonists, melatonin, and others (Kim et al., 2021).

The main reason that a drug for the treatment of tinnitus is not effective in all patients is that tinnitus itself cannot be considered as a disease but rather as a symptom. Tinnitus is a heterogeneous and complex condition with multiple associated biological, psychological and contextual contributors, which are difficult to diagnose and treat (Procházková et al., 2018; Trochidis et al., 2021). The aetiology might be otological, neurological, cardiovascular, endocrinological, metabolic, musculoskeletal or mental and the pharmacological therapeutic approach should take the suspected possible cause in each case into consideration. The use of a food supplement such as MemoVigor 2 which contains a combination of therapeutic substances has the advantage that it may be successful in several categories of patients with tinnitus since a combination of substances interfering with multiple neurotransmitter systems might result in better effects than substances acting on a single receptor.

MemoVigor 2 is a dietary supplement that contains a combination of ingredients, such as dry extract from G. biloba leaves and Bilberry fruits, phospholipids, L-acetylcarnitine, vitamins B, E and C, as well as trace minerals, such as selenium, magnesium and potassium. Most of them are antioxidants that have been previously used for tinnitus, and also for the treatment of other peripheral and central vestibular syndromes, and of lesions of the cochlear and the facial nerve.

Antioxidants are substances that act against the effects of oxidative stress, triggered by oxidizing compounds and free radicals, such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) (Fujimoto and Yamasoba, 2014). Since oxidative stress seems to be involved in the pathogenesis and progression of several diseases, antioxidants are important because they inhibit damage to DNA and to macromolecules, thus alleviating the cumulative damage that can trigger these diseases. Cochleae with the high metabolic demands of their mechanosensory hair cells are extremely vulnerable to oxidative stress because of the damaging effects of mitochondrial ROS (Gonzalez-Gonzalez, 2017). Elevated ROS concentration leads to genetic and cellular alterations and induces impaired blood flow to the cochlea, fused hair cell stereocilia and degeneration of the stria vascularis, the supporting structures and nerve fibers. These changes result in permanent cochlear degeneration and apoptosis.

In relation to tinnitus, there are reports of higher plasma concentrations of oxidative stress biomarkers and low antioxidant activity, supporting the role of oxidative status in the pathogenesis of tinnitus (Koç et al., 2016; Celik and Koyuncu, 2018). Antioxidant therapy in patients with idiopathic tinnitus could reduce oxidative stress and damage to the inner ear, also reducing tinnitus loudness and discomfort. However, research data on the efficacy of antioxidant supplementation in tinnitus are scarce and conflicting, although there are some recent reports that show tinnitus improvement after treatment with antioxidants (Procházková et al., 2018; Oppitz et al., 2022). Additionally, emerging evidence suggests that neuroinflammation may play a large role in the development of tinnitus and the influence of various proinflammatory cytokines such as TNF-α, IL-6, β-2GP1 and IL-1 has been described. Neuroinflammation is the central nervous system’s response to potentially harmful stimuli such as injury, infection, disease, or abnormal neural activity. It was demonstrated that hearing loss or noise exposure causes chronic neuroinflammation in the peripheral and central auditory pathways. Consequently, noise trauma or hearing loss-related disorders might trigger a neuroinflammatory response in which pro-inflammatory cytokines influence synaptic transmission that results in an excitation–inhibition imbalance, speculated to be the mechanism of tinnitus (Adcock and Vanneste, 2022). Anti-TNF-α therapy, such as Etanercept, was studied to prevent noise-induced hearing loss (Dhukhwa et al., 2019), and was recently studied in tinnitus as well (Shulman et al., 2021).

Extracts from the leaves of the plant G. biloba, which is native to China and East Asia in general, have been used for many years in various neurological and other disorders, such as dementia, cognitive disorders, headaches, dizziness, mood disorders, cardiovascular diseases and coronary heart disease (Liu et al., 2023). G. biloba extracts have also been used for the treatment of tinnitus. Its major metabolites are flavonoids and terpenoids, and it has been proven that it possesses antioxidant activity, increases tolerance to hypoxia, improves blood flow, increases the flexibility of the cellular elements of blood and improves microcirculation. It also affects the levels of neurotransmitters, increases neuroplasticity, provides neuroprotection and prevents cerebral edema (Luetzenberg et al., 2020; Liu et al., 2023). Such action mechanisms may help in the treatment of tinnitus, reducing damage caused by free radicals to the cochlea, or by increasing the blood flow of the inner ear.

