To investigate the effects of high frequency repetitive transcranial magnetic stimulation (rTMS) on speech in patients affected by primary progressive apraxia of speech.

Apraxia of speech (AOS) is a motor speech disorder affecting the programming of motor speech production, resulting in the inaccurate production of sounds. When AOS is the presenting symptom of a neurodegenerative condition, it is called primary progressive apraxia of speech (PPAOS). The mainstay of treatment in PPAOS is speech therapy; however, efficacy is limited especially as the underlying disease continues to progress¹. High frequency rTMS is a neurostimulation technique which uses magnetic energy to increase neuronal excitation in specific brain areas. It has been used to facilitate language recovery after stroke and improve language function in neurodegenerative disease, including PPAOS in one previously published case report^2-9, and in another patient presented by our group in the past. However, the role of rTMS in PPAOS has not been systematically studied.

In this pilot study, two subjects with PPAOS underwent 10 sessions of high frequency rTMS targeting the dorsolateral prefrontal cortex (DLPFC), over a 4-week period. The target was chosen based on the results of the patients’ functional MRIs, which showed decreased BOLD-activation patterns in this area during several speaking and language tasks.

Subjects were found to have a mean improvement of 1.25 points (on a scale of 0-4) on the AOS Rating Scale overall score as scored by blinded raters after rTMS. One subject perceived significant improvement post-TMS (score of 2 on the Patient Global Impression of Change (PGIC) scale) while the other did not (score of 4 on the PGIC).

The results show potential benefit of high frequency rTMS in subjects with PPAOS. Next steps will involve repeating the protocol in other patients with this condition, and developing future studies to identify the best stimulation parameters/targets.