Does Transcranial Direct Current Stimulation (tDCS) combined with language therapy improve language outcomes in patients with Primary Progressive Aphasia (PPA) compared to language therapy alone?

Transcranial Direct Current Stimulation (tDCS) for Primary Progressive Aphasia

There is insufficient evidence to recommend transcranial direct current stimulation (tDCS) combined with language therapy over language therapy alone for improving language outcomes in patients with Primary Progressive Aphasia (PPA). 1, 2

Current Evidence on tDCS in PPA

The most recent high-quality evidence from a double-blind, randomized, cross-over, sham-controlled study found no significant differences between active tDCS combined with speech therapy versus sham tDCS with speech therapy in patients with PPA 2. While both interventions showed clinical improvement, the addition of tDCS did not provide superior language outcomes compared to speech therapy alone.

Earlier research had shown mixed results:

• Some studies suggested tDCS might enhance generalization to untreated items and maintain treatment effects longer 3
• Different effects were observed across PPA variants, with semantic variant PPA showing no advantage from tDCS 4
• Methodological heterogeneity across studies makes definitive conclusions difficult 5

Evidence-Based Approach to PPA Management

Core Treatment Recommendations

• Speech-language therapy interventions should be the primary treatment for PPA, targeting both linguistic and motor speech deficits 6
• Treatment should focus on five core outcome constructs identified as most important to patients and families:
  1. Participating in conversations
  2. Getting words out
  3. Improving fluency
  4. Conveying messages
  5. Understanding what others are saying 1, 6

Assessment and Treatment Planning

1. Identify specific speech-language deficits
2. Evaluate functional communication needs
3. Determine preserved cognitive abilities that can support intervention 6
4. Select treatments based on predominant speech-language deficits:
   • Script training with audiovisual support
   • Structured grammatical exercises
   • Compensatory strategies 6

Therapy Implementation

• Early intervention is recommended, starting within the first 4 weeks post-diagnosis when possible 1
• For chronic aphasia (>6 months), intensive therapy may be beneficial:
  • At least 10 hours/week of therapist-led individual or group therapy for 3 weeks
  • Plus 5+ hours/week of self-managed training 1
• Regular reassessment (every 3-6 months) and strategy adjustment as the disease progresses 6
• Consider augmentative and alternative communication (AAC) before severe communication breakdown 6

Clinical Considerations and Caveats

1. PPA Variant Matters: Different PPA variants may respond differently to interventions, with semantic variant PPA showing less response to tDCS in some studies 4

2. Focus on Functional Outcomes: Prioritize functional communication and quality of life outcomes rather than just performance on standardized tests 6

3. Monitoring Disease Progression: Current treatments cannot stop disease progression but can improve quality of life and maintain communication abilities longer 6

4. Alternative Approaches: Consider computerized treatment to supplement therapy provided by a speech-language pathologist 1

5. Communication Partners: Involve family members and communication partners in therapy to enhance outcomes 1

While tDCS remains an area of active research in PPA, the current evidence does not support its routine use over speech-language therapy alone. Speech-language therapy focused on the five core outcome constructs remains the mainstay of treatment for patients with PPA.