Bilateral Occipitoparietal Regions Research Articles

Clinical characteristics of Taiwanese patients with Hereditary spastic paraplegia type 5.

ObjectivesTo investigate the clinical, electrophysiological, neuroimaging characteristics and genetic features of SPG5 in Taiwan.MethodsMutational analysis of the coding regions of CYP7B1 was performed by utilizing targeted resequencing analysis of the 187 unrelated Taiwanese HSP patients. The diagnosis of SPG5 was ascertained by the presence of biallelic CYP7B1 mutations. The SPG5 patients received clinical, electrophysiological, and neuroimaging evaluations. Disease severity was assessed by using the Spastic Paraplegia Rating Scale (SPRS) and the disability score. Two microsatellite markers as well as 18 single‐nucleotide polymorphism (SNP) markers flanking CYP7B1 were genotyped to assess the founder effect of the CYP7B1 p.R112* mutation.ResultsNineteen SPG5 patients from 17 families were identified. They typically presented an insidious onset progressive spastic paraparesis with proprioception involvement beginning at age 8 to 40 years. Their MRIs often showed white matter abnormalities in bilateral occipito‐parietal regions, spinal cord atrophy, and mild cerebellar atrophy. Six different mutations in CYP7B1 were recognized, including three novel ones (p.N131Ifs*4, p.A295V, and p.L439R). CYP7B1 p.R112* was the most common mutation and present in 88.2% of the 17 SPG5 pedigrees. The patients with homozygous CYP7B1 p.R112* mutations had a milder clinical severity. Detailed haplotype analyses demonstrated a shared haplotype in the 25 individuals carrying at least one single allele of CYP7B1 p.R112*, suggesting a founder effect.InterpretationThis study delineates the distinct clinical and genetic features of SPG5 in Taiwan and provides useful information for the diagnosis and management of SPG5, especially in patients of Chinese descent.

Frontal lobe signs after posterior fossa surgery: Is hypoperfusion ignored?

Sir, Behavioral manifestations constitute major burden of patients suffering from brain tumors.[2] Cerebellar mutism syndrome, known to occur following surgery for posterior fossa tumors, is not commonly associated with behavioral symptoms. A 12-year-old boy, diagnosed with posterior fossa mass lesion underwent ventriculoperitoneal shunt followed by definitive surgery. He developed acute mutism symptoms after the surgery and presented with hyperactivity, inattention, and inappropriate social behavior in the form of soiling and urinating in public. Single-photon emission computed tomography was performed 15 days after surgery for these symptoms and it showed cerebral hypoperfusion in right frontal and thalamoganglionic regions [Figure 1]. Figure 1 Brain single-photon emission computed tomography showing moderately reduced perfusion in right inferior orbitofrontal region, right lateral temporal, right thalamic, right basal ganglia, and bilateral occipito-parietal regions (right > left) Altered speech and other manifestations after posterior fossa surgery are often secondary to edema or hypoperfusion adjacent to the surgical trauma.[4] Remote localized deficits after posterior fossa surgery are however not common, though crossed cerebello-cerebral diaschisis due to involvement of dentato-thalamo-cortical pathway has been occasionally reported.[1] Some of these atypical remote presentations were described possibly due to vascular phenomena.[3] However, extensive remote hypoperfusion as described above have not been reported much. Perfusion deficits in these atypical presentations indicate the impact of surgery on brain is more generalized than the operated area similar to the systemic nature of head injury.[4] In addition, perfusion tests may not only help to evaluate patients with atypical postoperative symptoms, but also open up therapeutic avenues as well as for prognosis. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Neural Mechanism for Mirrored Self-face Recognition.

