What causes palatal myoclonus?

Causes of Palatal Myoclonus

Palatal myoclonus is primarily caused by lesions in the brainstem, particularly those affecting the Guillain-Mollaret triangle pathway, with stroke being the most common identifiable etiology. 1

Pathophysiological Classification

• Essential (Primary) Palatal Myoclonus:

  • No identifiable structural lesion on brain imaging 2
  • May develop following viral upper respiratory tract infections in approximately 40% of cases 3
  • Normal brain MRI findings 2

• Secondary (Symptomatic) Palatal Myoclonus:

  • Associated with identifiable lesions in the brainstem or cerebellum 2
  • Stroke is the most common defined cause 1
  • MRI typically shows ischemic areas in the brainstem 2
  • Variable delay between the initial lesion and the appearance of myoclonic movements 1

Anatomical Basis

• Involves a specific anatomical pathway known as the Guillain-Mollaret triangle:

  • Pathway leaves the contralateral dentate nucleus 1
  • Passes through the superior cerebellar peduncle 1
  • Crosses the posterior commissure before joining the central tegmental tract 1
  • Descends to the ipsilateral inferior olive 1

• Pathological findings show transsynaptic hypertrophic degeneration of the inferior olivary nucleus 1

• The degeneration occurs due to a lesion of a specific inhibitory anatomic pathway 1

Clinical Characteristics

• Characterized by sudden, brief, lightning-like jerks of specific muscles 4
• Involves rhythmic involuntary contractions of the soft palate, pharynx, and larynx 1
• Movements are continuous and involuntary 1
• Consciousness is preserved during episodes 4
• Patients are often unaware of the movements themselves 1
• May persist for life in the majority of patients 1

Associated Symptoms

• Clicking sounds in one or both ears (often the initial symptom) 2, 1
• Audible clicks due to opening and closing of the Eustachian tube 5
• Can involve other muscles derived from embryonal branchial arches 1
• May present with oculopalatal myoclonus involving nystagmus-like eye movements 1
• Can be associated with tinnitus 6, 3

Less Common Associations

• May be associated with orofacial buccal dystonia (rare) 5
• Can follow Leber's optic atrophy involving the brainstem (rare) 1
• May present with rhinolalia (nasal speech) in some cases 3

Clinical Presentation Patterns

• Predominant presenting symptoms include:
  • Clicking tinnitus (46.7% of cases) 3
  • Non-audible awareness of palatal movements (20% of cases) 3
  • Both clicking tinnitus and awareness of movements (33.3% of cases) 3
  • Co-incident involvement of pharyngeal musculature in over half of cases (53.3%) 3

Diagnostic Considerations

• EEG recording during episodes can help identify awareness and potential epileptic correlates 4
• Brain MRI to identify or rule out structural lesions 2
• Audiometry may show bilateral neurosensory loss in some cases 2

Understanding the underlying cause of palatal myoclonus is crucial for appropriate management, as essential and secondary forms may require different treatment approaches despite sharing similar clinical features 2.