Temporal lobe epilepsy with hippocampal scerosis, MTLE-HS

Etiologies: Predominantly unilateral, but also bilateral involvement (It is more likely to occur in dual pathology, which can co-occur with other structural brain abnormalities, including malformations of cortical development and vascular malformations). The pathological features of hippocampal sclerosis are the loss of pyramidal neurons (mainly in the CA1 area), the dispersion of granulosa cells, and the proliferation of glial cells. In addition, prolonged febrile seizures in childhood (about 25% of hippocampal sclerosis patients have a history of febrile seizures, or pre-existing structural deformities of the hippocampus may itself predispose to febrile seizures) and other brain damage may be causes of hippocampal sclerosis. It is believed that the role of hippocampal sclerosis in epilepsy is attributed to the remodeling of synapses in the hippocampal region, and the increased sensitivity to glutamate may be an important reason.These changes make the residual hippocampal neurons discharge abnormally supersynchronous [1-2].

Age of onset and epidemiological data: Usually onset between the ages of 4-16 years, accounting for about 30-60% of temporal lobe epilepsy, and about 70% of refractory temporal lobe epilepsy [1-2].

Seizure characteristics: Consciousness is often impaired as the seizure progresses, and there may be cessation of movement, staring, or sluggishness, often accompanied by automatism (unilateral automatism is often on the same side of the lesion), motor seizures include head and eye deviation to one side (early head deviation is usually on the same side of the epileptogenic focus, later head deviation is usually on the opposite side of the lesion), local rigidity, dystonic posture (can be seen in about 20-30% of patients, symptoms often occur on the opposite side of the origin lesion), a few can be secondary to GTCS. Paroxysmal or postictal aphasia and delayed recovery are seen mainly after the dominant temporal lobe seizure. After the seizure, there is often a hazy state for a long time, which may be accompanied by automatism, disorientation, language disturbance or lethargy [1-2].

EEG: Background: mostly normal, some may slow down slightly. Interictal: may manifest as sharp waves, spike waves, or focal slow wave activity in one or both anterior temporal regions (sometime can also see in the forehead region), and more than one-third of patients may have bilateral temporal regions independent epileptiform discharge, sometimes accompanied by temporal intermittent rhythmic delta activity (TIRDA) can be seen in the sclerotic side of the hippocampus, and epileptiform discharges will increase during sleep, adding lower temporal electrodes, sphenoid electrodes, or T1/T2 electrodes can increase the detection rate of epileptiform abnormalities. Ictal: during the aura phase, the scalp EEG mostly did not change significantly, or the epileptiform discharge activity disappeared during the interictal period, and the local voltage in the temporal region decreased. In the early stage of seizure, 5-7Hz rhythmic theta activity or sharp wave rhythmic release in one side of temporal area can be seen (highly suggesting the origin of hippocampus), and sometimes, 5-7Hz positive rhythm often can also appear in the parietal region or parasagittal region (considering the electric dipole electric field corresponding to the discharge at the bottom of the temporal lobe) [2].

Brain MRI: High-resolution MRI (with a coronal view) is best, showing hippocampal atrophy and changes in signal (high T2 and FLAIR signal), and up to one third of patients have dual pathology (hippocampal sclerosis co-existing with other structural brain abnormalities).

Developmental progress and curative effect: Patients with a long course of disease can have varying degrees of cognitive impairment, memory loss and mental behavior abnormalities. In addition, many of these patients often have poor therapeutic effects of antiepileptic drugs, and most of the surgical treatment can achieve good results.

Reference

1. Panayiotopoulos.  癫痫综合征及临床治疗.  北京 : 人民卫生出版社, 2012.
2. 刘晓燕.  临床脑电图学. 第2版.  北京 : 人民卫生出版社, 2017.