Neurological Causes of Taste Disorders

In caring for patients with taste disorders, the clinical assessment should include complete examination of the cranial nerves and, in particular, gustatory testing. Neurophysiological methods such as blink reflex and masseter reflex allow the testing of trigeminofacial and trigeminotrigeminal pathways. Modern imaging methods (MRI and computed tomography) enable the delineation of the neuroanatomical structures which are involved in taste and their relation to the bony skull base. From a neurological point of view, gustatory disorders can result from damage at any location of the neural gustatory pathway from the taste buds via the peripheral (facial, glossopharyngeal and vagal nerve) and central nervous system (brainstem, thalamus) to its representation within the cerebral cortex. Etiopathogenetically, a large number of causes has to be considered, e.g. drugs and physical agents, cerebrovascular disorders including dissection of the carotid artery and pontine/thalamic lesions, space-occupying processes - in particular tumors compressing the cerebellopontine angle and the jugular foramen of the skull base - head trauma and skull base fractures, isolated cranial mononeuropathy (e.g. Bell's palsy) or polyneuropathy, epilepsy, dementia, multiple sclerosis and major depression. In addition to this, aging can also lead to diminished taste perception. Due to the broad differential diagnostic considerations, it is essential to look for additional, even mild, neurological signs and symptoms. Treatment must relate to the underlying cause. Zinc may be tried in idiopathic dysgeusia.