With chronic poisoning, a myriad of neurologic symptoms may be present signifying both PNS and CNS toxicity. When making a neurotoxic diagnosis, consider certain factors such as the dose-response relationship, temporal relationships between exposure and symptoms, immediate injury vs. delayed effect, the identity of the toxicant, and changing signs and symptoms. The dose-response relationship evaluates the exposure dose or quantity and duration of exposure to the toxic compound. A massive exposure is likely to precipitate an immediate toxic response. The patient is able to report knowledge of exposure.
Temporal relationships refer to the time between exposure and the onset of symptoms.
Acute exposures are most consistent. Prolonged exposure may manifest confusing symptoms that change over time as PNS, CNS, and other systems become damaged by the toxicant. Delayed neuronal death and degeneration may also present unusual temporal relationships. Symptoms may progress despite the abatement of exposure. There are very few pathognomonic signs and symptoms that illicit the immediate neurotoxic diagnosis.