Differentials
Syncope
SIGNS / SYMPTOMS
Refers to the sudden loss of muscle tone, posture, and consciousness associated with reduced systemic BP.
There is often a prodrome with a feeling of non-specific sickness, which may be associated with nausea, vertigo, and skin pallor.
Typical attacks last about 10 seconds without a postictal period.
Tussive syncope is brought about by a coughing spell.
Convulsive syncope is similar to syncope but is followed by spasm of the torso and limbs, clenching of the fists, brief shaking, and, rarely, tongue biting and incontinence.
Family history may be positive for syncope. Documentation of low BP during an attack is often helpful.
INVESTIGATIONS
Electroencephalogram often shows non-specific diffuse slowing or attenuation.
ECG may show an arrhythmia, premature ventricular contractions, or even asystole.
A tilt table test may reproduce the patient's symptoms and therefore be diagnostic. However, occasionally, patients with seizures may also have abnormal tilt table tests.
Transient ischaemic attack (TIA)
SIGNS / SYMPTOMS
May involve sensory, motor, speech, vestibular, or memory symptoms and lasts <20 minutes.
There may rarely be brief limb shaking.
TIAs last longer than focal seizures and may be associated with an increase in BP; the symptoms can follow a particular arterial distribution (e.g., middle cerebral artery or vertebral artery).
INVESTIGATIONS
MRI brain may reveal the presence of small vessel ischaemic disease or past stroke.
The electroencephalogram (EEG) is often normal but may reveal intermittent focal slowing.
Abnormalities in other aspects of the stroke evaluation, including carotid artery patency, echocardiogram, and lipid profile.
Sleep disorders
SIGNS / SYMPTOMS
Sleepwalking or somnambulism starts 1-2 hours after sleep. The person walks about in a trance and may carry out purposeful activity.
Sleep terrors present with manifestations of fear during an arousal from slow-wave sleep. Often heralded by a loud vocalisation.
INVESTIGATIONS
Simultaneous electroencephalogram is normal without evidence of epileptiform discharges or seizure 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.
Electroencephalogram features associated with epileptic seizures are absent.
Chorea
SIGNS / SYMPTOMS
Continuous, involuntary, rapid, random movements that tend not to be repeated stereotyped movements.
Chorea is commonly due to Sydenham's chorea (one of the clinical manifestations of acute rheumatic fever).[51][52]
INVESTIGATIONS
Diagnosis is usually based on history and physical examination.
Tremor
SIGNS / SYMPTOMS
Involuntary, oscillatory movement of a body part that is rhythmic compared with the movements due to focal seizures.
INVESTIGATIONS
Diagnosis is usually based on history and physical examination.
Migraine
SIGNS / SYMPTOMS
Suggestive features include a more severe, unilateral pulsatile headache, photo- and phonophobia, nausea, vomiting, and family history of migraine.
The aura of migraine is often longer (>5 minutes) and has a more gradual onset and offset.
INVESTIGATIONS
Brain MRI is either normal or reveals small, scattered white matter signal changes that do not enhance with gadolinium.
An electroencephalogram may reveal focal slowing (theta and delta) and is usually normal between headaches.
Transient global amnesia (TGA)
SIGNS / SYMPTOMS
Usually occurs in people older than 50 years.
Sudden onset of amnesia that lasts for several hours.
Patients maintain alertness but are confused and ask questions repeatedly.
INVESTIGATIONS
MRI of the brain may be normal or may show evidence of past pathology (e.g., old ischaemic disease). Occasionally, unilateral or bilateral punctate restricted diffusion is seen in the hippocampus, but this is not necessary for diagnosis.[53][54][55]
The electroencephalogram is usually normal; slowing is also possible.
No test can definitively make the diagnosis of TGA.
Meniere's disease
SIGNS / SYMPTOMS
Episodic vertigo, tinnitus, nausea, and vomiting may occur.
A key differentiating factor is the presence of hearing loss, which exists even between attacks.
INVESTIGATIONS
Audiogram should be abnormal.
Electronystagmography is often abnormal.
Functional seizures (non-epileptic seizures)
SIGNS / SYMPTOMS
Episodes of altered movement, sensation, emotion, or experience that have the appearance of epileptic seizures but are not caused by paroxysmal, hypersynchronous electrical activity of the brain.[56]
Functional seizures similar to focal impaired awareness seizures are common, but the clinical appearance of functional seizures may mimic virtually any seizure type.
Some features more likely to suggest functional seizures include: eyes being tightly closed, tearfulness, duration more than 2 minutes, hyperventilation during a seizure, and side-to-side head shaking.[57]
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.[57] Psychological comorbidities - especially anxiety, panic, and depression - are common, affecting over 50% of patients.[58]
A significant minority of people with functional seizures will have co-existent epilepsy, so it is important to determine whether the patient has a number of different types of spells.
INVESTIGATIONS
The only reliable diagnostic test to differentiate functional from epileptic seizures is video/electroencephalogram (EEG) (long-term monitoring). 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.
Correct diagnosis is usually based on the semiology of the event and the absence of epileptiform EEG correlate.
Dissociative disorders
SIGNS / SYMPTOMS
Partial or complete loss of normal integration between past memories, immediate sensations, identity, and movements. Often senses derealisation, depersonalisation, and out-of-body experiences.
INVESTIGATIONS
The electroencephalogram (EEG) is often normal but may have non-specific (non-diagnostic) findings, such as focal or diffuse slowing.
Video EEG may be helpful in characterising the notion that the abnormal experience does not represent focal seizures.
Panic attacks
SIGNS / SYMPTOMS
Subjective sense of dread, with acute onset of autonomic symptoms such as palpitations, sweating, nausea, paraesthesias, 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 electroencephalogram (EEG) are usually normal with panic attacks.
There should be no ictal EEG changes during video/EEG monitoring.
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