Table 1

Some conditions that might mimic epilepsy in infancy

Condition	Main features
Mainly rapid movements
Benign sleep myoclonus	Onset within a few weeks of age. Dramatic myoclonic movements confined to sleep occur in flurries, migrating from one limb then another in clusters of a few per second. Precipitated by gently rocking the sleeping infant. They do not wake nor distress the child. Settles within months.
Benign neonatal myoclonus or benign myoclonus of early infancy (BMEI)	Also referred to as ‘benign non-epileptic infantile spasms’, and with a recent suggestion that it be referred to as ‘Fejerman syndrome’. This is associated with myoclonus, spasm-like movements, head nodding, blinking, and/or shuddering. The EEG is normal. Onset is usually between 1 and 12 months, and resolution by 3 years old. (Distinguish from ‘benign myoclonic epilepsy of infancy’ (see table 2)).
Shuddering attacks	When presented with an interesting or new object/dinner, the child typically holds arms out and shudders involuntarily involving the whole body. Common variant of normal infant behaviour. Considered by some to be a variant of BMEI.
Jitteriness or tremulousness	Well recognised in the early neonatal period but can occur up to 6 weeks corrected age. The movements have symmetrical amplitude and speed in both directions, in contrast with clonus where one direction is faster. May be provoked by stimulus and settle with handling.
Mainly sustained movements
Gastro-oesophageal reflux and Sandifer syndrome	Gastro-oesophageal reflux in infants can cause tonic or repetitive truncal extension that may mimic seizures. It can also cause apnoea, which can also be mistaken for an autonomic seizure.
Self-gratification disorder	Older infants. Particularly in high chairs/car travel seats fitted with a strap between the legs AND if the child is bored. The insides of the thighs are rubbed together whilst legs are adducted in extension. Infant may be flushed and unresponsive. May be mistaken for tonic seizures or dystonia.
Benign paroxysmal torticollis	Recurrent episodes of cervical dystonia with typical onset in age range of 2–8 months. Apparent torticollis lasts hours to days and is associated with pallor and vomiting. There may be associated hearing impairment. Episodes usually stop by age 3 years but cases develop a tendency to migraine in later life.
Paroxysmal dyskinesia	Occur in infancy. Kinesiogenic (movement induced) or non-kinesiogenic.
	Kinesiogenic—dystonia of unilateral leg. Often prodromal sensation. May have chorea or ballismus. Episodes last seconds to minutes, at a frequency of 100 s/day. Responds well to treatment.
	Non-kinesiogenic—dystonia or choreoathetosis in face and limbs. Communication difficulties. Episodic ataxia. Lasts minutes–hours, at a frequency of 3/day to 2/year. Precipitated by fatigue, alcohol, caffeine and vibration. Tend to be refractory to treatment.
Transient idiopathic dystonia of infancy	Described by Willemse. Onset before 6 months old. Dystonic posturing of an upper limb, typically with pronation and wrist hyperflexion, and sometimes posturing of the trunk and lower limb. The posturing usually resolves with intentional movements. Such dystonia has also been described in infants exposed in utero to cocaine.
Hyperekplexia	Neonates markedly startle at sudden sounds or being touched (especially on the nose), resulting in severe total body stiffening. Life-threatening apnoea can result. Spells can be terminated by forcibly flexing the neck. Valproate and clonazepam may help.
Eye movements a prominent feature
Spasmus nutans	A triad of asymmetrical ocular oscillations (pendular nystagmus), head nodding and torticollis or other unusual head positioning. Benign and self-limiting but need to rule out intracranial lesions.
Paroxysmal tonic upgaze of infancy	A rare condition with onset typically before 10 months. Episodes of intermittent or sustained upward tonic gaze deviation that may last hours and downbeat nystagmus on downward gaze. Worse if fatigued or during an intercurrent illness. Should resolve by 3 years of age. Levodopa may help symptom control.
