Geller Andrew M, Hudnell H Ken, Vaughn Bradley V, Messenheimer John A, Boyes William K
Neurotoxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Doc Ophthalmol. 2005 Jan;110(1):121-31. doi: 10.1007/s10633-005-7350-0.
Visual disruption in patients diagnosed with epilepsy may be attributable to either the disease itself or to the anti-epileptic drugs prescribed to control the seizures. Effects on visual function may be due to perturbations of the GABAergic neurotransmitter system, since deficits in GABAergic cortical interneurons have been hypothesized to underlie some forms of epilepsy, some anti-epileptic medications increase cortical GABA levels, and GABAergic neural circuitry plays an important role in mediating the responses of cells in the visual cortex and retina. This paper characterizes the effects of epilepsy and epilepsy medications on the visual evoked response to patterned stimuli. Steady-state visual evoked potentials (VEP) evoked by onset-offset modulation of high-contrast sine-wave stimuli were measured in 24 control and 54 epileptic patients. Comparisons of VEP spectral amplitude as a function of spatial frequency were made between controls, complex partial, and generalized epilepsy groups. The effects of the GABA-active medication valproate were compared to those of carbamezepine. The amplitude of the fundamental (F1) component of the VEP was found to be sensitive to epilepsy type. Test subjects with generalized epilepsy had F1 spatial frequency-amplitude functions with peaks shifted to lower spatial frequencies relative to controls and test subjects with complex partial epilepsy. This shift may be due to reduced intracortical inhibition in the subjects with generalized epilepsy. The second harmonic component (F2) response was sensitive to medication effects. Complex partial epilepsy patients on VPA therapies showed reduced F2 response amplitude across spatial frequencies, consistent with previous findings that showed the F2 response is sensitive to GABA-ergic effects on transient components of the VEP.
被诊断为癫痫的患者出现视觉障碍，可能归因于疾病本身或用于控制癫痫发作而开具的抗癫痫药物。对视觉功能的影响可能是由于GABA能神经递质系统的紊乱，因为据推测，GABA能皮质中间神经元的缺陷是某些形式癫痫的基础，一些抗癫痫药物会提高皮质GABA水平，并且GABA能神经回路在介导视觉皮质和视网膜中细胞的反应方面发挥重要作用。本文描述了癫痫和抗癫痫药物对图案刺激视觉诱发电位的影响。在24名对照者和54名癫痫患者中测量了由高对比度正弦波刺激的起始-偏移调制诱发的稳态视觉诱发电位（VEP）。比较了对照组、复杂部分性癫痫组和全身性癫痫组之间作为空间频率函数的VEP频谱幅度。将GABA活性药物丙戊酸盐的作用与卡马西平的作用进行了比较。发现VEP的基波（F1）成分的幅度对癫痫类型敏感。全身性癫痫的测试对象的F1空间频率-幅度函数的峰值相对于对照组和复杂部分性癫痫的测试对象向更低的空间频率偏移。这种偏移可能是由于全身性癫痫患者皮质内抑制作用减弱所致。二次谐波成分（F2）反应对药物作用敏感。接受丙戊酸治疗的复杂部分性癫痫患者在各个空间频率上的F2反应幅度均降低，这与之前的研究结果一致，即F2反应对VEP瞬态成分上的GABA能作用敏感。
