Biomedical subjects

F Vargha-Khadem

Publications and source records attributed to F Vargha-Khadem.

At least 55 records · Page 3Linked to original sources

PubMed1997

Onset of speech after left hemispherectomy in a nine-year-old boy.

Case Alex, with Sturge-Weber Syndrome affecting the left hemisphere, failed to develop speech throughout early boyhood, and his comprehension of single words and simple commands remained stagnant at an age equivalent of 3-4 years. But then, following left hemidecortication at age 8.5 years and withdrawal of anticonvulsants when he was more than 9 years old, Alex suddenly began to acquire speech and language. He also showed an unusual degree of residual motor capacity on his right side. Alex's remarkable progress in learning speech and language, and the development of his other cognitive abilities, were measured periodically from the age of 9 to 15 years. His most recent scores on tests of receptive and expressive language place him at an age equivalent of 8-10 years. Comparison with the level of function attained in these domains by nine other left hemispherectomized patients with early onset of disease and comparable IQ (range, 40-68) but with early development of speech and language, suggests that, surprisingly, Alex has suffered no permanent disadvantage from his protracted period of mutism and severely limited comprehension. Although the findings in Alex, as in other left-hemispherectomized patients, indicate define limits to the cognitive and linguistic capacity of the isolated right hemisphere, Alex's achievements appear to challenge the widely held view that early childhood is a particularly critical period for acquisition of speech and language or any of their selective aspects, including phonology, grammar, prosody and semantics. It is concluded that clearly articulated, well structured, and appropriate language can be acquired for the first time as late as age 9 years with the right hemisphere alone.

Adolescent↗

PubMed1996

Effects of hemispheric side of injury, age at injury, and presence of seizure disorder on functional ear and hand asymmetries in hemiplegic children.

Dichotic listening, manual functions, and IQ were measured in a large group of hemiplegic children with unilateral hemispheric damage. In the children without a history of seizure disorder, only manual functions were impaired, but in those with such a history (and hence a regime of anticonvulsant medication), all measures were affected. Some children with congenital left hemisphere lesions (with and without siezure disorder) showed a left ear advantage for dichotic digits as well as greater impairment in right hand function than those who showed the usual right ear advantage. The latter result suggests that the hemipheric damage in the subgroup with altered ear asymmetry was greater than in the others and extensive enough to encroach on language areas, shifting language representation to the right.

Adolescent↗

PubMed1996

Lateralization of brain function in childhood revealed by magnetic resonance spectroscopy.

We used proton magnetic resonance spectroscopy (1H MRS) for the assessment of focal brain pathology in 22 right-handed children with a diagnosis of intractable temporal lobe epilepsy, and we related this pathology to cognitive dysfunction. Cognitive assessment was based on measurements of verbal IQ, performance IQ, and the Paired Associate Learning subtest of the Wechsler Memory Scale. Five of the 22 children showed no abnormalities of the temporal lobes on 1H MRS, seven showed unilateral pathology, and 10 showed bilateral abnormalities. We found that left-sided pathology is associated with a loss of verbal cognitive functions, whereas right-sided pathology is associated with a loss of nonverbal functions. These findings are consistent with the pattern of lateralization of brain function that has been observed in adults.

Adolescent↗

PubMed1995

Praxic and nonverbal cognitive deficits in a large family with a genetically transmitted speech and language disorder.

A pronounced speech and language disorder affecting half of the 30 members of the four-generational KE family has been attributed by some researchers to a specific defect in the generation of morphosyntactic rules. The reported selectivity of the impairment has led to the view that the affected members suffer from a grammar-specific disorder. Our investigations of the same KE family indicate that the inherited disorder has a broad phenotype which transcends impaired generation of syntactical rules and includes a striking articulatory impairment as well as defects in intellectual, linguistic, and orofacial praxic functions generally. Although the evidence from this family thus provides no support for the existence of "grammar genes," their linguistic difficulties do constitute a prominent part of their phenotype. Investigations of the neural and genetic correlates of their disorder could therefore uncover important clues to some of the bases of the primary human faculties of speech and language.

Cognition Disorders↗

PubMed1995

Intellectual performance after presymptomatic cranial radiotherapy for leukaemia: effects of age and sex.

