Monocular contrast sensitivity in 3- to 36-month-old human infants

A recently developed psychophysical "card" technique was used to evaluate monocular contrast sensitivity in ninety 3-, 6-, 12-, 24-, and 36-month-old human infants. Results showed that for 3-, 6-, 24-, and 36-month-olds, monocular contrast sensitivity functions were very similar to binocular contrast sensitivity functions estimated in a previous experiment. However, at 12-months, monocular contrast sensitivity functions were significantly lower (about 1 octave) than binocular contrast sensitivity functions, a trend also observed in developmental studies of visual acuity. This asymmetry suggests that the neural substrate underlying the development of monocular and binocular spatial vision undergoes different rates of development, at least during the months surrounding the end of the first postnatal year.

Nursing assessment of visual function in children with neurologic diagnosis

Many neurologic disorders cause acute or chronic hydrocephalus. Visual loss, diplopia, cranial nerve palsies, strabismus, and papilledema suggest hydrocephalus. Evaluation of these signs and symptoms aid in determining the etiology of the hydrocephalus.

Infant peripheral vision: the development of monocular visual acuity in the first 3 months of postnatal life

Quantitative data on the early morphological development of the human retina show that the peripheral region is relatively more mature than the central region. These results have stimulated researchers to compare the development of visual functions in the central and peripheral regions of the visual field. Here, we used preferential looking to evaluate 1-, 2- and 3-month-old infants' central and peripheral (10 degrees and 30 degrees) monocular visual acuity. There were three findings: (i) both central and peripheral acuities were poor at 1 month, improved over the age range tested, but were still about 3 octaves worse than adults' acuity; (ii) at all ages monocular acuity decreased with increasing eccentricity; (iii) 2- and 3-month-olds showed higher acuity for gratings in the temporal than in the nasal visual field at 30 degrees. The implications of these results for issues in visual development are discussed.

Stroke in children and young adults

This selective review of stroke in children and young adults addresses: (1) stroke in sickle cell disease, particularly the prognostic use of transcranial Doppler, (2) oral contraceptives as a stroke risk factor, (3) stroke in pregnancy, and (4) the prognosis of ischemic stroke in young adults. Factors relevant to the primary prevention and outcome of stroke are emphasized.

Further exploration of human neonatal chromatic-achromatic discrimination

Newborn (n = 140) and 1-month-old (n = 120) human infants were habituated to achromatic ("white") squares of varying luminance (.35 to 1.16 log cd/m2) and then tested for recovery of habituation with chromatic stimuli from particular spectral locations. Results showed that newborns appear to discriminate 32 degrees yellow-green (dominant lambda = 565 nm) from white, but not 16 degrees or 32 degrees blue (450 nm), 16 degrees blue-green (493 nm), 16 degrees or 32 degrees yellow-green (572 nm), or 16 degrees purple from white. Performance of 1-month-olds was marginally better than that of newborns. Combined with our previous results with the habituation method, these data imply that newborns show little ability to make any chromatic-achromatic discriminations when stimulus size is smaller than 8 degrees, and that even with very large stimuli (e.g. 32 degrees) performance is relatively poor in the blue and yellow-green spectral regions. Although several models were considered, these limitations in the short- and mid-wavelength regions may best be accounted for by the argument that young infants possess general rather than selective immaturities or inefficiencies within their chromatic mechanisms.

Bile acid dysfunction after clam enterocystoplasty

OBJECTIVE

To determine if the bowel dysfunction that develops in approximately 12% of patients after a clam enterocystoplasty is due to disruption of the enterohepatic circulation of bile acids.

PATIENTS AND METHODS

Fourteen symptomatic patients (mean age 36 years, range 21-65) who had undergone clam enterocystoplasty were investigated by bowel frequency charts, hydrogen breath tests of expired air and the retention of radioactive 75Se-labelled homocholic acid-taurine (SeHCAT), a synthetic bile acid. Patients with abnormal results were commenced on anion-exchange resins and the symptoms evaluated 6 weeks later.

RESULTS

The interruption of bile acid circulation, as estimated by SeHCAT, occurred in most of the patients studied and was due to surgical resection of the terminal ileum. All hydrogen breath tests were normal, excluding bacterial overgrowth as a cause of diarrhoea. Bowel frequency correlated well with the percentage of SeHCAT retained. Anion-exchange resins were successful in relieving the symptoms if patients complied well with the treatment.

