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THE VALUE OF EEG IN THE INVESTIGATION OF UNEXPLAINED SYNCOPE IN A GENERAL HOSPITAL POPULATION
  1. Pamela Pillai Velasamy,
  2. John Murray,
  3. Allan Kermode,
  4. Athanasios Gaitatzis
  1. The University of Western Australia Medical School & Sir Charles Gairdner Hospital, Nedlands, Western Australia; SEIN–Epilepsy Institute in The Netherlands Foundation, Heemstede, The Netherlands

    Abstract

    Background Many physicians request EEG in order to differentiate between syncope and seizure in individuals presenting with transient loss of consciousness (TLOC). This is particularly the case in people taken to hospital following a collapse, where a witness account is not always available.

    Purpose We aim to investigate the usefulness of EEG in the assessment of unexplained TLOC in a large, unselected group of patients presenting in an emergency department. We also assess the risk of seizure development and clinical course following initial presentation.

    Methods We retrospectively reviewed referral forms of all routine and urgent EEGs performed at Sir Charles Gairdner Hospital, Perth, Western Australia between April 2010 to November 2011 to identify recordings performed for the investigation of suspected syncope or TLOC. Cases with identifiable cause at initial assessment, and cases suggestive of seizure, previous diagnosis of epilepsy and falls without loss of consciousness were excluded. Diagnosis at discharge and EEG reports were obtained through electronic patient records, EEG archive, and case notes as required. EEGs were classified as normal, abnormal (non–epileptiform abnormalities only), and showing definite epileptiform discharges (EDs). Detailed clinical information including subsequent development of seizures or death was collected for a subgroup of patients with 1–year follow–up after first presentation across all hospitals in the greater Perth area through health electronic linkage. General practitioners and patients were also contacted in order to obtain additional information as needed. The death rate and standardised mortality ratio (SMR) were calculated according to standard methods based on life table 2008–2010 of the Australian Bureau of Statistics.

    Results We identified 197 cases with unexplained TLOC (age range 18–98 years). No further clinical information was available for 11 cases. The EEG was abnormal in 1/3 of all cases, and in 50% of those over 65 years. EDs were identified in 2 patients (1%); of those, a diagnosis of seizure was made in one patient who was subsequently started on antiepileptic treatment, with no final diagnosis made in the other. Diagnosis at discharge was made in 129 cases (65%) with 23 (18%) of those receiving a seizure diagnosis. The 1–year follow up group consisted of 82 patients (age range 20–95 years); 52 (63%) people were multimorbid (defined as having ≥2 conditions). None of the patients without a seizure diagnosis presented with seizures during follow–up. During this period there were 11 deaths (age range 30–94 years), all in multimorbid people, and none in people with seizure diagnosis. The case fatality rate was 13.4% and SMR 4.27 (95% Fisher's exact CI, 2.13–7.42).

    Discussion This study demonstrates that the EEG has a very low diagnostic yield in patients presenting with unexplained TLOC. EEG was helpful in diagnosis of 1 of 2 cases, while a seizure diagnosis was made on clinical grounds in 22 of 23 cases. The high mortality associated with TLOC almost exclusively affected multimorbid patients above 65 years, suggesting high risk of death from an underlying medical cause and not from seizures in this group of patients.

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