Characteristics of Respiratory Physiology in a Case of Stiff-Man Syndrome

Abstract

A 54 year old male with stiff-man syndrome was examined in terms of respiratory function. A restrictive pattern on spirograms without marked abnormalities in small airways function (V₅₀, V₂₅, and dynamic compliance) was attributed to respiratory muscle stiffness, because Pes max and static compliance were quite normal. Hypercapnic ventilatory response was markedly blunted, whereas hypoxic ventilatory response was normal. These changes were in accord with findings in arterial blood gases (normal PaO₂ and high PaCO₂). Hypercapnia was probably a product of either excessive CO₂ production or blunted respiratory chemosensitivity to CO₂.
Intravenous administration of diazepam (20mg) induced an increase in VC and MVV and a decrease in V_E, V_T, V_O2, V_CO2, and R. Ventilation and hypercapnic ventilatory response decreased and PaCO₂ increased after the administration of diazepam.
The postmortem examination disclosed diffuse proliferation of glia cells in the anterior columns of the spinal cord. Histology of the medulla oblongata was not available due to so-called “respirator brain.”
These abnormalities in respiratory functions might be a precursor of clinically manifest respiratory failure. Treatment of this disabling disease by diazepam must be performed with great care because of its depressant effect on respiratory chemosensitivity to CO₂.