Change in Connectivity After mTBI Depending on Cognitive Reserve

Different Courses of Change in Connectivity After mTBI Depending on Cognitive Reserve and How This is Related to Symptoms and Symptom Resolution?

The purpose of this study is to investigate the role of cognitive reserve in change in connectivity in the brain (measured with functional magnetic resonance imaging, fMRI) and how this is related to symptoms and symptom resolution.

The population-based rate of mild traumatic brain injury (mTBI) is estimated to exceed 600/100000 population per year in total, if including only patients seeking emergency care the estimated rate is approximately 100-300/100000. Many patients recover within 3 months after injury but a sustainable proportion suffer from persisting symptoms, for instance fatigue, headaches, irritability. As conventional neuroimaging techniques have failed to detect the subtle alterations that may be important for prognosis and long-term outcome after mTBI, studies using fMRI have shown some interesting results. Other variables, for instance demographic and cognitive variables, also need to be incorporated with imaging biomarkers when investigating the relationship between fMRI biomarkers with outcome after mTBI. A marker related to demographic status and cognition that have shown to be relevant for outcome in brain injury or pathology is cognitive reserve. Cognitive reserve is defined as an aspect of the brain's function or structure that impacts the relationship between injury/pathology and outcome. Higher cognitive reserve is related to better outcome in conditions ranging from Alzheimer, MS and mTBI.

In this study 15 patients with mTBI and 15 patients with minor orthopedic injury underwent assessment, including cognitive testing, self-assessment of symptoms, testing of visual functions and resting-state fMRI at approximately one week after injury and 4 months after injury. Cognitive reserve was assessed with a lexical decision test designed to measure pre-morbid IQ.

Descriptive statistics will be used to depict demographics, injury characteristics, results on neuropsychological tests and psychological screening instruments. Multi-subject and multi-session analysis based on general linear model will be performed and assessed using statistical tools including regression analysis and 2-way ANOVA.

Inclusion Criteria mTBI group:

• presenting at the emergency departement between January 2015 and April 2016 due to an mTBI to such an extent that CT was indicated.
• mTBI was defined by a Glasgow Coma Scale score between 13-15 and one or more of the following symptoms: <30 minutes loss of consciousness, <24 hours post-traumatic amnesia and/or a transient neurological deficit according to the WHO Collaborating center of Neurotrauma Task Force

Inclusion Criteria orthopedic group:

• presenting at the emergency departement between January 2015 and April 2016 due to minor traumatic injuries to the hand, foot, arm or leg that did not require surgical intervention.

Exclusion Criteria:

• uncertain duration of loss of consciousness
• contraindications to MR
• previously acquired brain injury, a progressive neurological disorder or another injury/illness with short expected survival
• were dependent of help in daily living before the current damage
• severe visual impairment
• non-Swedish speaking.