Study context and objectives

The distinction between oromandibular dystonia (OMD) and prolonged condylar dislocation constitutes a major clinical challenge due to their symptomatic overlap. Both pathologies can manifest as mandibular deviation, facial asymmetry, and speech disorders, sometimes leading to therapeutic orientation errors. This study documents two clinical cases illustrating care trajectories where patients, suspected of OMD, received botulinum toxin injections without success before a dental and maxillofacial evaluation revealed a structural origin.

The objective of this work is to demonstrate that the lack of response to botulinum toxin should not be interpreted by default as pharmacological resistance, but must imperatively trigger a diagnostic re-evaluation. The authors test the hypothesis that mechanical disorders of the temporomandibular joint act as dystonia mimics, masking a physical obstruction with apparent muscular hyperactivity. Through these paradigms, the study aims to identify clinical signs to differentiate a focal neurological disorder from a perennial joint pathology, the management of which is exclusively surgical or prosthetic.

Design and presentation of cases

This clinical perspective presents two illustrative case reports of female patients initially misdiagnosed with oromandibular dystonia (OMD) and who failed botulinum toxin treatment. The analysis is based on a multidisciplinary clinical evaluation including neurology and maxillofacial surgery.

• Subject 1: 65-year-old female, edentulous, presenting with an inability to close the mandible and orofacial pain evolving for 15 years, with a marked worsening over the past 3 years.
• Subject 2: 64-year-old female, with a history of stroke (1 year prior), presenting with mandibular asymmetry and speech and swallowing disorders.

Evaluation and management protocol

The diagnostic and therapeutic pathway followed several key stages:

• Initial evaluation: Analysis of failures of botulinum toxin injections (masseters) performed in neurology prior to referral.
• Clinical examination: Evaluation of facial asymmetry, mandibular deviation, lingual movements and occlusion.
• Imaging: Use of panoramic radiography to evaluate the position of the condyles in relation to the articular eminence.
• Surgical procedures:
  • Case 1: Open bilateral eminectomy and capsular stabilization.
  • Case 2: High condylectomy with disc repositioning, followed by prosthetic rehabilitation.

Post-operative follow-up allowed for a comparison between the resolution of mechanical symptoms and persistent or secondary neurological signs.

Therapeutic failure and diagnostic recovery: Analysis of two cases

This study reports two clinical cases illustrating initial diagnostic errors where chronic condylar dislocations were mistaken for oromandibular dystonia (OMD). In both cases, the administration of botulinum toxin (BoNT) proved ineffective before a dental and maxillofacial evaluation rectified the diagnosis.

Case n°1: Chronic bilateral dislocation

A 65-year-old edentulous female patient presented with almost total inability to close the mandible for 3 years, associated with a deviation to the right and involuntary contractions. The history revealed preauricular pain dating back 15 years.

• Initial failure: Several sessions of BoNT injections into the masseters without clinical improvement.
• Clinical observations: Marked facial asymmetry, bilateral TMJ tenderness and severely restricted eccentric movements.
• Imaging: Panoramic radiography revealed bilateral anterior displacement of the condylar heads beyond the articular eminence.
• Surgical outcome: After open bilateral eminectomy and capsular stabilization, mandibular closure and facial symmetry were restored, despite slight residual involuntary movements.

Case n°2: Unilateral luxation and hyperplasia

A 64-year-old female patient, with a history of stroke one year prior, presented with mandibular asymmetry and speech/swallowing disorders.

• Initial failure: One BoNT injection session in the masseters without benefit.
• Clinical observations: Right mandibular deviation, inability to establish stable bilateral occlusal contact and abnormal lingual movements (considered secondary to the mandibular position).
• Imaging: Anterior and inferior displacement of the left condyle associated with condylar hyperplasia.
• Surgical outcome: A high condylectomy with disc repositioning and prosthetic rehabilitation allowed for complete resolution of the asymmetry and functional disorders.

Clinical differentiation: TMD vs Condylar Luxation

The study highlights that while both pathologies share common traits (deviation, asymmetry, speech disorders), their semiological characteristics differ radically:

Analysis of results and clinical perspectives

These two case reports demonstrate that long-standing condylar dislocation can clinically simulate oromandibular dystonia (OMD), leading to repeated therapeutic failures with botulinum toxin. The major interest of this study is to highlight a "pseudo-stereotypy" mechanism: while dystonia is neurological, the mechanical locking of the condyle beyond the articular eminence produces constant mandibular deviation and inability to close that mimic patterned dystonic contractions.

The authors emphasize that the absence of cardinal signs of dystonia — such as sensory tricks (antagonistic gestures), task specificity, or morning benefit — should alert the practitioner. In both cases presented, symptoms were persistent and independent of the time of day or activity, contrary to the fluctuating nature of OMD. The resolution of symptoms after surgery (eminidectomy or condylectomy) confirms that the origin was structural and not primary neurological, although secondary motor adaptation may persist, as observed in the patient of the first case.

The limitations of this study lie in its case series format (n=2) and an inherent selection bias. Furthermore, the lack of precise data on the botulinum toxin protocols initially used (doses, EMG or ultrasound guidance) limits the analysis of the initial pharmacological failure. Nevertheless, these results confirm that when faced with a suspicion of OMD resistant to treatment, an occlusal examination and panoramic imaging are essential to exclude temporomandibular joint (TMJ) pathology.

Summary of results

This two-case study demonstrates that prolonged condylar dislocation constitutes a critical differential diagnosis of oromandibular dystonia (OMD), explaining the initial failure of botulinum toxin injections. Diagnostic correction via panoramic radiography enabled clinical resolution through surgical interventions (bilateral eminectomy or high condylectomy), correcting a mechanical blockage mistaken for neurological muscular hyperactivity.

In concrete terms, for the practitioner:

• Look for dystonic markers: In the absence of task specificity, sensory tricks (antagonistic gestures) or morning benefit, suspect a structural rather than neurological origin.
• Imaging reflex: In the event of zero or insufficient response to botulinum toxin, systematically prescribe a panoramic radiograph or a CBCT to check the position of the condyles relative to the articular eminence.
• Identify fixed locking: A constant mandibular deviation, an anterior open bite, or a mechanical impossibility to reach full occlusion should point towards a long-standing condylar dislocation rather than a dystonic contraction.

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