Hippocampal Pathology in California Sea Lions with Domoic Acid-Induced Temporal Lobe Epilepsy

In 1987, over 100 Canadians became ill after eating cultivated mussels from Prince Edward Island. Symptoms included the typical gastrointestinal issues, but serious neurological findings such as disorientation, confusion, and memory loss were also observed (Perl et al., 1990). In the worst cases, the patients developed seizures or went into coma. Three elderly people died. The cognitive changes were persistent, and had not resolved within a two year follow-up.The toxin was identified as domoic acid, which received the well-deserved moniker of Amnesiac Shellfish Poison. Domoic acid is a potent excitatory amino acid that activates kainate and AMPA receptors, the binding sites for the ubiquitous excitatory neurotransmitter glutamate. It acts as an excitotoxin by overstimulating these receptors, causing a flood of calcium ions into the cells. Particularly vulnerable are neurons in medial temporal lobe structures such as the amygdala and the hippocampus, which is critical for memory. Postmortem examination of four brains revealed hippocampal pathology that could account for the clinically significant anterograde amnesia seen in other (still living) patients (Teitelbaum et al., 1990). The pattern of neuronal loss was consistent with the damage observed in kainic acid animal models of epilepsy.Fig. 3 (modified from Teitelbaum et al., 1990).  Panel A: Section o...
Source: The Neurocritic - Category: Neurologists Source Type: blogs