Disorders of cranial nerves
Olfactory nerve (I) lesion
The olfactory receptors lie in the olfactory epithelium in the upper part of the superior turbinate and the nasal septum. The axons form bundles which pass through the cribiform plate (ethmoid bone) to the olfactory bulb. The bundles are wrapped in meninges. The olfactory bulb neurones project through the olfactory tract to the frontal cerebral hemispheres, the medial temporal lobe and the basal ganglia.
Trauma, frontal lobe tumour, meningitis.
Diminished sense of smell and taste (closely linked to smell) although this may be found in elderly patients without olfactory nerve lesions. Test ability of each nostril to detect several common smells.