Various studies as well as several systematic reviews have been conducted for the usefulness of G. biloba in the treatment of tinnitus, but the existing evidence from these studies remains inconclusive for the effectiveness of G. biloba extract. Han et al. (Han et al., 2012) studied a group of 38 patients with tinnitus in a randomized crossover study. Patients received G. biloba EGB 761 extract, or clonazepam for the first 3 weeks and switched to the other drug after a 2-week washout when no medication was taken. For the final 3 weeks, subjects were instructed to increase the dose until they perceived a satisfactory improvement in their tinnitus or intolerable side effects. The authors found that clonazepam was effective but EGB 761 had no significant effect on tinnitus. Polanski et al. (2016) studied in a randomized, double-blinded, placebo-controlled trial 58 elderly subjects with tinnitus and associated sensorineural hearing loss treated with G. biloba dry extract (120 mg/day) and several other antioxidants and did not find any benefit from the treatment. In a recent Cochrane Database review of 12 studies with 1915 participants (Sereda et al., 2022), the authors concluded that there is uncertainty about the benefits and harms of G. biloba for the treatment of tinnitus when compared to placebo.

On the other hand, several studies have found positive results in the use of G. biloba for the treatment of tinnitus. Procházková et al. (Procházková et al., 2018) in a recent double-blind randomized trial of 200 subjects with sub-chronic or chronic tinnitus who received either G. biloba Egb 761 extract or pentoxifylline over 12 weeks found significant improvement in all tinnitus questionnaires used. Nishad et al. (Nishad et al., 2019) evaluated the effect of treatment with a single intravenous injection of caroverine and G. biloba extract (60 mg twice a day) in 86 patients with tinnitus. They found that a single dose infusion of caroverine immediately improved tinnitus in 54.5% of the patients, but the improvement was not sustained at a 3-6 months follow-up. G. biloba was also effective in improving tinnitus in 31.8% of cases and improvement was sustained even after 3 months of cessation of treatment. The authors concluded that G. biloba should be used for 3 months to provide sustained and long-lasting relief.

Von Boetticher (von Boetticher, 2011), in a review of double-blind studies with placebo control, found that only 3 of the numerous reports that studied the efficacy of G. biloba in the treatment of tinnitus fulfilled the necessary criteria for inclusion in the review, and 5 more that studied efficiency not only in tinnitus but also in other agnosia disorders and dementia. According to the author, all 8 studies showed statistically significant superiority of active treatment versus placebo. Therefore, he concluded that the extracts of G. biloba are suitable for the treatment of tinnitus, as either a single symptom or in combination with dementia or age-related cognitive disorders.

Carnitine, another ingredient of MemoVigor 2, has a strong antioxidant activity and possesses a key role in mammalian lipid metabolism. It is mainly required in the transport of activated fatty acids from the cytosol into the mitochondrial matrix for subsequent oxidation and it may enhance the mitochondrial bioenergy and biogenesis (Berni et al., 2008). L-Carnitine, a form of carnitine used pharmacologically, acts as a scavenger of reactive oxygen species, a possible cause of tinnitus in patients (Wu et al., 2011). Τhis is the reason why L-carnitine has been successfully used in the treatment of tinnitus (Gopal et al., 2015).

MemoVigor 2 contains vitamins of groups B, E and C. Vitamins of groups E and C are known for their antioxidant action. Savastano et al. (Savastano et al., 2007) treated 31 patients with tinnitus with glycerophosphorylcholine, glycerophosphorylethanolamine, b-carotene and vitamins C and E for three courses of 6 weeks with a period of 2 weeks between each course. The patients showed a significant reduction in their tinnitus measured using VAS and tinnitus loudness. The complex of vitamin B is a family of vitamins that have been grouped because of their interaction with the functions of the human enzyme systems, and because of their allocation in natural food sources. A deficiency of vitamin B complex, specifically B12, was associated with tinnitus, while intake may improve symptoms (Shemesh et al., 1993; Singh et al., 2016). Α mechanism implicated in Vitamin B12 deficiency neuropathy is hypomethylation in the central nervous system. Cochlear function is dependent on the normal functioning of nerve tissue and the existence of adequate vascular supply. Vitamin B12 deficiency may cause the demyelination of neurons in the cochlear nerve, resulting in hearing loss. Additionally, low levels of Vitamin B12 is associated with the destruction of the microvasculature of the stria vascularis, which might result in decreased endocochlear potential and in hearing loss and tinnitus (Krumholz et al., 1981).

MemoVigor 2 contains also trace minerals: magnesium, potassium and selenium. Magnesium is essential for numerous cellular processes including enzymatic reactions, metabolic cycles, cellular signaling, DNA/RNA stabilities, and serves as a major regulator of calcium channels involved in neurotransmission (Yamanaka et al., 2019). Therefore, magnesium plays a significant role in neural and central auditory pathways. Oral magnesium therapy was reported to be effective in the prevention of cochlear damage in noise-induced hearing loss because magnesium prevents apoptosis in hair cells by reducing calcium flow into the cell and reduces ischemia by causing vasodilatation in the cochlear arterioles (Attias et al., 2004; Abaamrane et al., 2009). It has also been used successfully in the treatment of tinnitus (Cevette et al., 2011).

