Evolution of white matter lesions in neurofibromatosis type 1: MR findings.

To characterize further the evolution of white matter lesions in neurofibromatosis type 1, we reviewed 68 MR images in 43 patients (age, 1-31 years), including 25 follow-up studies (mean interval, 27 months). Lesion number, location, morphology, signal characteristics, and contrast enhancement were assessed. Lesion characteristics and changes thereof were correlated with the patients' ages. Thirty-four patients (79%) had white matter lesions. These lesions were hyperintense on T2-weighted images, were isointense on T1-weighted images, and showed no mass effect or contrast enhancement in 31 patients; in three patients, T1-prolongation was observed (one with significant mass effect). None of the lesions evolved into a glioma. The most common locations were the cerebellum (49%), brainstem (22%), and internal capsule (19%). Nineteen patients had white matter lesions and follow-up studies. Lesions decreased in size or number in seven patients (average age, 13 years), showed no change in three (average age, 12 years), increased in size or number in four (average age, 5 years), and showed a mixed pattern (increased/decreased size/number) in four (average age, 7 years). White matter lesions in neurofibromatosis type 1 frequently increase in size or number early in childhood; this did not indicate neoplasia in our study. The lesions tend to resolve with increasing age. Lesion progression in a child more than 10 years old warrants close follow-up to rule out a neoplasm.     

Hydrogen peroxide-mediated inhibition of T-cell response to mitogens is a result of direct action on T cells

Hydrogen peroxide, a reactive oxygen intermediate produced by activated neutrophils, has been shown to inhibit the response of human T lymphocytes to mitogens and alloantigens. Since hydrogen peroxide is known to react with iron and to induce lipid peroxidation, we compared the effects of hydrogen peroxide and a lipid peroxidation product, malondialdehyde, on the response of human peripheral blood mononuclear cells to T-cell mitogens. Peripheral blood mononuclear cells pretreated with 1 mmol/L of malondialdehyde, washed, and resuspended in fresh medium exhibited no inhibition of phytohemagglutinin responsiveness. Peripheral blood mononuclear cells treated in the same manner but with 200 mumol/L of hydrogen peroxide were inhibited by more than 95%. The addition of ferric edetate did not alter the inhibitory effects of 50 to 100 mumol/L of hydrogen peroxide, nor did the addition of deferoxamine, an iron chelator. These studies suggest that exogenous lipid peroxidation does not affect lymphocyte activation but that hydrogen peroxide has a direct inhibitory effect. Although monocytes are necessary for T-cell mitogenic responses, the effect of hydrogen peroxide was found to be directed at T lymphocytes. Exposure of T cells to a single dose of 200 mumol/L of hydrogen peroxide resulted in more than 71% suppression of the proliferative response measured 48 hours later, but the effect was spontaneously reversed by 72 to 96 hours. Repeated exposure of the cells to hydrogen peroxide resulted in continued inhibition of the proliferative response. These findings suggest that hydrogen peroxide produced by inflammatory phagocytic cells might be capable of suppressing the immune response of nearby T lymphocytes.     

Utricular dysfunction in patients with benign paroxysmal positional vertigo.

OBJECTIVE: The objective of this study was to test the hypothesis that utricular function is impaired in patients with idiopathic benign paroxysmal positional vertigo. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary dizziness clinic and vestibular research laboratory. PATIENTS: Twelve patients with unilateral idiopathic benign paroxysmal positional vertigo were examined 1 week and 1 month after successful treatment with positioning maneuvers and compared with 24 healthy subjects. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Otolith function was assessed with estimation of the subjective visual vertical and analysis of the torsional otolith-ocular reflex. Unilateral stimulation of the utricle was performed on a rotator that allowed eccentric lateral displacement of the patient during earth-vertical rotation with constant velocity. The otolith-ocular reflex was recorded with three-dimensional video-oculography. RESULTS: There was no difference in the estimation of the subjective visual vertical between patients and controls. The peak-to-peak amplitude of the otolith-ocular reflex torsional eye position was smaller in patients than in the control group. The gain of the unilateral otolith-ocular reflex was reduced in patients on both sides on first testing. After several weeks, only the affected labyrinth showed a reduced otolith-ocular reflex gain. CONCLUSION: Our findings document otolith dysfunction in patients with idiopathic benign paroxysmal positional vertigo possibly secondary to degeneration of the utricular macula. This finding may account for the transient mild imbalance and dizziness that some patients with benign paroxysmal positional vertigo experience even after resolution of positional vertigo.