Cognitive outcome, as measured by verbal and performance IQs, was compared in 35 girls and 47 boys who were in first remission for acute lymphoblastic leukaemia. All children had received presymptomatic cranial radiotherapy and intrathecal methotrexate. The mean age at diagnosis was 4.2 years and the mean elapsed time from initial diagnosis to intellectual assessment was 7.1 years. Results showed that children irradiated before the age of 4 years were impaired in certain aspects of non-verbal ability, as well as in measures of short term memory and attention, calculated by factor scores derived from selected subtests of the IQ test. Subtests requiring verbal and non-verbal reasoning showed the greatest impairment after early diagnosis and treatment. In addition girls were selectively impaired in verbal IQ and other aspects of verbal ability, with the degree of impairment exacerbated by early treatment. No relationship was found between degree of impairment and either time since treatment or number of methotrexate injections. It is concluded that early age at irradiation increases the risk of impaired intellectual outcome, particularly in girls.

Adolescent↗

PubMed1995

Verbal memory impairment after right temporal lobe surgery: role of contralateral damage as revealed by 1H magnetic resonance spectroscopy and T2 relaxometry.

We assessed performance on selected tests of verbal memory in 48 patients who had undergone either anterior temporal lobectomy or selective amygdalo-hippocampectomy for the relief of pharmacologically intractable epilepsy. We related performance both to the side of surgical excision and to the presence or absence of abnormalities in the contralateral, unoperated, temporal lobe, as revealed by proton magnetic resonance spectroscopy (1H MRS) or T2 relaxometry. There were abnormalities on the unoperated side detected by 1H MRS in 50% of the 34 patients who successfully underwent spectroscopy, and by T2 relaxometry in 33% of the complete series of 48 patients. There was no systematic relationship between seizure outcome and the presence or absence of abnormalities on the unoperated side. Verbal memory deficits were present in patients with left-sided excision, regardless of whether there were abnormalities on the unoperated side. The patients with right-sided excision also had verbal memory deficits, but only in the group with magnetic resonance abnormalities on the contralateral (ie, left) side and only on delayed recall. The study extends previous findings on the role of the temporal lobes in memory and highlights the role of these new magnetic resonance techniques in relating cognitive processes to brain structures.

Adult↗

PubMed1994

Agnosia, alexia and a remarkable form of amnesia in an adolescent boy.

Childhood cases of global anterograde amnesia, visual agnosia or alexia without agraphia, either alone or in any combination, are extremely rare. Here we report the case of a male adolescent, Neil (a pseudonym), who consequent to a pineal tumour began to exhibit all three disorders in the presence of normal verbal intelligence. The most surprising aspect of Neil's case, however, is his ability to retrieve postmorbid memories through the act of writing without being able to provide any oral account of the content of his written reports. His memory retrieval thus has some of the character of 'automatic writing'. This evidence pointing to Neil's possession of a dissociated form of episodic memory presents a new challenge to our understanding of the organization of memory and of the cerebral systems underlying it.

Adolescent↗

PubMed1994

1H magnetic resonance spectroscopy in the investigation of intractable epilepsy.

We have been using proton magnetic resonance spectroscopy (1H MRS) in the investigation of adults and children with intractable epilepsy. Spectra were obtained from 2 x 2 x 2 cm cubes in the medial region of the temporal lobe, and were analyzed on the basis of signals from N-acetylaspartate (NAA), creatine+phosphocreatine (Cr), and choline-containing compounds (Cho). In comparison with control subjects, the epilepsy patients as a group show significant reductions in the NAA signal and in the NAA/Cho+Cr ratio, with increases in the Cho and Cr signals. The reduction in NAA is interpreted in terms of neuronal loss or damage, while the increase in Cr and Cho signals may be a reflection of reactive astrocytosis.

Adult↗

PubMed1994

Neuropsychological and neurological outcome after relapse of lymphoblastic leukaemia.

Fourteen children who relapsed after initial remission of leukaemia were studied. Six received a second course of cranial radiotherapy, while the remaining eight children were given total body irradiation before bone marrow transplantation. The postirradiation somnolence syndrome was common after cranial radiotherapy. All children had mild/soft neurological signs, mostly of coordination. None had a major motor disability. All but the youngest child had cataracts; two children required an operation for these. All children were growth hormone deficient. Verbal IQ, attention, and concentration were selectively reduced (with respect to normative levels). The time between the two treatments, age at relapse, and higher doses of radiotherapy all correlated with cognitive outcome, with girls showing greater impairments than boys. Only two children were performing at age appropriate levels on measures of academic achievement. It is concluded that neurological and neuropsychological morbidity is significantly increased by the current treatments prescribed after the relapse of leukaemia.

