Temporal lobe epilepsy is characterized by complex partial seizures with either primary intracranial neoplasms or other non-neoplastic lesions. We reviewed 64 cases of surgically resected temporal lobes and amygdalo-hippocampal regions for temporal lobe epilepsy ansed by non-neoplastic lesions to elucidate the incidence and histologic features of each histologic group for a period of 2 years. The patient's age ranged from 12 to 49 years and the ratio of male to female was 42:22. There were 37 cases(57.8%) with single pathology and an additional 20 cases(31.3%) with dual pathology. The emaining 7 cases(10.9%) had no structural alternations. The most common temporal lobe pathology was hippocampal sclerosis in 41 cases(64.1%), diagnosed alone in 21 cases and as dual lesions in 20 cases. The hippocampal neuron loss was most pro,omemt in CA1, followed by CA4, CA3, and CA2.
Amygdaloid sclerosis was present in 28 cases(43.8%), lases had 13 dual lesions, 25 cases also had hippocampal sclerosis. The 20 dual lesions showed that 6 cortical dysplasia, 10 microdysgenesis, 1 chronic non-specific inflammatory lesion, and 3 cysticercosis were associated with the various degree of mesial temporal sclerosis.
Neuronoglial malformative lesions were identified in 21 cases(32.8%) including 16 dual lesion cases, which composed of 15 microdysgenesis and 6 cortical dysplasia.
Neurofilament immunostain for cortical dysplasia revealed abnormally beaded disarray of axons in dysplastic pyramidal cells. The remaining pathologic lesions observed were 1 cysticercosis, 1 chronic non-specific inflammatory lesion, 3 arteriovenous malformation, 2 fibrous nodule, and 1 fibrous adhesions of the arachnoid.
Pharmacologic therapy is still the primary management for epilpsy; however, surgical treatment is a reasonable therapeutic option for patients suffering from medically intractable seizures, especially temporal lobe epilepsy having a documented unilateral epileptogenic area. Thirty nine patients with pharmaco-resistant complex partial seizures underwent anterior temporal lobectomy and hippocampectomy in 38 cases and frontal cortisectomy in one case. On pathological examination, hippocampal sclerosis was a predominent pathologic finding and was identified in 18 cases. Other non-neoplastic lesions consisted of 5 cases of vascular lesions(2 cavernous angiomas, 2 arteriovenous malformations and 1 angiomatosis), 3 cases of fibrous nodule, 2 cases of cicatrical changes of cerebral cortex, and 1 case of parasitic infection. Neoplasms including two cases of oligodendroglioma and one case of anaplastic astrocytoma were also noted. In seven cases, there was no detectable lesion on gross and microscopic examination. On post-operative follow-up, seizures were completely terminated in most cases(31 cases, 79%). The rest of the patients also displayed marked alleviation of symptoms. The seizures tended to recur more aften among the patients with neoplasm or no pathologically detectable lesion. In order to detect any minute pathological lesion, thorough gross and microcsopic examinations are considered to be essential.
This study was designed to identify expression of calcium-binding proteins and synaptic reorganizations of dentate mossy fibers in hippocampal sclerosis of human temporal lobe epilepsy. Hippocampal neuronal density was quantitively analyzed in temporal lobe epilepsy group (n=50) to investigate the degree of hippocampal sclerosis and it was compared with that of autopsy control (n=3). To verify the distribution of calcium-binding proteins in neurons of epileptic hippocampi, the parvalbumin (PV)-immunoreactive and calbindin-D28K (CB)-immunoreactive neurons were quantitively analyzed in each area of Ammon's horn by immunohistochemical stain. Also, to clarify synaptic reorganizations of the dentate mossy fibers, a part of each hippocampus was examined under light microscopy and transmission electron microscopy using Timm sulphide silver method. In epileptic hippocampi, severity of hippocampal sclerosis (HS) was graded four, which consisted of 3 cases with no HS, 6 mild HS, 12 moderate HS, and 29 severe HS. The hippocampal neuronal loss was most prominent in CA1, followed by CA4 and CA2. Expression of calcium-binding proteins was more prevalent in CA2 of all groups. The proportion of PV-immunoreactive neurons in CA1 and CA4 significantly increased in the moderate and severe HS group, whereas the proportion of CB-immunoreactive neurons did not correlated with the severity of HS. Timm granules were noted in inner molecular supragranular layer of dentate gyrus of epileptic hippocampi and they tended to increase in proportion along with the severity of hippocampal sclerosis.
Transmission electron microscopy showed that supragranular Timm granules corresponded to synaptic terminals of mossy fibers. These results suggest that parvalbumin appears to have more protective effect against neuronal loss and that mossy fiber synaptic reorganization seems to play a major role in pathogenesis of hippocampal sclerosis of human temporal lobe epilepsy.
Many pathological surveys of brain tissue in patients with intractable epilepsy have been reported. There have been, however, few studies focused on the differences between childhood and adults in pathological alterations of brain.
We retrospectively analyzed histopathology of 164 lobectomy specimens for intractable epilepsy in view of the differences between children and adults. Among 164 cases, 28 cases were children (less than 15 years) and 136 cases adults. We compared frequency of histopathologic features, distribution of involved cortex (temporal or extratemporal lobe), previous injury histories, such as brain trauma, encephalitis or febrile seizure, and coexistence of other lesions (dual pathology) between two groups. Pathologic alterations were encountered in 92% of 164 patients. In children focal cortical dysplasia (n=16, 57.1%), neoplasm (n=8, 28.6%), hippocampal sclerosis (n=6, 21.4%), cortical tuber (n=1, 3.6%), leukomalacia (n=1, 3.6%), and Rasmussen's encephalitis (n=1, 3.6%) were observed, whereas focal cortical dysplasia (n=81, 59.6%), hippocampal sclerosis (n=80, 58.8%), neoplasm (n=19, 14%), and cerebral cysticercosis (n=3, 2.2%) were found in adults.
Pediatric patients had a higher proportion of severe focal cortical dysplasia (17.9% in children, 0.7% in adults). Neoplasia and extratemporal lobe involvement were more commonly found in children (28.6%, 50%) than in adults (14.0%, 24.3%), whereas hippocampal sclerosis and dual pathology were more common in adults (58.8%, 44.9%) than in children (21.4%, 17.9%). Previous injury history was statistically significant in patients with hippocampal sclerosis, and lent support to the hypothesis that hippocampal sclerosis is related with acquired lesions.
Incidence of focal cortical dysplasia was nearly similar in both adult (59.6%) and pediatric groups (57.1%), and supported the hypothesis that focal cortical dysplasia is developmental abnormality occurring during a prenatal period.