Blackouts and ‘funny do’s’

Tonic-clonic seizure

These may occur at any time and in any position (Fig. 1). The patient may have a warning (aura), such as a smell or taste or simply a strange feeling (see below). The aura is usually brief (a few seconds). There may be no warning. The patient may be observed to go blank or be lip smacking before losing consciousness. The patient then goes stiff and lets out a grunt. The arms and legs go stiff for a period and the jaw is clenched tight. This may be followed by a jerking of the limbs. This usually goes on for 2–3 min. The patient usually goes into a deep sleep. On coming round, the patient is muddled. Patients frequently bite their tongue and pass urine.

Fig. 1 Time course of syncope and tonic-clonic seizure.

Syncope

Syncope results from a fall in blood pressure leading to cerebral hypoperfusion. Syncope is usually preceded by a feeling of lightheadedness, dimming of vision, a sweaty feeling and a feeling of becoming distant. This may be brief but usually lasts minutes. Some patients get no warning. The patient goes pale and sweaty and slumps to the ground, occasionally falling more stiffly. They then lie still, or there are often a few small twitching movements. The period of unconsciousness is usually brief, less than 30 s, and is followed by a rapid recovery. Incontinence of urine occurs quite often. Tongue biting is very rare. Syncope in older patients or those with known ischaemic heart disease, or occurring on exertion, suggests a significant cardiac cause.

N.B. A patient who has a syncopal event but is kept upright or who has a prolonged cerebral hypotensive episode for some other reason may go on to have a tonic-clonic seizure (see above). This is a provoked ‘reflex-anoxic’ seizure.

There may be factors in the situation of the blackout that suggest syncopal episodes:

If it occurred after prolonged standing, in a hot place or after some distress such as the sight of blood. All these suggest a vasovagal syncope.

If it is preceded by a palpitation, occurs without any prodrome or occurs with exertion – all suggest cardiac syncope, e.g. due to an arrhythmia or obstructive cardiomyopathy.

If it occurred on prolonged standing – suggesting postural hypotension.

If it occurred in particular situations, e.g. micturition (micturition syncope) or cough (cough syncope).

Syncope can be physiologically induced, e.g. by hyperventilation or Valsalva manoeuvre. Patients may be unaware that they are hyperventilating. In these patients there may be a sensation of breathlessness and tingling in the arms and legs.

Syncope can occur recurrently, which may reflect carotid hypersensitivity or malignant vasovagal syndrome.

Subarachnoid haemorrhage

This may present with sudden severe headache followed by loss of consciousness.

Intermittent hydrocephalus

This may present with sudden loss of consciousness often without warning. This is a ‘classical’ (meaning very rare but everyone remembers it) presentation of the rare colloid cyst of the third ventricle.

Drop attack

In this condition the patient suddenly drops to the ground. Often it is not clear whether the patient has lost consciousness. This may be a form of seizure, cardiac arrhythmia or may reflect structural brain disease. Most commonly it is seen in older women and no cause is found.

Sleep disorders

These can enter the differential diagnosis of blackouts: a tendency to fall asleep suddenly and unexpectedly is seen in narcolepsy and sometimes in obstructive sleep apnoea. Patients with narcolepsy also may have episodes of loss of muscle tone at times of high emotion, such as laughter or tears: cataplexy.

Hypoglycaemia

Hypoglycaemia presents with lightheadedness, sweating and often a feeling of fear. The patient becomes dizzy. This usually presents no diagnostic problems in diabetics. However, if there is a coexistent autonomic neuropathy, then prodromal symptoms are lost. Hypoglycaemia is also common in alcoholics (poor dietary intake and reduced hepatic glycogen stores combined with the hypoglycaemic effect of alcohol). Insulinomas are very rare causes.

Non-epileptic attacks, pseudo-seizures and psychogenic seizures

These present a common and difficult diagnostic problem. The attacks are usually different from epileptic seizures: they are variable, longer lasting and fluctuate during the attack. Movements often seem more purposeful or semi-purposeful and they more often resist those attending them: ‘It took five people to hold me down’. There is no associated cyanosis or respiratory changes. The differential diagnosis is with frontal seizures and rare intermittent movement disorders.

Absences

Absences typically occur in children as a manifestation of primary generalized epilepsy. The child is still and stares. The eyelids may flutter and there may be some mouth movement. They are usually very brief but may last minutes. They occur frequently. An EEG shows 3 Hz spike and wave discharges.

Partial seizures and complex partial seizures

These are focal onset seizures either with (complex partial seizures) or without (partial seizures) loss of consciousness. The prodromal sensations that occur are the same in either situation whether or not consciousness is lost. The manifestations depend on the site of onset of the seizure. Either type of seizure may go on to a secondary generalized seizure so these may constitute the aura of a generalized seizure.

Common patterns include:

all are brief (usually seconds or very occasionally minutes)

a smell or taste often associated with an unpleasant feeling in the stomach (temporal lobe onset)

a feeling of déjà vu (temporal lobe onset)

a sensation of numbness or tingling (parietal lobe onset)

jerking of one limb or head turning, or occasionally more stereotyped movements, e.g. cycling (frontal lobe onset)

a flash of light (occipital lobe onset).

A witness may describe a patient with complex partial seizures as going glassy eyed, changing colour, making lip-smacking movements or other semi-purposeful movements with their hands. The patient is often confused afterwards.

Transient ischaemic attacks

The sudden onset of loss of any function of the nervous system can arise from vascular causes. Only rarely is consciousness lost (p. 70).

Transient global amnesia

This is a moderately common condition in adults aged over 40 years. For a period of 2–6 h, there is almost total failure to acquire new information and patients appear confused. They characteristically ask the same question again and again, ignoring any answers. Otherwise they can do quite complicated things such as driving. The recurrence rate is about 10%. The condition is associated with migraine, but not epilepsy or cerebrovascular disease.

Migraine

Migraine may cause focal neurological symptoms of gradual onset over about 15–30 min. Typically these are visual symptoms, though numbness, tingling or speech disturbance can occur. The typical headache usually follows (p. 42), but may not, which may lead to consideration of other differential diagnoses (Table 1).

Table 1 Pattern of sensory and other symptoms in different types of attack