Temporal lobe tumors are one of the causes of temporal lobe epilepsy. Some of these tumors do not have intracranial occupancy signs and present clinically only with recurrent seizures, and such epilepsies often present with drug-refractory features and are not detected during preoperative imaging until the patient seeks surgical treatment for epilepsy, or even in some patients, the tumor is not confirmed until postoperative pathologic histology. This is a significant difference from the clinical features of brain tumors commonly seen in neurosurgery. Encounter Tao, Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University
Tumors associated with intractable temporal lobe epilepsy are mostly slow-growing, low-grade tumors located in the cortex, subcortex, or medial temporal lobe structures. They are usually WHO grade I-II, with individual WHO grade III, and present a clinical behavior that tends to be benign biologically. After adequate resection (usually anterior temporal lobectomy), recurrence is rare. This study shows that the most common of these tumors is a group of mixed glial-neuronal tumors, including ganglion cell gliomas, embryonic dysplastic neuroepitheliomas, and atypical mixed neuronal-glial tumors. The vast majority of these temporal lobe epilepsy-associated tumors have a good prognosis, with a survival rate of 98% over 5 years, usually without further radiotherapy or chemotherapy after surgical resection. Nevertheless, there is a small chance that these tumors may become malignant, and therefore, adequate resection and careful pathological examination of the tumor need to be emphasized. This article further emphasizes that mastering the clinicopathologic features of these tumors can help avoid overtreatment, which can affect the quality of patient survival.
In this study, the clinical features of these tumors causing intractable temporal lobe epilepsy include: (1) they are usually seen in children and adolescents; (2) the imaging manifestations are mostly focal abnormal signals located in the cortex or subcortex, without obvious edema, sometimes without obvious occupying effects, often with cystic changes, and sometimes without obvious imaging changes; (3) the neurological examination is rarely positive. The imaging manifestations are particularly important to note, and may only show focal abnormal signals, sometimes involving only the hippocampus, amygdala or parahippocampal gyrus, which can be easily confused with hippocampal sclerosis. Understanding these features can help increase the accuracy of preoperative diagnosis and develop the correct surgical plan.
Our data show that brain tumors with intractable epilepsy are often associated with different forms of cortical dysplasia, which may also contribute to the cause of seizures. The incidence of cortical dysplasia in embryonic dysplastic neuroepithelial tumors has been shown to exceed 80%, with disorganized cortical layering, increased number of residual neurons in the molecular layer, and focal neuronal aggregates in the neocortex and hippocampus near the tumor.
In addition, temporal lobe tumors are often associated with hippocampal sclerosis, showing dual pathology. Thirty percent of the cases in this group showed significant hippocampal sclerosis pathology, while the remaining cases also showed mild hippocampal neuronal loss or gliosis. This suggests that such temporal lobe tumors are closely associated with hippocampal sclerosis. It has been suggested that repeated afferent epileptic discharges may release excitotoxins and that the mechanism of calcium overload can cause sclerotic hippocampal injury; others suggest that some temporal lobe tumors are a form of congenital cortical dysplasia with a common developmental origin with medial temporal lobe sclerosis. Based on the above pathological features, we can further explore the surgical treatment modalities. Studies have shown that performing resection of the tumor lesion alone is not very effective, and simultaneous resection of the tumor lesion, hippocampal tissue, and/or surrounding cortex is the most appropriate modality to maximize seizure control. In our group of patients, we mainly used the resection method of simultaneous resection of tumor lesion, hippocampal tissue and surrounding cortex, and the seizure control was satisfactory with 90% of basic seizure-free, and the chance of tumor recurrence was minimal. However, it should be noted that while advocating adequate resection, care should be taken to assess the patient’s temporal lobe function, especially the possible effects of the dominant temporal lobe resection on language and memory functions, and not to cause serious effects as much as possible.