Neurological dysfunction in asymptomatic HIV-1 infected men: evidence from evoked potentials. HNRC Group

Multifocal electroretinography in HIV-positive patients without infectious retinitis

PURPOSE

To evaluate early changes in the central retinal response in human immunodeficiency virus (HIV)-positive patients without infectious retinitis using multifocal electroretinography (mfERG).

DESIGN

Case control study.

METHODS

We evaluated three cohorts: HIV-negative controls and two groups of HIV-positive patients separated according to their nadir CD4 counts (>or= 100 cells/mm(3) and < 100 cells/mm(3) for a minimum of six months). mfERG first-order kernels (FOKs) and second-order kernels (SOKs) were analyzed separately by areas of rings, quadrants, and individual hexagons for each cohort.

RESULTS

Of 103 hexagon locations of FOK results, there were no significant differences in amplitudes of P1 and N1 across the groups (.05 < P < .50), although there was a trend for an overall reduction in the amplitudes. Similarly, latency N1 did not differ (.28 < P < .95). There were significantly delayed latencies of P1 between cohorts across 103 hexagons in both kernels. SOK results also showed significant delay in latencies of P1 and a trend of reduced P1 amplitudes across studied locations among cohorts (.24 < P < .08).

CONCLUSIONS

The results demonstrate widespread delay in latency in HIV-positive patients, especially in those with prolonged low (below 100 cells/mm(3)) CD4 nadir counts. These findings suggest early diffuse dysfunction of the inner retina results from severe HIV disease even in the HAART era.

Recommendations for the clinical use of somatosensory-evoked potentials

The International Federation of Clinical Neurophysiology (IFCN) is in the process of updating its Recommendations for clinical practice published in 1999. These new recommendations dedicated to somatosensory-evoked potentials (SEPs) update the methodological aspects and general clinical applications of standard SEPs, and introduce new sections dedicated to the anatomical-functional organization of the somatosensory system and to special clinical applications, such as intraoperative monitoring, recordings in the intensive care unit, pain-related evoked potentials, and trigeminal and pudendal SEPs. Standard SEPs have gained an established role in the health system, and the special clinical applications we describe here are drawing increasing interest. However, to prove clinically useful each of them requires a dedicated knowledge, both technical and pathophysiological. In this article we give technical advice, report normative values, and discuss clinical applications.

ASSESSMENT OF RETINAL FUNCTION IN PATIENTS WITH HIV WITHOUT INFECTIOUS RETINITIS BY MULTIFOCAL ELECTRORETINOGRAM AND AUTOMATED PERIMETRY

PURPOSE

To determine if multifocal electroretinogram (mfERG) testing shows abnormalities that correspond to perimetric defects in HIV positive patients without infectious retinitis.

METHODS

We studied three groups of patients: HIV negative controls, HIV high CD4 nadir patients (lowest CD4 T cell count is over 100) and low CD4 nadir patients (below 100 for over 6 months). Twenty-six HIV positive eyes and 16 HIV negative control eyes were studied by mfERG. A subset of 10 eyes also underwent computerized perimetry for comparison. We analyzed mfERG by hexagons as well as by quadrants and rings.

RESULTS

Of 103 hexagon locations there was no significant difference in the amplitudes P1 and N1 (nV/degree) between the three studied groups (p>0.05), similarly, the latencies were not different (p>0.05). All eyes with significant visual field defects at the 0.01 and 0.005 level (Humphrey pattern deviation; 24-2) were compared to mfERG amplitudes and latencies at those locations-there were no corresponding defects in mfERG data (p>0.2).

CONCLUSION

In the era of HAART there are still demonstrable visual field defects and other evidence of damage to the retinal nerve fiber layer in HIV patients. Our mfERG studies show that the damage appears to affect the inner retina, the outer retina is spared. Further studies of inner retinal structure and function are indicated to elucidate this process.

