Memory In Mesial Temporal Lobe Epilepsy

Background and ObjectivesThe memory impairments in the patients with mesial temporal lobe epilepsy are characterized by the deficits in explicit memory and the retention in implicit memory, so MTLE was considered as a model to understand human memory. Memory is important for study and work and is affected by many factors in the patients with MTLE. The studies in the different groups of patients with MTLE are to prove the mechanism of memory impairment and plasticity in MTLE, and quantitative MRI was applied to explain the contribution of mesial temporal lobe structure to memory consolidation. The study is valuable for the therapy and prevention of the congnitive disorders in MTLE.Materials and MethodsAll patients with normal intelligence who were diagnosed as MTLE by the clinical information, EEG and MRI between Jun. 2006 and Dec. 2007 were investigated including age, age onset, duration, education level, occupation, farmer or not, the past history, seizure and medication. All cases were classified as the left MRI-positive (MRI (+)) group, the right MRI (+) group, the MRI (—) group, the bilateral MRI (+) group by high-quality MRI protocol, as the less than 5 year-old group, the 5 to 14 year-old group, the adult group by the first cerebral damage age, also as the drug-resistant group and the drug-responsive group. The Clinical Memory Scale was administered as memory assessment of MTLE. MQ, the scale scores by age of the direct memory, the associated study, the free picture recall, the non-sense graphics recognition, the recognition memory test for faces and the primary scores of the unrelated memory were analyzed. Four studies for the different groups of cases were performed. The first part was a case-control study between 54 patients with MTLE and 33 patients with IGE who were 14 to 30 year-old and had the similar occupation and education. In the second part, the general linear model multivariate analysis of variance and covariance were used to analyze the data of 190 patients with MTLE. ANOVA was used to analyze the data among the groups with the different MRI results. The third part was the correlative study between the MRI quantitative data: the Z scores or asymmetry index and the memory scale scores about 89 patients with ~1H-MRS and 64 patients with MRI volumetric measurement of the hippocampus, the amygdala, and the entorhinal area. A 1 year follow-up study in the refractory MTLE was carried out in the forth part. 10 seizure-free patients with the surgery and 10 seizure-free patients with the new anti-epilepsy drugs (AEDs) addition therapy were tested by CMS I before the therapy and repeated by CMS II during 4 months to 1 year after the therapy. The repeated measures analyse of variance was used to analyzed the data.Results1. MQ, the scores of the unrelated memory, the non-sense graphics recognition and the recognition memory test for faces in the MTLE group were significantly lower than those in the IGE group, only the score of the unrelated momory in the drug-responsive group was lower than the IGE group.2. MQ, the scores of the associated study, the unrelated memory, the non-sense graphics recognition and the recognition memory test for faces in the less than 5 year-old group were significantly lower than those in the IGE group, only MQ and the score of recognition memory test for faces in the 5～14 year-old group were lower than the IGE group. The left hippocampal volumes in the less than 5 year-old group were significantly smaller than those in the 5～14 year-old group and the adult group, amygdalic volumes in the adult group were significantly larger than the other two groups.3. For the patients with MTLE, occupation affected the direct memory and the recognition memory test for faces, drug-response affected the unrelated memory, medication affected MQ, the direct memory, the associated study, the difference in the MRI results affected MQ, the unrelated memory and the recognition memory test for faces, age affected the associated study and the recognition memory test for faces, duration affected the direct memory.4. The scores of the direct memory, the associated study, the unrelated memory in the left MRI(+) group were significantly lower than those in the MRI(-) group, the scores of the direct memory in the left MRI(+) group were lower than those in the right MRI(+) group, the scores of the recognition memory test for faces in all MRI(+) groups were lower than those in the MRI(-) group. However, the scores of the non-verbal tests, such as the free picture recall and the non-sense graphics recognition, showed no significant difference among groups.5. The asymmetry index of entorhinal area was positive correlated with the scores of the direct memory, the unrelated memory and the free picture recall, the asymmetry index of amygdala was negtive correlated with the scores of the associated study, the non-sense graphics recognition and the recognition memory test for faces, the left hippocampal volumes were negtive correlated with the scores of the unrelated memory, and the right hippocampal volumes were positive correlated with the scores of the recognition memory test for faces.6. The scores of the recognition memory test for faces in either the new anti-epilepsy drugs (AEDs) addition therapy group or the surgery group were improved after the therapy, the more significant in the surgery group. In the new anti-epilepsy drugs (AEDs) addition therapy group, the scores of the non-sense graphics recognition were worse after the therapy.7. The scores of the recognition memory test for faces in the right MTLE group were better than those in the left MTLE group before the surgery. The verbal memory, especially in the direct memory was worse in the left MTLE group and improved in the right MTLE group after the surgery. For the non-verbal memory, the data showed no significant difference.Conclusion1. The patients with MTLE have the general and special memory impairment.2. CMS is valuable for the memory assessment of MTLE, the recognition memory test for faces is the most sensitive sub-scale that is valuble to estimate the memory function of bilateral temporal lobe especially left temporal lobe or the minut change of memory.3. The memory impairment is bilateral in the patients with either the left or the right MTLE, the faces recognition or naming function of memory is easier for the damage or the recovery.4. The memory impairment is more general and significant in the patients with the early cerabral damage.5. Memory can be improved by seizure-free through the medication or the surgery.6. Duration and medication affect the verbal memory in the patients with MTLE.7. The verbal memory was worse in the left MTLE group and improved in the right MTLE group after the surgery.8. The amygdala and the entorhinal area that affect verbal memory or non-verbal memory are the important structure of memory consolidation.