Rattlesnake envenomation with neurotoxicity refractory to treatment with crotaline Fab antivenom

Neurotoxicity following rattlesnake envenomation is reported with certain crotaline species. In some instances, crotaline Fab antivenom therapy that effectively halts progression of local tissue edema and hemotoxicity fails to reverse neurologic venom effects.

A 50-year-old man presented following a rattlesnake envenomation to the left ring finger. He had swelling and pain in the affected hand and complained of dyspnea and dysphonia. Significant fasciculations were seen in the face, tongue, neck, trunk, and arms. The patient received crotaline Fab antivenom but continued to develop worsening respiratory distress. His respiratory insufficiency requiring ventilatory support appeared related to respiratory muscle incoordination as extremity motor function remained intact. Initial control of local edema progression and hematologic parameters was achieved with antivenom, but diffuse fasciculations involving the entire body worsened despite aggressive antivenom treatment. In another case, a 9-year-old boy was envenomated by a rattlesnake on the left thenar eminence. He presented with pain and swelling up to the forearm and fasciculations of the tongue, face, and upper extremities. The progression of edema was halted at the mid-bicep level and hematologic parameters normalized with crotaline Fab antivenom. However, fasciculations continued for two days despite antivenom treatment.

We describe two cases of neurotoxicity following rattlesnake envenomation in which treatment with crotaline Fab antivenom adequately obtained initial control of local swelling and hematologic effects, but neurotoxic venom effects remained refractory to antivenom therapy. This phenomenon is anecdotally recognized following certain crotaline species envenomations.