The chicken with four legs: A case of semantic amnesia and cryptogenic epilepsy

Here we describe the unusual condition of selective semantic amnesia related to cryptogenic temporal lobe epilepsy. XY, an adult male patient, presented with partial seizures and disabling dysnomia. Neuropsychological tests revealed seriously impaired semantic memory. Electroencephalography documented ictal epileptic abnormalities in the left temporal lobe. Positron emission tomography showed reduced metabolism in the temporoparietal regions, but the results of magnetic resonance imaging and spectroscopy were normal. After 11 years, neuropsychological tests showed selective impairment of semantic memory and computed tomography provided normal results. This case shows that semantic memory may be selectively and lastingly altered, highlighting a distinction between semantic amnesia and global amnesia. Moreover, it is unique in that it occurred without evidence of gross temporal lobe pathology. The pathophysiological pattern of epileptic abnormalities in the left temporoparietal cortex supports the role played by dysfunctional neuronal networks (as provoked by focal epileptic discharges) in determining selective semantic amnesia.