CONCLUSIONS

After clam enterocystoplasty, some patients have bowel dysfunction caused by the interruption of the enterohepatic circulation of bile acids. These patients can be identified using bowel frequency charts and treated by anion-exchange resins.

Risk of recurrent stroke in patients with sickle cell disease treated with erythrocyte transfusions

OBJECTIVE

To determine the effect of a transfusion program on risk of stroke recurrence in children with sickle cell disease.

DESIGN

The clinical course and experience with transfusion therapy at eight centers were reviewed for subjects whose initial stroke occurred after January 1988.

RESULTS

Sixty subjects were observed for 191.7 patient-years. Eight had a single recurrent stroke (two intracranial hemorrhages and six infarctions) for a prevalence of 13.3%, or one recurrence for each 24 patient-years of observation. Thirteen subjects had 15 transient neurologic events; two of these had subsequent strokes, but the overall risk was similar for those who did and those did not have transient events. Hemoglobin S levels were greater than the desired maximum of 30% at the time of 7 of 16 transient events and five of six recurrent infarctions. The stroke recurrence rate was similar to those in previous reports of children receiving long-term transfusion therapy but significantly less than that reported for children who did not receive transfusions (p < 0.001).

CONCLUSIONS

We conclude that maintenance of hemoglobin S at a level less than 30% appears to be effective in reducing the rate of recurrent infarction but does not prevent transient neurologic events. Transient neurologic events are common but do not appear to be related to recurrent stroke.

Strategic information systems and libraries

The data collected for management information purposes by libraries can form the basis for a strategic information system. Examines the potential for SIS in libraries, possible development paths and applications. Suggests that libraries should examine the applications of such techniques and how data for them could be effectively collected.

Development of chromatic discrimination in early infancy

Combining a habituation-recovery paradigm with procedures to minimize brightness cues, we evaluated 1-3-month-olds' ability to discriminate among broadband mid- and long-wavelength stimuli. One-month olds showed evidence of discriminating a red (dominant lambda = 650 nm) from green (dominant lambda = 545 nm) but failed to discriminate either of these from a yellow (dominant lambda = 585 nm). At 2 months, infants showed evidence of discriminating 545-nm green from 585-nm yellow, but only at 3 months do they appear to discriminate 650-nm red from the yellow. Consistent with previous work, these data imply that chromatic discrimination emerges slowly over the first three postnatal months. Moreover, the developmental pattern is consistent with the notion that early human vision is limited by general rather than selective immaturities within the requisite retinal and neural mechanisms.

Management issues for patients with ischemic stroke

This review briefly summarizes the acute management of cerebral infarction and cardiac comorbidity in patients with stroke, with a focus on more general aspects of care. Important aspects of the acute management of cerebral infarction are its prompt recognition, use of appropriate emergency medical services, including 911, initial treatment, and prevention of complications. Secondary prevention begins with the diagnostic workup for the cause of the initial stroke. Although the optimal workup depends on the patient, a minimal workup consists of a history and physical examination sufficient to establish vascular risk factors and the neurologic and medical status of the patient, basic laboratory tests, ECG, chest x-ray, cranial CT, evaluation of carotid arteries, and a search for cardiac sources and the presence of atrial fibrillation. Further workup may include a search for coagulopathies, less common sources of embolism, and intracranial intravascular disease. Better education of patients at risk of vital importance. Patients with cerebral infarction share vascular risk factors with those who have coronary disease, and the presence of both coronary and cerebrovascular disease is highly likely. The likelihood of finding coronary artery disease in patients with transient ischemic attack and ischemic stroke with noninvasive testing, as well as management recommendations for these patients are reviewed.

Transcranial Doppler correlation with angiography in detection of intracranial stenosis

BACKGROUND AND PURPOSE

The purpose of this study was to evaluate the use of velocity criteria applied to transcranial Doppler (TCD) signals in the detection of stenosis of the middle cerebral (MCA), distal vertebral, and basilar arteries.

METHODS

Sixty-five patients who underwent both cerebral angiography and transcranial Doppler examinations in the workup of acute cerebral ischemia were reviewed. Angiography was performed a mean of 7 +/- 5 days (range, 1 to 28 days) after TCD. Interpretation of the angiogram was performed without input regarding the TCD findings. TCD interpretation was performed according to standard criteria.