Optic nerve axonal pathology is related to abnormal visual evoked responses in AIDS

Electrophysiological studies in subjects with HIV/AIDS demonstrate subtle changes in the visual pathway even in the absence of visual symptoms. But the pathological correlate of the electrophysiological abnormalities is largely unknown. This study attempts to correlate pathological changes in the retina and intraorbital portion of optic nerve in four drug naïve patients of AIDS caused by HIV-1 clade C, who had abnormalities in the visual evoked potentials recorded antemortem. Three had no visual complaints and one patient had sudden loss of vision in the right eye. In all four patients, the visual evoked potentials disclosed variable prolongation of P100 latencies. Histologically axonal cytoskeletal breakdown and depletion in the optic nerves was the cardinal finding with variable myelin loss, even in the absence of overt visual dysfunction, or infective retinitis. The axonal loss was maximal in the symptomatic case. Retinal ganglion cell depletion was seen in only two patients. Sectoral infiltration of the optic nerve by cryptococci and Cryptococcal choroiditis was the only opportunistic infection to involve the eye. Axonal pathology in the optic nerve appears to be related to the abnormalities recorded in visual evoked potentials even in the absence of overt clinical symptoms. Opportunistic infections could be contributing to the axonal pathology in the optic nerve in patients with AIDS.

Early detection of neurophysiological abnormalities in infection by human immunodeficiency virus

The human immunodeficiency virus causes serious, progressive and irreversible deterioration of the immunocompetence system and of the nervous system, so neurological pathology in infected patients is frequent (30-40%), affecting both the central and the peripheral nervous systems. There are different clinical and laboratory indicators of bad prognosis, considering the important neurotropism of the virus. This study attempts to evaluate which neurophysiological parameters are altered during the initial phases of infection by HIV. A total of 46 individuals were studied, 30 seronegative and 16 seropositive in stage A of the CDC-93 classification. Motor and sensory conduction studies were carried out on all of them on the upper and lower extremities, as well as visual, somatosensory and auditory evoked potentials and endogenous potentials, mainly P300. The analysis of the neurophysiological parameters evaluated in our series, showed alterations of the conduction velocity of the sural nerve, latency of N1 of the SSEP of median and posterior tibial nerves and P300 in the initial phases of the infection even in the absence of clinical symptomatology.

Early physiological abnormalities after simian immunodeficiency virus infection

Central nervous system (CNS) damage and dysfunction are devastating consequences of HIV infection. Although the CNS is one of the initial targets for HIV infection, little is known about early viral-induced abnormalities that can affect CNS function. Here we report the detection of early physiological abnormalities in simian immunodeficiency virus-infected monkeys. The acute infection caused a disruption of the circadian rhythm manifested by rises in body temperature, observed in all five individuals between 1 and 2 weeks postinoculation (p.i.), accompanied by a reduction in daily motor activity to 50% of control levels. Animals remained hyperthermic at 1 and 2 months p.i. and returned to preinoculation temperatures at 3 months after viral inoculation. Although motor activity recovered to baseline values at 1 month p.i., activity levels then decreased to approximately 50% of preinoculation values over the next 2 months. Analysis of sensory-evoked responses 1 month p.i. revealed distinct infection-induced changes in auditory-evoked potential peak latencies that persisted at 3 months after viral inoculation. These early physiological abnormalities may precede the development of observable cognitive or motor deficiencies and can provide an assay to evaluate agents to prevent or alleviate neuronal dysfunction.

Postural reflexes in patients with HIV-1 infection

OBJECTIVE

We studied whether medium latency (ML) and long latency (LL) postural reflexes, which are abnormal in a number of neurological conditions including basal ganglia disorders, provide an early marker of CNS involvement in HIV-positive patients.

METHODS

Leg reflexes were elicited in 9 neurologically normal HIV-positive patients and 10 healthy controls who were standing upright, using toe-up forceplate rotations of varying amplitude (4 degrees and 10 degrees) and predictability (serial and random).

RESULTS

For predictable amplitude perturbations, posturally destabilizing ML and stabilizing LL responses in HIV-seropositives did not differ from controls. However, for unpredictable amplitude perturbations, HIV-positive patients inappropriately manifested a mid-size default LL response, in contrast to healthy subjects who showed a maximum size default response.

CONCLUSIONS

These results suggest that impaired modulation of LL reflex processing occurs in early stages of HIV infection, prior to the onset of clinical postural instability, and this dysregulation may be influenced by cognitive factors.

