Effect of Fixed vs. Tailored Intensity tDCS for Attention Deficit After TBI

Traumatic brain injury (TBI) is an important global health concern. It is estimated that about 70 million individuals will suffer a traumatic brain injury (TBI) each year. Serious TBIs for hospitalization or death is at least 10 million annually. In 2006, Langlois et al reported that, 50,000 patients die directly from or complications related to TBI in the united states alone, and at least 5.3 million Americans suffer from long-term disabilities related to TBI.

Recently, advances in neurocritical care have led to an increase in the number of severe TBI patients recovering cognitive and physical function, eventually returning to independent life.

With the rising recovery rate of TBI patients, the number of complications of TBI is also rising. One of the most common sequalae of TBI is cognitive deficit. In 2004, Whiteneck et al reported that about 65% of patients who experienced moderate to severe TBI suffer from long-term cognitive deficit. Mild TBI patients show fewer and lighter symptoms of cognitive deficit. However, about 15% of patients suffer from persisting cognitive, emotional, behavioral, and physical disabilities after one year (Roe et al. Disabil Rehabil. 2009).

Common symptoms of post-TBI cognitive deficit are attention deficit, memory loss, and impaired cognitive proceessing (Salmond et al. Curr Opin Crit Care. 2005). Current treatment strategy of post-TBI cognitive rehabilitation constitute multimodal approach including "conventional" occupational therapy, computerized neurocognitive training (CNT), pharmacotherapy, and physical medicine.

Transcranial direct current stimulation (tDCS) is a treatment approach where direct current is applied transcranially, aiming to modulate local neuronal excitability. Previous researches have established that repeated tDCS is safe, cost-effective, and easily administered to various neurological disorders including TBI, stroke, Parkinsonism, Alzheimer's dementia, and multiple sclerosis.

Although cognitive improvements are reported, a standardized protocol of tDCS for TBI patients is yet to be established (Kang, J Korean Neurol Assoc. 2017). The repertoire of researches that studies the efficacy of tDCS on post-TBI cognitive deficits is limited, and further study is warranted to establish standardized protocol (Ulam et al. Clinical Neurophysiology 2015; Kang et al. Journal of Rehabilitation Medicine 2012; Sacco et al. Front. Behav. Neurosci. 2016; Lesiank et al. J Head Trauma Rehabil. 2014; Rushby et al. Neuropsych Rehabil 2020; Motes et al J. Neurotrauma 2020).

This trial aims to determine 1) the efficacy of tDCS on post-TBI cognitive deficits, and 2) and optimized protocol of tDCS on post-TBI cognitive deficits via a three-arm double-blind, randomized controlled trial. The hypotheses of this experiment are as follow:

• Sham group and actual stimulation group will show significantly different aCPT response time after 10 tDCS sessions.
• Within the actual stimulation group, tailored tDCS subgroup will show significantly better aCPT response time than conventional tDCS subgroup after 10 tDCS sessions.
• Patients with EEG biomarker change will show significantly better aCPT response time than those without.

Inclusion criteria

• 19 years or older
• At least 6 months since traumatic brain injury
• Cognitive disability measured by:

A) K-MoCA score 25 or below, or B) Trail making test A > 50.25s or B > 142.53s

Exclusion criteria

• Infection, open wound, bleeding, skull defect, or metal plates at or near tDCS site
• history of seizure
• Language disorder
• Serious cognitive deficit with K-MoCA score below 10
• Pregnancy or possibility of pregnancy
• MRI contraindications
• Previous medical history that may affect the patient's cognitive abilities (i.e. previous stroke, hypoxic ischemic encephalopathy, schizophrenia)
• Change in dosage of the following medications within the previous 2 weeks
• rivastigmine
• donepezil
• memantine
• antiepiletic medications