1.
Abnormal visual field maps in human cortex: a mini-review and a case report.
Haak, KV, Langers, DR, Renken, R, van Dijk, P, Borgstein, J, Cornelissen, FW
Cortex; a journal devoted to the study of the nervous system and behavior. 2014;:14-25
Abstract
Human visual cortex contains maps of the visual field. Much research has been dedicated to answering whether and when these visual field maps change if critical components of the visual circuitry are damaged. Here, we first provide a focused mini-review of the functional magnetic resonance imaging (fMRI) studies that have evaluated the human cortical visual field maps in the face of retinal lesions, brain injury, and atypical retinocortical projections. We find that there is a fair body of research that has found abnormal fMRI activity, but also that this abnormal activity does not necessarily stem from cortical remapping. The abnormal fMRI activity can often be explained in terms of task effects and/or the uncovering of normally hidden system dynamics. We then present the case of a 16-year-old patient who lost the entire left cerebral hemisphere at age three for treatment of chronic focal encephalitis (Rasmussen syndrome) and intractable epilepsy. Using an fMRI retinotopic mapping procedure and population receptive field (pRF) modeling, we found that (1) despite the long period since the hemispherectomy, the retinotopic organization of early visual cortex remained unaffected by the removal of an entire cerebral hemisphere, and (2) the intact lateral occipital cortex contained an exceptionally large representation of the center of the visual field. The same method also indicates that the neuronal receptive fields in these lateral occipital brain regions are extraordinarily small. These features are clearly abnormal, but again they do not necessarily stem from cortical remapping. For example, the abnormal features can also be explained by the notion that the hemispherectomy took place during a critical period in the development of the lateral occipital cortex and therefore arrested its normal development. Thus, caution should be exercised when interpreting abnormal fMRI activity as a marker of cortical remapping; there are often other explanations.
2.
Peri-ictal water drinking and other ictal vegetative symptoms: Localizing and lateralizing the epileptogenic zone in temporal lobe epilepsy? Two case reports and review of the literature.
Errguig, L, Lahjouji, F, Belaidi, H, Jiddane, M, Elkhamlichi, A, Dakka, T, Ouazzani, R
Revue neurologique. 2013;(11):903-10
Abstract
Peri-ictal behavior disorders can be helpful in localizing and lateralizing seizure onset in partial epilepsies, especially those originating in the temporal lobe. In this paper, we present the case of two right-handed women aged 36 and 42 years who presented with partial seizures of mesial temporal type. Both of the patients had drug resistant epilepsy and undergone presurgical evaluation tests including brain magnetic resonance imaging, video-EEG monitoring and neuropsychological testing. The two patients had hippocampal sclerosis in the right temporal lobe and exhibited PIWD behavior concomitant with right temporal lobe discharges documented during video-EEG recordings. Anterior temporal lobectomy was performed in one case with an excellent outcome after surgery. The patient was free of seizures at 3 years follow-up. We reviewed other publications of peri-ictal autonomic symptoms considered to have a lateralizing significance, such as peri-ictal vomiting, urinary urge, ictal pilo-erection. Clinicians should search for these symptoms, even if not spontaneously reported by the patient, because they are often under-estimated, both by the patients themselves and by physicians. Additionally, patients with lateralizing auras during seizures have a significantly better outcome after epilepsy surgery than those without lateralizing features.
3.
Pearls & Oy-sters: selective postictal aphasia: cerebral language organization in bilingual patients.
Aladdin, Y, Snyder, TJ, Ahmed, SN
Neurology. 2008;(7):e14-7
Abstract
BACKGROUND Ictal and postictal language dysfunction is common and strongly predictive of language laterality in monolingual patients. For bilingual patients, selective dysfunction has been reported for a single language with focal cerebral lesions, electrical brain stimulation, and intracarotid sodium amytal. METHODS Two right-handed Ukrainian-English bilingual patients with left perisylvian structural lesions, late onset complex-partial seizures, and postictal aphasia for English are presented and discussed with regard to mechanisms of selective aphasia and factors contributory to language lateralization in bilingual patients. RESULTS Ukrainian was the native language of both patients with English acquired after 7 years of age. Regular/video-EEG showed left temporal epileptogenesis. A 56-year-old man, who had a left hemorrhagic stroke at age 50 and had not spoken Ukrainian for 40 years, was unable to speak English for approximately 20 minutes postictally but had global preservation of Ukrainian. A 71-year-old woman, who had a left temporal epidermoid cyst and had not spoken Ukrainian since childhood, had 10- to 15-minute postictal expressive aphasia in English but not Ukrainian and preservation of comprehension in both languages. CONCLUSIONS These cases are instructive and consistent with the literature on cerebral organization of language in bilingual individuals. For both patients, postictal aphasia with preservation of Ukrainian is consistent with findings from clinical and experimental studies indicating that later age of second language acquisition (>6 years) rather than language proficiency is a primary factor in language laterality. Second, global aphasia in the man with a late lesion vs expressive aphasia with preservation of comprehension of English in the woman with a prenatal/early lesion is consistent with the atypical language laterality described for individuals with left-sided lesions sustained prior to age 5. Although neither Wada test nor fMRI was done to assure left hemisphere laterality of spoken Ukrainian and English, this is probable, and the selective postictal aphasia observed for both patients is consistent with the differential intrahemispheric organization reported for the two languages of bilingual individuals. Possible mechanisms of selective postictal aphasia, e.g., active inhibition, and differences in language networks in bilingual patients are discussed.