Differentials
Functional seizures (non-epileptic seizures)
SIGNS / SYMPTOMS
Patients with functional (non-epileptic) seizures will often present with continuous limb shaking similar to generalised tonic-clonic seizures, but with suggestive elements: variable maintenance of consciousness; eye closure; side-to-side head shaking; pelvic thrusting; waxing/waning course; prolonged convulsive activity; lack of response to benzodiazepines; oral trauma across the tip of the tongue (in contrast to the lateral tongue bites that are more often seen in epileptic seizures).[49]
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.[49] Psychological comorbidities - especially anxiety, panic, and depression - are common, affecting over 50% of patients.[50]
INVESTIGATIONS
Video-electroencephalogram (EEG) monitoring is the definitive test to differentiate epileptic from functional seizures.[51]
The EEG during functional seizures is either normal or obscured by movement or muscle artefact. The video during functional seizures allows the observer to view the details of the behaviours present.
Convulsive syncope
SIGNS / SYMPTOMS
Vasovagal syncope can often present with brief convulsive activity (<15 seconds) in the limbs shortly after loss of consciousness.
A detailed history of the event itself is often useful and critical for the diagnosis; a typical syncope is often position-dependent and briefly preceded by light-headedness and tunnelling of vision. Further, the loss of consciousness is typically very brief, and there is a relatively quick return to baseline.
INVESTIGATIONS
An accurate clinical history is seen as more important than any test. A tilt-table test can be utilised, but is a relatively non-specific assessment.
Serum creatine kinase drawn serially can be used to differentiate from an epileptic seizure, although it is not routinely used.[52]
Cardiac arrhythmia
SIGNS / SYMPTOMS
Primary cardiac arrhythmias often present with sudden loss of consciousness, sometimes preceded by a feeling of palpitations or sudden anxiety. Generally, arrhythmias occur abruptly and without the prolonged evolution of convulsions that are typical of a generalised tonic-clonic seizure. Additionally, patients with arrhythmia often return to baseline relatively rapidly.
INVESTIGATIONS
An ECG is indicated for any patient with a potential cardiac arrhythmia. For those patients with a normal ECG and a high index of suspicion, a Holter monitor or a loop recorder is warranted.
Transient ischaemic attack (TIA)
SIGNS / SYMPTOMS
In some cases, TIAs can present with either a sudden alteration in consciousness or focal motor movements (limb-shaking TIA). Although these are rarely confused with generalised tonic-clonic seizures, they must be considered.
A thorough history and neurological examination are indicated to evaluate for TIA.
INVESTIGATIONS
A non-contrast head CT or MRI can be used to assess vascular abnormalities that suggest a TIA. If available, EEG can be used to evaluate for epileptiform activity.
Tic disorders
SIGNS / SYMPTOMS
Tics usually involve the head, neck, and shoulders, and may be complex movements. They may be temporarily suppressed.
Physical examination is typically normal, except for observed tics.
INVESTIGATIONS
Diagnostic studies in tic disorders are often normal.
EEG features associated with epileptic seizures are absent.
Tremor
SIGNS / SYMPTOMS
Involuntary, oscillatory movement of a body part that is rhythmic compared with the movements due to seizures.
INVESTIGATIONS
Diagnosis is usually based on history and physical examination.
Panic attacks
SIGNS / SYMPTOMS
Subjective sense of dread, with acute onset of autonomic symptoms such as palpitations, sweating, nausea, paresthesias, feeling faint, and abdominal or chest discomfort; often lasting 10-30 minutes.
Consciousness is rarely lost, and derealisation, as well as depersonalisation, is more common with panic attacks than with focal seizures.
Panic attacks are more common in younger age groups but may occur at any age.
INVESTIGATIONS
Clinical diagnosis.
Neuroimaging and EEG are usually normal with panic attacks.
There should be no ictal EEG changes during video-EEG monitoring.
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