RESULTS

When we used a mean velocity (MV) cutoff of > or = 80 cm/s in the MCA as the criterion for stenosis, 10 of 12 stenoses of any degree were detected by TCD, with 11 of 87 false-positives. Nine of 12 MCA stem (M1) stenoses were detected when a cutoff of > or = 90 cm/s was used, with 7 of 87 false-positives. When we used an MV cutoff of > or = 70 cm/s as the criterion for > or = 50% stenosis of the vertebrobasilar system, 5 of 6 stenoses were detected, with 15 of 85 false-positives. The most important confounding factor was the presence of > or = 75% stenosis of the extracranial internal carotid artery, resulting in both false-positive (from collateral flow) and false-negative (decreased volume flow from the proximal stenosis without adequate collateral flow) errors in TCD interpretation. When patients with > or = 75% stenosis of the cervical internal carotid artery were excluded from analysis, a TCD MV cutoff of > or = 80 cm/s identified 9 of 10 M1 lesions with 7 of 61 false-positives, and an MV of > or = 70 cm/s identified 3 of 4 vertebrobasilar lesions causing > or = 50% stenosis with 7 of 56 false-positives.

CONCLUSIONS

TCD may be an effective screening test for M1 stenosis when velocity criteria alone are used. TCD may less reliably detect intracranial vertebral and basilar artery stenosis.

Intracerebral infusion of TNF-alpha and IL-6 failed to activate latent SIV infection in the brains of macaques inoculated with macrophage-tropic neuroadapted SIVmac

Lymphocyte-tropic (L-tropic) SIVmac predictably causes immunosuppression and AIDS in rhesus macaques. SIV encephalitis, on the other hand, is caused mainly by macrophage-tropic (M-tropic) SIVmac. We have previously described the derivation of M-tropic, neuroadapted SIVmac from molecularly cloned, L-tropic SIVmac239. In this report we show that inoculation of four macaques with neuroadapted virus resulted in L-tropic SIVmac-related diseases in all four but neurological disease in only two of the four animals. Because cocultivation of infected macrophages with CD4+ lymphocytes results in production of tumor necrosis factor alpha and interleukin-6, we asked whether infiltration of supernatant fluids containing these cytokines into the brains of macaques infected with neuroadapted virus would enhance the development of neurological disease. These procedures failed to promote productive virus replication in the brain. Thus, although different degrees of immunosuppression and AIDS could be induced predictably with L-tropic virus, induction of neurological disease was not predictable even when animals were inoculated with neuroadapted M-tropic virus and inflammatory cytokines were infiltrated into the brains of these animals.

Neuropsychological impairment in children with sickle cell anemia and cerebrovascular accidents

Neuropsychological functioning of children with sickle cell anemia (HbSS) who have experienced a single stroke has not been extensively investigated. In this study, the neuropsychological functioning of 10 children with HbSS who were receiving transfusion therapy following stroke with no identifiable recurrence was examined. The patients were subgrouped into children with only left hemisphere stroke (LCI), N = 4, and those with only right hemisphere stroke (RCI), N = 6. Results indicated that these youngsters experienced significant impairments of cognitive functioning following stroke. It was found that the LCI and RCI children tended to perform more like adult stroke patients than what has been typically reported in children with infantile hemiplegia. These findings support the need for periodic neuropsychological evaluation following stroke in order to identify patterns of higher cortical dysfunction and assist in the development of appropriate rehabilitation and special education programs. Further, pediatricians, child neurologists, and psychologists who care for these children must act as strong advocates on their behalf in order to ensure that they receive appropriate rehabilitation and the special education services necessary for maximal recovery and future educational success.

Systematic measurement of human neonatal color vision

We used a new time-efficient method to evaluate chromatic-achromatic discrimination in newborn (n = 36) and 1-month-old (n = 34) human infants. Results showed that 74% of newborns discriminated a 10.5 x 17.5 deg broadband red patch from all relative luminances of an achromatic background, but only 14% of newborns did so with a blue, 36% with a green, and 25% with a yellow patch. Most infants who "failed" did so at relative luminances very close to the respective photopic luminance match. At 1 month, performance improved somewhat although infants still show clear evidence of discriminating only the red patch. These results, the first to be obtained from individual newborns with a method incorporating a systematic variation of luminance, imply that early color vision is very limited. Possible photoreceptoral and neural bases for these immaturities are discussed.

