A network meta-analysis of effects of non-invasive neuromodulation techniques on language function in patients with aphasia after stroke

Abstract

OBJECTIVE: Many studies have shown that non-invasive neuromodulation techniques can effectively improve the symptoms of non-fluent aphasia after stroke. However, the optimal stimulation protocols for these techniques still need to be further verified and explored. This article used a network meta-analysis method to systematically evaluate the effects of different non-invasive neuromodulation techniques on improving the language function of patients with non-fluent aphasia after stroke. METHODS: The CNKI, WanFang, VIP, CBM, PubMed, Cochrane Library, Embase, and Web of Science databases were searched for randomized controlled trials on the treatment of non-fluent aphasia after stroke with non-invasive neuromodulation techniques, with the search deadline of June 1, 2025. The control group received conventional treatment or sham stimulation, while the experimental group received non-invasive neuromodulation techniques in addition to the control treatment. Outcome measures included the Western Aphasia Battery, Chinese Aphasia Battery, and Communicative Abilities in Daily Living Scale. Stata 17.0 software was used for traditional meta-analysis and network meta-analysis, and GRADE was used to evaluate the evidence level of outcome measures. RESULTS: A total of 33 randomized controlled trials involving 10 non-invasive neuromodulation methods were included. (1) Traditional meta-analysis results showed that low-frequency repetitive transcranial magnetic stimulation (rTMS) over the right Broca's area, transcranial direct current stimulation (tDCS) over bilateral Broca's area, and tDCS over the left Broca's area improved Western Aphasia Battery scores (P < 0.001); low-frequency rTMS over the right Broca's area, low-frequency rTMS over the posterior superior temporal gyrus, and low-frequency rTMS over the right Broca's area combined with high-frequency rTMS over the left Broca's area improved Chinese Aphasia Battery scores (P < 0.05); low-frequency rTMS over the right Broca's area, tDCS over bilateral Broca's area, continuous theta burst stimulation over the right Broca's area combined with intermittent theta burst stimulation over the left Broca's area, high-frequency rTMS over the right Broca's area, and low-frequency rTMS over the right Broca's area combined with high-frequency stimulation over the left Broca's area improved Communicative Abilities in Daily Living Scale scores (P < 0.05). (2) Network meta-analysis results showed that low-frequency rTMS over the right Broca's area was more effective in improving Western Aphasia Battery scores [SMD=1.13, 95%CI(0.59, 1.67), P < 0.05] and Chinese Aphasia Battery scores [SMD=4.73, 95%CI(1.28, 8.18), P < 0.05], while tDCS over bilateral Broca's area was more effective in improving Communicative Abilities in Daily Living Scale scores [SMD=1.81, 95%CI(0.51, 2.12), P < 0.05]. (3) GRADE evidence level evaluation showed that the evidence levels for Western Aphasia Battery, Chinese Aphasia Battery, and Communicative Abilities in Daily Living Scale outcome measures were all low. CONCLUSION: Different non-invasive neuromodulation techniques can improve the language function of patients with non-fluent aphasia after stroke. Low-frequency rTMS over the right Broca's area has significant efficacy in improving multi-dimensional language function, especially in spontaneous speech coherence, auditory comprehension accuracy, and naming fluency; tDCS over bilateral Broca's area is more focused on improving patients' daily communication ability. However, the results are affected by the quantity and quality of included studies, and the evidence level is low, requiring more high-quality studies for further verification.

1. Introduction

Approximately one-third of patients experience speech dysfunction after stroke, with the pathological basis being damage to the language centers in the dominant hemisphere, making it more common than Parkinson's disease and muscular dystrophy [1]. Non-fluent aphasia is a common type of post-stroke aphasia, accounting for 41.25% of aphasia cases, and is closely related to lesions in the left inferior frontal gyrus. It is characterized by effortful speech, reduced verbal output, frequent pauses, and non-fluent sentence production, encompassing various types such as motor aphasia, transcortical motor aphasia, and global aphasia [2]. The impact of aphasia extends beyond language function, posing challenges in emotional well-being, social participation, and the ability to return to work [3].

Currently, clinical treatment primarily involves conventional speech training combined with medications, acupuncture, and manual therapy to improve post-stroke speech disorders. For example, drugs such as donepezil, memantine, and piracetam are often used in conjunction with speech training [4-5]. In recent years, neuromodulation techniques have developed rapidly, expanding from initial applications in stroke-related limb dysfunction to the treatment of depression, Parkinson's disease, and Alzheimer's disease [6-9]. Non-invasive neuromodulation techniques mainly include repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), theta burst stimulation, and transcranial alternating current stimulation. These techniques are easy to operate and have low risk, showing significant application potential in the clinical intervention of post-stroke aphasia [10]. Current research [11-13] has demonstrated that non-invasive neuromodulation can improve language function in aphasia patients, but the optimal stimulation parameters and protocols remain to be determined.