The value of PET scan (and MRI and Wada test) in patients with bitemporal epileptiform abnormalities
S. R. Benbadis, N. K. So, M. A. Antar, G. H. Barnett and H. H. Morris
Department of Neurology, Cleveland (Ohio) Clinic Foundation, USA.
BACKGROUND: Lateralization remains difficult in patients with bitemporal
epileptiform abnormalities. OBJECTIVE: To evaluate the reliability of the
interictal fluorodeoxyglucose F18-positron emission tomographic (PET) scan
in this setting. METHODS: We analyzed PET scan findings in 25 patients who
required bilateral depth electrodes for lateralization of temporal lobe
epilepsy. The contribution of magnetic resonance imaging and the
intracarotid amobarbital procedure was also analyzed. RESULTS: Positron
emission tomographic scan revealed lateralized hypometabolism in 15
patients. This was in agreement with the depth evaluation in 10 cases
(67%). In five cases (33%), the PET and depth findings were in
disagreement, with no predominant side of seizure origin by depth
electroencephalography (EEG) in four cases and PET lateralization opposite
to depth findings in one case. In 10 of the 25 patients, PET scans could
not lateralize hypometabolism to one temporal lobe, of which six were
confirmed by depth EEG not to have a predominant side of seizure onset. The
overall sensitivity of PET for concordant lateralized seizure onset was
67%. Ten of 14 patients who underwent a lobectomy had a successful outcome,
including three of four patients whose temporal lobe epilepsy was
lateralized by depth EEG but not by PET. One patient had PET lateralization
opposite to the depth EEG and side of surgery and failed to improve.
CONCLUSIONS: In this highly selected group of patients, the lateralizing
value of PET and magnetic resonance imaging was somewhat diminished, and
the intracarotid amobarbital procedure was not found useful for
lateralization. Positron emission tomography and magnetic resonance
imaging, when pointing to the side opposite depth EEG, may indicate a poor
prognosis.