Self-face recognition in the mirror is considered to involve multiple processes that integrate 2 perceptual cues: temporal contingency of the visual feedback on one's action (contingency cue) and matching with self-face representation in long-term memory (figurative cue). The aim of this study was to examine the neural bases of these processes by manipulating 2 perceptual cues using a “virtual mirror” system. This system allowed online dynamic presentations of real-time and delayed self- or other facial actions. Perception-level processes were identified as responses to only a single perceptual cue. The effect of the contingency cue was identified in the cuneus. The regions sensitive to the figurative cue were subdivided by the response to a static self-face, which was identified in the right temporal, parietal, and frontal regions, but not in the bilateral occipitoparietal regions. Semantic- or integration-level processes, including amodal self-representation and belief validation, which allow modality-independent self-recognition and the resolution of potential conflicts between perceptual cues, respectively, were identified in distinct regions in the right frontal and insular cortices. The results are supportive of the multicomponent notion of self-recognition and suggest a critical role for contingency detection in the co-emergence of self-recognition and empathy in infants.

Balint Syndrome in the Pediatric Population: A Case Report of Three Patients (P02.179)

Objective: To discuss occurrence of Balint syndrome in the pediatric population. Background Balint syndrome is a clinical symptom triad of simultagnosia, ocular apraxia and optic ataxia, without occurrence of visual agnosia and with sparing of visual acuity. This occurs secondary to damage of bilateral occipito-parietal regions. This has been described in adults, usually secondary to strokes or tumors. The syndrome is rarely reported in pediatric literature. Design/Methods: Described is a case report of three children seen at a tertiary pediatric hospital, diagnosed with Balint syndrome. Results: Case 1 was a 7 year old male with severe traumatic brain injury, following a motor vehicle accident. Imaging showed damage to the parietal regions, along with minor damage to the cerebellar, frontal and temporal lobes. He showed difficulties in multi-tasking and in maintaining attention, along with the Balint9s symptom triad. He had improvement by 6 months, though he had residual hemiparesis along with memory and attention problems. Case 2 was a 5 year old female with a strong family history of stroke, presenting with new onset seizures. Imaging suggested bilateral parieto-occipital damage, secondary to stroke. However, magnetic resonance spectroscopy suggested a demyelinating disorder. Further workup indicated a mitochondrial disorder. Within a year of presentation, she had significant improvement with resolution of her Balint syndrome. Case 3 was a two and a half year old female who developed herpes encephalitis, resulting in damage to bilateral hippocampi and occipitoparietal regions. Along with the symptom triad, she had marked anterograde amnesia and emotional lability. Her symptoms improved, with only mild deficits in daily living skills one year later. Conclusions: Balint syndrome occurs in children, though the symptom complex may not be easily recognized. Etiologies may vary. In children, resolution is common. Disclosure: Dr. Amin has nothing to disclose. Dr. Ehrreich has nothing to disclose. Dr. Kelly has nothing to disclose. Dr. Lebby has nothing to disclose. Dr. Hutchison has nothing to disclose.

Posterior reversible encephalopathy syndrome as the first manifestation of chronic kidney disease

Posterior reversible encephalopathy syndrome (PRES), a term coined in 1996, describes a clinico-radiologic entity characterised by headache, seizures, decreased vision, impaired consciousness and white matter oedema in bilateral occipito-parietal regions [1]. Hypertensive encephalopathy, eclampsia, immunosuppressive/cytotoxic drugs, organ transplantation, renal disease, autoimmune diseases and vasculitides are reported risk factors of PRES [1, 2]. Although potentially reversible, delay in treatment can result in permanent brain damage [3, 4].

