Can Alzheimer's disease cause protrusion of the tongue?

Alzheimer's Disease and Tongue Protrusion

Alzheimer's disease does not typically cause tongue protrusion as a primary symptom, though oral-motor abnormalities can occur in advanced stages as part of broader neurological deterioration.

Oral-Motor Dysfunction in Alzheimer's Disease

Alzheimer's disease (AD) primarily affects cognitive functions, but as the disease progresses, it can impact various motor functions including those related to oral-motor control. The evidence regarding tongue protrusion specifically in AD is limited, but we can understand the relationship through several mechanisms:

Speech and Orofacial Apraxias

• Patients with AD demonstrate significant impairments in speech praxis and orofacial praxis compared to normal controls 1
• These apraxias become more pronounced with disease progression, with severity significantly associated with dementia progression 1
• Orofacial apraxia in AD affects the ability to perform voluntary movements of the face, mouth, tongue, and related structures

Swallowing and Oral Phase Dysfunction

• Dysphagia (swallowing difficulties) develops in 13-57% of patients with different types of dementia, becoming most common in later stages of AD 2
• Factors contributing to oral phase dysphagia in AD include:
  • Inability to recognize food
  • Oral-tactile agnosia
  • Swallowing and feeding apraxia 2

Structural Changes in Oral Musculature

Recent research in an AD rat model has shown:

• Structural changes in pharyngeal and tongue muscles that may contribute to dysphagia 3
• Histopathological evidence of amyloid beta accumulation in tongue and pharyngeal muscles 3
• These findings suggest that dysphagia in AD may result not only from central nervous system changes but also from local involvement of the tongue and pharynx

Differential Diagnosis for Tongue Protrusion

When tongue protrusion is observed, clinicians should consider other neurological conditions that more commonly cause this symptom:

• Severe tongue protrusion dystonia can occur in:

  • Neuroacanthocytosis
  • Pantothenate kinase-associated neurodegeneration
  • Lesch-Nyhan syndrome
  • Postanoxic and tardive dystonia 4

• Episodic involuntary tongue movements have been reported in:

  • Epilepsy
  • Brain tumors
  • Stroke 5

Clinical Evaluation Approach

When evaluating a patient with dementia who displays tongue protrusion:

1. Determine if the tongue movement is:

   • Involuntary vs. voluntary
   • Episodic vs. continuous
   • Associated with other neurological symptoms

2. Consider comprehensive cognitive-behavioral assessment to identify the specific syndrome present 2

3. Evaluate for dysphagia and related oral-motor dysfunction:

   • Videofluoroscopy can detect early signs of dysphagia 2
   • Assessment of oral phase (lip closure, lingual elevation, tongue movement) 2
   • Assessment of pharyngeal phase (soft palate elevation, laryngeal elevation, tongue base retraction) 2

Management Considerations

For patients with AD who develop oral-motor dysfunction:

• Dietary modifications may be necessary:

  • Adapting food texture (soft, semisolid, or semiliquid) to compensate for poor oral preparation 2
  • Thicker liquids may be better alternatives to thin liquids for patients with delayed swallowing 2

• Postural maneuvers may help:

  • Chin-tuck posture can protect airways during swallowing 2
  • Head rotation may be indicated in cases of hypertonicity 2

Key Takeaway

While tongue protrusion is not a typical or diagnostic feature of Alzheimer's disease, oral-motor dysfunction including speech apraxia, orofacial apraxia, and dysphagia are common in advanced stages. When prominent tongue protrusion is observed in a patient with dementia, clinicians should consider alternative or additional neurological conditions that more commonly cause this specific symptom.