Olfactory dysfunction in patients with neuromyelitis optica

Abstract

Background. Neuromyelitis optica (NMO) is a severely disabling autoimmune disorder of the CNS, which mainly affects the optic nerves and spinal cord. However, recent studies have shown that extra-opticospinal are more common in NMO than previously thought. Objective. To investigate olfactory function (OF) in patients with neuromyelitis optica (NMO) versus healthy controls (HC). Methods. Psychophysical testing of the orthonasal OF was performed using the Threshold-Discrimination-Identification test (TDI), measuring different qualities of olfaction, in 10 unselected NMO patients and 10 HC. Results. Five of 10 NMO patients (50%) showed hyposmia, while all 10 HC were normosmic. Moreover, NMO patients had significantly lower mean TDI-scores compared to HC, based on a poorer performance in both the Discrimination and the Identification subtests. Conclusions. Our results suggest that hyposmia might be part of the expanding clinical spectrum of NMO.

Figure 1

Binding of serum NMO-IgG to the olfactory bulb as demonstrated by indirect immunohistochemistry on formalin-fixed rat tissue cryosections. Binding of the patient's IgG is shown in green (AF488). See method section for details. The figure shows a transverse section through the right olfactory bulb near the medial surface. Arrowheads = pia mater; arrows = microvasculature; GL = olfactory glomeruli; ON = peripheral olfactory nerves (ON); NL = nerve fibre layer; CT = connective tissue next to the medial surface of the olfactory bulb.

Figure 2

Binding of serum NMO-IgG to the inner portion of the rat olfactory bulb as demonstrated by indirect immunohistochemistry. See results section for details. Binding of the patient's IgG is shown in green (AF488); cell nuclei are shown in blue (4′,6-diamidino-2-phenylindole). Arrowheads = microvasculature; ExtPL-external plexiform layer; ML-mitral cell layer; IntPL = internal plexiform layer; GrL = granular layer.