Reading normal and degraded words: Contribution of the dorsal and ventral visual pathways

Fast, parallel word recognition, in expert readers, relies on sectors of the left ventral occipito-temporal pathway collectively known as the visual word form area. This expertise is thought to arise from perceptual learning mechanisms that extract informative features from the input strings. The perceptual expertise hypothesis leads to two predictions: (1) parallel word recognition, based on the ventral visual system, should be limited to words displayed in a familiar format (foveal horizontal words with normally spaced letters); (2) words displayed in formats outside this field of expertise should be read serially, under supervision of dorsal parietal attention systems. We presented adult readers with words that were progressively degraded in three different ways (word rotation, letter spacing, and displacement to the visual periphery). Behaviorally, we identified degradation thresholds above which reading difficulty increased non-linearly, with the concomitant emergence of a word length effect on reading latencies reflecting serial reading strategies. fMRI activations were correlated with reading difficulty in bilateral occipito-temporal and parietal regions, reflecting the strategies required to identify degraded words. A core region of the intraparietal cortex was engaged in all modes of degradation. Furthermore, in the ventral pathway, word degradation led to an amplification of activation in the posterior visual word form area, at a level thought to encode single letters. We also found an effect of word length restricted to highly degraded words in bilateral occipitoparietal regions. Those results clarify when and how the ventral parallel visual word form system needs to be supplemented by the deployment of dorsal serial reading strategies.

Mild Cognitive Impairment after Lacunar Infarction: Voxel-Based Morphometry and Neuropsychological Assessment

Background: The aim of the present study was to investigate whether there were differences in neuroradiological features, including white-matter lesions and gray-matter volumes, between patients with lacunar infarction with and without mild cognitive impairment of the vascular type (MCI-V). Methods: A total of 40 patients with lacunar infarction were studied within 1 month after stroke. Results: MCI-V was found in 22 patients, who in comparison with patients without cognitive impairment were significantly older and had fewer years of formal education. MRI subcortical hyperintensities especially in the basal ganglia (putamen and thalamus) were significantly more frequent in the MCI-V group. In the voxel-based morphometric study, patients with MCI-V showed more atrophy bilaterally in the middle temporal gyrus, right and left frontal and posterior bilateral occipitoparietal regions including the posterior cingulate as well as in the cerebellum. A region of interest analysis restricted to the parahippocampi and hippocampi showed further reduced bilateral parahippocampal gyrus and right hippocampus volume reductions in this group of patients. Finally, the amount of white-matter lesions among MCI-V showed negative correlations with gray-matter volume in frontal and temporal areas as well as with the thalamus and mesencephalon. Conclusions: The present findings provide support for an anatomical substrate of the MCI entity in patients with lacunar infarction. Both gray- and white-matter changes seem to contribute to the cognitive impairment of such patients.

Reversible Hypertensive Encephalopathy in Childhood

Reversible hypertensive encephalopathy (RHE) is clinically characterized by sudden onset of headache, visual changes, altered mental functioning and seizures. Typical MRI features include bilateral cerebral lesions depicted as hyperintense in T2 sequences and iso or hypointense in T1 images. These areas of vasogenic oedema are best visualized by diffusion-weighted imaging (DWI) sequences and apparent diffusion coefficient (ADC) maps. The neuroradiological changes usually resolve completely at follow-up. The pathogenesis of RHE is poorly understood. A number of factors have been implicated including an elevated systemic blood pressure breaking through the autoregulation capacity of the cerebral vascular system, but also immunosuppressant medication like ciclosporine A and tacrolimus as well as interferon alfa. A retrospective study of the five-year period 1999–2004 was undertaken on patients admitted to our Institution with clinical and neuroradiological features compatible with a diagnosis of RHE. Neuroradiological investigation disclosed hypodense areas on CT scan in four out of five cases and hyperintense images in T2 and FLAIR MRI sequences in eight out of eight patients, mainly affecting the unilateral or bilateral occipitoparietal regions. Clinical symptoms and MRI findings had normalized at follow-up in five cases between 2 and 11 weeks, whereas three patients died from complications of the underlying disease. RHE is not an uncommon complication arising in childhood cancer. MRI with DWI sequences is the gold standard for the detection and differential diagnosis of RHE-induced changes allowing adequate treatment and follow-up monitoring.

