Q: Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
The pathogenesis of restless legs syndrome (RLS) is unknown. Although iron deficiency anemia (IDA) is related with RLS, the mechanism of this relationship is still unknown. Therefore, we decided to examine some neurophysiological parameters that reflect the function of brainstem, spinal cord and peripheral nervous system. 34 patients diagnosed with IDA at the hematology department were questioned with a structured battery for RLS and additional symptoms. Of those, 14 patients had symptoms of RLS, while remaining 20 had no signs of this disorder. In both groups, electrophysiological examination including motor and sensory nerve conduction, F-responses, H-reflex, blink-reflex, and mixed nerve silent periods was performed. Neurological examination of all patients was normal. The two groups were identical for age and sex, and the difference between both groups concerning motor and sensory nerve conduction, F-wave, H-reflex, blink-reflex, and mixed nerve silent periods was insignificant. Results suggest that IDA does not cause electrophysiological changes in the peripheral nerves, spinal cord and brainstem, and therefore, measurement of these parameters in IDA patients does not seem effective for the confirmation of RLS.
A:
Which deficiency is the cause of restless leg syndrome?