Simple Partial Status of Forced Thinking Originated in the Mesial Temporal Region: Intracranial Foramen Ovale Electrode Recording and Ictal PET
A 50-year-old, ambidextrous woman was referred for the management of intractable partial seizures which began at the age of 13. During the first several years, she reported experiencing recurrent episodes of flash-backs which she described as “very familiar scenes passing by me”. She also reported olfactory hallucinations which consisted of odd smells. At the age of 17, she started to have complex partial seizures (CPS) which were associated with different types of psychic auras such as déjà-vu, jamais-vu, and FT. These auras were experienced alone or in various combinations. She also had experienced two prolonged episodes of continuous FT which lasted for several days after clusters of CPS. She recalled these episodes of FT as “I forgot something that I should do”. Despite systematic trials of antiepileptic drugs (AED), she was still having two to three episodes of CPS monthly, and she decided to receive epilepsy surgery.\nShe had no prior medical history, including febrile seizure. A bedside neurological examination was unremarkable. Neuropsychological test revealed an average level of intelligence, and her memory was average in visual and borderline in verbal modalities. Magnetic resonance imaging showed left hippocampal sclerosis ().\nVideo-EEG monitoring disclosed interictal epileptiform discharges in the left temporal region with a maximum amplitude at the sphenoidal electrode (SP1). Two episodes of CPS without aura were recorded after AED withdrawal. These started with brief eye blinking, subtle limb automatisms, and body rocking. She then developed moaning, right facial tonic spasms, right arm dystonia, and left head and body rotations. The ictal EEGs showed diffuse attenuation of background activity before the clinical onset, followed by delayed rhythmic 5–6 Hz theta activity in the left temporal region, 15s and 28s after the clinical onset, respectively.\nIctal 99mTc-ethylcysteinate dimer single photon emission computed tomography showed increased blood flow in the left temporal and parietal lobes (). We elected to place intracranial foramen ovale electrodes (FOE) under local anesthesia because the ictal EEG onset was diffuse and there was a significant delay of lateralizing discharges after the clinical ictal onset.\nInterictal EEG showed frequent epileptiform discharges at the left FOE without any obvious changes in the scalp electrodes. After the placement of the FOE, she experienced 18 episodes of brief CPS overnight. Ictal EEG revealed that the onset in the left FOE consisting of rhythmic β fast activity with superimposed polyspikes for 6–10s. This evolved to higher amplitude rhythmic theta activity in the left temporal scalp electrodes, 10–20s later.\nThe CPS clustering was successfully terminated by the intravenous administration of lorazepam, and she resumed taking AEDs including lamotrigine 100 mg, valproate 300 mg, topiramate 150 mg, and pregabalin 75 mg bid. However, she started complaining of continuous FT. The content of FT, quoted as her saying, was “I have something that I must do”, and the similar content of FT had occurred as either habitual auras or prolonged aura episodes after CPS cluster. She well recognized that there was nothing that she actually should do, but she was not able to stop this line of thinking. These thoughts caused unnecessary anxiety. The EEG showed a continuous 1–1.5 Hz periodic pattern of polyspikes and slow wave complexes on the left FOE during the persistent FT (). Her bedside neurological examination including memory function did not show any definite abnormality. She did not have any problem in daily life. The simple partial status persisted for five days.\nBrain 18F-fluorodeoxyglucose PET during the episode of FT showed a focal hypermetabolism in the left mesial temporal region (). The PET data was analyzed using MRIcro () and statistical parametric mapping 8 (SPM8) (). The patient’s PET images were initially transferred to the Analyze format with MRIcro and spatially normalized to our institutional PET template using the affine transformation of SPM8. Afterwards, the images were smoothed with a 12-mm FWHM Gaussian kernel and a statistical analysis was set up to compare the patient and the control subjects (n=32) with a two-sample t-test. We used a voxel height threshold at p=0.001 (uncorrected) and the minimal cluster size as 100 voxels. The SPM map was superimposed on the normalized T1 template using ANALYZE 5.0 (Biomedical Imaging Resource, Mayo Foundation, Rochester, MN, USA).This demonstrated increased metabolism in the left hippocampus, the left parahippocampal gyrus, and the right cerebellum (). A Wada test with intracarotid injection of thiopental revealed bilateral language and right memory dominance (6 versus 0 out of 10 items). The patient underwent a left anterior temporal lobectomy. The pathology was consistent with hippocampus sclerosis. No further seizure including aura had developed during the 56 months follow-up after the surgery.