In conjunction with National Epilepsy week 2022 I have been asked to pen the following article regarding epilepsy and medico-legal.

In medico-legal practice involving head injury, experts are often asked to give an assessment of the risk of post-traumatic seizures. In this article I will discuss this issue as well as giving some illustrative examples.

Epilepsy is a common condition with a lifetime risk of around 4%. There is, therefore, a background risk which is increased by a positive family history, certain drugs (such as anti-depressants), excessive alcohol intake or any insult to the brain, such as head injury, brain tumour, intracranial infection or conditions such as multiple sclerosis.

Alcohol is interesting in that in the acute situation alcohol will act as an anti-convulsant but, as the level drops, it makes the brain more prone to seizures.  This is the reason why admissions with seizures tend to occur over the weekend following binge drinking on Fridays and Saturdays.  Ultimately alcohol damages the brain and nervous system and people with chronic large alcohol intake develop seizures unrelated to acute alcohol binges.

apparent mild head injury can have evidence of brain damage on detailed 3 Tesla MRI scans with appropriate diffusion weighted and gradient echo sequences. Annegers classified head injury into mild, moderate or severe; mild brain injuries were characterised by an absence of fracture and loss of consciousness or post traumatic amnesia for less than 30 minutes. Moderate traumatic brain injuries were diagnosed on the basis of loss of consciousness or post-traumatic amnesia lasting 30 mins – 24 hours or a skull fracture.  Severe traumatic brain injuries were diagnosed on the basis of focal neurological signs (based on observation or a CT scan), intracranial haematoma or loss of consciousness or post-traumatic amnesia for more than 24 hours.  The risk of epilepsy after a mild head injury was doubled for 4 years and after a moderate to severe injury the risk was greater and lasted longer than 10 years.

The Mayo Classification (The Mayo Classification System for traumatic brain injury by Malec. Journal of Neurotrauma 24:1417 to 1424.  September 2007) incorporates imaging in to the classification system ; it is now widely used and  divides brain injury into symptomatic (possible), mild (probable) and moderate to severe (definite).

In Table 1, I have documented the classification which I use and find useful in clinical practice.  This takes into account patients with mild head injury who have subsequent abnormalities found on detailed brain imaging..  However, even this classification can be unreliable and in particular the duration of post-traumatic amnesia can be uncertain when patients require emergency surgery for orthopaedic injuries or those who require sedation and ventilation.  It can also be difficult to assess Glasgow Coma Score in patients who are intoxicated.  Nevertheless this table takes into account the main features of head injury and Table 2 gives the risk of seizures after mild, moderate and severe head injury.  I would regard complicated mild head injuries as causing a risk of seizures somewhere between mild and moderate.

In Table 2 the risk of seizures is given after various degrees of severity of head injury.

The risk, therefore, after a mild head injury is doubled for four years but then returns to the background risk of the general population which is in the region of 40 per 100,000 per year.  For moderate head injury the risk of 6 x greater for the first year, 3 x greater for the next four years and then twice greater for life.  After a severe head injury the risk is 100 x greater for the first year, 20 x greater for the next four years, 10 x greater for the next five years and then 4 x greater for life.

It is important to remember that the risk gradually falls with the passage of time.  There is no reliable data after 20 years, but my personal view is that there is still a small but diminishing risk of seizures even after 20 years, particularly in patients with severe head injury.

I will now give a few illustrative examples:

This is a common experience; patients with pre-existing epilepsy may have an increase in seizures following trauma.  Although there is no evidence of brain damage on imaging a recurrence of seizures in this case may well be due to pain, stress or sleep deprivation.  Most neurologists would accept that there can be an aggravation of pre-existing epilepsy for a six month period or thereabouts after a mild head injury.  After a moderate or severe head injury there may be a more long-lasting aggravation.

Mr M, aged 25, had a moderate head injury with more prolonged loss of consciousness and post-traumatic amnesia. He has no past history of epilepsy and he has had no seizures in the two years following the index accident. His solicitors are keen to know the risk of post traumatic seizures and whether they can be controlled on anti-convulsant medication.

After a moderate head injury when two years have elapsed the risk of seizures is 3 x greater than the general population for the next two years and then twice greater for life, although this will be a diminishing risk. He is 25 years old and assuming a life expectancy of 85, Mr M has another 60 years of life. Assuming a background risk of 40 per 100,000 per year the risk for Mr M will be 3 x greater than the background risk for two years then twice greater risk for life. The background risk in a man of 25 of developing epilepsy in the next 60 years is 2.4% whereas for Mr M the lifelong risk will be just over double that 4.9%. After 20 years the risk will only be minimally above that of the general population. If he were to develop post-traumatic seizures there is a 75% chance they would be well controlled or completely controlled on anti-convulsant medication.

It is therefore possible, with appropriate appreciation of the severity of the head injury, to assess the lifetime risk of post-traumatic seizures. It is however important to bear in mind other factors such as positive family history, alcohol intake and medications which are potentially epileptogenic.

There has been considerable interest in whether post-traumatic seizures can be prevented by a course of anti-convulsant medication. Trials of currently undergoing and at present there is no conclusive evidence that a course of anti-convulsants will reduce the risk of post-traumatic seizures.

It is also important to mention that some patients may develop functional or dissociative seizures following head injury. I have seen this on a number of occasions in patients after mild head injury. It is always important, therefore, to obtain a witness account of the seizure and to carry out appropriate investigations such as an EEG (brain wave recording). It is therefore possible to give a reasonable estimate of the risk of post-traumatic seizures and if seizures have already occurred it is important to establish that they are genuine epileptic seizures rather than functional or dissociative events.

About the Author:

Dr Cleland has been a Consultant Neurologist since 1984 and is a vastly experienced expert witness acting on behalf of both the plaintiff and defendant. Whilst he retired from his full time post at Sunderland Royal Hospital and Newcastle General Hospital in 2017, Dr Cleland still undertakes weekly outpatient clinics at Sunderland Royal Hospital. He has carried out a number of research projects in the fields of epilepsy, headache, vascular disease and tropical medicine and is still involved in both undergraduate and postgraduate teaching.

Dr Cleland has written over 40 peer reviewed articles on various aspect of neurology and tropical medicine as well as chapters in several books.

Dr Cleland can be contacted for all medico-legal work and to request his CV at pcleland@inneg.co.uk.