Age Factors↗

PubMed1994

A review of cognitive outcome after unilateral lesions sustained during childhood.

Views on human brain organization early in development have swung back and forth between the extreme notions of complete equipotentiality and adult-like specialization. Recent research on the cognitive effects of early brain damage supports an intermediate position and suggests that many claims on the older literature must be re-examined in the light of new evidence that cognitive impairments are sometimes attributable to previously ignored factors, such as a history of seizures, time since injury, and unsuspected lesions that are now detectable with neuroimaging techniques.

Adolescent↗

PubMed1993

Functional mapping of activated human primary cortex with a clinical MR imaging system.

Functional activation of the human brain can be visualized with magnetic resonance (MR) imaging, but most studies so far have used echo-planar imaging or magnetic fields of 2 T and above, neither of which are at present widely available. The authors used a standard 1.5-T MR imaging system to map regions of the brain that are activated with visual and motor tasks, using a long echo time (60 msec) fast low-angle shot sequence. Eleven visual and 14 motor studies were performed, and activation was seen in all cases. Up to 15% signal intensity change was apparent in gray matter but not in white matter. The precise anatomic location and extent of activation were defined by reference to T1-weighted images acquired during the same examination. This method of relating brain structure to function uses equipment that is widely available, which has considerable implications for the investigation of many neurologic and neurosurgical diseases and for our understanding of brain function and dysfunction.

Adult↗

PubMed1992

Possible blindsight in infants lacking one cerebral hemisphere.

Patients with damage to the striate cortex have a subjectively blind region of the visual field, but may still be able to detect and localize targets within this region. But the relative roles in this 'blindsight' of subcortical neural systems, and of pathways to extra-striate visual areas, have been uncertain. Here we report results on two infants in whom one cerebral hemisphere, including both striate and extra-striate visual cortex, needed surgical removal in their first year. Single conspicuous targets in the half-field contralateral to the lesion could elicit fixations, implying detection and orienting by a subcortical system. In contrast, binocular optokinetic nystagmus (OKN), for which a subcortical pathway has often been thought adequate, showed a marked asymmetry. In normal neonates, fixation shifts and OKN have both been taken to reflect subcortical control; our results are consistent with subcortical control for fixation but not for OKN.

Brain↗

PubMed1992

A review of cognitive outcome after hemidecortication in humans.

This review of the effects of hemidecortication in humans has been limited to studies of cognitive outcome published during the last 20 years. More directly than in the case of split-brain patients, the patients reviewed here attest to the remarkable ability of a single hemisphere, whether left or right, to support at least at modest levels a wide range of cognitive functions--from visual perception, through memory and intellectual processes, to language and even speech. In some cases, as has been indicated, the surgical removal of a diseased hemisphere has resulted in improvement of cognitive function. This positive outcome has occurred more frequently in patients with early (i.e. congenital or perinatal) onset of seizure disorders than in those with late onset (e.g. Rasmussen's disease). But even for the latter patients, the cognitive costs of the surgery per se have rarely been severe. And in both types of case, the incidence of either complete or substantial postoperative relief from intractable seizures has been high, ranging around 80-90%. Although the therapeutic efficacy and small cognitive costs of the surgery are now quite well established, little is known yet regarding the specific cognitive defects that arise from the loss of one as opposed to the other cerebral hemisphere. Intelligence levels have been found to be equally low, averaging in the mid-60s and almost never rising above 100 in patients with either left or right hemidecortications, and memory quotients have most often appeared to fall in line with the IQ scores, again without clear evidence of any difference in the effects of left and right removals. Even in the case of visual spatial perception, considered to be a hallmark of right hemisphere function, the evidence is unclear, one study reporting selective impairment on difficult visuospatial tasks in right hemispherectomised patients, but another not. Only in regard to language processes is there a consensus regarding the differential effects of left and right hemidecortication, and here the differences are apparent only in the relatively subtler aspects of language. Thus, the isolated right hemisphere is at a significant disadvantage compared with the left in the comprehension of abstract, low frequency words, in phonetic feature analysis, and in the subtleties of grammar, such as the comprehension of passive negative constructions and the correct use of morphological markers in unfamiliar contexts (e.g. application of comparative and superlative forms of an adjective to nonwords.(ABSTRACT TRUNCATED AT 400 WORDS)

Brain Damage, Chronic↗

PubMed1992

Development of intelligence and memory in children with hemiplegic cerebral palsy. The deleterious consequences of early seizures.

