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Photosensitive epilepsies
These are more common in adolescence. They are most often detected around 12–14 years
of age, although careful history-taking may elicit an earlier onset. Two-thirds of subjects are
female. The photosensitive epilepsies do not constitute a single syndrome. It is always
important to define the syndrome in which the photosensitive epilepsy occurs, such as JME
or JAE, so that specific information on treatment and prognosis can be given.

Reading epilepsy
This is a rare, benign form of epilepsy with a mean age of onset of 17–18 years. It is more
common in males. There is a strong genetic predisposition. Diagnosis is confirmed by the
very characteristic motor/sensory aura: after reading for a period, abnormal sensations or
movements occur (with full consciousness), involving the tongue, throat, jaw, lips and face.
If the patient does not stop reading, this aura may progress to a tonic-clonic seizure. If the
subject stops reading when the aura occurs, tonic-clonic seizures can often be avoided and
treatment with AEDs may not be necessary. If treatment is given then sodium valproate
appears to be the drug of choice. The inter-ictal EEG is usually normal.

Subacute sclerosing panencephalitis (SSPE)
This condition, which typically follows measles infection very early in life (under two years
of age), usually presents in either in late childhood or in the teenage years with relentless
deterioration and eventual death. Initially there may be subtle loss of intellectual ability but
myoclonic jerks or more complex abnormal movements soon become evident and the ensuing
dementia is all too obvious. The EEG pattern is characteristic, with a discharge in all the leads
when each jerk occurs. Measles antibody is raised in blood and is high in cerebrospinal fluid
(CSF).

Epilepsy from cortical brain tumours
Cortical brain tumours can occur at any age. Because of this, serious consideration should be
given to neuroimaging of adolescents who present with partial seizures. The exception would
be those who have characteristic benign partial seizures with a single seizure or cluster of
seizures, no abnormal neurological signs and no recurrence.

Investigation

The investigations of epilepsy in adolescence are similar to those at other ages. Basic blood
tests for full blood count, creatinine and electrolytes, calcium, and liver function tests should
be performed. An EEG with photic stimulation should be obtained. Neuroimaging should be
considered but will not be necessary in those conditions which are obviously benign, as
described above. In selected cases a urine toxicology screen for substance misuse or testing
for neuronal antibodies may be appropriate. The latter may be particularly indicated if the
presentation is unusual, especially if there are psychiatric symptoms or other signs of limbic
encephalitis10 (which may or may not be detectable on MRI scanning).

Treatment

It is very important not to group the epilepsies of adolescence together as a single entity. For
example, benign partial seizures in adolescence should not be treated whereas treatment of
JME with sodium valproate is strongly recommended and often needs to be continued long
term.

The mainstay of treatment is with AEDs. First-line drugs, such as carbamazepine and sodium
valproate, should generally be used. Sodium valproate is usually effective for JME and for
absence seizures. However, valproate is also associated with a risk of neural tube defects and
impaired verbal IQ in offspring of mothers who take this drug during pregnancy. It is also