Differentials
Functional seizures (non-epileptic seizures)
SIGNS / SYMPTOMS
Episodes of altered movement, sensation, emotion, or experience that have the appearance of epileptic seizures but are not caused by paroxysmal, hypersynchronous electrical activity of the brain.[35]
The clinical appearance of functional seizures may mimic virtually any seizure type.
Some features more likely to suggest functional seizures include: eyes being tightly closed, tearfulness, duration more than 2 minutes, hyperventilation during a seizure, and side-to-side head shaking.[36]
Functional seizures are usually considered a functional neurological symptom disorder. Some patients will have had adverse life events, but, importantly, these are neither necessary nor sufficient for the diagnosis.[36] Psychological comorbidities - especially anxiety, panic, and depression - are common, affecting over 50% of patients.[37]
A significant minority of people with functional seizures will have co-existent epilepsy, so it is important to determine whether the patient has a number of different types of spell.
INVESTIGATIONS
The only reliable diagnostic test to differentiate functional from epileptic seizures is video electroencephalogram (EEG) (long-term monitoring). The EEG during functional seizures is either normal or obscured by movement or muscle artefact.
Correct diagnosis is usually based on the semiology of the event and the absence of epileptiform EEG correlate.
Breath-holding spells (prolonged cyanotic expiratory apnoea)
SIGNS / SYMPTOMS
Often precipitated by anger or frustration.
Typically vigorous cry is followed by a period of blocked respiration resulting in cyanosis, loss of consciousness, and sometimes opisthotonic posturing (i.e., muscle spasm leading to pronounced hyper-extension with head and lower limbs bent backwards and the trunk arched forwards).
INVESTIGATIONS
ECG during the event may show initial tachycardia followed by bradycardia.
Long QT syndrome
SIGNS / SYMPTOMS
Often positive family history.
History of syncope triggered by pain, fear, or exercise.
INVESTIGATIONS
ECG shows prolonged corrected QT interval.
No epileptic discharges on EEG during the episode but, depending on the duration of asystole, hypoxic slowing of the EEG may be seen during the attack.
Syncope
SIGNS / SYMPTOMS
Often happens in standing position and is accompanied by pallor and sweating.
May be precipitated by painful stimuli.
Usually quick recovery and no post-ictal phase.
INVESTIGATIONS
Tilt-table testing can confirm a diagnosis of vasovagal syncope, the most common type.
12-lead ECG is the only test needed and excludes prolonged QT syndrome.
Parasomnias
SIGNS / SYMPTOMS
Occur mostly in the first few hours of sleep and usually not repetitive in same night.
Sleep behaviours such as sleepwalking and eating while asleep may be present.
INVESTIGATIONS
Normal EEG during the event.
Paroxysmal movement disorders
SIGNS / SYMPTOMS
Includes tics, episodic ataxias, or paroxysmal dyskinesias.
Occasionally characteristics of the movements (e.g., location, speed, frequency) are different from seizure.
INVESTIGATIONS
Normal EEG during the event.
Gastro-oesophageal reflux
SIGNS / SYMPTOMS
Characterised by child gasping and becoming suddenly apnoeic and stiff.
May be a change of skin colour.
Child may appear startled.
Bizarre posturing that may accompany this event is known as Sandifer syndrome.
Usually occurs within 1 hour or so of a feed.
INVESTIGATIONS
Trial of treatment with H2 antagonists, proton-pump inhibitors, or antacids terminates the events.
Inattention/daydreaming
SIGNS / SYMPTOMS
Episodes can be interrupted and do not finish suddenly.
Not accompanied by automatisms.
INVESTIGATIONS
Inter-ictal and ictal EEG are normal.
Panic disorders
SIGNS / SYMPTOMS
Panic attacks usually occur during periods of stress.
May be accompanied by chest pain or paraesthesias.
No post-ictal phase.
INVESTIGATIONS
Normal EEG during the event.
Self-gratification behaviour
SIGNS / SYMPTOMS
Infantile masturbation may be confused with seizure disorder.
Rhythmic hip flexion and adduction accompanied by a distant expression.
Period of sleepiness afterwards should not be confused with post-ictal phase.
INVESTIGATIONS
Normal EEG during the event.
Reflex anoxic seizures
SIGNS / SYMPTOMS
Also called reflex asystolic syncope.
Usually precipitated by mild injury.
Cerebral hypoxia may lead to opisthotonic posturing and brief clonic movements.
No post-ictal phase.
INVESTIGATIONS
An ECG during the event will document asystole.
Febrile seizures
SIGNS / SYMPTOMS
Presence of fever.
INVESTIGATIONS
Diagnosis is clinical.
EEG is normal.
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