Post-traumatic ageusia

Olfactory and Gustatory Function in Patients With Different Types of Maxillofacial Trauma

OBJECTIVES/HYPOTHESIS

To investigate olfactory and gustatory function in patients with maxillofacial trauma and associated fractures.

STUDY DESIGN

Retrospective cohort study.

METHODS

Olfactory and gustatory function was assessed psychophysically in 124 patients who had sustained maxillofacial trauma with an associated fracture. Five groups were defined based on the fracture type: Le Fort, mandibular, nasal, orbital, and zygomatic. Olfaction was measured with Sniffin' Sticks (threshold, discrimination, identification [TDI] score) and gustation with the taste spray method. Patients self-rated olfactory and gustatory function on a visual analog scale prior to formal testing.

RESULTS

Ten out of 124 patients were found to be anosmic (8%), with half of them found in the Le Fort (skull base) group. The Le Fort fracture group had significantly lower olfactory function than other fracture types (TDI score = 22.4 ± 10.7; P = .01; possible range = 1-48). The mean gustatory spray test score was 3.82 ± 0.4 (possible range = 0-4) without any intergroup differences. Self-rated olfactory function showed a correlation with the measured scores (r = 0.61, P < .001) across all groups.

CONCLUSIONS

The present data show a significant effect of maxillofacial fracture type on the development of anosmia. Maxillofacial fractures involving the skull base, such as Le Fort fractures, are more likely to cause permanent smell loss, whereas the other fracture types are rarely associated with anosmia.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E331-E337, 2021.

The influence of head injury on olfactory and gustatory function

Head injury, particularly that resulting in brain injury, is a significant public health concern. For example, annual incidence rates of traumatic brain injury, a common consequence of head injury, range from 54 to 60 million people worldwide, including 2.2-3.6 million people whose trauma is moderate to severe. Trauma to the face and brain, including blast injuries common in modern warfare, can result in alterations in the ability to both smell and taste. In the case of smell, these include total loss of function (anosmia), decreased sensitivity (hyposmia), alterations in odor quality (dysosmia), and hallucination (phantosmia). Although taste dysfunction, i.e., altered perception of such basic taste-bud-mediated sensations as sweet, sour, bitter, salty, and savory (umami), can be similarly influenced by head trauma, the effects are typically more subtle and less studied. The present review provides an up-to-date assessment of what is known about the impact of head injury on quantitative measures of taste and smell function, including the influences of severity, type of injury, location of insults, prognosis, and approaches to therapy.

Post-traumatic taste disorders: a case series

Since 1800s there are reports of post-traumatic anosmia, but few studies investigated post-traumatic gustatory deficit and adopted validated evaluation tests. Peripheral and/or central mechanisms may be involved in the genesis of post-traumatic gustatory dysfunction. Beyond a reduction/loss (hypogeusia/ageusia) of gustatory function following a trauma, qualitative taste changes (dysgeusia) may occur. Especially when persistent, taste deficits might be particularly relevant for patient's quality of life and activities of daily life, but knowledge on this topic is limited. Fifty-three consecutive patients with previous head trauma were recruited. Every patient underwent a careful history taking and thorough olfactory and gustatory chemosensory testing by Sniffin'Sticks Extended test, Whole Mouth Test and Taste Strips Test. All patients had olfactory abnormalities (hyposmia: n = 10, functional anosmia: n = 43), while 10 of them (19%) showed taste deficits (dysgeusia: n = 3, dysgeusia with hypogeusia: n = 1, hypogeusia: n = 5, ageusia: n = 1). Here, we report clinical and neuroimaging data and detailed description of four meaningful cases representing central and peripheral injury patterns. Chemosensory evaluation might be useful to explore taste disorder, a still neglected and underestimated sequela of head trauma.

Case Report: Diagnosis of hypogeusia after oral exposure to commercial cleaning agent and considerations for clinical taste testing

Few reports in the literature document acute taste disturbance following exposure to toxic chemicals. We describe the case of a 54-year-old man who presented with primary complaint of tongue numbness and persistent problems with taste 1.5 years following oral exposure to a commercial cleaning agent. A test of olfaction revealed normosmia for age and gender. Lingual tactile two-point discrimination testing showed reduced somatosensation. Taste threshold testing using a 3-drop method demonstrated severe hypogeusia, though the patient was able to discriminate tastants at lower concentrations with a whole mouth swish and spit test. We conclude that clinical evaluation of dysgeusia can be performed using a number of previously published testing methods, however, determining causative factors may be confounded by duration since exposure, lack of knowledge of baseline taste function, and medications. Although many testing options exist, basic taste testing can be performed with minimal expertise or specialized equipment, depending on the patient history and goals of evaluation.