Functional MRI of motor sequence acquisition: effects of learning stage and performance

Neural networks of motor control are well understood and the motor domain therefore lends itself to the study of learning. Neuroimaging of motor learning has demonstrated fronto-parietal, subcortical, and cerebellar involvement. However, there is conflicting evidence on the specific functional contributions of individual regions and their relative importance for early and advanced stages of learning. Using functional MRI (fMRI), we examined hemodynamic effects in seven right-handed men during brief episodes of explicit learning of novel six-digit sequences (experiments 1 and 2) and during prolonged learning of an eight-digit sequence (experiment 3), all performed with the dominant hand. Brief episodes of new learning were predominantly associated with bilateral activations in premotor and supplementary motor areas, superior and inferior parietal cortices, and anterior cerebellum. In experiment 2, which included a control condition matched for complexity of motor execution, we also found unexpectedly strong activation in the bilateral inferior frontal lobes. In experiment 3, analysis of task by learning stage interactions showed greater involvement of the bilateral superior parietal lobes, the right middle frontal gyrus, and the left caudate nucleus during early stages, whereas left occipito-temporal and superior frontal cortex as well as the bilateral parahippocampal region were more activated during late learning stages. Analysis of task by performance interactions (based on each subject’s response times and accuracy during each scan) showed effects in bilateral fronto-polar, right hippocampal, and anterior cerebellar regions associated with high levels of performance, as well as inverse effects in bilateral occipito-parietal regions. We conclude that superior parietal and occipital regions are most intensely involved in visually driven explicit digit sequence learning during early stages and low performance, whereas later stages of acquisition and higher levels of performance are characterized by stronger recruitment of prefrontal and mediotemporal regions.

Older people with impaired mobility have specific loci of periventricular abnormality on MRI.

Recent investigations using MRI suggest that older persons with mobility impairment have a greater volume of abnormal cerebral white matter compared with persons with normal mobility, thus raising the possibility that those with impairment have lesions in areas critical for the control of mobility. To utilize automated image analysis methods to localize the specific regions of abnormal white matter that distinguish subjects with lower mobility from subjects with higher mobility. Tissue classification was performed on subjects' dual-echo long repetition time spin-echo MRI using computer algorithms operating on intensity criteria integrated with anatomic information. Statistical analysis of group differences was obtained after spatially normalizing each brain to a standard reference brain. Four discrete periventricular regions, including bilaterally symmetric frontal and bilateral occipitoparietal regions, were identified as being sensitive (frontal) or specific (occipitoparietal) in discriminating the subjects with lower mobility from subjects with higher mobility. The symmetry of these lesions in individual subjects suggested pathology other than arteriolar infarction. These results suggest that damage to discrete frontal and occipitoparietal periventricular white matter locations may be associated with a mobility disorder of aging.

Neuromagnetic signals associated with reading a kanji character formed by combining two kanji radicals

To find out which brain regions are responsible for the mental construction and recognition of a kanji character initiated by visually presented kanji radicals, rather than by information retained in the memory, a left hen radical and the corresponding right tsukuri radical were simultaneously presented randomly to either the left or right visual field of seven subjects. Thirty left hen radicals and the corresponding right tsukuri radicals were prepared as stimuli; this combination formed over 500 real or pseudo kanji characters. Instead of their usual left and right positions, the left hen radical was always presented above the right tsukuri radical. As quickly and correctly as possible, the subjects released a key when two kanji radicals constituted a single real kanji character and released another key otherwise. We recorded neuromagnetic responses as well as accuracy and reaction time. Left visual field superiority was observed as regards accuracy. This is in good agreement with previous neuropsychological results. Equivalent current dipoles were localized mainly in the left and/or right occipitotemporal regions (ventral visual pathways), the bilateral occipitoparietal regions (dorsal visual pathways) including the supramarginal region, and the areas surrounding the left superior temporal cortex. We suggest that these regions are related to reading and the mental construction of a kanji character from its radicals.