rTMS as a Treatment for PPA

Overview

Primary progressive aphasia (PPA) includes three variants. Two such variants, the non-fluent/agrammatic variant (nfvPPA) and the logopenic variant (lvPPA), are characterized by progressive word-finding difficulties and effortful speech. Efforts to slow or halt this progression have been largely unsuccessful. As such, there is a desperate need for novel treatment strategies in PPA. Repetitive transcranial magnetic stimulation (rTMS) is a safe, non-invasive way of stimulating cortical targets in a focal and reproducible manner. Therapeutic benefits from rTMS have been demonstrated when it is applied in many sequential sessions. For example, repeated sessions of rTMS to left dorsolateral prefrontal cortex (dlPFC) is approved by the US Food and Drug administration as a treatment for major depressive disorder. With respect to language, high frequency rTMS increases the response rate for picture naming in healthy individuals. rTMS has also been shown to improve the number of correct naming responses in patients with Alzheimer's disease. Further, in a sham controlled study, Cotelli and colleagues demonstrated that in a group of 10 nfvPPA patients high frequency rTMS over the left and right dlPFC during object and action naming tasks improved the percent of correct responses for action, but not object naming. Finally, in a sham controlled single case study, Finocchiaro et al. applied high frequency rTMS to the left inferior mid-frontal gyrus for 3 sessions consisting of five consecutive days (treatment or sham). They found a significant and lasting improvement in the patient's performance on verb production when comparing active rTMS to sham rTMS or baseline. These studies have contributed valuable insights into the potential use of rTMS in treating the language symptoms of PPA patients.

15-20 patients with a confirmed diagnosis of either nfvPPA or lvPPA (made by a specialized clinician) will be recruited. Patients must have a mild to moderate language impairment and must be native English speakers. Exclusion criteria include contraindications to receiving Magnetic Resonance Imaging (MRI) scanning or rTMS (e.g. metallic or electromagnetically activated implants, cranial mass lesions, surgical aneurysm clips), the presence of significant medical, neurological or psychiatric co-morbid symptoms and patients without study partners. It will take approximately 2 weeks to complete this research study, but the exact timing will vary according to patient, investigator and equipment availability. Each patient will have a total of up to 11 study visits. Greater than 11 visits may take place in the event that patients' language improves significantly following rTMS in order to test the sustainability of the improvement. Visits will take place at the MGH Martinos Center for Biomedical Imaging. The first visit (lasting 3-4 hours) will include obtainment of informed consent, baseline assessments, and a baseline MRI scan (which will be used for subsequent rTMS targeting). After this, patients will return for two blocks of 20Hz rTMS to left dlpfc: one in which they receive active rTMS and one in which they receive sham rTMS. Both active and sham rTMS will be delivered as high frequency stimulation (20 hertz, 20Hz). To accomplish this, an rTMS coil capable of delivering active or sham stimulation will be employed. Order of active and sham blocks will be counterbalanced across participants. During each block rTMS (active or sham) will be administered daily for 5 days (Monday through Friday). Neuropsychological testing, including thorough language evaluations, will be done before and after each block of rTMS. Repeat MRI imaging will be performed at the end of each of the two blocks. rTMS visit durations will be as follows: Monday visits will last approximately 3-4 hours, Tuesday, Wednesday and Thursday visits will last approximately 1-2 hours and Friday visits will last approximately 5 hours.