Case Report: Diagnosis of hypogeusia after oral exposure to commercial cleaning agent and considerations for clinical taste testing

Few reports in the literature document acute taste disturbance following exposure to toxic chemicals. We describe the case of a 54-year-old man who presented with primary complaint of tongue numbness and persistent problems with taste 1.5 years following oral exposure to a commercial cleaning agent. A test of olfaction revealed normosmia for age and gender. Lingual tactile two-point discrimination testing showed reduced somatosensation. Taste threshold testing using a 3-drop method demonstrated severe hypogeusia, though the patient was able to discriminate tastants at lower concentrations with a whole mouth swish and spit test. We conclude that clinical evaluation of dysgeusia can be performed using a number of previously published testing methods, however, determining causative factors may be confounded by duration since exposure, lack of knowledge of baseline taste function, and medications. Although many testing options exist, basic taste testing can be performed with minimal expertise or specialized equipment, depending on the patient history and goals of evaluation.

Traumatic Dysgeusia, an Unusual Complication of Facial Trauma: A Case Report

The chemical senses of taste and smell are important to human life, because they play an important role in detecting potential environmental hazards. Humans can identify countless different flavors by the simultaneous perception of taste and smell. Reports of sensory loss after craniocerebral trauma began to appear in the medical literature in the middle 1800s. Dysgeusia associated with head injuries is rare and its reported incidence is 0.4 to 0.5%. This report describes the clinical case of a 32-year-old man with Le Fort I and III fractures treated with surgical reduction and fixation. The patient presented with dysgeusia after slight improvement of his preoperative anosmia. The prognosis is favorable and the treatment is prospective.

Taste and smell function in chronic disease: a review of clinical and biochemical evaluations of taste and smell dysfunction in over 5000 patients at The Taste and Smell Clinic in Washington, DC

PURPOSE

To describe systematic methods developed over 40 years among over 5000 patients at The Taste and Smell Clinic in Washington, DC to evaluate taste and smell dysfunction.

MATERIALS AND METHODS

A tripartite methodology was developed. First, methods to determine clinical pathology underlying the multiple disease processes responsible for taste and smell dysfunction were developed. Second, methods to determine biochemical parameters responsible for these pathologies were developed. Third, methods to implement these techniques were developed to form a unified basis upon which treatment strategies can be developed to treat these patients.

RESULTS

Studies were performed in 5183 patients. Taste loss was present in 62% of patients, smell loss in 87%. Most patients with taste loss (52%) exhibited Type II hypogeusia; most patients with smell loss (56%) exhibited Type II hyposmia. Sensory distortions were present in 60%. Four common diagnostic entities were found: post influenza-type hyposmia and hypogeusia (27% of patients), idiopathic causes (16%), allergic rhinitis (15%) and post head injury (14%). Regardless of clinical diagnosis the major biochemical abnormality found in most patients (~70%) was diminished parotid salivary and nasal mucus secretion of cAMP and cGMP.

CONCLUSIONS

Taste and smell dysfunctions are common clinical problems associated with chronic disease processes. These symptoms require a systematic, integrated approach to understand their multiple and complex components. The approach presented here can and has led to effective treatment.

[Post-traumatic taste and smell disorders: forensic aspects]

The impact of anosmia or ageusia may be considerable for some occupations. Expert assessment shows how difficult it is to prove the diagnosis. A specialist is usually needed to demonstrate the asserted disorder. Damage compensation is based on the patient's occupation and coverage.

Effects of head injury on olfaction and taste

Traumatic events such as motor vehicle accidents, falls, or assaults can lead to dysfunction in olfaction or gustation. Mechanisms of posttraumatic olfactory dysfunction include direct injury to the sinonasal tract or olfactory epithelium, shearing effect on olfactory fibers at the cribriform plate, or brain contusion or intraparenchymal hemorrhage. Posttraumatic gustatory dysfunction is rare, but may occur as a result of direct injury to the tongue, injury to cranial nerves VII or IX, or brain contusion or hemorrhage. Evaluation of head-injured patients presenting with olfactory or gustatory complaints should include a thorough history, including assessment for pre-and posttraumatic chemosensory dysfunction and potential mechanisms of injury, complete head and neck examination including nasal endoscopy and cranial nerve testing, and focused radiographic imaging, usually CT of the sinuses and skull base. Formal olfactory and gustatory testing may be performed using various techniques, although in cases potentially involving litigation, methodologies able to detect malingering should be used. Treatable causes of chemosensory disturbance, most notably conductive olfactory losses caused by chronic rhinosinusitis or nasal obstruction, should be ruled out. In the event of neurosensory deficits, recovery may occur up to 12 to 18 months after the traumatic event. All patients should be counseled regarding the risks of their chemosensory deficits, and given suggestions for appropriate compensatory strategies.

