JC: is Persistent Functional deficit following Mild Traumatic Brain Injury more common than we thought?

Annually, around 1.4 million people in England and Wales attend emergency departments (EDs) following a head injury. This may sound like a lot, but actually, the incidence of death in this cohort is very low. Unsurprising, at least 95% of these patients present with a normal or minimally impaired conscious level.

A normal CT brain on top of this may be reassuring, but a growing pool of evidence suggest that mild traumatic brain injury (TBI) is not as innocuous as it may seem at first. Many patients suffer with persistent symptoms following a diagnosis of mild TBI, restricting their daily lives and affecting their livelihoods.

In this study (Outcomes in Patients With Mild Traumatic Brain Injury Without Acute Intracranial Traumatic Injury), Debbie Madhok and her team show that following mild TBI, a fairly high number of patients continue to suffer with persistent symptoms at 2 weeks and 6 months. The abstract is below, but as always we strongly recommend you read the full paper yourself.

The Paper

What kind of study is this?

This was a prospective, observational cohort study. Observational studies tell us how things are: we observe a group (or cohort) and then measure and record certain predefined characteristics. Cohort studies tend to follow a group over time, tracking the predefined characteristics within that group. Observational studies may suggest associations between group members and characteristics, but are not robust enough to definitively prove association in the same way randomised control trials (RCTs) can. Although RCTs are better, they are also more complex, costly and can be impractical or even unethical within certain contexts.

Tell me about the patients

Patients were recruited from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) dataset. The TRACK-TBI group specifically investigates recovery after mild TBI. The paper reviewed in this blog, is also by the TRACK-TBI investigators. The TRACK-TBI dataset includes the data from patients enrolled at 18 level I US trauma centres, between January 2014 and December 2018.

For this study, the investigators included patients 17 years or older, that presented with head trauma within 24 hours of injury, with a GCS of 15 and a CT brain showing no acute injury, who reported either alteration in consciousness or amnesia. The latter was of particular importance and was included to meet the American Congress of Rehabilitation Medicine’s definition for mild TBI. These criteria include: any period of loss of consciousness; any loss of memory pre- or post-events ; and any mental state alterations (including being dazed, disoriented or confused); or focal neurological deficits (transient or not).

The investigators excluded patients with life-threatening illness, incarceration, debilitating mental health concerns, pregnancy and non-survivable trauma. Some patients were also excluded based on language (only 4 of the 18 sites recruited Spanish speaking patients).

What are the outcomes?

For the primary outcome participants were followed up at 2 weeks and 6 months for functional recovery. The investigators used the Glasgow Outcome Scale-Extended (GOS-E, see below) for this purpose. A GOS-E score of 2 defines a vegetative state, whereas a score of 8 defines a return to baseline function. Investigators applied the GOS-E score in a binary fashion, with a score of 8 vs any score less than 8. Given the mild nature of TBI included (GCS of 15 and a normal CT brain), very low scores were less likely from the outset.

Journal of Neurotrauma. 2021;38(17):2435-46.

There was also a secondary outcome: investigators measured severity of TBI symptoms at 2 weeks and 6 months. They used the Rivermead Post Concussion Symptoms Questionnaire (RPQ) to record new or worsened symptoms since the injury, such as: headache, dizziness, nausea, cognitive, mood, and sleep disturbances.

What are the main results?

The main result was that only 27% of patients with mild TBI after injury were back to baseline at 2 weeks, increasing to 44% at 6 months (so less than half had fully recovered by the end of the study). Those who did not recover fully described difficulty with returning to social activities outside the home, disruptions in family relationships and friendships, and an inability to return to a functional baseline. Unsurprising, the findings at 2 weeks were associated with those described at 6 months.

Should we change practice?

The point this study makes is that persistent symptoms following mild TBI are more common than I think the average emergency clinician expects. Certainly more than I expected. It is likely that many patients suffer longer with mild TBI than they ought to, without the necessary follow-up and referral. The NICE guidelines do discuss follow-up, but not in substantial detail. In a nutshell, a fair number of patients with mild TBI are likely to benefit from follow-up and referral for persistent symptoms.

The inclusion of a normal CT brain, although necessary in the context of the study to show no structural damage as a result of TBI, is a bit of a real world confounder. According to the NICE guidelines, transient alteration in consciousness or amnesia do not necessarily result in a CT brain, unless the patient is 65 years or older, has a history of bleeding or clotting disorders, a dangerous mechanism, or the amnesia is retrograde and lasts more than 30 minutes.

Likewise, the Canadian CT Head Injury/Trauma Rule recommends CT brain for retrograde amnesia to the event lasting more that 30 minutes, but only as a medium risk. The NEXUS Head CT Instrument is less specific and recommends CT brain for any of the following: delayed or inappropriate response to external stimuli; excessive somnolence; disorientation to person, place, time, or events; inability to remember three objects at 5 mins; or perseverating speech.

Elsewhere, clinical decision rules for ordering CT brain in the context of TBI are used less ubiquitous, and may depend largely on available resources and access to imaging.

My guess is that in the context of mild TBI, it is recognising the symptoms that may lead to ongoing functional deficit that is important. A normal CT brain, although reassuring from an acute perspective, does not mean functionally normal. It can always be included later, if it wasn’t indicated at initial presentation. In the UK, Headway, provides support for patients with persisting symptoms after mild TBI. Although I have signposted patients to Headway, my impression has always been that only a handful of patients require follow up. Perhaps follow up and referral after mild TBI are less formalised than it ought to be?

I’d be interested to know whether there are already EDs in the UK (or elsewhere) with structured early follow up for patients with mild TBI. If you are aware of one, or work in one, please let us know in the comments.




References & further reading

Cite this article as: Stevan Bruijns, "JC: is Persistent Functional deficit following Mild Traumatic Brain Injury more common than we thought?," in St.Emlyn's, January 29, 2023, https://www.stemlynsblog.org/jc-is-persistent-functional-deficit-following-mild-traumatic-brain-injury-more-common-than-we-thought/.

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1 thought on “JC: is Persistent Functional deficit following Mild Traumatic Brain Injury more common than we thought?”

  1. A really interesting study and post. One would assume that there are many other mTBI patients that do not meet the criteria for neuroimaging in the ED, but are also incompletely recovered by 6 months, albeit probably a lower proportion than those who were featured in the study. There is a very strong case for a follow-up screening process to be in place for mTBI patients (either via F2F review, telephone follow-up or an online tool) to identify and refer on those with persisting symptoms/functional deficit. The added challenge though, is having the specialist services in place to refer these patients to (i.e. a multi-disciplinary mTBI / concussion clinic).

Thanks so much for following. Viva la #FOAMed

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