Isolated amnesia following a bilateral paramedian thalamic infarct. Possible etiologic role of a whiplash injury.

A previously healthy 45 years old carpenter suffered a whiplash injury in a road accident on July, 18th, 1990. He continued to work in spite of occipital headache, episodic sweatening and slight hypersomnia. On August, 8th, 1990 while parking his car into the deck of a ferry-boat he was found slightly confuse and markedly amnestic. A post-traumatic subdural haematoma was suspected. As a CT-scan of the brain was normal, a toxic encephalopathy or an hysterical amnesia were proposed. However, a MRI performed on August, 22th, 1990, apart from a small infarct in the white matter of the left occipital lobe, showed two small bilateral paramedian thalamic infarcts. The last lesions usually follow a thrombotic or embolic occlusion of the "basilar communicating artery" (BCA) belonging to the vertebro-basilar system. The possible etiologic relationship between this syndrome and the previous whiplash injury has been considered. Six months later, while a control MRI showed a reduction of the brain lesions, a neuropsychological examination revealed a slight improvement of memory dysfunction evident also at a distance of further 6 months. This case is interesting because it tests the high sensitivity of MRI in amnestic syndromes and because of the possible role of a whiplash injury in the etiology of BPTI.