Transient global amnesia like episode in a dialysis patient with severe hyperhomocysteinaemia

Aims: Transient global amnesia (TGA) is a type of memory disorder characterized by an episode of amnesia and bewilderment lasting for several hours. Clinical symptoms consist of retrograde amnesia for the recent past combined with an ongoing anterograde amnesia without impairment of consciousness, motor or sensory functions. Usually, mental functions recover completely after a maximum of 24 hours. Etiology of TGA is still unknown.

Case report: We here report a 58-year-old male patient treated with renal dialysis for 12 years who presented with typical clinical symptoms of TGA. However, deviating from the usual clinical picture, he showed a prolonged course of the amnestic episode for nearly three days, and he and his wife reported that he had been showing a general impairment of cognitive function and mood disturbances for months. Additionally, he suffered from arteriosclerosis and had developed several thrombotic occlusions of the haemodialysis shunts in the past.

Clinical investigation revealed a moderate axonal-demyelinating polyneuropathy. EEG and MRI showed no relevant abnormalities. Laboratory investigations showed elevated MCV, low folate (1.8ng/ml; normal: 3–17), low vitamin B12 (87pg/ml; normal: 180–920), and severe hyperhomocysteinemia (139micromol/l; normal: 5–12). After 12 days of vitamin substitutuion, vitamin and homocysteine levels as well as cognitive function and mood had normalized.

Discussion: Hereditary severe hyperhomocysteinemia (over 50micromol/l) usually presents with vascular disease, mental retardation and seizures, but even mild hyperhomocysteinemia (13–25micromol/l) is associated with thrombosis and cognitive impairment e.g. due to hippocampal dysfuction. Renal insufficiency and a lack of vitamin B12 and of folate can lead to hyperhomocysteinemia, thus, the severely increased homocysteine values in this case supposedly were result of a combination thereof. TGA-like episodes due to severe hyperhomocysteinemia have not been reported so far. However, in this case a causal relationship with the TGA-like episode and with the psychopathological findings may be assumed. Additionally, hyperhomocysteinemia might have been unfavourable concerning the shunt occlusion. We suggest that in patients with renal insufficiency, vitamins and homocysteine levels should be controlled. Severe hyperhomocysteinemia might be a rare differential diagnosis in cases of TGA-like episodes and in cases of mood disorders and cognitive impairment.