Abstracts

Rationale: Tilt-table testing is a common procedure for the evaluation of complaints of ""giddiness and dizziness"", or syncopе. Significant overlap exists between the symptoms of ""fainting"" and ""dizziness"", and epileptic events. Many of the patients referred for tilt testing also get an EEG. We developed a collaboration with the Faint-And-Fall Clinic at the University of Utah to do concurrent tilt-table and EEG testing. There is a general belief that ""fainting"" involves interruption of cerebral oxygenation due to transient hypoperfusion, with an EEG accompaniment of slowing and/or attenuation, as seen during cross-clamping of the carotid artery. We explored this correlation as a part of tilt-table cum EEG testing.Methods: A total of 52 patients over the course of 2.5 years had tilt-table testing combined with EEG. They had no previous diagnosis of autonomic, vasovagal, cardiogenic or other disorder, and this testing was usually a first step in their evaluation. They also had no diagnosis of epilepsy. EEG was obtained for 10-15 minuted of baseline, and for the entire duration of the provocative testing. EEG records were reviewed by an expert epileptologist, and correlated with the clinical symptoms.Results: 24 patients had ""positive"" outcome clinically. Only 12 were ""EEG-positive"" as well, with a definite correlate to their clinical events, which ranged from significant presyncopal complaints to complete syncope with atonic collapse. These patients had one of the following three patterns in the EEG corresponding to their symptoms: - moderately severe, diffuse delta followed by attenuation (N=5) - nonspecific milder polymorphic slowing (N=2) - FIRDA, frontal intermittent rhythmic delta activity (N=5) None had an epileptiform EEG.Conclusions: This was an attempt to correlate tilt-table testing symptomatology with simultaneous EEG findings. Somewhat predictably, many patients had no EEG correlate despite having their typical symptoms, or ""near-typical"" symptoms, or no significant clinical change. Of those who had a clinical change with an EEG correlate, the correlates ranged between predictable, expected diffuse slowing and attenutation, and a completely unpredictable finding of FIRDA. This is a pattern most often seen with increased intracranial pressure (ICP), or with predominantly frontal encephalopathies in many metabolic, infectious, and dementing disorders. To see FIRDA in the context of a true positive on tilt-table testing is novel, and somewhat hard to explain in terms of neurophysiology. The physiological correlate of FIRDA, other than increased ICP or severe frontal dysfunction, is not known. We are left with theorizing, that as cerebral perfusion fails, as suggested by the symptoms and by global hypotension measured conventionally, there is a pathological neuronal synchronization resulting in high-amplitude slow rhythmic bifrontal activity, manifesting electrographically as FIRDA. Clinical use of combined EEG-tilt table testing remains to be explored. Factitious or psychogenic syncope may be ruled out by this method, that confirms the presence or lack of EEG corelate to the patient's typical symptomatology.