Masseter hyperactivity: a therapeutic lever for somatosensory tinnitus?

Tinnitus, affecting approximately 14.4% of the global adult population, often remains an etiological enigma. Among its manifestations, the somatosensory subtype is garnering increasing interest: here, non-auditory stimuli, particularly those originating from the masticatory system, directly modulate sound perception. The masseter muscle is at the heart of this mechanism via its connections with the dorsal cochlear nucleus (DCN), the point of convergence for auditory and trigeminal pathways.

This scoping review, for which the literature search was completed on May 31, 2026, aims to synthesize the anatomical and neurophysiological rationale linking masseter hyperactivity to somatosensory tinnitus. The study evaluates the hypothesis that botulinum toxin type A (BoNT/A), by reducing this muscular hyperactivity, could attenuate the aberrant somatosensory signals responsible for tinnitus modulation.

L'analyse repose sur une sélection rigoureuse : sur 284 dossiers initialement screenés, quatre études ont été retenues, complétées par un rapport de cas identifié manuellement. L'objectif est de déterminer si cette intervention, déjà établie pour les dysfonctions temporo-mandibulaires, constitue une piste thérapeutique crédible nécessitant une validation clinique approfondie.

Scoping review methodology

This study was conducted according to the PRISMA-ScR methodology (Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews). The objective was to map the anatomical and neurophysiological evidence linking masseter hyperactivity to somatosensory tinnitus. The researchers explored the MEDLINE and EMBASE databases up to May 31, 2026, using three complementary search lines.

The data selection protocol followed a rigorous evaluation process:

• Initial assessment: 284 records were identified and reviewed during the initial screening.
• Final selection: 4 studies met the eligibility criteria (3 from specific research on BoNT/A and tinnitus, and 1 concerning masticatory dysfunction).
• Additional source: 1 additional record (Ranoux and Levine, 2024) was integrated via a manual search for its data on muscular injections.
• Data analysis: The authors extracted in a structured manner the study design, population size, intervention protocols (injection sites) and outcome measures.

Due to the lack of primary data sufficiently homogeneous for a meta-analysis, the authors prioritized a qualitative synthesis of the mechanisms. The analysis focused on the role of the dorsal cochlear nucleus (DCN) as a convergence zone for trigeminal signals from the masseter and auditory pathways, in order to evaluate the therapeutic relevance of botulinum toxin type A (BoNT/A).

Synthesis of research data and results

This scoping review, conducted according to PRISMA-ScR guidelines, identified a limited but informative body of evidence regarding the link between masseter hyperactivity and somatosensory tinnitus. Out of a total of 284 records initially identified in the MEDLINE and EMBASE databases, only 4 articles met the eligibility criteria. An additional source was integrated via a manual search.

Compiled epidemiological data indicate that the global prevalence of tinnitus in adults is estimated at 14.4%. In this context, the somatosensory subtype is distinguished by a modulation of sound perception via non-auditory stimuli (cranio-cervical and cranio-mandibular movements or pressures).

From a clinical perspective, the authors report notable qualitative observations from the work of Ranoux and Levine (2024). Two patients suffering from non-pulsatile tinnitus showed improvement after injections of botulinum toxin type A (BoNT/A) into the periauricular muscles and the splenius capitis. It is important to note that injection into the masseter and temporal muscles was proposed as an alternative site in this protocol, reinforcing the hypothesis of the masseter as a potential therapeutic target.

Neurophysiological analysis highlights that the convergence of trigeminal somatosensory inputs (from the masseter) with auditory pathways occurs at the level of the dorsal cochlear nucleus (DCN). Although BoNT/A is an established option for reducing muscle hyperactivity in the context of bruxism or temporomandibular disorders, the authors emphasize that direct clinical evidence for the specific treatment of tinnitus remains insufficient to date. The use of BoNT/A in this indication must therefore be considered experimental and requires validation through prospective controlled trials.

The masseter: a pathophysiological "hub" for tinnitus

This scoping review highlights a major neurophysiological convergence: somatosensory impulses from the trigeminal nerve, originating from the masseter, converge with auditory pathways within the dorsal cochlear nucleus (DCN). For the practitioner, this means that muscular hyperactivity or bruxism is not merely a mechanical or articular issue, but a potential source of modulation for sound perception. This link explains why some patients experience variations in the intensity of their tinnitus during mandibular movements.

The use of BoNT/A to treat this subtype of tinnitus is based on a compelling therapeutic hypothesis. By reducing abnormal somatosensory input to the DCN through muscle relaxation, the toxin could theoretically alleviate the symptom. However, the results of this synthesis mandate caution. Out of the 284 files identified during the search, only four studies and one conference abstract were selected. Direct clinical evidence of tinnitus improvement via BoNT/A injection remains insufficient and fragmentary.

The main limitation of this study lies in the heterogeneity of protocols and the low number of reported cases. While BoNT/A is already well-established for treating masseter hyperactivity within the framework of temporomandibular disorders (TMD), its specific application to tinnitus must still be considered experimental. In the dental practice, the approach must remain cautious: somatosensory tinnitus requires a rigorous multidisciplinary evaluation to identify patients truly likely to respond to a neuromuscular intervention.

Study summary

This scoping review highlights a plausible neurophysiological link between masseter hyperactivity and somatosensory tinnitus, affecting a portion of the 14.4% of the adult population suffering from tinnitus. Although botulinum toxin (BoNT/A) is effective in reducing masticatory muscle disorders, direct clinical evidence of its efficacy on the auditory symptom remains limited to isolated case reports (e.g., improvement in 2 patients after perisutural and splenius capitis injections).

In concrete terms, for the practitioner:

• Systematic screening: During your bruxism or TMD assessments, ask the patient about the presence of tinnitus and test whether pressure or mandibular movement modulates sound perception.
• Experimental approach: Consider BoNT/A injection into the masseter primarily to treat muscle hyperactivity; improvement of tinnitus should be presented to the patient as a potential but non-guaranteed benefit.
• Multidisciplinary collaboration: Integrate the examination of somatosensory tinnitus into a care pathway including ENT specialists and dental surgeons to isolate cases where targeted neuromuscular intervention is relevant.

Technical Lexicon

Somatosensory tinnitus (ST): Subtype of tinnitus where sound perception is modulated by physical stimuli. It is characterized by an interaction between the somatosensory, somatomotor systems and the central auditory pathways, often triggered by movements or pressures of the cranio-cervico-mandibular sphere.

Dorsal cochlear nucleus (DCN): A true neurophysiological crossroads located in the brainstem. It is the primary convergence site where somatosensory fibers of the trigeminal nerve (originating notably from the masseter) meet the auditory pathways, mechanically explaining the modulation of tinnitus by muscular activity.

Botulinum toxin type A (BoNT/A): Neurotoxin used here as an experimental therapeutic lever. Its role is to reduce the hyperactivity of the masticatory muscles to decrease the abnormal somatosensory afference to the central nervous system, thus hoping to alleviate the perception of tinnitus.

Temporomandibular disorders (TMDs): A set of clinical conditions affecting the temporomandibular joint and masticatory muscles. In this study, they are identified as frequent comorbidities in patients suffering from somatosensory tinnitus.

Masseter muscle: Main elevator muscle of the mandible, divided into superficial and deep bundles. It acts as a pathophysiological hub: its innervation by the mandibular branch of the trigeminal nerve links it directly to central auditory modulation processes in cases of hyperactivity.

PRISMA-ScR: Methodological rigor protocol (Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews) used by the authors to systematically map available evidence and identify research gaps regarding the masseter-tinnitus link.

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