Postconcussive complaints after mild traumatic br

Authors: Harm J van der Horn Edith J Liemburg Myrthe E Scheenen Myrthe E de Koning Jacoba M Spikman Joukje van der Naalt

Publish Date: 2015/12/14

Volume: 10, Issue: 4, Pages: 1243-1253

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Abstract

The aim was to investigate brain network function during working memory WM task performance in patients with uncomplicated mild traumatic brain injury mTBI in the subacute phase postinjury We were particularly interested in differences between patients with PCCpresent and without postconcussive complaints PCCabsent Fiftytwo patients and twenty healthy controls HCs matched for age sex education and handedness were included Two patient groups were created based on reported postconcussive complaints at two weeks postinjury PCCpresent n = 32 and PCCabsent n = 20 Functional MRI scans were made at approximately four weeks postinjury Participants performed an nback task consisting of three conditions 0 1 and 2back with increasing difficulty General linear model analysis was performed to investigate activation patterns Independent component analysis was used to identify brain networks The frontal executive network FEN frontoparietal network FPN and default mode network DMN were selected for further analyses based on their highest taskrelatedness Task accuracy and reaction times were similar for patients with mTBI and HCs During high WM load 2vs0back contrast mTBI patients exhibited lower activation within the medial prefrontal cortex compared to HCs No differences were found between PCCpresent and PCCabsent patients Regarding network function PCCabsent patients showed stronger deactivation of the DMN compared to PCCpresent patients and HCs especially during difficult task conditions Furthermore functional connectivity between the DMN and FEN was lower in PCCabsent patients compared to PCCpresent patients Interestingly network function did not differ between PCCpresent patients and HCs suggesting that noninjury related factors may underlie postconcussive complaints after mTBIAnnually millions of people sustain a traumatic brain injury TBI with the vast majority 85–90  incurring a mild injury mTBI Corrigan et al 2010 Patients with mTBI frequently report cognitive and/or affective complaints which most often resolve within weeks but may persist for months to years in a subgroup of patients Willer Leddy 2006 However with conventional magnetic resonance imaging MRI sequences usually no lesions are detected that might explain these complaints in patients with mTBI Bazarian et al 2006 Iverson et al 2000Functional MRI fMRI studies using working memory WM paradigms have provided more insight into the concept of mTBI WM involves shortterm storage and manipulation of information and is considered crucial for higherorder cognitive functioning Owen et al 2005 Already in 1999 it was demonstrated that altered brain activation patterns may be related to cognitive complaints in patients with mTBI despite the fact that WM performance was unimpaired McAllister et al 1999 Since then several studies have been published on this subject with varying results Mayer et al 2015a Some studies have reported higher activation whereas others reported lower activation postmTBI and differences may be partly explained by task design and difficulty Bryer et al 2013 However to date there is still no clear explanation for the occurrence of postconcussive complaints after mTBIIn recent years evidence has accumulated that dysfunction of brain networks plays a major role in the pathophysiology of mTBI Studies have reported alterations within the default mode network DMN and stronger connectivity between the DMN and parts of executive networks during resting conditions Borich et al 2015 Mayer et al 2011 Sours et al 2013 Zhou et al 2012 Zhu et al 2015 However in contrast to severe TBI no study so far has investigated brain network function during WM performance in patients with mTBI Palacios et al 2012 Furthermore the link between network function and the presence or absence of postconcussive complaints remains unclearThis study was conducted as part of a larger prospective multicenter followup study UPFRONT study Fiftyfive patients age 18–65 years old with mTBI were prospectively included at the University Medical Center Groningen The Netherlands a level 1 trauma center between March 2013 and February 2015 The diagnosis of mTBI was based on a Glasgow Coma Score of 13–15 and/or loss of consciousness ≤30 min Vos et al 2012 The following exclusion criteria were applied lesions on admission computed tomography CT scans neurological or psychiatric comorbidity prior admission for TBI drug or alcohol abuse mental retardation and contraindications for MRI implanted ferromagnetic devices or objects pregnancy or claustrophobia A group of twenty healthy controls HCs was recruited among social contacts and via advertisements Healthy controls did not have any history of TBI or other neurological or psychiatric diseases and did not suffer from current psychiatric or neurological conditions MTBI patients and HCs were groupmatched for age gender educational level and handednessTwo subgroups patients with PCCpresent and without PCCabsent post concussive complaints were created based on their answers on a postconcussive questionnaire administered at two weeks postinjury This questionnaire is derived from the Rivermead Postconcussion symptoms Questionnaire RPQ King et al 1995 and composed of 19 complaints Preinjury as well as current complaints were measured on a scale from 0 to 2 0 = never 1 = sometimes 2 = often PCCpresent was defined as ≥3 complaints with at least one complaint within the cognitive or affective domain PCCabsent was defined as 3 complaints The presence of complaints following the moment of scanning was determined based on answers on followup questionnaires administered at three to six months postinjury and data from outpatient appointments

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