Prevalence and causes of severe taste loss in a chemosensory clinic population

Although complete or near-complete olfactory loss has been extensively documented and described, few published reports have documented severe generalized gustatory loss (across qualities and neural fields) with rigorous psychophysical testing, and none have explored the prevalence or causes of such losses in a large clinical population. This study retrospectively reviews our chemosensory clinic's experience of 1,176 patients evaluated for complaints of chemosensory dysfunction in order to address these issues. Our series confirms that despite the complex, bilateral innervation and regenerative capacity of the gustatory system, severe generalized taste loss does occur as a clinical entity, albeit rarely: only 0.85% (n = 10) of our patients evidenced such a deficit, as compared to 32% (n = 371) who were found to have a profound olfactory deficit. Combinations of systemic and/or acute events may underlie many cases of severe taste loss, and in half of our cases, these patients evidenced moderate to complete smell loss as well.

Bitter taste perception and severe vomiting in pregnancy

Hyperemesis gravidarum or severe vomiting during pregnancy is a condition of elusive etiology that can harm both mother and fetus. This study examined the association between increased bitter-taste perception and history of hyperemesis gravidarum. Bitter-taste perception varies genetically and can be altered with conditions that damage taste-related cranial nerves. Sixty women were divided into high- (n = 21) and low-vomit (n = 39) groups based on vomiting exposure across all pregnancies and were screened for genetic variation in taste with bitterness of saturated 6-n-propylthiouracil (PROP) delivered on filter paper. Supertasters perceive PROP as intensely bitter; nontasters, as only weakly. Each reported their history of dysgeusia (persistent taste) and taste-related pathology (otitis media and head trauma). The vomit groups did not differ in the frequency of supertasters, but the high-vomit group had fewest nontasters. The high-vomit group also reported dysgeusia most frequently. A subsample (13 high-vomit and 18 low-vomit women) rated the taste intensity of sodium chloride (1 mol), sucrose (1 mol), citric acid (0.0032 mol), and quinine hydrochloride (0.001 mol) applied to areas innervated by cranial nerves VII and IX. The groups only varied significantly in bitterness of quinine hydrochloride. High-vomit women tasted least bitterness on the anterior tongue (chorda tympani branch of VII) and highest bitterness on the posterior tongue (cranial nerve IX) and palate (superficial petrosal branch of VII). In high-vomit women, elevated bitterness on the posterior tongue and palate does not appear related to hydrochloric acid exposure in vomitus; it may explain the occurrence of dysgeusia. This pattern of spatial taste perception may indicate altered oral sensations that if present during pregnancy, could increase the risk of hyperemesis.

Taste and smell phantoms revealed by brain functional MRI (fMRI)

PURPOSE

Our goal was to demonstrate the appearance of phantom tastes and smells (phantageusia and phantosmia, respectively) by use of functional MRI (fMRI) of the brain and to demonstrate the efficacy of drug treatment that inhibited both the subjective presence of these phantoms and the fMRI brain activation initiated by these phantoms.

METHOD

Multislice FLASH MR or echo planar MR brain scans were obtained in two patients with phantageusia and phantosmia in response to memory of two tastants (salt and sweet); memory of two odors (banana and peppermint); actual smell of amyl acetate, menthone, and pyridine; and memory of phantom tastes and smells before and after treatment with thioridazine and haloperidol. Activation images were derived using correlation analysis, and ratios of brain area activated to total brain area were obtained.

RESULTS

Prior to treatment, both patients experienced persistent birhinal and global oral obnoxious tastes and smells in the absence of any external stimulus. The fMRI response to memory of phantoms was activation in sensory-specific brain regions for taste and smell, respectively. fMRI activation was greater than for memory of any tastant or odorant or for actual smell of any odor. After treatment with thioridazine or haloperidol, which successfully inhibited each phantom in each patient, fMRI response to phantom memory was significantly inhibited and was significantly lower than for memory of any tastant or odorant or actual smell of any odorant.

CONCLUSION

These results demonstrate that (a) phantom taste and smell can be revealed by fMRI brain activation, (b) brain activation in response to taste and smell phantoms is localized in sensory-specific brain regions for taste and smell, respectively, (c) brain activation in response to memory of each phantom initiated the greatest degree of activation we had previously measured, and (d) treatment with thioridazine or haloperidol inhibited both the presence of each phantom and its associated fMRI brain activation. This is the first study in which phantom tastes and smells have been demonstrated by an objective technique and treatment that inhibited the phantoms was characterized by objective inhibition of fMRI activation. These two patients represent a relatively common group that may be classified as having primary phantageusia and phantosmia distinct from those with phantoms or auras secondary to neurological, migrainous, psychiatric, or other causes.

Disorders in taste and smell

Although many conditions and medications have been associated with chemosensory disturbances, data from major chemosensory clinical research centers support three major disorders as being causative: nasal and paranasal sinus disease (21%), post-upper respiratory tract viral infection (19%), and head trauma (14%). Despite extensive evaluation, 22% of patients do not demonstrate identifiable causation.

