In Denmark, most children with epilepsy and other paroxysmal events are treated in the local paediatric departments. Admission to the only tertiary epilepsy centre in Dianalund is free for the patients. All medical doctors can refer a child to the centre. This means that if the parents want a second opinion they can go to their general practitioner for a referral to Dianalund, even though the local paediatrician may not find a referral necessary.
The total annual incidence of childhood epilepsy in Denmark is about 600. Expecting about 25% (150) of these to be difficult to treat, the number of children (159) admitted to Dianalund for the first time in 1997 seems to indicate that the majority of the “intractable” cases in Denmark will be admitted at least once during their lifetime. Furthermore, the geographical distribution of the children was evenly spread from all over Denmark. Even though this is not a strict population based study we believe that the figures in the present study are reasonably representative for Danish children with continuing seizures treated by paediatricians.
The difficulties of obtaining a final decision of the epilepsy diagnosis are illustrated by the fact that 12 of the 87 non‐epileptic children had been admitted in previous years. Some of these children had been misdiagnosed at the previous admission; new clinical observations emerged during the admission in 1997 that made it possible to discard the epilepsy diagnosis. Others are thought to have outgrown a previously possible epilepsy. This is in accordance with a prospective study in which experienced child neurologists had to change their first diagnosis of epilepsy to non‐epileptic paroxysmal events in 4.6% at later follow up.12
It has also been shown by the same study group that among child neurologists the agreement was only fair to moderate13
on the diagnosis of epileptic seizures based on the description of 100 first paroxysmal events. The agreement improved somewhat using predefined descriptive definitions of epilepsy and panel discussions. In contrast to the Dutch study our results are based on a comprehensive evaluation during admission of children with continuing paroxysmal events. In spite of this some uncertainty on the diagnosis seems to exist in a small number of cases. In a prospective study it would be reasonable to include a category of children where no firm diagnosis could be made. This might reduce the percentage of misdiagnosis. We doubt, however, that a prospective study with predefined work up of the children would have changed the results. A planned ictal video‐EEG would, for instance, seldom be possible to obtain, even during a three week admission.
The incidence of 30% where the referring doctor expressed no doubt about the diagnosis is surprisingly high. We have not found any study calculating the percentage of misdiagnosis where the referral cases all were thought to be epilepsy.
The results of a diagnostic evaluation of suspected epilepsy after a referral to a tertiary epilepsy centre are better documented. In a Scottish study only 54% referred with paroxysmal phenomena had epilepsy.14
Among 666 Australian children who had intensive EEG monitoring done, 43% had non‐epileptic seizures.15
In a study from the USA, 22.5% of 199 children were discharged without epilepsy diagnosis after video‐EEG.16
However, in these studies the reasons for referral were not specified. Other small observational studies have documented the problem of misdiagnosis in childhood epilepsy.2,17
Disproving the diagnosis of epilepsy is important from several points of view. Unnecessary drug treatment as well as concerns about development and social coping and restriction imposed on the child's lifestyle can come to an end. In our series, medication could be stopped in 34 children (15% of all admitted). This is a somewhat higher percentage than found in the US study of 883 children referred for EEG monitoring (5%)16
and children evaluated at the adolescent clinic in the UK (4%).17
The explanation for their lower figures is probably that more children were referred to these clinics for an early diagnostic evaluation.
What is already known on this topic
- The diagnosis of epilepsy is difficult
- A consultant paediatrician in England misdiagnosed 618/1948 (31.7%) children as having epilepsy
What this study adds
- The rate of misdiagnosis of epilepsy in a national sample of difficult‐to‐treat patients from a developed country is extremely high, with more than 30% of those with definite epilepsy not having epilepsy at all
The majority of non‐epileptic events in the present series were staring episodes, confirming results from other studies.15,16
Most often this is seen in mentally retarded children with non‐specific EEG abnormalities which are over‐interpreted as “epileptiform”. One study showed, however, that it was found just as often in normal children.7
Another study found some descriptive features distinguishing epileptic from non‐epileptic events; the sensitivity was low, however.18
PNES were found less often than in other studies,16
probably because of our strict definition of PNES: paroxysmal events of non‐physiological nature, but which are regarded and treated as epileptic and
play an important role in the emotional interaction between the child and the parent/environment. This means that the diagnosis was only used if a psychological evaluation could add these positive criteria. Except for gastro‐oesophageal reflux, shuddering attacks, paroxysmal torticollis, tonic upward gazing, long Q‐T syndrome, and alternating hemiplegia, all the differential diagnoses most frequently mistaken for epilepsy seem to be represented in our material.
The problem of misdiagnosis in epilepsy is not restricted to children. A recent study has shown high figures in adults as well, syncopal episodes being among the most frequent.19
In the present study, video‐EEG monitoring played an important role as 62% of the children had this investigation done. In the remainder, the diagnostic work‐up was based on clinical observation combined with careful history taking, and interictal EEG. The role of each diagnostic procedure is difficult to evaluate because each forms part of a comprehensive procedure.