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3 Assessment and treatment of mild brain injury
This section describes the post-acute assessment of patients who later present to primary care services
complaining of ongoing symptoms in the aftermath of mild traumatic brain injury (MTBI).
3.1 EPIDEMIoloGy AND DEfINITIoNS
The incidence rate of mild brain injury varies substantially depending on the specific definition used and the
population studied. The point at which the minimum criteria are set for distinguishing between brain injury,
as opposed to a head injury in which the brain was unaffected, will have a significant effect on the incidence
rate as milder injuries are much more common. Worldwide, the incidence rates for MTBI are between 100-
300 per 100,000 population with mild injuries accounting for between 70-90% of all TBIs. 22 Incidence figures
1, 23-25
from Scotland are consistently at the upper end of this range.
The definition of what constitutes an MTBI varies. Differing criteria including measures of GCS, duration of
total loss of consciousness and duration of post-traumatic amnesia have been recommended and adopted in
different settings. Following comprehensive review of the scientific literature the World Health Organisation
(WHO) recommended the following definition: 26
“Mild traumatic brain injury is an acute brain injury resulting from mechanical energy to the head from
external force. Operational criteria for clinical identification include:
(i). One or more of the following: confusion or disorientation, loss of consciousness for 30 minutes or
less, post-traumatic amnesia for less than 24 hours, and/or other transient neurological abnormalities
such as focal signs, seizure, and intracranial lesion not requiring surgery;
AND
3 • Assessment and treatment of mild brain injury
(ii). GCS score of 13-15 after 30 minutes post head injury or later upon presentation for health care. These
manifestations of MTBI must not be due to drugs, alcohol, medications, caused by other injuries
or treatment for other injuries (eg systemic injuries, facial injuries or intubation), caused by other
problems (eg psychological trauma, language barrier or coexisting medical conditions) or caused
by penetrating craniocerebral injury”.
Clinicians need to be aware that this imposes a categorical definition for convenience of clinical decision
making on a dimension of severity. Whilst the vast majority of injuries will be easily classified within this
definition there will be injuries which lie at the cusp of the definition which may require separate consideration
to the general guidance contained below; in particular, injuries where there is skull fracture, or substantive
haematoma (this is sometimes referred to as complicated mild brain injury), are not generally considered
as mild.
The description of acute assessment of severity is described within SIGN guideline 110. 3 The criteria will
require to be applied retrospectively when reviewing patients after the acute phase. The assessment of posttraumatic
amnesia can be made retrospectively but may, in some circumstances, be less reliable. Review of
emergency department (ED) records (or discharge letter) may be required, as may supplementary questions
about patients’ behaviour during any putative amnestic period; for example, to determine if they had shown
evidence of goal-directed behaviour that would indicate the presence of intact cognitive function, such as
managing to go to work.
B The diagnosis of mild traumatic brain injury should be made according to WHo task force
operational criteria, subject to clinical judgement when complicating factors are present, eg skull
fracture, seizures, or a haematoma.
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