Progressive peripheral and central sensory tract lesion in HIV-infected patients evidenced by evoked potentials (a three-year follow-up study)

OBJECTIVE

To investigate progression of peripheral and central sensory tract lesion and its correlation to immunological deterioration.

METHODS

Clinical and neurophysiological investigation (evoked potentials of the median and tibial nerve) and immunological parameters (CD4-cells, beta 2-microglobuline) were followed up in 160 patients (24 females, 136 males, HIV infection for 2.7 +/- 2.3 years, mv +/- 1 sd) up to four times over approximately 3 years regardless of disease stage and evidence of neurological symptoms. Recordings were done using needle electrodes over the Th12 and C7 spinous process and from the scalp (10/20 system) in the conventional manner. Statistical analysis was performed intraindividually and in comparison to normal laboratory values (n = 96).

RESULTS

All parameters deteriorated during the follow-up period. Statistical analysis showed significant differences between probands and patients for evoked potentials, but also a significant deterioration for evoked potentials after three years at the end of the follow-up study. A significant correlation between progressive impairment of evoked potentials and laboratory data was found.

CONCLUSION

HIV infection induces a progressive lesion of the ascending sensory tracts. The results indicate a peripheral neuropathy as well as a progressive lesion of the ascending central sensory tracts. Pathogenesis of polyneuropathy and of central sensory tract lesion is up to now conjectural. Laboratory investigations indicate a clear-cut correlation between immunological alterations induced by HIV infection and its neurologic manifestation on ascending sensory tracts.

Diagnostic value of multimodal evoked potentials in HIV-1 infected children

Evoked potentials (EP) help guide the diagnosis of central nervous system involvement in demyelinating pathologies regarding both children and adults, and in human immunodeficiency virus-1 (HIV-1) correlated pathologies only in regard to adult patients. EP have been shown to be useful in highlighting early signs of the disease. We therefore studied EP in HIV-1 infected children with the aim of verifying the association of results with disease progression, clinical signs and electroencephalogram, and individualizing the most reliable test. Thirty-six patients (20 male and 16 female subjects, age range: 10 months to 12 years) belonging to a group of 45 symptomatic subjects seen at the Pediatric Department were included into the study from November 1991 to December 1994. Ten presented with neurological signs as of disease onset, eight others developed encephalopathy during the follow-up. One hundred seventeen EP, i.e., 27 pattern visual, 64 flash visual and 26 brain stem auditory EP, were recorded. Univariate statistical analysis using the Wilcoxon-Mann-Whitney U test and Student's t test was done. As a whole, we found 22.5% of abnormal EP in subjects without neurological signs and 28.3% in subjects with neurological signs. Results that were obtained suggested a close relationship between both the pattern of visual and brain stem auditory EP exams and disease progression.

Progressive encephalopathy associated with CD4/CD8 inversion in adult FIV-infected cats

Experimental intravenous challenge of five adult cats with the feline immunodeficiency virus Maryland isolate (FIV-MD) was investigated for its ability to induce neurologic abnormalities associated with the onset of immunodeficiency. Five 8-month-old cats were inoculated with 1000 median tissue culture infective dose of FIV-MD isolate, with five age-matched cats serving as uninfected controls. All FIV-MD-infected cats tested positive for serum antiviral antibodies and plasma viral DNA as detected by polymerase chain reaction at 2, 4, 10, and 16 months postinfection (PI). At 10 and 16 months PI, there was a significant reduction in the CD4/CD8 lymphocyte ratio, with all cats having a CD4/CD8 ratio of 1 or less. Total protein electrophoretic analysis of cerebrospinal fluid demonstrated a significantly increased albumin quotient at 4 and 16 months PI, representing a disrupted blood-brain barrier (BBB). At 16 months PI, all cats demonstrated a preferential increase in frontal cortical slow-wave activity compared with control cats. Serial evaluation of brainstem auditory evoked potential recordings revealed a prolongation of the interpeak latencies times over the study time. At least one abnormality was found over time in visual and somatosensory evoked potential testing in three and four infected cats, respectively. Comparing lymphocyte subtype ratios with neurologic testing revealed that every FIV-MD-infected cat exhibited an abnormality in at least one neurologic functional test with a concurrent CD4/CD8 count ratio of 1 or less. Overall, this study demonstrated that FIV-MD infection in adult cats results in a delayed-onset, progressive encephalopathy that parallels the decline in the CD4/CD8 lymphocyte ratio. Compared with prior information from pediatric FIV-MD-infected cats, these results indicate that age of infection influences the onset and severity of disease and may be associated with CD4 cell depletion in FIV-MD-infected cats, as seen in HIV-1-infected humans.

