FREE BOOK CHAPTER: The Severity of a Traumatic Brain Injury (From 'A Practical Guide to Subtle Brain Injury Claims' by Pankaj Madan)
03/02/17. One Scale used to assess consciousness is called the Glasgow Coma Scale which is abbreviated in notes to (“GCS”). This is the most extensively used system for assessing the level of consciousness. The scale is based on the motor (M) verbal (V) and eye-opening (E) responses of the patient and is used to classify injury as “minor”, “moderate” or “severe”. The scale does not go to 0. The minimum score representing complete unconsciousness is 3. Traditional thinking is as follows:-
13-15 means you may be likely to be dealing with a Mild or Minor injury
9-12 means you may be likely to be dealing with a Moderate injury
Less than or equal to 8 usually means a severe injury
Note that 15/15 on the GCS scale means fully conscious. Nevertheless, subtle traumatic brain injury is still possible even where ambulance notes or especially the A&E notes document a GCS of 15/15. These scores are often recorded many minutes after an accident has occurred.
Other factors can also affect the level of consciousness such as alcohol or the administration of sedating drugs such as some pain relieving medication (although usually only by 1 or 2 points).
Equally, sometimes these factors are assumed to be the cause of impaired consciousness when in fact the cause may well be a brain injury.
A GCS score of 3, the lowest score, represents no eye opening to pain, no verbal response and no motor response to pain. This would be recorded in the notes as E1, V1, M1.
A fully conscious score of 15 would be recorded as E4, V5, M6.
It is not just the total score that matters. Claimants with the same total score but differing components of the scores can have different outcomes.
It is easily forgotten that there may be other signs of brain injury and in the medico-legal context there can be an over-emphasis of the importance of GCS scores.
Signs of injury on the scalp such as bruising and lacerations, depressed skull fractures, sub-conjunctival haemorrhages bleeding, and discharge of CSF from the ear or nose may be indicators of brain injury. The latter are particularly associated with skull base fractures. Anosmia or loss of the sense of smell may also be an indicator of brain injury.
It is also wrong to assume that any fall in the level of consciousness with time cannot be due to brain injury. It may be falsely associated with medical treatment. In fact, raised intra-cranial pressure may also cause a decrease in the level of consciousness over time in the aftermath of the hours after the traumatic event. The cranium is of course a rigid box containing the brain. Any increase in volume caused by blood, swelling of the brain or CSF can cause raised intra-cranial pressure and a fall in the level of consciousness. If left untreated, death may soon occur.
Such victims of brain injury are the “walking wounded”. Seemingly normal at first but with a fatal outcome. This is why of course CT scanning in the accident and emergency context is extremely useful. It is being used to detect and exclude the possibility of a bleed leading to raised intra-cranial pressure and the possibility of a severe outcome or death.
The Mayo system
The Mayo system is a different classification system of brain injury.
It was developed to deal with some of the difficulties arising from the use of GCS to identify a Mild Traumatic Brain Injury. The Mayo system has several main categories:-
- Definite moderate-severe traumatic Brain Injury;
- Probable moderate traumatic brain injury
- Possible Traumatic Brain Injury
The scale utilises multiple criteria including loss of consciousness, post-traumatic amnesia, skull fracture and evidence of neuro-radiological abnormalities. To fall into the moderate severe category there would usually have to be loss of consciousness of 30 minutes or more and Post traumatic amnesia of more than 24 hours.
The Mayo system is generally thought of as far more reliable than GCS scale score at identifying brain injury and the severity of it.
Post-traumatic amnesia is a very important component of identifying whether or not there has been a brain injury and the severity of it.
Post-traumatic amnesiais the interval from injury until the patient can form and lay down and recall new memories.
One research paper by Nakase-Richardson et al (2011) concluded that:-
- a PTA of 0-14 days was classified as a moderate TBI,
- a PTA of 15-28 days was classified as a moderately severe TBI,
- and a PTA of 29-70 days or more was classified as a severe TBI.
Other factors are also taken into account including the presence of dizziness and nausea and headache.
The Mayo system of classification is multi-factorial and has been shown to be sensitive with a high degree of reliability on predicting brain injury and the outcome of it.
One problem however particularly in the in the UK is that there is usually no prospective tool used for the assessment of post-traumatic amnesia in the clinical setting. Assessments of PTA are therefore being made retrospectively. Friedland, writing in an article in “Spine” 2013, S4, states that the retrospective analysis of post-traumatic amnesia can yield false positives in terms of diagnosing and individual as suffering from a TBI
The “Russell” System of Classification of brain injury
The Russell system depends heavily on the level of Post traumatic amnesia and injuries are classified as follows:-
- Mild – PTA of less than 1 hour
- Moderate – PTA of more than 1 hour but not more than 24 hours
- Severe – PTA or more than 24 hours but not more than 1 week
- Very severe – PTA of more than 1 week but less than 1 month
- Extremely severe – PTA of more than 1 month
It is difficult in a legal book of this size to give a comprehensive analysis. A brief summary however is as follows:- A TBI is moderate to severe if one or more features exist:-
- Loss of consciousness of 30 minutes or more
- Post traumatic amnesia of 24 hours or more
- The lowest GCS score in the first 24 hours is 12 or less
- Haemorrhagic contusion, Penetrating TBI, Sub-arachnoid haemorrhage, brain stem injury, intra-cerebral heamatoma, sub-dural heamatoma or any of them are present.
- The length of post traumatic amnesia (the length of time before continuous memory is re-established) is one of the better indicators of traumatic brain injury.
- Abnormalities on neuro-imaging will influence the conclusion.
Mild to moderate TBI may be diagnosed if there is :
- Loss of consciousness of less than 30 minutes
- Post traumatic amnesia of less than 24 hours
- Depressed, basilar or linear skull fracture without penetration of the dura mater
A diagnosis of symptomatic possible TBI may be made if one or more of the following signs are present:-
Blurred vision, confusion, dizziness, headache or nausea and/or vomiting.
It is worth remembering however that there is no “gold standard” in relation to classification systems for brain injury. It is important that they are understood and the various limitations of each appreciated.