29. Neurological disorders - Seizures Flashcards
Definition of a Seizure
A seizure is a paroxysmal abnormality of motor, sensory,
autonomic, and/or cognitive function, due to transient
brain dysfunction.
The term includes epileptic, syncopal
(anoxic), brainstem (hydrocephalic, coning), emotional
or functional (psychogenic pseudo-seizures), and as
yet undetermined.
Regarding seizures as epileptic or
non-epileptic will guard against the misdiagnosis of
epilepsy, which is common.
Epileptic seizures
Epileptic seizures are due to…
(As opposed to a non-epileptic seizure)
What makes a seizure epileptic is the nature of the
underlying electrical activity in the brain, especially in
the cerebral cortex, so it can sometimes be difficult to
tell from a non-epileptic (especially a syncopal seizure)
clinically.
Epileptic seizures are due to excessive and
hypersynchronous electrical activity, typically in neural
networks in all or part of the cerebral cortex.
Convulsions
A convulsion is a seizure (epileptic or non-epileptic)
with motor components, particularly stiff (tonic), a
massive jerk (myoclonic), jerking (clonic), trembling
(vibratory), thrashing about (hypermotor); as opposed
to a non-convulsive seizure with motor arrest, e.g. an
unresponsive stare (as in generalized epileptic absence
seizures and some focal epileptic seizures), or drop
attack (as in an epileptic atonic seizure).
Epilepsies
What is an Epilepsy
An epilepsy is a brain disorder that predisposes the
patient to have unprovoked epileptic seizures.
Generally,
an epilepsy can be recognized after two or more
unprovoked epileptic seizures have occurred.
Acute symptomatic epileptic seizures
What characterizes an acute symptomatic epileptic seizure?
When epileptic seizures are provoked by an acute brain
injury, e.g. from acute cortical ischaemia during arterial
ischaemic stroke, or from a cerebral contusion during a
traumatic brain injury, or cortical inflammation during
meningitis. They do not constitute an epilepsy, even
if there were recurrent injuries. These are called acute
symptomatic epileptic seizures. The causes of seizures
are listed in Box 29.2.
Febrile seizures
What is a febrile seizure?
Occur between the ages of…
The seizure usually occurs…
What type of seizures are they usually?
What should also be considered on the causation of the fever?
What is required in children less than 18 months of age suspected of meningitis?
If there is a history of prolonged seizures (>5 min)…
A “febrile seizure” or “febrile convulsion” is an epileptic
seizure accompanied by a fever in the absence of
intracranial infection.
These occur in 3% of children,
between the ages of 6 months and 6 years.
There is
a genetic predisposition, with a 10% risk if the child
has a first-degree relative with febrile seizures.
The
seizure usually occurs early in a viral infection when
the temperature is rising rapidly.
They are usually
brief generalized tonic-clonic seizures.
About 30–40% will have further febrile seizures.
This is more likely the younger the child, the shorter the duration of illness before the seizure, the lower the temperature at the time of seizure and if there is a positive family history.
_Simple febrile seizures do not cause brain damage;
the child’s subsequent intellectual performance is the
same as in children who did not experience a febrile
seizure._There is a 1–2% chance of subsequentally
developing an epilepsy, similar to the risk for all
children.
However, complex febrile seizures; i.e. those which
are focal, prolonged, or repeated in the same illness, have an increased risk of 4–12% of subsequent
epilepsy.
The acute management of seizures is described in
Chapter 6. Examination should focus on the cause of
the fever, which is usually a viral illness, but a bacterial
infection including meningitis should always be
considered.
The classical features of meningitis such
as neck stiffness and photophobia may not be as
apparent in children less than 18 months of age, so
an infection screen (including blood cultures, urine
culture, and lumbar puncture for cerebrospinal fluid)
may be necessary.
If the child is unconscious or has
cardiovascular instability, lumbar puncture is contraindicated
and antibiotics should be started immediately.
Parents need reassurance and information. Advice
sheets are usually given to parents. Antipyretics
may be given but have not been shown to prevent
febrile seizures. The family should be taught the first
aid management of seizures. If there is a history of
prolonged seizures (>5 min), rescue therapy with
buccal midazolam can be supplied. Oral prophylactic
antiepileptic drugs are not used as they do not reduce
the recurrence rate of seizures, and have a relatively
high risk of adverse effects. An EEG is not indicated as
it does not predict seizure recurrence.
Paroxysmal disorders
There is a broad differential diagnosis for children with
paroxysmal disorders (‘funny turns’). Epilepsy is a clinical
diagnosis based on the history from eyewitnesses
and the child’s own account. If available, videos of the
seizures can be of great help. The diagnostic questions
are: was it an epileptic seizure, and if so does the child
have an epilepsy? Epilepsies can be further delineated
as outlined below. If non-epileptic or uncertain, further
delineation of the nature of the seizure or paroxysmal
event is required (Fig. 29.1). The most common pitfall
is that of syncope leading to an anoxic (non-epileptic)
tonic-clonic convulsive seizure.
The key to the diagnosis lies in a detailed history,
review of video if available, which, together with the past history and clinical examination, will lead to a
diagnosis of “epilepsy”, acute symptomatic or febrile
seizure, or non-epileptic seizure. Interictal EEG is useful
in categorizing an epilepsy once diagnosed. Ictal EEG
can be helpful in difficult to diagnose cases when
seizures are frequent enough to capture or can be
triggered.
Transient loss of consciousness is most commonly
due to syncope, which is caused by a transient
impairment of brain oxygen delivery, generally due to
impaired cerebral perfusion (see Chapter 18).