Visual acuity in infants and children with Down syndrome

The authors used the Teller acuity cards to assess the visual acuity of 51 infants and children with Down syndrome aged between two months and 18 years. The success rate and test times were comparable to those reported for normally developing children. Even those subjects in the study who were free of ocular disorders and/or who were wearing optical correction during testing showed significantly poorer visual acuity than individuals without Down syndrome. The development of visual acuity in infants and children with Down syndrome lags behind that of age-matched peers without Down syndrome, especially after the age of six months. These findings are discussed in terms of the neurological and optical factors that might account for the deficits in visual acuity that were observed.

Pathogenesis of SIVmac infection in Chinese and Indian rhesus macaques: effects of splenectomy on virus burden

The spleen and lymph nodes are the predominant sites of viral replication in SIV and HIV infections. We studied splenectomized and control unsplenectomized rhesus macaques of both the Indian and the Chinese subspecies of Macaca mulatta. All animals were inoculated with SIVmac239, a molecularly cloned strain of SIV. Our data showed: (1) splenectomized animals, particularly among the Indian subspecies, had a lower virus burden and longer survival than unsplenectomized controls, (2) the Chinese macaques controlled virus replication more effectively than did the Indian animals, and (3) that a higher infectious virus burden was present in LN/spleen than in blood in both splenectomized and control animals.

Alpha thalassemia and stroke risk in sickle cell anemia

In an effort to identify possible risk factors for stroke in Sickle Cell Anemia (Hb SS), we analyzed the distribution of alpha-globin gene deletions in a group of Hb SS patients with and without stroke. The group with stroke consisted of 44 patients, (27 male, 17 female) with a mean of 7.5 years at time of stroke. The control group (non-stroke) had 256 Hb SS patients (126 male, 130 female) with a mean age of 7.7 years. There were 9 patients with heterozygous alpha-thalassemia in the stroke group (20.5%). In the control group, there were 93 patients with heterozygous alpha-thalassemia and 5 with homozygous alpha-thalassemia. The incidence of alpha-thalassemia in Hb SS patients without stroke (38%) was comparable to that reported for the African-American population in general. The incidence in the stroke population (20.5%) was significantly lower (P = 0.02) These results indicate that alpha-thalassemia is associated with a lower risk of stroke in Hb SS. This observation should be confirmed in studies involving larger numbers of patients. Possible protective effects of alpha-thalassemia are unknown but may be related to decreased hemolysis and more favorable rheologic properties of red blood cells.

Mutations at the PAX6 locus are found in heterogeneous anterior segment malformations including Peters' anomaly

Mutation or deletion of the PAX6 gene underlies many cases of aniridia. Three lines of evidence now converge to implicate PAX6 more widely in anterior segment malformations including Peters' anomaly. First, a child with Peters' anomaly is deleted for one copy of PAX6. Second, affected members of a family with dominantly inherited anterior segment malformations, including Peters' anomaly are heterozygous for an R26G mutation in the PAX6 paired box. Third, a proportion of Sey/+ Smalleye mice, heterozygous for a nonsense mutation in murine Pax-6, have an ocular phenotype resembling Peters' anomaly. We therefore propose that a variety of anterior segment anomalies may be associated with PAX6 mutations.

Early activation of PBMC and appearance of antiviral CD8+ cells influence the prognosis of SIV-induced disease in rhesus macaques

We studied 15 macaques inoculated with SIV and identified three phases of infection. Phase 1 was characterized by activated lymphocytes in blood and infected cells in the CSF. In phase 2, activated cells were not detected but virus was recovered from mitogen-stimulated PBMC, while in phase 3, virus was recovered from mitogen-stimulated PBMC only after depletion of CD8+ lymphocytes, indicating effective control of the virus in peripheral blood. Early development of phase 3 status correlated with a longer period of clinical normalcy.

Antigenic variation of molecularly cloned SIVmac239 during persistent infection in a rhesus macaque

Eight rhesus macaques inoculated with molecularly cloned SIVmac239 developed viremia and virus-binding antibodies, but only one (macaque 2D) developed neutralizing antibodies to the virus. Viremia persisted in macaque 2D even in the presence of neutralizing antibodies. Neutralizing antibodies in the plasma collected from macaque 2D late in infection neutralized virus isolated early in infection. In contrast, these antibodies failed to neutralize the plasma viruses isolated after the appearance of neutralizing antibodies. Only antigenic variants were isolated from blood, spleen, and lymph nodes. Viruses isolated from other macaques that did not develop neutralizing antibodies were neutralized by 2D serum and were of the parental (SIVmac239) phenotype. The variant viruses maintained their strict tropism for lymphocytes, similar to the parental virus.