Neurophysiologic and Neurocognitive Case Profiles of Andean Patients with Chronic Environmental Lead Poisoning

Abstract

This report presents case profiles of three siblings in a family of lead (Pb) glazing workers living in a Pb-contaminated Andean village who presented with extreme plumbism (blood Pb levels: 47 to 128 μg/dl) from childhood to adolescence. These cases are examples of persons who have chronic Pb poisoning as a result of prolonged occupational and environmental exposure in a Pb-glazing ceramic cottage industry in the study area. Using behavioral and physiological techniques for measuring the integrity of the peripheral and central auditory systems, including otoacoustic emissions, and replicated auditory brainstem electrophysiological potentials, the authors found normal auditory neurosensory function in each patient, thus ruling out hearing impairment as a basis for adverse neurocognitive outcomes. This finding is contrary to the prevailing view regarding the detrimental effects of Pb poisoning on the cochlear and auditory brainstem of children. Performance on tests of visual spatial intelligence and auditory memory/attention was below average in these patients, which may underlie their reported learning disabilities. In two of the cases, there was an improvement in cognitive performance following a lowering of PbB levels from chelation therapy and Pb prevention education, suggesting some level of reversibility of their neurocognitive deficits. Nevertheless, these case profiles suggest that if the patients persist in Pb-glazing activities, in spite of repeated chelation therapy and family counseling, they may continue to be re-intoxicated and remain at risk for learning disabilities and other neurological impairments.

Acknowledgements

This study was conducted under the auspices of Universidad San Francisco de Quito Medical School in Quito, Ecuador. The authors thank Dr. Enrique Noboa, Dean of the College of Health Sciences, Universidad San Francisco de Quito; Dr. José Izurieta, Director of Health, Cotopaxi Province; Dr. Galo Tapia, Director of Pujilí Hospital; Dr. Cecilia Zambrano, Director of La Victoria Subcentro de Salud; Gladys Pacheco, nurse, Subcentro de Salud, La Victoria; and Universidad San Francisco de Quito Medical School for continued support of this project. The authors are also grateful to Dr. Nader Rifai, Patricia Nolan Hoover, Aruna Rabari, and Gary Bradwin of the Department of Laboratory Medicine, Children's Hospital Boston, for generous laboratory support. The authors thank Anthony B. Jacobs for his continued excellent technical support. The authors are grateful to the David Rockefeller Center for Latin American Studies at Harvard, and its director, Dr. Merilee Grindle, for support of this project. Dr. David Rosenthal and Benedict J. DiRusso, Jr., R.Ph., of the Harvard University Health Services are thanked for their support. The authors acknowledge the advice and counsel of their esteemed collaborator in the Ecuadorian lead exposure studies, Dr. Michael W. Shannon, Professor of Pediatrics at Harvard Medical School and Children's Hospital Boston, who died unexpectedly on March 10, 2009.