Central and peripheral nervous systems may be involved in primary hyperparathyroidism (PHP). The efficacy of parathyroidectomy in reversing neurological symptoms is still a matter of controversy. We describe the case of a 71-year-old white male with a 10-year history of PHP who developed progressive cognitive dysfunction and severe sensorimotor axonal polyneuropathy. Successful parathyroidectomy reversed with a different temporal course both the central and peripheral nervous system involvements.