Effects of transcranial direct current stimulation (tDCS) on speech and quality of life of a total glossectomy patient: a case report

INTRODUCTION: The tongue is essential for maintaining speech and swallowing, articulating vowels and consonants, and manipulating and ejecting the food bolus. Studies indicate that speech-language rehabilitation improves speech intelligibility by 18 to 42% in individuals who have undergone total glossectomy. Non-invasive brain stimulation techniques have been developed to promote neuroplasticity. Transcranial direct current stimulation (tDCS) applies low-intensity, safe, painless electrical stimulation, targeting neuronal excitability (anodal electrode) and hyperpolarization of the membrane potential (cathodal electrode). No study has addressed its effectiveness after treatment for head and neck cancer. OBJECTIVE: To evaluate the impact of tDCS associated with myofunctional exercises and articulatory compensation training on speech intelligibility and quality of life specifically regarding speech and swallowing in a total glossectomized subject previously submitted to speech-language therapy. METHODS: This exploratory, prospective, observational case report approached a total glossectomy participant previously submitted to traditional speech-language therapy for speech and swallowing rehabilitation. She underwent 14 sessions over 40 days, associating myofunctional exercises, articulatory training, and tDCS. The anodal electrode was positioned in the primary motor cortex (C3) and the cathodal electrode, in the right supraorbital region (Fp2), according to the International 10-20 System, providing 2 mA electrical stimuli for 20 minutes. The following instruments were applied on the 1st, 10th, and 14th days: Percentage of Consonants Correct (PCC), MD Anderson Dysphagia Questionnaire (MDADI), Speech Handicap Index (SHI), and auditory-perceptual evaluation based on automatisms, spontaneous speech, and naming through the phonological competence of the Child Language Test (ABFW). RESULTS: In the PCC naming domain, there was a 7% increase at the end of the intervention and an evolution from 96% to 99.2% in spontaneous speech. The participant acquired the precise production of unrounded vowels, consolidated the adequate compensation of the /k/, /z/, and /l/ phonemes, and reduced the omissions of the /r/ consonant group when produced in simple and complex onset. The SHI decreased from 37 points and self-assessed "average" speech before tDCS to 24 after 10 days of application and 31 at the end, with self-reported “good” speech quality on the 10th and 14th days of intervention. The MDADI score evolved from 48 points on day 1 to 63 points at the end of the study. CONCLUSION: The tDCS associated with myofunctional exercises and articulatory compensation training improved the speech-related quality of life, increased the PCC, and reduced the substitutions and omissions in speech. The improvements remained up to 30 days after the end of the intensive intervention. Moreover, the impact of dysphagia on the subject's quality of life decreased after the intervention.