Transient Global Amnesia in a Patient with Postherpetic Neuralgia

Abstract

Transient global amnesia (TGA) is a clinical syndrome of reversible anterograde amnesia that occurs in the middle-aged and elderly individuals. The etiology is obscure, and many underlying factors have been reported. We describe an 83-year-old man with postherpetic neuralgia (PHN) for which he received pregabalin, fentanyl, and a serotonin-norepinephrine reuptake inhibitor (SNRI). Pain intensity on a numeral rating scale (NRS) was 8/10. He had no history of vascular disease or epilepsy.

On November 28th 20XX he visited our hospital and underwent intercostal nerve block with phototherapy as usual. He was slightly feverish and had a body temperature of 37.8°C with no other symptoms. After 15 minutes rest, he left our hospital and tried to return to his home, but he was unsure which train to take. About 4 hours later, he suddenly knew where he was and got back to his home uneventfully. He had been amnetic for several hours. Two weeks later, he was referred to a neurologist, and the episode was diagnosed as TGA. Brain magnetic resonance imaging (MRI) showed non-specific cerebral atrophy with signs of aging at that point. Differential diagnoses include ischemia, migraine, epileptic seizures, and thromboembolic cerebrovascular disease. The cause of TGA remains controversial. However, drugs such as GABAergic drugs, SNRIs, and opioids are known to have effects on cognitive function. Polypharmacy can result in substantial drug-drug interactions, especially in elderly patients. The trigger of this episode in our patient is unclear, but multiple analgesics might have been a causal factor of his symptoms of TGA.