Traumatic Brain Injury (TBI) Prognosis

OVERVIEW

Traumatic Brain Injury (TBI) is a devastating condition in terms of personal, societal and wider economic impact

• prognosis in TBI is difficult but important:
  • guides appropriate treatment
  • try to limit the proportion of patients left in a persistent vegetative state (PVS)
  •  aids the family in coming to terms with their loved one’s condition and with future planning
• clinical, physiological variables, radiological predictors and biological markers exist
• all are more useful for prediction at the population level than for guiding decisions concerning individual patients

TBI OUTOMES

MRC CRASH study in 2008 (n = 10,000 TBI patients with GCS <15) had these outcomes:

• 1 in 5 dead at 2 weeks
• 1 in 4 dead at 6 months
• 1 in 3 dead or severely disabled at 6 months

Extended Glasgow Outcome Scale is used to classify TBI outcomes, primarily in the research setting:

• Death
• PVS
• Severe disability: lower grade (dependent for ADLs), upper grade (self caring but unable to work)
• Moderate disability: lower grade (able to travel independently and work in sheltered environment), upper grade (able to work in reduced capacity, deficits in speech, memory and personality change)
• Good recovery: lower grade (can participate socially), upper grade (resumption of normal life, minor neurological/psychological deficits)

CLINICAL PREDICTORS

• age (>40 years, worse with increasing age)
• initial GCS post-resuscitation
• hypotension
• hypoxia
• pupil size and reaction to light (i.e fixed and dilated is bad!)
• ICP
• nature & extent of the intracranial injuries (worst to least, subdural -> extradural -> SAH)
• co-morbidities
• low-to-middle income countries

RADIOLOGICAL PREDICTORS

CT Brain

• obliteration of third ventricle/basal cisterns (absence of basal cisterns is the strongest predictor of six month mortality)
• midline shift
• petechial haemorrhages
• subarachnoid haemorrhage
• unevacuated hematoma
• brainstem injury

MRI

• at 6-8 weeks: injuries to corpus callosum, corona radiata and dorsolateral brainstem predict PVS

Experimental

• Diffusion tensor imaging
  • allows detection of traumatic DI by providing information on integrity of white matter
  • correlates with functional outcome at 1 year
• magnetic resonance spectroscopy
  • measures brain metabolism and amounts of particular metabolites (creatinine, choline, lactate…)
  • correlates with outcome
• SSEPs and cEEG

BIOMARKERS

Primarily experimental at present:

• serum S-100β protein (severe TBI biomarker that most consistently demonstrates the ability to predict injury and outcome in adults)
• neuron-specific enolase (NSE)
• IL-10
• myelin basic protein
• GFAP
• protein degradation products (e.g. spectrin breakdown product, c-tau, and amyloid-beta(1-42))

TBI PROGNOSIS CALCULATORS

• CRASH Head Injury Prognosis Calculator
• IMPACT Head Injury Prognosis Calculator

These are based on prognostic models that combined data from patients involved in clinical trials to predict clinical outcome, and should be used with caution:

•  their outcomes apply to populations — caution is needed if applying them to individual patients
• the models were externally validated against one another — they are yet to be validated on patients not selected from clinical trials

References and Links

LITFL

• CCC – Traumatic brain injury: Overview
• CCC – Limitations of CT in Traumatic Brain Injury
• CCC – Evoked Potentials in Critical Care

Journal articles

• Predicting outcome after traumatic brain injury: practical prognostic models based on large cohort of international patients. MRC CRASH Trial Collaborators. BMJ 2008;336:425 [Full Text]
• Nichol AD, Toal F, Fedi M, Cooper DJ. Early outcome prediction after severe traumatic brain injury: can multimodal magnetic resonance imaging assist in clinical prognostication for individual patients? Crit Care Resusc. 2011 Mar;13(1):5-8. PubMed PMID: 21355822. [fulltext pdf]
• Stevens RD, Sutter R. Prognosis in severe brain injury. Crit Care Med. 2013 Apr;41(4):1104-23. PMID: 23528755.
• Steyerberg EW, Mushkudiani N, Perel P, Butcher I, Lu J, et al. (2008) Predicting outcome after traumatic brain injury: Development and international validation of prognostic scores based on admission characteristics. PLoS Med 5: e165. doi:10.1371/journal.pmed.0050165.
• Young NH, Andrews PJD (2008) Developing a Prognostic Model for Traumatic Brain Injury—A Missed Opportunity? PLoS Med 5(8): e168. doi:10.1371/journal.pmed.0050168