Although substantial data exist regarding the consequences of early lateralized cerebral lesions on intelligence and language ability, little is known about the development of other cognitive functions after such lesions. We examined the development of both verbal and nonverbal memory in 82 hemiplegic children, grouped according to hemispheric side of injury and presence or absence of seizure disorder. The control group consisted of 41 age-matched normal children, most of them siblings of the patients. Measures were obtained of intelligence and of immediate and delayed recall for prose passages, word paired associates and geometric designs. Electrophysiological and neuroradiological measures were available for a majority of the patients. The scores of the hemiplegic children on the IQ and memory tests did not exhibit the pattern seen in brain-damaged adults, in that the children's deficits showed no relation to hemispheric side of damage. Indeed, early cerebral damage to either hemisphere, even if extensive, resulted in relatively few and mild deficits if the damage was unaccompanied by seizure activity. By contrast, early lateralized lesions that were accompanied by a seizure disorder resulted in both a high incidence and degree of deficit that was unrelated to lesion side.

Cerebral Palsy↗

PubMed1991

Development of language in six hemispherectomized patients.

The development of language skills in the isolated right hemisphere was investigated by comparing the performance of 3 left hemispherectomized with that of the 3 right hemispherectomized patients and three groups of control subjects on baseline clinical measures of language and on production and judgement of morphological markers. The initial brain insult in the hemispherectomy patients of each group had occurred either during early, middle or late childhood. The left hemispherectomy patients were severely impaired in language processing across all three stages of language development. The consequences of a right hemisphere insult on language development were more restricted, with deleterious effects being apparent only in the case in which the lesion was acquired during early childhood.

Adolescent↗

PubMed1989

Reading with one hemisphere.

The subjects of this study were 2 originally right-handed teen-aged girls who had undergone complete hemispherectomy (1 left, 1 right) for intractable epilepsy. Both subjects had developed normal language and reading capacities before the onset of their illness. The reading performance of H.P. (whose right hemisphere had been removed), while not as advanced in level as that of a normal 17-yr-old, showed no abnormality in any subcomponent of reading skill. The reading performance of N.I. (whose left hemisphere had been removed) was poor, but with a pattern of retained and impaired subskills strikingly similar to adult deep dyslexic patients and to split-brain patients given reading tasks lateralized to the left visual field (right hemisphere). The results are discussed with regard to implications for the reading capacity of the nondominant right hemisphere and also its putative contribution to normal reading.

Adolescent↗

PubMed1985

Development of speech and language following bilateral frontal lesions.

Language and speech were studied in a young child with perinatally acquired bifrontal lesions. Bilateral frontal pathology seriously interfered with the development of intelligible speech and resulted in a persistent expressive aphasia. Analysis of the neuropsychological profile indicated impairments in intelligence and language comprehension. These deficits, however, were considered secondary to the profound speech programming disorder. The findings indicate that, despite the plasticity of the immature central nervous system, bilateral frontal injury sustained at an early age precludes the development of intelligible speech. Furthermore, structurally intact cortical regions outside the territories of the speech zones fail to mediate normal speech and language development.

Aphasia↗

PubMed1985

Aphasia and handedness in relation to hemispheric side, age at injury and severity of cerebral lesion during childhood.

The effects of the variables of hemispheric side of lesion, age at injury and severity of cerebral damage on language performance and hand dominance were investigated in groups of hemiparetic children. Severity of cerebral damage was defined by the degree of structural abnormality shown on computed tomography (CT) scans. Tests of auditory verbal comprehension and object naming were used as indicators of productive and receptive language skills. The responses to a series of questions on a handedness inventory provided a rated measure of hand dominance. The results indicated that language deficits characterize the performance of all patient groups with left cerebral injuries. Impairments are more profound, however, in the case of left hemisphere injuries acquired after the age of 5 years. In addition, prenatal and early postnatal left cerebral lesions consistently result in strong sinistrality. It is concluded that the crucial variable underlying the demonstration of language deficits and left hand dominance is not severity of lesion but age at injury and hemispheric side of lesion.

Adolescent↗