Delayed-onset central neurotoxic syndrome with predominant cerebellar dysfunction following combined chlorpyrifos and cypermethrin poisoning: a case report.

Organophosphate (OP) poisoning typically manifests in three phases: the acute cholinergic crisis, the intermediate syndrome, and OP-induced delayed neuropathy (OPIDN). Delayed central nervous system sequelae with predominant cerebellar dysfunction are exceptionally rare and poorly characterized. We report the case of a woman in her early thirties with a history of chronic alcohol use who ingested a commercial insecticide containing chlorpyrifos (50%) and cypermethrin (2%). Following the resolution of an acute cholinergic crisis and a brief period of cardiac arrest (return of spontaneous circulation within 3 minutes), she demonstrated neurological recovery. However, 21 days post-ingestion, she developed acute-onset gait unsteadiness. Neurological examination revealed predominant cerebellar dysfunction, including limb dysmetria, gaze-evoked nystagmus, and ataxic gait, together with bilateral extensor plantar responses, while cognition remained preserved and there was no evidence of distal motor neuropathy. Neuroimaging (magnetic resonance imaging) was unremarkable, and metabolic, infectious, autoimmune, and hypoxic causes were carefully evaluated, with no supporting evidence identified. The patient showed gradual improvement with supportive care. This case highlights a rare delayed central neurotoxic syndrome distinct from OPIDN. The delayed onset of a central neurotoxic syndrome with predominant cerebellar dysfunction, likely exacerbated by pyrethroid synergism, emphasizes the need for prolonged neurological surveillance in mixed pesticide poisonings, even when initial imaging is normal.