Two cases of MND/ALS developing the syndrome of inappropriate secretion of antidiuretic hormone.

We report 2 autopsy-proven cases of motor neuron disease/amyotrophic lateral sclerosis (MND/ALS), who developed the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) prior to the respiratory failure. With respect to the underlying mechanisms of SIADH in the cases, we considered two factors; 1) dysfunction of the feedback system in ADH secretion via intrathoracic volume receptors caused by changes in intrathoracic circulation, and 2) primarily functional abnormalities in the limbic system which could influence hypothalamic osmoreceptors. It appears that SIADH can be followed by an exacerbation of respiratory dysfunction in MND/ALS.