Morphology of the human olfactory epithelium

The human olfactory epithelium has been previously studied with scanning electron microscopy; however, most studies have been limited to examining the epithelial surface. In an attempt to examine structures below the surface, we scanned epithelial fractures that occurred during tissue preparation. This made it possible to obtain unique three-dimensional images of cell profiles from the mucosal surface through the full depth of the epithelium. We examined supporting cells, olfactory neurons, basal cells, and a fourth cell type, the microvillar cell. Supporting cells had a microvillar surface and were in close contact with olfactory neurons and their processes. Olfactory neurons were primarily located in the middle and lower epithelial regions. Basal cells occurred alone or in clusters adjacent to the basal lamina. Microvillar cells were always observed in the upper epithelial region. They were flask- or pear-shaped, had a tuft of microvilli that extended into the nasal cavity, and a thin axon-like process that passed basally towards the lamina propria. This study represents the first comprehensive scanning electron microscopy examination of the human olfactory epithelium. Three-dimensional images obtained for each epithelial cell type allowed us to examine cell processes and their close contacts, especially between supporting cells and olfactory neurons. These results also revealed the irregular and patchy distribution of olfactory receptors within the human nasal cavity. Further studies that examine the detailed morphology of the human olfactory epithelium should provide a better understanding of the physiological mechanism and clinical disorders that affect olfactory function in humans.

On a neural mechanism for cortical processing of taste quality in the rat

The responses of 31 chorda tympani fibers and 47 cortical neurons were recorded in response to 6 concentrations of NaCl, and single concentrations of sucrose, HCl, and quinine hydrochloride solutions applied to the anterior portion of the tongue in rats. The neural responses were analyzed in terms of the two hypotheses of quality coding: across-neuron response pattern and across-region response pattern notions. In a behavioral experiment, animals were given a conditioned taste aversion to one of 5 concentrations of NaCl solution by pairing it with a gastrointestinal illness caused by i.p. injection of 0.15 M LiCl. Behavioral taste profiles were constructed for each stimulus from the suppression of drinking, which indicates the extent of generalization of aversion to each of the 4 basic taste stimuli. Among the two neural analyses employed for the chorda tympani and cortical units, across-region correlation coefficients for cortical neurons that were derived from the across-region response pattern theory showed the highest correlation (r = 0.89) with the behavioral suppression rates. Across-neuron correlation coefficients in the chorda tympani fibers also showed a good correlation (r = 0.81) with the behavioral data. However, the taste profile for 1.0 M NaCl in chorda tympani fibers was very similar to that for the lower concentrations of NaCl, in spite of the suggestion from the behavioral experiment and the neural analyses of cortical responses that 1.0 M NaCl has HCl and quinine components besides the NaCl component. The present result confirmed the idea that processing of taste information in the cortex involves differences in both response magnitude across neurons and the spatial localization of those neurons.

Quality-specific taste changes in multiple sclerosis

Taste sensitivity in 79 patients with multiple sclerosis (MS) and 65 age- and sex-matched control subjects was measured with a sip-and-spit, suprathreshold scaling, magnitude estimation procedure using six concentrations each of sodium chloride, sucrose, citric acid, and quinine hydrochloride. Results were analyzed with a taste scoring system and by plotting psychophysical functions (log concentration versus log magnitude estimate) normalized to 1.0 M sucrose. Gender did not affect taste scores, but age was inversely related, so the results were analyzed by an analysis of covariance with age as the covariant. There was a significant alteration in taste sensitivity in the subjects with MS for sodium chloride and quinine hydrochloride stimuli but not for sucrose and citric acid; these results were confirmed by a separate analysis of the psychophysical functions. Some of the MS taste scores correlated with MS functional and physical disability scores. Taste sensitivity was not correlated with clinical history or presence of facial symptoms.

Abnormalities of taste and smell after head trauma

Abnormalities of taste and smell were studied in 29 patients after head trauma. These abnormalities included decreased taste acuity (hypogeusia), a distortion of taste acuity (dysgeusia), decreased smell acuity (hyposmia), and a distortion of smell acuity (dysosmia). This syndrome can occur even after minimal head trauma and can begin months after the moment of injury. The patients exhibited a significant decrease in total serum zinc concentration (patients, 77 ± 3 μg/100 ml, mean ± 1 SEM, vs controls, 99 ± 2 μg/100 ml, P>0·001) and a significant increase in total serum copper concentrations (113 ± 4 μg/100 ml vs 100 ± 2 μg/100 ml, P<0·001) compared with control subjects. Symptoms of hypogeusia, dysgeusia, and dysosmia are frequent sequelae of head injury and are important to the patients and to their care after trauma.