Post-traumatic amnesia is a transient state
following a traumatic brain injury, where brain function is temporarily
altered, disrupting cognitive and behavioural functioning (Parker et al.,
2022). The accurate diagnosis of post-traumatic amnesia is critical for
understanding the appropriate clinical management and prognosis of the patient
following a traumatic brain injury. However, in many cases these impairments
are not accurately diagnosed, negatively impacting clinical care as well as
medicolegal claims.
Post-traumatic amnesia was first
described in 1930s by British neurologists Ritchie Russell and Charles Symonds
(Russel, 1932; Symonds, 1937). Post-traumatic amnesia refers to the time
between the onset of a traumatic brain injury and the time that patients can
encode and retrieve new memories. It was noted that patients typically exhibit
a range of cognitive, behavioural and perceptual deficits, as well as
considerable variation in their clinical presentations. Russell and Symonds
coined the term “post-traumatic amnesia” because memory function returned to
normal following the resolution of this transient state.
The term “post-traumatic amnesia” is misleading
and unhelpful because this state is characterised by a broad range of
cognitive, behavioural and perceptual deficits, not limited to memory impairment.
As a result, many clinicians fail to carry out appropriate assessments to
identify other aspects of cognition and behaviour that are impaired, apart from
memory function (Parker et al., 2022). As a result, there has been a call from
neurologists to refer to this state as “post-traumatic confusional state” or
“post-traumatic delirium” (Parker et al., 2022).
Cognitive impairments exhibited during the
post-traumatic amnesia/confusional state include deficits in attention,
executive functioning, processing speed, memory loss for events prior to the
injury and an inability to encode and form new memories (Parker et al., 2022).
Therefore, comprehensive clinical histories, neuroimaging, as well as
comprehensive cognitive and neuropsychological assessments are needed following
a traumatic brain injury to determine the likely severity of cognitive
impairments and the likely prognosis.
Behavioural disturbances exhibited during the
post-traumatic amnesia/confusional state include agitation, restlessness,
confusion and sometime aggression (Parker et al., 2022). Some patients in the
post-traumatic amnesia/confusional state also experience hallucinations and are
often misdiagnosed with psychosis. Other differential diagnoses that should be
ruled out include Wernicke’s encephalopathy, intracranial haemorrhage, fat
embolism syndrome as well as alcohol and/or illicit drug use and/or withdrawal.
However, some patients who have experienced a traumatic brain injury may
experience psychosis secondary to the effects of opioid analgesics. It can also
be particularly challenging to properly assess patients who experience a
traumatic brain injury if they are intoxicated at the time of the injury since
this can confound the results of the cognitive and neuropsychological tests.
Understanding whether a cognitive impairment
arising from a traumatic brain injury is transient or permanent is critical for
medicolegal claims. However, it can be challenging to distinguish between
permanent deficits and impairments that are plausibly related to a transient
state of post-traumatic amnesia. This is especially challenging since the
duration of the post-traumatic amnesia/confusional state can vary considerably
between patients. Therefore, repeated and detailed cognitive,
neuropsychological and neuroimaging tests are needed to help establish the
nature of the cognitive impairments following a traumatic brain injury (Parker
et al., 2022).
The duration of the post-traumatic amnesia state
is a significant predictor of functional outcomes following a traumatic brain injury
(Nakase-Richardson et al., 2011). Therefore, the accurate and timely diagnosis
of post-traumatic amnesia is crucial. If the duration of this is not accurately
measured, this will negatively impact the accuracy of the likely prognosis of
the patient. It is also critical that timely and accurate diagnoses are made to
support the clinical management of the patient. If for example, an individual
is incorrectly diagnosed with psychosis and prescribed typical antipsychotics
such as haloperidol, this could inadvertently worsen functional outcomes since
antipsychotics have been shown to increase the duration of post-traumatic
amnesia (Rao et al., 1985) linked with poorer functional outcomes
(Nakase-Richardson et al., 2011).
These findings highlight the importance of
rigorous, accurate and timely cognitive, neuropsychological and neuroimaging
assessments to understand the nature, severity and duration of the
post-traumatic amnesia/confusional state to support the clinical management and
medicolegal claims of individuals who have experienced a traumatic brain
injury.