Potassium is the major electrolyte in the intracellular fluid. Potassium channels regulate excitability in neuronal, sensory and muscular cells and they control cell volume, proliferation, differentiation and survival. In mice, it has been shown that tinnitus generation after noise exposure is related to increased spontaneous firing of fusiform cells within the dorsal cochlear nucleus (Li et al., 2013). This hyperactivity is caused by decreased potassium currents mainly through the Kv7 channels. Although the potential involvement of potassium channels in tinnitus pathophysiology has been the subject of several studies (Li et al., 2015; Langguth et al., 2016), the effect of drugs that act on Kv7 channels on tinnitus, such as flupirtine and retigabine has not been adequately investigated. In addition to Kv7, Pilati et al. (2012) showed that the reduction in Kv3 channel activity underlies increased fusiform cell bursting as well. Together with increased excitatory neurotransmission and decreased inhibitory neurotransmission, changes in intrinsic membrane excitability within the dorsal cochlear nucleus are associated with the development of tinnitus. However, a clinical trial of AUT00063, an experimental new medicine that has been demonstrated to suppress spontaneous hyperactivity by modulating the action of Kv3 voltage-gated potassium channels in central auditory cortical neurons of a rodent model, showed that AUT00063 was not effective in alleviating tinnitus symptoms in humans (Hall et al., 2019).

Selenium is associated with the activity of glutathione peroxidase, which is a cochlear anti-oxidant enzyme that deactivates ROS and RNS and specifically detoxifies H2O2 which induces ciliary dysfunction and apoptosis of hairy cells of the inner ear (Atila et al., 2021). A deficiency of selenium reduces the effectiveness of glutathione peroxidase increasing H2O2 level and oxidative stress, and for this reason, it has been used in combination with B and E vitamin complexes in the treatment of idiopathic sudden hearing loss (Kaya et al., 2015).

Finally, phospholipids are contained in MemoVigor 2. These are a large class of fatlike, phosphorus-containing metabolites that participate in the structure of cell membranes and are oxidized by free radicals in OH or COH thus compromising the membrane integrity. Therefore, phospholipid sufficiency is essential, because they are membrane stabilizers (Dai et al., 2021). Patients with idiopathic tinnitus may have high levels of ROS in their blood samples (Neri et al., 2002). Oxidative stressors induce the production of ROS, which interact with the phospholipidic membrane of the sensory cells producing aldehyde lipids such as the 4-hydroxynonenal, a mediator of apoptosis for auditory neurons and hair cells and it has been found that the use of phospholipids in the treatment of tinnitus may have favourable results (Savastano et al., 2007).

The administered food supplement in this study, which contains a combination of the previously described ingredients with antioxidant, vasoactive and neurogenic properties, had a positive outcome in our intervention group. It appears that treatment with antioxidants in patients with idiopathic tinnitus reduces oxidative stress which harms the inner ear tissues, whereas vasoactive and neurogenic properties of the included ingredients improve circulation and structural integrity of neural circuits. Moreover, we have found that patient tolerance towards tinnitus improves. It should be noticed that tinnitus in the placebo group patients has also improved, although in a lesser degree in comparison with the intervention group. This agrees with the results of a well-designed systematic review and meta-analysis of controlled trials assessing tinnitus interventions (Phillips et al., 2018). The authors of this review concluded that patients demonstrate a small but statistically significant improvement in self-reported global tinnitus severity scores over time, despite receiving no intervention, a finding that provides statistical evidence that tinnitus generally improves over time, albeit the effect is highly variable across individuals.

The large sample size, the high treatment adherence and the application of a complete set of tinnitus evaluation tests including audiometric measures, specific measures of tinnitus perception and tinnitus questionnaires, may be considered as strengths of this trial. Limitations of the study are the single-centre setting and the inclusion exclusively of patients with recent onset tinnitus. Further randomized double-blind placebo-controlled trials are needed to investigate the effectiveness of MemoVigor 2 in the treatment of persistent tinnitus.

We showed that the use of a therapeutic supplement, which contained phospholipids, L-acetylcarnitine, G. biloba and Bilberry dry extracts, several vitamins and trace minerals, improved recent-onset tinnitus, as proved by a set of tests performed for its evaluation, including audiometric measures, specific measures of tinnitus perception and tinnitus questionnaires. Tinnitus in the placebo group improved too but to a lesser degree.