Relationship of CD4 Counts to Neurophysiological Function in HIV-1-Infected Homosexual Men

Abstract

• Objective. —To explore the relationship of immune dysfunction to neurophysiological measures of brain-stem conduction time. Design. —Three-year longitudinal prospective cohort study; results of time 1 analyses reported. Setting. —San Francisco (California) General Hospital, Departments of Psychiatry and Epidemiology. Patients. —Volunteer sample of 55 human immunodeficiency virus (HIV)-positive and 37 HIV-negative homosexual men recruited from a larger cohort of homosexual men followed up since 1983 at San Francisco General Hospital as part of an ongoing study of the natural history and course of HIV type 1 infection. Intervention. —None. Main Outcome Measures. —Auditory brain-stem responses and somatosensory evoked potentials for subjects stratified separately on HIV serostatus, Centers for Disease Control and Prevention symptom groupings, and absolute CD4 counts. Results. —The HIV-positive subjects had an increased wave III-V interpeak latency of the right ear auditory brain-stem response compared with the HIV-negative subjects (t test, P<.05). There were no significant differences among the three Centers for Disease Control and Prevention groupings on any evoked potential measure. When HIV-positive subjects were stratified on a measure of immune functioning, ie, CD4 counts, individuals with greater immune suppression were more impaired on speed of auditory brain-stem conduction time (Mann-Whitney U test, P<.05). Furthermore, 85% of subjects impaired on this evoked potential measure had CD4 counts of less than 0.40×10⁹/L (400/μL), whereas only 15% of those impaired on this measure had CD4 counts of greater than 0.40×10⁹/L. Conclusions. —Asymptomatic HIV-positive subjects who do not have evidence of immune suppression do not appear to be at greater risk for neurophysiological impairment than HIV-negative subjects. The HIV-positive individuals who are immune suppressed (even while asymptomatic) appear to have an increased likelihood of central conduction time slowing as measured by evoked potential procedures.