<P> Olfactory problems can be divided into different types based on their malfunction . The olfactory dysfunction can be total (anosmia), incomplete (partial anosmia, hyposmia, or microsmia), distorted (dysosmia), or can be characterized by spontaneous sensations like phantosmia . An inability to recognize odors despite a normally functioning olfactory system is termed olfactory agnosia . Hyperosmia is a rare condition typified by an abnormally heightened sense of smell . Like vision and hearing, the olfactory problems can be bilateral or unilateral meaning if a person has anosmia on the right side of the nose but not the left, it is a unilateral right anosmia . On the other hand, if it is on both sides of the nose it is called bilateral anosmia or total anosmia . </P> <P> Destruction to olfactory bulb, tract, and primary cortex (brodmann area 34) results in anosmia on the same side as the destruction . Also, irritative lesion of the uncus results in olfactory hallucinations . </P> <P> Damage to the olfactory system can occur by traumatic brain injury, cancer, infection, inhalation of toxic fumes, or neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease . These conditions can cause anosmia . In contrast, recent finding suggested the molecular aspects of olfactory dysfunction can be recognized as a hallmark of amyloidogenesis - related diseases and there may even be a causal link through the disruption of multivalent metal ion transport and storage . Doctors can detect damage to the olfactory system by presenting the patient with odors via a scratch and sniff card or by having the patient close their eyes and try to identify commonly available odors like coffee or peppermint candy . Doctors must exclude other diseases that inhibit or eliminate' the sense of smell' such as chronic colds or sinusitus before making the diagnosis that there is permanent damage to the olfactory system . </P> <P> The common causes of olfactory dysfunction: advanced age, viral infections, exposure to toxic chemicals, head trauma, and neurodegenerative diseases . </P>

Where are gustatory and olfactory nerves to be found