What is the possible mechanism behind lacrimation (excessive tearing) in the right eye causing middle ear myoclonus (involuntary muscle contraction) in the right ear?

The Neuroanatomical Connection Between Lacrimation and Middle Ear Myoclonus

The connection between right eye lacrimation and right ear middle ear myoclonus likely involves the facial nerve (cranial nerve VII) and its parasympathetic branches, which innervate both lacrimal glands and middle ear muscles.

Anatomical Pathway

• The facial nerve (CN VII) provides parasympathetic innervation to both the lacrimal glands and the stapedius muscle in the middle ear 1
• The greater petrosal nerve, a branch of the facial nerve, carries parasympathetic fibers to the lacrimal gland via the pterygopalatine ganglion 1
• The stapedius branch of the facial nerve innervates the stapedius muscle, which can undergo myoclonic contractions 2

Proposed Mechanisms

1. Aberrant Neural Signaling

• Abnormal neural activity in the facial nerve nucleus or along its course could simultaneously affect both lacrimal and stapedius branches 1
• This could represent a form of synkinesis (unwanted co-activation of muscles) similar to what is seen in facial nerve regeneration after Bell's palsy 1

2. Trigeminal-Facial Nerve Interaction

• The trigeminal nerve (CN V) carries sensory information from the eye and can trigger lacrimation reflexively 1
• Cross-talk between trigeminal and facial nerve pathways could explain how eye irritation (causing tearing) might trigger middle ear myoclonus 1

3. Autonomic Nervous System Dysregulation

• Both lacrimation and middle ear muscle tone are under parasympathetic control 1
• Dysautonomia affecting parasympathetic branches could cause simultaneous dysfunction in both systems 1

Clinical Implications

• Middle ear myoclonus presents as objective tinnitus with clicking sounds that can be heard by an examiner 3
• The condition can be psychologically distressing and impact quality of life 4
• Diagnosis often requires ruling out other causes of objective tinnitus such as vascular abnormalities 3

Management Options

• Botulinum toxin injection directly into the middle ear muscles has shown promise in recent studies 5

  • This approach temporarily paralyzes the myoclonic muscles
  • Can serve as both a diagnostic and therapeutic tool

• Surgical sectioning of the stapedius and tensor tympani tendons may provide definitive treatment in severe cases 3

• Non-invasive techniques such as self-administered zygomatic pressure may provide relief in some patients 4

Special Considerations

• The condition appears to be rare in children but has been documented 6
• Neuroimaging may be warranted to rule out central causes of myoclonus 6
• Careful otoneurological examination is essential for proper diagnosis 6

Pitfalls in Diagnosis

• Middle ear myoclonus can be misdiagnosed as palatal myoclonus or vascular tinnitus 3
• The clicking sound may be mistaken for temporomandibular joint dysfunction 1
• Continuous high-frequency objective tinnitus caused by middle ear myoclonus is particularly rare and may be overlooked 3

Understanding this neuroanatomical connection is crucial for proper diagnosis and management of patients presenting with the unusual combination of lacrimation and middle ear myoclonus.