Analysis of visual dysfunctions in HIV-positive patients without retinitis

PURPOSE

To investigate visual dysfunctions in ophthalmoscopically normal human immunodeficiency virus (HIV)-positive patients and to correlate the results to the stage of HIV disease and neuropsychological status.

METHODS

Fifty-one randomly selected eyes (26 right, 25 left) of 51 HIV-positive patients with visual acuity measurements of 20/20 or better and no ophthalmoscopically detectable disorders were prospectively examined using achromatic and short-wavelength automated perimetry, color vision testing, and contrast sensitivity testing. CD4+ T-lymphocyte count, presence of systemic infection, hemoglobin, hematocrit, serum beta 2-microglobulin levels, and results of neuropsychological testing were also analyzed.

RESULTS

On achromatic automated perimetry, 21.6% (11/51) of patients performed abnormally according to the mean defect and 27.5% (14/51) according to the Glaucoma Hemifield Test; 29.4% (15/51) performed abnormally on short-wave-length automated perimetry according to the mean defect and 23.5% (12/51) according to the Glaucoma Hemifield Test. On contrast sensitivity, 5.9% (3/51) of patients performed abnormally in the 1.5-cycles per degree (cpd) line, 2.0% (2/51) in the 3-cpd line, 23.5% (12/51) in the 6-cpd line, 25.5% (13/51) in the 12-cpd line, and 33.3% (17/51) in the 18-cpd line. On the Farnsworth-Munsell 100-hue test, 29.4% (15/51) of patients performed abnormally. After correction for multiple correlations, two statistically significant correlations were found: sum of log contrast sensitivity with achromatic automated perimetry and sum of log contrast sensitivity with the Farnsworth-Munsell 100-hue test.

CONCLUSIONS

A significant percentage of HIV-positive patients with visual acuity of 20/20 or better and no ophthalmologic evidence of retinitis performed abnormally on visual psychophysical tests. The severity of visual dysfunction was not correlated with the stage of HIV infection or the degree of neuropsychological dysfunction.

Multimodal evoked potentials in HIV-1-seropositive patients: relationship between the immune impairment and the neurophysiological function

Multimodal evoked potentials (PRVEP, BAEP, mSEP) were recorded in 56 HIV-1 seropositive outpatients free from opportunistic CNS pathologies and/or overt HIV-1 encephalopathy. EPs were altered in 17 of 39 (43.6%) seropositive subjects without AIDS (group A) and in 13 of 17 (76.5%) patients with AIDS (group B). A high incidence of subclinical alterations (30.8%) were found in group A patients. Significant BAEP (I-III, III-V, I-V) interpeak latency and mSEP (N9-N13, N9-N20) conduction time prolongations were found in group A and B patients. PRVEP P100 was significantly prolonged only in group B. An inverse relationship between BAEP interpeak latencies and CD4 count was found. Our findings support the hypothesis of an important role of immunodepression in the development of neurophysiologic abnormalities, together with a preferential involvement of acoustic pathways, in the course of HIV-1 infection.

Interleukin-1 beta facilitates afferent sensory transmission in the primary somatosensory cortex of anesthetized rats

The effect of topical application of human recombinant interleukin-1 beta (IL-1) on afferent sensory transmission to the neurones in the primary somatosensory (SI) cortex was determined in anesthetized rats. Quantitative determination of the effect of IL-1 was made by generating post-stimulus time histograms of unit responses to the stimulation of receptive field. IL-1 (0.01, 0.1, 1.0 U) significantly facilitated afferent sensory transmission in SI cortical neurones (n = 22). IL-1-induced facilitation fully recovered by 60 min after drug. In control experiments (n = 10), saline solution containing 0.2 bovine serum albumin, used as a vehicle, did not affect afferent sensory transmission. Our results suggest that IL-1 may be involved in the processing of afferent sensory information in the SI cortex of rats.