The Predictive Value of FDG-PET for Lateralizing Wada Memory Dominance and Epileptic Focus in Patients with Temporal Lobe Epilepsy

Backgroud : To examine the predictability of regional cerebral glucose metabolism in determining Wada memory dominance and lateralizing epileptic focus. METHODS: 1 8 F-fluorodeoxyglucose positron emission tomography (FDG-PET) and Wada test were performed in 18 patients with temporal lobe epilepsy (TLE). Regions of interest were determined in mesial, polar, anterior-lateral, mid-lateral, and posterior-lateral regions of the temporal lobe. The asymmetry indices of FDG-PET (PET-AI) were calculated in each ROI of temporal lobe, and those of Wada memory test (Wada-AI) were obtained as well. RESULTS: Pearson correlation coefficient showed Wada-AI was significantly correlated with PET-AI in mesial (r=0.67, p=0.001), polar (r=0.55, p=0.010), anterior-lateral (0.55, p=0.009) and mid-lateral (r=0.51, p=0.016) temporal regions. However, after simple linear regression analysis, PET-AI of mesial temporal region alone was significantly correlated with Wada-AI (p=0.008). In localizing epileptic focus, Wada-AI could correctly lateralize the seizure focus in 90% of the left TLE and 75% of the right TLE patients. No false lateralization by Wada-AI was observed except two patients showing prolonged confusion after amobarbital injection who were not included in this study. The PET-AI of the mesial temporal region showed the highest sensitivity of seizure lateralization (100% of left TLE and 87.5% of right RLE). CONCLUSIONS: Although FDG-PET hypometabolism is observed both at mesial and lateral regions of the temporal lobe in mesial TLE, mesial temporal region appeared to be a dominant and leading area for lateralizing Wada memory dominance and epileptic focus.

A Case of Primary Lymphoma Presenting as Cauda Equina Syndrome

Primary CNS lymphoma (PCNSL) which is localized in the cauda equina of the spinal cord is very rare. A 75-year-old man had pain in both legs and gait disturbance for the last 45 days. Painful paresthesia and weakness in both legs worsened during a one month period and he was unable to stand up by himself. In a physical examination, lym-phadenopathy nor organomegaly was found. A neurological examination revealed a dominantly proximal muscle weak-ness of the lower extremities. All modalities of sensation were decreased in both legs and a Romberg test was found positive. A CSF cytology demonstrated a large B-cell lymphoma. Following an extensive evaluation of the patient, the lymphoma was found to be limited in the cauda equina. The patient was treated with systemic dexamethasone. After the treatment, his symptoms were improved and a follow up lumbar spine MRI showed shrunken cauda equina lesions.