The role of EEG in the erroneous diagnosis of epilepsy

Amin U, Benbadis SR. The Role of EEG in the Erroneous Diagnosis of Epilepsy. J Clin Neurophysiol. 2019 Jul;36(4):294-297.

Abstract

Errors in diagnosis are relatively common in medicine and occur in all specialties. The consequences can be serious for both patients and physicians. Errors in neurology are often because of the overemphasis on 'tests' over the clinical picture. The diagnosis of epilepsy in general is a clinical one and is typically based on history. Epilepsy is more commonly overdiagnosed than underdiagnosed. An erroneous diagnosis of epilepsy is often the result of weak history and an 'abnormal' EEG. Twenty-five to 30% of patients previously diagnosed with epilepsy who did not respond to initial antiepileptic drug treatment do not have epilepsy. Most patients misdiagnosed with epilepsy turn out to have either psychogenic nonepileptic attacks or syncope. Reasons for reading a normal EEG as an abnormal one include over-reading normal variants or simple fluctuations of background rhythms. Reversing the diagnosis of epilepsy is challenging and requires reviewing the 'abnormal' EEG, which can be difficult. The lack of mandatory training in neurology residency programs is one of the main reasons for normal EEGs being over-read as abnormal. Tests (including EEG) should not be overemphasized over clinical judgment. The diagnosis of epilepsy can be challenging, and some seizure types may be underdiagnosed. Frontal lobe hypermotor seizures may be misdiagnosed as psychogenic events. Focal unaware cognitive seizures in elderly maybe be blamed on dementia, and ictal or interictal psychosis in frontal and temporal lobe epilepsies may be mistaken for a primary psychiatric disorder.

______________________________________________________________________

From the srticle

Errors in diagnosis are relatively common in medicine and occur in all specialties. The rate of diagnostic error is estimated at 10% to 15%. The consequences can be serious for both patients and physicians. Diagnostic errors, including incorrect or delayed diagnosis, can result in harm to patients and also increase cost. Factors that can cause or contribute to diagnostic errors fall into two categories: system-related errors or cognitive factors. Examples of system-related errors include problems with policies and procedures, inefficient communication and teamwork, and increasing time constraints for clinicians. Examples of cognitive errors include premature diagnostic closure (failure to continue considering alternative diagnoses after the initial diagnosis was made), faulty perception, using standardized algorithms, and erroneous “context generation” (overemphasis on tests and errors in interpreting the results of the test). Failure by the patient or family to provide an accurate medical history or an atypical or masked presentation of a disease are also important factors...

The diagnosis of epilepsy in general is a clinical one and is typically based on the history. Most epilepsy patients have normal brain MRIs and normal routine EEGs, so obtaining a detailed history is the key. It not only can lead to the correct diagnosis of epilepsy but may even help characterize the type of epilepsy. Seizure history has to include the following:

A detailed semiology of the events including preictal warning signs and symptoms, ictal phase (from both the patient and observers who have witnessed the event), and postictal phase

Frequency of events

Triggers

Seizure risk factors including history of febrile or childhood seizures, family history of epilepsy, history of central nervous system infections and history of traumatic brain injury

Prior work-up including brain MRIs and EEGs

Previous and current antiepileptic medications, reason for discontinuation and possible side effects

Review home (cell phone) videos, which can provide an extension of the history with a more objective lens and may help the neurologist reach a correct diagnosis quickly.

An appropriate suggestive history of epilepsy even with a normal interictal EEG is enough for correct diagnosis and is probably the most common scenario in general neurology practices. A good history plus a strong interictal EEG abnormalities allow for a diagnosis with a high degree of confidence. An erroneous diagnosis of epilepsy is often the result of a weak history and a weak (“overread”) EEG. A definite diagnosis usually requires capturing a seizure with EEG-video monitoring and having both a clinical (video) and an EEG seizure. Unfortunately, simultaneous EEG and video recordings are only practical for patients with frequent (“intractable”) seizures...

This [the overdiagnosis of epilepsy] is by far the most common scenario encountered at referral epilepsy centers. Approximately 25% to 30% of patients previously diagnosed with epilepsy who do not respond to initial antiepileptic drug (AED) treatment do not have epilepsy. This number has been consistent across continents and different age groups. The erroneous diagnosis is often a result of the “dangerous formula” of a weak history plus an overread EEG, with overemphasis of the EEG. Clinicians perceive missing an epilepsy diagnosis as riskier than overdiagnosing it, which is somewhat understandable. This can result in unnecessary treatments and side effects, driving restrictions, employment difficulties, psychological and socioeconomic consequences, and the stigma associated with the diagnosis of epilepsy. Some patients have an incorrect diagnosis for >10 years...

Sometimes reaching the correct diagnosis can be challenging. It should start with a thorough history, a good eye-witness account, a detailed physician examination, and selecting and interpreting the necessary laboratory and imaging studies correctly. When in doubt, referring patients to subspecialists and having multidisciplinary team approaches to discuss individual cases are key. After reaching the correct diagnosis, optimizing communication between healthcare providers is crucial. Very importantly, EEG should not be over-emphasized with respect to the history...

Reversing the diagnosis of epilepsy is difficult. An EEG that was overread as epileptiform will not be canceled by multiple subsequent normal EEGs because EEG is a test of cerebral activity during a specific period, and it can vary from time to time. The only way in undoing the erroneous diagnosis is to rereview the “abnormal EEG.” This can be difficult as previous records are not always available or accessible and not all digital EEG systems are compatible.

Lack of mandatory training in EEGs and the erroneous assumption that all neurologists are competent electroencephalographers are the main reasons for an “abnormal EEG” overread. Taking an accurate and thorough history and performing a detailed neurologic examination are by far the best and most valuable tools for any physician, including neurologists, to establish a correct diagnosis. Complementing history with home (cell phone) videos of the seizure-like episodes can be very helpful. Also, clinicians should always be mindful that the diagnoses may be wrong and routinely question and review diagnoses. It has been shown that experts are more likely to admit to diagnostic uncertainty than nonspecialists. Finally, EEG and other tests should not be overemphasized over the clinical picture and clinical judgment.