[Description and analysis of olfactory disorders after head trauma. Review of the literature].

Olfactory disorders subsequent to head trauma can raise medicolegal problems when the olfactory deficit occurs after a work accident or a traffic accident and also raises the problem of psychological and functional tolerance when the patient consults late for a therapeutic solution. We studied the epidemiology of olfactory disorders after head trauma. Such disorders have been recognized since the XIX(th) century. Several studies have attempted to determine the prevalence of olfactory sequelae after head trauma. We then describe the pathophysiology of these lesions and emphasize that the degree of severity is related with the gravity of the head trauma and that the prevalence of these disorders varies considerably depending on the site of the trauma. Mechanisms which can lead to lesions of the olfactory system include, damage to the olfactory nerve bundles, naso-sinus lesions, or lesions of the cerebral olfactory centers. Brain MRI in anosmic patients after head trauma allows a visualization of intracranial lesions. The degree of reversibility of olfactory disorders after head trauma is imperfectly evaluated and discordant results have been reported. Some authors consider loss of olfaction is definitive. Others suggest an improvement in olfaction the year following head trauma. We reviewed the literature on these different elements. Expert opinions concerning patients complaining of olfactory disorders should relate this disorder to the initial trauma and determine the personal and occupational impact of the deficit. Attribution of cause must take into account all the clinical, radiological and psycho-olfactory factors.