Blackouts and ‘funny do’s’

Published on 10/04/2015 by admin

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Last modified 10/04/2015

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Blackouts and ‘funny do’s’

Blackouts are one of the most common presentations in neurology, accounting for 18% of new neurological outpatients. The most common causes are seizures or syncope. While a list of possible causes is long, the clinical history, particularly with an account from a witness, will usually define the nature of the attack and direct investigations.

History

‘Blackout’ is a term that is usually used to mean episodes of loss of consciousness but some patients use it to mean episodes of altered consciousness. Other patients can mean a range of other things including dizzy feelings, memory loss or occasionally even episodes of weakness without impaired consciousness. It is important to find out what they mean. To help you do this, the range of feelings most often included within the term are discussed below. Other key aspects of the history include a detailed description of the blackout – what the patient was doing, any precipitating factors and the time course of the blackout, including any prodromal symptoms, aura immediately before the blackout, features of the blackout (ictus) itself and any post-ictal effects are all important in making the diagnosis. A witnessed account of what happened is essential. The widespread availability of mobile phones makes tracking down the person who saw the event easier.

Examination

The examination is usually normal in patients with blackouts of all causes. Examinations of the cardiovascular system and the nervous system are particularly important – look for pulse irregularity, evidence of cardiac failure, murmurs, extracranial bruits, erect and supine blood pressures and any focal neurological signs.

Types of blackouts and ‘funny do’s’

Episodes with collapse

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.

image

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:

image 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.
image 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.
image If it occurred on prolonged standing – suggesting postural hypotension.
image If it occurred in particular situations, e.g. micturition (micturition syncope) or cough (cough syncope).
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