Utility of cystatin C for renal function in amyotrophic lateral sclerosis.

OBJECTIVES: Creatinine (Cr) as a marker of renal function has limited value in amyotrophic lateral sclerosis (ALS) because patients with ALS have reduced muscle mass. Thus, there is a need for alternative methods of assessing renal function. Cystatin C (CysC), which is unaffected by muscle mass, is potentially an ideal biomarker of nephrotoxicity in ALS; however, its utility requires validation. MATERIAL AND METHODS: One hundred and six subjects were recruited for the study: 76 ALS patients and 30 healthy controls. We compared the Cr-based estimated glomerular filtration rate (eGFR) with the CysC-based eGFR in the ALS patients and healthy controls. The results were further analysed according to the severity of ALS in the patients. RESULTS: The mean Cr-based eGFRs were 257.2 ± 383.1 ml/min/1.73 m(2) in the ALS group and 98.1 ± 34.9 in the control group; however, the mean CysC-based eGFRs were not significantly different between both groups. Thus, the Cr-based eGFR in the ALS group was markedly higher than any of the other values. Although serum CysC levels did not correlate with the severity of ALS according to the ALS Functional Rating Scale-Revised, strong simple correlations were observed between serum Cr levels and the severity of ALS (correlation coefficient = 0.734, P < 0.001). CONCLUSIONS: This study demonstrates the potential usefulness of CysC as a biomarker of renal function in ALS patients. Furthermore, its applicability could be extended to other neuromuscular diseases.

Effects of light scatter, defocusing, mean luminosity, contrast, and central scotoma on the PVER amplitude-check size function curve.

We analyzed the effects of various stimulus parameters, ie, light scatter, defocusing, mean luminosity, contrast, and central scotoma, on the normal pattern reversal visual evoked response (PVER), amplitude-check size function curve in six normal subjects. The steady-state PVER was recorded with five check sizes ranging from 160 to 10 min in 1-octave increments. The PVER amplitude, especially with the smaller check sizes, was markedly decreased by light scatter induced by acrylic sheets. The function curve quickly changed to a low pass filter shape when +2.0 diopters of defocus were added, with the decrease most marked in the small check sizes. When the mean luminosity was decreased, the function curve maintained its normal inverted-U shape up to 5 cd/m2, but the shape flattened with lower luminosity. Amplitude decreases were seen with all check sizes in low luminosity. With contrast changes from 95 to 24%, the function curve maintained its normal shape, but with slightly reduced amplitudes. The amplitude decrease was moderate even with the lowest contrast. With a two-degree central scotoma, the PVER amplitude was reduced more with the smaller than the larger check sizes. The function curve became somewhat flatter, with its peak shifting to the larger check sizes. Results indicated that the shape of the PVER amplitude-check size function curve changes in response to different modes of stimulation.

Effect of hemifield stimulation on simultaneous steady-state pattern reversal electroretinogram and visual evoked response.

Steady-state pattern reversal electroretinograms (PERG) and pattern reversal visual evoked responses (PVER) were recorded simultaneously in 4 normal subjects using hemifield stimulation of the upper/lower and nasal/temporal conditions with 95 and 60% stimulus contrasts. A square-wave checker-board pattern (check size 40 min of arc) was used. The temporal frequency (reversal rate) was 6 Hz (12 reversals/s). With nasal/temporal hemifield stimulation, neither the PERG nor the PVER amplitudes differed significantly with either stimulus contrast. With the upper/lower hemifield stimulation, PERG amplitudes were not significantly different; PVER showed a significantly larger amplitude for lower than for upper hemifield stimulation with both contrasts (ANOVA test: p = 0.0064, 95% contrast; p = 0.0018, 60% contrast). PVER amplitudes recorded with lower hemifield stimulation were 2.05 and 2.63 times larger than those elicited with upper hemifield stimulation, for the 95 and 60% contrasts, respectively. The difference in response to the upper/lower hemifield stimulation, observed only in PVER, suggests that the lower stimulus field dominancy may be processed in a visual pathway proximal to the retinal level.

Effect of light scatter on the pattern reversal visual evoked response: comparison with psychophysical results.

The effect of light scatter on the pattern reversal visual evoked response (PVER) was studied in 6 normal subjects. The results were compared with contrast visual acuity, contrast sensitivity function, and glare disability. Light scatter was induced by translucent acrylic sheets. Visual acuity measured with the low-contrast charts decreased significantly (P < 0.0001) even with a small degree of light scatter. Contrast sensitivity decreased with a small degree of light scatter especially for high spatial frequencies. PVER amplitudes decreased especially at the smaller checks with its peak shifted to larger checks. PVER was equally sensitive to light scatter compared to psychophysical tests.

Effect of stimulus contrast on simultaneous steady-state pattern reversal electroretinogram and visual evoked response.

We studied the effect of stimulus pattern contrast on the simultaneously recorded pattern reversal electroretinogram (PERG) and pattern reversal visual evoked response (PVER) at 5 check sizes. The stimulus contrast ranged from 24 to 95% in 6 steps of 0.1- or 0.15-log unit increments. PERG amplitude showed a linear increase with an increase in pattern contrast at all check sizes. PVER amplitude showed an increase up to a certain pattern contrast, but was saturated upon further increase in stimulus contrast at all check sizes. The PERG amplitude-check size function curve showed a flattened, inverted-U shape only with the highest contrast and low-pass filter shape or flat shape with lower contrasts. The PVER amplitude-check size function curve showed an inverted-U shape (bandpass filter shape) at all contrasts. These characteristics to the changes in contrast and the spatial frequency tuning suggest that PVER is processed in a different location of visual pathway than PERG.

Best's macular dystrophy with a macular hole.

The occurrence of a macular hole with Best's dystrophy is an extremely rare finding with only one reported case in the literature. We wish to report two cases with typical Best's dystrophy in one eye and a macular hole in the contralateral eye. In one case the Pattern Reversal VER (PVER) was also recorded and graphed as an amplitude-check size function curve. The PVER changes in this case were grossly subnormal in both the eyes, suggesting a significant degree of bilateral macular impairment. This implies that a significant amount of functional impairment occurs at the vitelliform stage itself, though how this stage progresses to a macular hole is unclear.

Electrophysiological findings in peripheral uveitis.

Nine patients with peripheral uveitis were studied clinically and electrophysiologically. Electroretinographic findings varied widely from supernormal to nonrecordable responses, depending on the disease duration and severity. These results suggest that the pathology in peripheral uveitis is not necessarily limited to the inferior pars plana but can be diffuse and widespread. In the final stage of the disease, the fundus showed extensive pigmentation and narrow retinal arteries associated with a nonrecordable electroretinogram, similar to retinitis pigmentosa. Burned-out peripheral uveitis should be considered in the differential diagnosis of secondary pigmentary degeneration.