Opsoclonus–myoclonus–ataxia syndrome	Opsoclonus refers to rapid, conjugate, irregular eye movements that are usually distressing for the child. It is often associated with myoclonus and ataxia as part of a paraneoplastic phenomenon associated with neuroblastoma.
Complex movements and behaviours
Overflow movements	These movements, such as ‘mirror movements’ of an upper limb, are involuntary and may rarely be mistaken for a focal seizure.
Stereotypies and self-stimulatory behaviours	Stereotypies are repetitive, patterned and rhythmic movements that are considered to be involuntary, non-reflex and not goal-directed. Common forms are hand flapping, and lower limb shaking. They are often associated with excitement, boredom or stress. Tics tend to have an older age of onset. Stereotypical hand movements can occur in conditions with increased risk of epilepsy, such as Rett syndrome.
Vitamin B12 deficiency	A movement disorder including mild choreoathetoid movements and/or a limb tremor resembling epilepsia partialis continua has been described in association with cobalamin deficiency.
Associated colour changes, loss of consciousness, or weakness WITHOUT a cardiac origin
Breath-holding spells	Now often called ‘reflex end expiratory apnoeic syncope’ or ‘prolonged expiratory syncope’. These can take cyanotic or pallid forms, both associated with vagal reflexes, bradycardia and decreased blood flow. Cyanotic episodes are usually provoked by anger or emotional upset, and are associated with apnoea in the expiratory phase of the breathing cycle. Pallid forms, usually referred to as ‘reflex anoxic seizures’ are discussed below.
Alternating hemiplegia of childhood	The typical prodrome is restlessness and screaming. There can also be nystagmus (often unilateral) and episodes of dystonia or stiffening. Subsequent lateralised weakness can last minutes to days and can be mistaken for a Todd's paresis.
Paroxysmal extreme pain disorder	This condition, formerly known as ‘familial rectal pain syndrome’, is associated with mutations in nociceptive and sympathetic neuronal sodium channels. Clinical features may include startling, screaming, skin flushing (including the ‘harlequin baby’ appearance), pallor, apnoea, hypersalivation and generalised tonic stiffening lasting up to minutes.
Reflex anoxic seizures	These ‘pallid’ episodes with altered consciousness may be reflex in nature but it is important to consider cardiac causes such as long-QT syndromes in addition to syncopal mechanisms, the common features being due to temporary inadequacy of cerebral blood flow. Reflex anoxic seizures are usually precipitated by surprise or minor trauma, and are more likely to have associated limb clonus.
Associated colour changes, loss of consciousness, or weakness WITH a possible cardiac origin
ALTEs and long-QT syndromes	Apparent life-threatening events (ALTEs), some of which are likely to be manifestations of cardiac long-QT syndromes, may be mistaken for primarily neurological events. Where loss of consciousness is a prominent feature, particularly where it is associated with exercise, ensure that an ECG is performed. Long QT2 is associated with events provoked by emotional or auditory stimuli, and long QT3 with events at rest and possibly in sleep.
Tetralogy spells	Episodes of cyanosis, dyspnoea and loss of consciousness associated with sudden right-to-left cardiac shunts. There may be associated secondary seizures due to hypoxaemia.
Other metabolic, iatrogenic or induced illnesses
Metabolic disturbances	Hypoglycaemia and hypocalcaemia, often in association with other metabolic disturbances, can cause altered consciousness or symptomatic seizures.
Midazolam withdrawal syndrome	This is commonly seen on paediatric intensive care units, and seems to be commoner where midazolam is combined with fentanyl. Features may include altered awareness, agitation, vomiting, tremors and choreoathetoid or dystonic movements.
Fabricated or induced illness	Infants are also susceptible to fabricated and induced illness, and it is prudent to keep this possibility in mind. It is useful to have corroborative evidence from several observers about the nature of onset of the events. Presentations can include suffocation or strangulation syncope, or administration of drugs that are detectable on urine toxicology screen.