Frontal cerebral hemodynamic changes in adults after mild traumatic brain injury using Functional NearInfrared Spectroscopy (fNIRS); a pilot study.

Traumatic brain injury (TBI) is one of the most frequent neurological disorders
worldwide. Approximately 80.000 persons with traumatic brain injurer admitted
to the Emergency Department in the Netherlands. The patients differ widely
concerning age, trauma mechanism, injury severity, course and eventual
recovery. Based on clinical criteria mild, moderate and severe TBI are
distinguished; the majority consists of mild TBI (80-85%). In patients with
mild TBI posttraumatic signs and symptoms can be present, both physical as
cognitive, that may prolong and have a great impact on daily life, for instance
on return to school or study and/or work.

Next to physical examination, radiological investigations are used to determine
injury severity in patients with mild TBI. In the acute phase especially
computed tomography (CT) scanning is used. However, in a large majority
(85-90%) of mild TBI patients no structural traumatic abnormalities are found
using CT scanning. In adult mild TBI patients changes in cerebral perfusion
were demonstrated using hemodynamic imaging techniques like the perfusion
CT-scan, whereas the regular CT-scan didn*t show any abnormalities. A decrease
in frontal cerebral blood flow was found that was associated with outcome six
months post-injury. Still, the perfusion CT-scan is time consuming and labour
intensive with additional radiation exposure.

By means of Functional Infrared Spectroscopy (fNIRS) it is possible to detect
and monitor cerebral hemodynamics non-invasively and without X-ray exposure.
Cerebral activity will result in an increase in oxygen use, leading to an
increase in cerebral blood flow through the so called *neurovascular coupling*.
This in turn will result in changes in tissue oxyhaemoglobin and
de-oxyhaemoglobin, which can be detected with fNIRS. Especially the frontal
lobes can be visualized using fNIRS. Considering the fact that fNIRS is
relatively easy to use and there is no radiation exposure, it is very much
suited to evaluate the cerebral hemodynamics, specifically in the acute setting
post-injury. Furthermore, fNIRS can be combined with attention and memory tasks
to get an impression of post-traumatic cognitive functioning in relation to
hemodynamic changes in the frontal cerebral areas.

In adult TBI patients no data is available on the feasibility of fNIRS in
combination with cognitive tasks, particularly in the acute phase post-injury
at the emergency department. The further aim of this study is to investigate
the potential of fNIRS as a screening tool in the acute phase to select
patients at risk for suboptimal recovery.

The goals of this study are therefore threefold:
1. Evaluation of the feasibility of fNIRS (including cognitive tasks) in adult
mild TBI patients during the acute phase.
2. Collecting fNIRS normal values (including cognitive tasks) in healthy adult
control subjects.
3. Examining the relation between frontal cerebral perfusion abnormalities and
outcome.

Within predetermined time windows all adult mild TBI patients will be
approached to participate in this study. Naturally, the treating physician will
be consulted. If the patient gives consent, he/she will be asked to complete
the first questionnaire followed by the fNIRS measurement (including cognitive
tasks).
Two weeks and three months post-injury/ after the emergency department visit
participating patients will be send two questionnaires by e-mail or regular
mail (the patient will be given the ability to chose from both options) to
complete and subsequently to return. When no response from the patient is
received, he/she will be contacted by e-mail and/or phone again as reminder.

fNIRS analysis encompasses no risks worth mentioning and we consider the time
investment asked acceptable. fNIRS is non-invasive.

The fNIRS measurement and completion of the first questionnaire will be
performed directly following the ED visit, which will therefore be somewhat
lengthened. The remaining two questionnaires can be completed at home (two
times) and subsequently returned by regular mail or even e-mail.