The North West Blackouts Group, Paul Cooper°*, Amir Zaidi, Alan Fitchet, Peter Clough*, Adam P. Fitzpatrick.
Manchester Heart Centre, The Royal Infirmary, Manchester, °David Lewis Centre for Epilepsy, Warford, *Department of Neurology, Centre for Clinical Neurosciences, Hope Hospital, Salford, UK
|
|
Blackouts are a common clinical problem, and
account for 3% of Casualty attendances and 1-6% of admissions to hospital1-3.
Detirmining their cause is compromised by the lack of a clear description of the event,
and the diagnosis may not be apparent with simple clinical evaluation. Often very
costly investigations are performed3-5 during prolonged periods in hospital, although
the yield of these investigation may be low1,4.
When a blackout is accompanied by abnormal movements patients are often thought
to have epilepsy, although cardiovascular disorders may cause blackouts complicated
by apparent seizure like activity due to generalised cerebral hypoxia, particularly
reflex forms of syncope such as vasovagal syncope6
and carotid sinus syncope7. These
may appear identical to true epileptic seizures, with convulsive
movements8; in
North America the term “convulsive syncope” alludes to the clinical similarities and
potential for confusion.
Idiopathic syncope is usually benign9;
but a diagnosis of epilepsy, in contrast, has a
number of serious consequences: it remains a stigmatized disorder, with implications
for employment, driving and insurance10,11,
it can result in the prescription of
potentially harmful drugs12, and is a significant drain on resources (ibid).
The extent of the misdiagnosis of epilepsy remains unclear: it is estimated that
approximately 20% of patients under long-term follow-up in hospital clinics do not
have epilepsy13, a recent study of patients referred to a specialist epilepsy clinic, on
antiepileptic medication, showed 26% misdiagnosed14, while in a community-based
study, 23% had been misdiagnosed15. Many of the patients misdiagnosed in these
studies had psychogenic attacks, but a significant number had a cardiac diagnosis.
In a recent prospective study by our group seventy-three patients with recurrent
seizures, previously diagnosed as epilepsy, had systematic cardiovascular
investigations. Criteria for inclusion were continued attacks despite adequate
treatment with anticonvulsant drugs (35 patients), or uncertainty about a diagnosis
of epilepsy, based on the clinical description of the seizures or the history (38 patients).
All patients underwent a resting 12-lead ECG, followed by head-up tilt test and carotid
sinus massage during continuous ECG, EEG and blood pressure recording.
We found an alternative diagnosis in 30 (41%) patients, including 12 of 35 (34%)
patients on anticonvulsant medication. Nineteen patients (26%) experienced their
typical seizures during head-up tilt, with profound hypotension or bradycardia,
confirming the diagnosis of vasovagal syncope. One patient suffered a classical panic
attack, identical to her usual symptoms, during the tilt test. One patient developed
psychogenic non-epileptiform shaking during head-up tilt. One further patient suffered
a typical vasovagal reaction during intravenous cannulation following the tilt test with
reproduction of her typical symptoms. Six patients (8%) had significant ECG pauses
during carotid sinus massage. In two patients episodes of prolonged bradycardia,
recorded using an implantable ECG recorder, correlated with their seizures.
The problems are those of perception and definition. Fundemental to the significant
misdiagnosis rates of seizures are the concepts that firstly loss of consiousness implies
a neurological disorder, and that secondly convulsive movements, or “seizure” implies
epilepsy. These misconceptions are held by not only patients and their relatives and
carers, but also by medical staff..
A seizure is a paroxsymal loss, or disturbance, of consiousness, accompanied by motor
features. These could include abnormal movements, such as convulsions or automatic
behaviour, as well loss of body tone, or rigidity. The neurological causes of sezures
include, but are not confined to, epilepsy, and seizures can also have cardiac,
metabolic and psychogenic causes.
In practice the usual distinctions are between epilepsy, in all its forms, cardiogenic
seizures and psychogenic attacks.
|
