Pseudoneurotoxic disease

Most instances of individual genuine neurotoxic disease in North America are pharmacologic; recognition of the causative agent is seldom difficult, for example, taxane neuropathy and chlorpromazine dyskinesia.¹ Syndromes associated with familiar industrial toxins or abuse chemicals such as n-hexane neuropathy and toluene leukoencephalopathy are also readily identified. The consulting neurologist, although seldom initially called to see occupation-related cases, has little difficulty recognizing these well-described entities.

Precise diagnosis of unusual neurotoxic diseases can be difficult. In such instances, clinical toxicologists are useful in defining genuine disorders with detectable body burdens, such as arsenic or mercury; neurologists are most helpful in excluding instances of clear-cut naturally occurring conditions. Knowledge of the cardinal tenets of neurotoxic disease assists in its recognition.² The basic dilemma is determining whether a symptomatic individual exposed to a putative neurotoxin has one of four conditions: a genuine neurotoxic disorder, the coincident new onset of a naturally occurring nervous system disease, psychogenic illness, or worsening of a pre-existing neurologic or psychological disorder. The latter three conditions represent three varieties (Types 1, 2, and 3) of a newly recognized entity: pseudoneurotoxic disease² (table). The cases presented here exemplify each type and are selected from the authors’ experience of >200 individuals with these conditions. We have modified nonrelevant details of Cases 2 and 3 to preserve the anonymity of the patients and the patients’ families.

Type 1 pseudoneurotoxicity attributes instances of a naturally occurring nervous system disease (multiple sclerosis, Alzheimer disease) or condition (age-related cognitive decline, relative performance weaknesses within the normal range) to coincident chemical exposure. This is exemplified by epidemics of “painters’ encephalopathy,” an illness attributed, primarily in Scandinavian reports, to chronic low-level organic solvent exposure.³ Most patients assigned this diagnosis have alternative …