1-27-07 Hunger strike-related Wernicke-Korsakoff's disease

Altered learning and transfer abilities in Korsakoff's syndrome depending on task complexity

Korsakoff's syndrome (KS) is characterized by episodic memory impairment due to damage to the medial diencephalic structures. Although commonly associated with chronic alcoholism, starvation due to the hunger strike is one of its nonalcoholic causes. Learning the stimulus-response associations and transferring the just-learned associations to novel combinations were previously tested by specific tasks in memory-impaired patients with hippocampal, basal forebrain, and basal ganglia damage. To add to this previous research, we aimed to use the same tasks in a group of patients with hunger strike-related KS presenting a stable isolated amnestic profile. Twelve patients with hunger strike-related KS and matched healthy controls were tested in two tasks varying in task complexity. Each task included two phases: the initial phase is feedback-based learning of (simple vs. complex) stimulus-response associations, and the following phase is transfer generalization (in the presence vs. absence of feedback). On a task involving simple associations, five patients with KS failed to learn the associations, while the other seven patients showed intact learning and transfer. On the other task involving more complex associations, seven patients showed slower learning and failed at transfer generalization, whereas the other five patients failed even at the acquisition phase. These findings of a task-complexity-related impairment on associative learning and transfer represent a distinct pattern from the spared learning but impaired transfer previously observed on these tasks in patients with medial temporal lobe amnesia.

Therapeutic effects of an acetylcholinesterase inhibitor (donepezil) on memory in Wernicke-Korsakoff's disease

Wernicke-Korsakoff's disease (WKD) is cognitively an amnestic state resulting from strategic lesions in the limbic system subserving the episodic memory network and resulting from thiamine deficiency. Neurochemical deficits have been implicated in the pathophysiology of amnesia based on the pathologic observations that various brainstem and basal forebrain nuclei are also affected. Previous treatment attempts with serotoninergic, noradrenergic, and cholinergic drugs have given controversial results. The objective of this study was to assess the effects of a cholinesterase inhibitor, donepezil, on memory, attention, and executive functions in patients with nonalcoholic WKD. Seven patients who developed WKD after a hunger strike were included in this single, blind, placebo-controlled, one-way, crossover study. The patients were administered donepezil during the first 30 days, and were administered placebo during the following 30 days. Neuropsychological tests to evaluate verbal and visual memory, and attention and executive function were performed on days 0, 31, and 61. All patients completed both phases of the study. There were no statistically significant differences between the three evaluations, except for a difference between active treatment and the placebo phase during recall of the Rey-Osterrieth complex figure, which was in favor of the placebo phase. There were no significant changes in favor of the active treatment. Cholinergic treatment with the cholinesterase inhibitor donepezil does not seem to provide marked beneficial effects in patients with WKD in this small, descriptive study. This may be because pathways mediating channel and state-dependent functions are impaired in this disease, and enhancement of state-dependent cholinergic transmission may not be sufficient. Subtle benefits, however, cannot be excluded because of the small sample size and the relatively short duration of the treatment.

Neuromuscular consequences of prolonged hunger strike: an electrophysiological study

OBJECTIVES

The purpose of this study was to determine the electrophysiological consequences of neuromuscular and central nervous system involvement in a group of patients presented with the neurological complications of a long-term hunger strike (HS).

METHODS

Motor and sensory nerve conduction (NCV), F wave, somatosensory evoked potential (SEP) and motor evoked potential (MEP) studies were performed in 12 male and 3 female patients (mean age: 29.4) following HS.

RESULTS

All patients whose weight loss was 11-31 (mean: 22.8) kg after 69-day HS, had neurological findings consistent with Wernicke's encephalopathy or Wernicke-Korsakoff syndrome. Abnormally prolonged latency and/or low amplitude sensory nerve action potentials were found in 7 patients. The amplitudes of compound muscle action potentials were significantly reduced in ulnar, median and tibial motor NCV studies as compared to the controls. F waves elicited by median nerve stimulation at wrist and muscle responses evoked by cervical and lumbar magnetic stimulation had significantly prolonged latencies. MEPs recorded from the lower extremities showed a slight prolongation in central conduction times. The cortical response latencies were prolonged in tibial SEPs.

CONCLUSIONS

The most prominent finding in this patient group was the low amplitude of CMAPs elicited in motor NCV studies which was concluded to be resulted from the reversible muscular changes. The other electrophysiological findings suggested that peripheral nerves and long central nervous system pathways were also mildly involved.