The yield and clinical utility of outpatient short-term video-electroencephalographic monitoring: A five-year retrospective study
Highlights
► 175 OVEM records of adults were analyzed retrospectively. ► The highest yield was found in psychogenic nonepileptic seizures (PNES) (37.1%). ► Other findings were interictal epileptiform discharges (17.2%) and epileptic seizures (6.9%). ► OVEM changed the pre-test diagnosis in 30.9% of patients. ► OVEM appears to be a useful diagnostic test for PNES.
Introduction
Inpatient long-term video-electroencephalographic monitoring (IVEM) is well established as a diagnostic tool in the presurgical evaluation of the epilepsies, characterization of epilepsy syndromes, documentation of seizure frequency, and confirmation of psychogenic nonepileptic seizures (PNES) [1]. It is also useful for detection of nonconvulsive status epilepticus in the intensive care unit [2], as well as for treatment monitoring of status epilepticus [3]. However, it is a resource and labor intensive test that is not widely available. Outpatient short-term video-electroencephalographic monitoring (OVEM) has emerged as another diagnostic tool which may be useful in some patients. The indications for this test and its place in routine clinical practice are not clearly defined. This study was undertaken to evaluate the yield and clinical utility of OVEM.
Section snippets
Methods
This study was conducted at Monash Medical Centre, a tertiary care teaching hospital in Australia, with approval from the Human Research Ethics Committee. We retrospectively analyzed all adult patients (≥ 16 y) who underwent OVEM from January 2005 to December 2009 in our neurophysiology laboratory. No patients were excluded based on the pre-test frequency of clinical events.
The demographic data of patients were retrieved from the electronic database of the neurophysiology laboratory. Provisional
Results
A total of 175 records from 175 patients were studied. There were 111 (63.4%) females and 64 (36.6%) males with an age range from 16 to 87 years (mean 36). The mean length of recording was 3.8 h (range 1 to 6.8). Pre-test frequencies of clinical events were ≤ 1 per week (30.1%), 2–6 per week (48.7%), and ≥ 7 per week (21.2%).
Focal slowing was found in 24 recordings (13.7%), whereas 18 (10.3%) demonstrated background slowing and generalized slowing. Interictal focal and generalized epileptiform
Discussion
In this series, we have demonstrated that OVEM has a higher yield for PNES than epileptic seizures and IED. The yield of PNES was more than five times that of epileptic seizures. We have also shown that OVEM resulted in diagnosis change from epilepsy to PNES in over one-fourth of patients. These figures indicate the clinical utility of OVEM in the diagnosis of PNES.
Conclusions
Comparison of our study with previous research is difficult due to heterogeneity in methodology and study populations. Within those limitations, we have been able to draw reasonable conclusions. In general, most studies indicate that OVEM has a high yield for PNES. The yield seems to depend on the characteristics of the study population including the frequency of the clinical events and the use of seizure induction techniques.
In conclusion, our study demonstrates that OVEM is a very useful tool
Funding
None.
Ethics approval
Human Research Ethics Committee, Monash Medical Centre.
Contributors
US: conception and design, analysis and interpretation of the data, drafting the article, final approval of the version to be published. ZR, AD, MB: contributions to the conception, acquisition of the data, final approval of the version to be published.
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