Australian Doctor 12th July Issue 2024 | Page 30

12 JULY 2024 ausdoc . com . au underlying CNS lesion that has caused the child to have seizures but is not always indicated after a diagnosis of epilepsy ( see box 3 ). 14

MRI ( see figure 6 ) is the modality of choice because of its superior anatomical resolution compared with CT . CT is more sensitive for detecting calcification or haemorrhage . 16 Children aged under seven require sedation for MRI scans . A repeat MRI may be indicated if the initial scan is inadequate , new clinical features appear , or if there is an atypical course for the suspected

14 , 15 epilepsy syndrome .

CT may be used in the acutely unwell child to assess for haemorrhage . Other modalities of neuroimaging may be considered by epilepsy specialists as part of further investigation .

Genetic testing

The diagnostic yields of genetic testing range from 9 % to 48 %, depending on the method used . 17 Finding a genetic diagnosis can assist in prognostication , management and future family planning . Consider genetic testing for those listed in box 4 , where it has the highest yield . 18

A chromosome microarray to detect copy number variants is the usual first test , with a yield of up to 23.5 % in individuals with epilepsy and developmental delay . 19

If this is negative , next-generation sequencing with epilepsy gene panels or whole-exome sequencing may be considered after discussion with an epilepsy specialist . A negative genetic test does not mean the individual does not have a genetic epilepsy .

Other investigations

A 12-lead ECG is performed as part of the evaluation of a person with a suspected first seizure , to identify cardiac mimics . 15 An epilepsy specialist may consider further testing of the blood , urine or CSF if a metabolic or autoimmune aetiology is suspected .

COMMON SEIZURE MIMICS

Syncope

SYNCOPE is a brief loss of consciousness and postural tone because of

20 , 21 insufficient global brain perfusion .

History may reveal a trigger , such as prolonged standing , dehydration , posture change , micturition or a 20 , 22 bowel motion .

The individual can often recollect warning symptoms of visual blurring , light-headedness , nausea and sweating before losing consciousness .

Non-stereotyped tonic and / or clonic movements are seen in up to 50 % of children with syncope . 22 There is typically rapid recovery ,

Box 2 . Aetiology of childhood epilepsy

• Structural epilepsy : — This results from a structural change in the brain , identified on neuroimaging . — The signs and symptoms of a seizure are dependent on the location of the lesion . — Examples include scarring from trauma or stroke ( see figure 1 ), tumours , vascular malformations and malformations of cortical development ( most commonly focal cortical dysplasia ; see figure 2 ). 6

• Genetic epilepsy : — This occurs when there is a definite or presumed genetic cause . — A genetic aetiology may be determined from an established molecular diagnosis , suspected from the history or inferred from previous clinical research without a gene being identified ( including syndromes such as childhood absence epilepsy ). 7 — One gene may cause a spectrum of disease , and one clinical syndrome may result from different genes .

• Metabolic disorders : — These include acquired causes ( organ failure , nutritional deficiencies , and drugs or toxin exposure ) or genetic disorders , also known as inborn errors of metabolism . 6 — These typically present in childhood . Seizures are poorly responsive to anti-seizure medications and require specific interventions to correct the metabolic defect . 6 , 7

• Infectious : — Epilepsy secondary to an infectious aetiology occurs in two settings : post-infectious epilepsy after a CNS infection or when seizures occur as a core symptom of the infection . 7

• Immune mediated : — There is a range of immune-mediated CNS disorders in which seizures are a core symptom — for example , anti-

N-methyl-D-aspartate receptor encephalitis . 6

Figure 1 . Loss of brain parenchyma and surrounding scarring after perinatal right middle cerebral artery stroke .

contrasting with the longer postictal period after a generalised seizure .

Investigation for a cardiac cause is indicated if there are associated palpitations , chest pain or shortness of breath , syncope triggered by exercise , fear or water immersion or if there

21 , 22 is a family history of sudden death .

Breath-holding attacks

These attacks occur in young children after they have been upset or startled . The child will cry , stop breathing in expiration , develop facial cyanosis and then experience a transient loss of consciousness , which may be accompanied by brief tonic posturing . 22

Iron deficiency anaemia can result in more frequent attacks . 22 The prognosis is excellent , and carers can be reassured .

Reflex asystolic syncope

Reflex asystolic syncope occurs in infants and young children . Events are often triggered by a trivial unpleasant stimulus , resulting in excessive vagal nerve stimulation that causes transient asystole , pallor and a brief

22 , 23 period of loss of consciousness . Events usually stop without intervention . In a minority who have recurrent episodes , an implanted cardiac pacemaker is required . 23

Shuddering attacks and benign myoclonus of infancy

These are benign movements occurring in infancy that can persist into the early school years .

They often occur in specific situations — for example , in a high chair — and children may demonstrate a spectrum of movements from a single jerk to sustained tonic posturing of the head , trunk and limbs with tremulous shaking . 24

Examination and development are normal . Videos are helpful . An EEG capturing the event may be necessary .

Benign neonatal sleep myoclonus

This is a normal sleep phenomenon in a neurodevelopmentally normal neonate . Rhythmic jerking movements typically involve all extremities and stop when the child is woken from sleep . 22

Parasomnias

Night terrors , sleep walking and confusional arousals are complex sleep-related behaviours that occur during non-REM sleep — typically in the first third of the night . 25 The child has no memory of the event .

The events tend to occur only once a night and usually last longer than 10 minutes . The features of parasomnias are more variable than nocturnal frontal lobe seizures ,

Box 3 . When is neuroimaging indicated ?

• Neuroimaging is not indicated in :

• Idiopathic generalised epilepsies .

• Self-limited epilepsy with centrotemporal spikes ( SeLECTS ). 15

• Neuroimaging is indicated in the following situations :

• Clinical evaluation suggests a localisationrelated epilepsy ( excluding SeLECTS ).

• Focal neurological deficits .

• Neurocutaneous stigmata .

• Microcephaly or macrocephaly .

• Significant developmental delay , arrest or regression .

• Change in seizure characteristics , uncontrolled / worsening seizures or loss of previously good seizure control . 14-16

Box 4 . Groups where genetic testing has the highest yield

• Onset of seizures in the neonatal period or in infancy .

• Drug-resistant epilepsies .

• Epilepsy with associated developmental delay , intellectual disability , autism , dysmorphic features or multisystem symptoms .

• Individuals with a family history of epilepsy .

which tend to be stereotyped in their appearance .

Daydreaming

This is a situational state in which a child is not engaged and appears motionless and stares .

Unlike absence seizures , daydreaming can be terminated with tactile stimulation . 22

Tics and stereotypies

These are paroxysmal , repetitive , stereotyped , purposeless movements or sounds that are common in childhood .

Tics are typically partly suppressible and accompanied by a premonitory urge . 22

Stereotypies often occur in the context of boredom , excitement or distraction . 21 The diagnosis is made clinically , and videos are useful .

Psychogenic non-epileptic seizures

Such events may resemble epileptic seizures ; they do not have