Evaluating the utility of inpatient video-EEG monitoring

Ghougassian DF, D'Souza W, Cook M and O'Brien TJ; Epilepsia 45 (8); 928-932

Commented by Professor Emilio Perucca, 22 Sep 2004

Background

Although inpatient video-EEG monitoring (VEM) is widely used for diagnostic purposes and for presurgical localization, its utility has been relatively little investigated.

Aim

To assess the proportion of patients whose pre-admission diagnosis and management were altered after VEM.

Methods

Retrospective analysis of consecutive patients undergoing inpatient VEM over a 3-year period in a tertiary referral hospital.

Results

Of 131 patients, 70% underwent VEM for diagnostic evaluation and 30% for presurgical workup. Over a mean evaluation period of 5.9 days, seizures could be recorded in 69% of patients. In 7 of the 40 patients in whom no seizures were observed, the EEG showed diagnostic interictal epileptiform abnormalities not detected previously.

After VEM, diagnosis was altered in 58% of patients, and management was altered in 73%, predominantly through drug therapy changes.

The most common diagnostic change was an increase in the proportion of patients considered not to have epilepsy (from 7% to 31%).

Comment

This is the second largest study assessing the impact of VEM on diagnosis in consecutively admitted patients. Overall, VEM led to a change of diagnosis in 58% of 131 patients. In previous studies, this proportion ranged from 20% of 183 children (ref. 1), to 37% of 100 patients (ref. 2), and 48% of 40 patients (ref. 3 ).

Of the 91 patients who had an ictal event recorded, preadmission diagnosis was changed in 76 (83%). These findings are remarkable, and are likely to be widely used by epileptologists who are being asked to justify the resource allocations for setting up a VEM service.

Inpatient VEM is expensive, its cost having been estimated at 1,100 to 1,700 per day in the U.S. in 1996 (ref. 4). However, savings from correcting diagnostic errors can be considerable. In particular, an increase from 7% to 31% in the diagnosis of non-epileptic disorder should reduce dramatically the costs of medication, additional diagnostic tests and emergency admissions (ref. 5 ).

While the authors should be commended for their research, a number of methodological shortcomings should be noted:

1. the study used a retrospective design, and bias could have been generated by having preadmission diagnosis ascertained by a physician who was aware of VEM findings;
2. during VEM, patients underwent additional investigations such as MRI, SPECT and/or fluorodeoxyglucose-PET, and the contribution of the latter to the diagnostic workup is unclear;
3. no comparison was made with alternative diagnostic procedures or VEM modalities (e.g., outpatient VEM);
4. most important, no attempt was made to assess the consequences of the diagnostic/management changes on patients’ outcome.

It is also unclear to what extent these findings can be generalized to other settings, as the utility of VEM is critically dependent on the skills of the referring physicians, the screening criteria for admission, and the competence of the VEM team.

Overall, this study confirms that, in good hands, VEM is a most valuable procedure for improving diagnosis and management. However, it also highlights the need for prospective and preferably randomized investigations to determine the optimal screening procedures, the impact of the revised diagnosis on long-term clinical outcome, and the comparative cost-effectiveness of the service under different modalities of use.

References

1. Yoshinaga H, Hattori J, Ohta H et al. Utility of the scalp-recorded ictal EEG in childhood epilepsy . Epilepsia 2001; 42:772-777

2. Chayasirisobhon S, Griggs L, Westmoreland S, et al. The usefulness of one to two hour video-EEG monitoring in patients with refractory seizures . Clin Electroencephalogr 1993; 24:78-84

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3. Sutula TP, Sacckellares JC, Miller JQ et al.Intensive monitoring in refractory epilepsy . Neurology 1981;31:243-247

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5. Martin RC, Gilliam FG, Kilgore M, et al.Improved health care resource utilization following video-EEG-confirmed diagnosis of nonepileptic psychogenic seizures. Seizure 1998; 7:385-390

Last updated: 22.09.2004