Ipsilateral disturbance of taste due to pontine haemorrhage

Bilateral hypogeusia and food aversion due to lacunar infarct in the right dorsomedial pontine tegmentum

A 70-year-old right-handed housewife suffered an acute loss of taste, an unpleasant change in the taste of foods and liquids, and a strong aversion to all kinds of food due to a small lacune in the right dorsomedial pontine tegmentum. Eating became so unpleasant that she lost 7 kg in three weeks. Olfaction and the sensibility of the tongue were spared. The right medial longitudinal fascicle, the central tegmental tract, or both, were injured by the tegmental lesion. A discrete right-sided lesion in the upper pontine tegmentum may cause a reversible syndrome consisting of bilateral hypogeusia which is more severe ipsilaterally.

Bilateral Ageusia and Tongue Anesthesia Following Unilateral Brainstem Infarct: A Case Report with a Brief Review of the Literature

We present the case of a 63-year-old male patient who suffered bilateral ageusia following a unilateral left-sided mesencephalon infarct. To the best of our knowledge, this is the first description of a mesencephalon lesion leading to ageusia. We discuss the literature on this rare but important symptom following a stroke.

Altered taste and stroke: a case report and literature review

Patients with altered taste perception following stroke are at risk for malnutrition and associated complications that may impede recovery and adversely affect quality of life. Such deficits often induce and exacerbate depressive symptomatology, which can further hamper recovery. It is important for clinicians and rehabilitation specialists to monitor stroke patients for altered taste perception so that this issue can be addressed. The authors present the case of a patient who experienced an isolated ischemic infarct affecting a primary cortical taste area. This case is unusual in that the isolated injury allowed the patient to remain relatively intact cognitively and functionally, and thus able to accurately describe her taste-related deficits. The case is further used to describe the relevant neurological taste pathways and review potential taste-related therapies.

Altered taste and stroke: a case report and literature review

Patients with altered taste perception following stroke are at risk for malnutrition and associated complications that may impede recovery and adversely affect quality of life. Such deficits often induce and exacerbate depressive symptomatology, which can further hamper recovery. It is important for clinicians and rehabilitation specialists to monitor stroke patients for altered taste perception so that this issue can be addressed. The authors present the case of a patient who experienced an isolated ischemic infarct affecting a primary cortical taste area. This case is unusual in that the isolated injury allowed the patient to remain relatively intact cognitively and functionally, and thus able to accurately describe her taste-related deficits. The case is further used to describe the relevant neurological taste pathways and review potential taste-related therapies.

Bilateral hypogeusia caused by a small lesion in the lower midbrain tegmentum

We report a case with multiple sclerosis which showed bilateral hypogeusia due to a small lesion in the lower midbrain tegmentum. Sweet taste was diminished only on the contralateral side in the territory of the chorda tympani, and salty, sour and bitter tastes were diminished bilaterally. All taste modalities were preserved in the territory of the greater petrosal nerve. The findings in our patient and in the literature suggest that the second gustatory fibres ipsilaterally ascend from the nucleus of the solitary tract to the midbrain and partially cross at the inferior border of the midbrain. The features of hypogeusia in our case suggest segregated channels in the gustatory pathway conveying taste perception of distinct taste modalities and from distinct innervation territories.

Clinical study of central taste disorders and discussion of the central gustatory pathway

The aim of this work is to examine the clinical findings of patients with taste disorders due to central lesions and also to study the central gustatory pathway in humans. We conducted a retrospective review of 13 patients with central taste disorders that visited Nihon University Itabashi Hospital. An additional 25 cases with central taste disorders previously reported in the literature were assessed in the study. We examined 38 patients with taste disorders due to central lesions. The sites of the central lesions and their frequencies, the laterality of taste disorders relative to the central lesions, and prognosis of taste disorders were studied. We identified the following taste-related regions in the central nervous system: the medulla, pons, midbrain, thalamus, internal capsule, putamen, corona radiata, and cerebral cortex. As for the laterality of the taste disorders, we observed more ipsilateral cases for lesions located from the medulla to the pons. We observed ipsilateral, contralateral, and bilateral cases for lesions located above the midbrain, but bilateral cases were more frequently detected. Taste disorders of 80% of the patients improved by 24 weeks. The prognoses of central taste disorders appeared to be good. We identified eight central regions supposed to be relate to taste disorders. From the laterality of the taste disorders relative to the central lesions, it was suggested that the central gustatory pathway ascends ipsilaterally from the medulla to the pons, branches at the upper pons, and then ascends bilaterally from the midbrain to the cerebral cortex.

Transient hemiageusia in cerebrovascular lateral pontine lesions

Knowledge of human central taste pathways is largely based on textbook (anatomical dissections) and animal (electrophysiology in vivo) data. It is only recently that further functional insight into human central gustatory pathways has been achieved. Magnetic resonance imaging studies, especially selective imaging of vascular, tumoral, or inflammatory lesions in humans has made this possible. However, some questions remain, particularly regarding the exact crossing site of human gustatory afferences. We present a patient with a pontine stroke after a vertebral artery thrombosis. The patient had infarctions in areas supplied by the anterior inferior cerebellar artery and showed vertical diplopia, right sided deafness, right facial palsy, and transient hemiageusia. A review of the sparse literature of central taste disorders and food preference changes after strokes with a focus on hemiageusia cases is provided. This case offers new evidence suggesting that the central gustatory pathway in humans runs ipsilaterally within the pons and crosses at a higher, probably midbrain level. In patients with central lesions, little attention has been given to taste disorders. They may often go unnoticed by the physician and/or the patient. Central lesions involving taste pathways seem to generate perceptions of quantitative taste disorders (hemiageusia or hypogeusia), in contrast to peripheral gustatory lesions that are hardly recognised as quantitative but sometimes as qualitative (dysgeusia) taste disorders by patients.

Laterality of human primary gustatory cortex studied by MEG

We examined the laterality of the human gustatory neural pathway by measuring gustatory-evoked magnetic fields (GEMfs) and demonstrating the activation of the human primary gustatory cortex (PGC). In patients whose chorda tympani nerve had been severed unilaterally on the right side, we stimulated the normal side (i.e., left side) of the chorda tympani nerve with NaCl solution using a device developed for measuring GEMfs. We used the whole-head magnetoencephalography system for recording GEMfs and analyzed the frequency and latency of PGC activation in each hemisphere. "The transitional cortex between the insula and the parietal operculum" was identified as PGC with the base of the central sulcus in this experiment. Significant difference was found in frequencies among bilateral, only-ipsilateral, and only-contralateral responses by the Friedman test (P < 0.05), and more frequent bilateral responses were observed than only-ipsilateral (P < 0.05) or only-contralateral responses (P < 0.01) by the multiple comparison tests. In the bilateral responses, the averaged activation latencies of the transitional cortex between the insula and the parietal operculum were not significantly different in both hemispheres. These results suggest that unilateral gustatory stimulation will activate the transitional cortex between the insula and the parietal operculum bilaterally in humans.

Taste Disorders in Acute Stroke

Background and Purpose— The aim of the study was to assess whether and how frequently patients with acute first-ever stroke exhibit gustatory dysfunction.

Methods— We performed a 1-year prospective observational study. Gustatory function was assessed using the standardized “taste strips” test. In addition, we assessed olfactory function, swallowing, stroke location, comorbidities, and the patients’ medication.

Results— A total of 102 consecutive patients were enrolled (45 female, 57 male; mean age, 63 years); 31 of them (30%) exhibited gustatory loss and 7 (6%) had lateralized impairment of taste function. Predictors of impaired taste function were male gender ( P =0.003), high National Institutes of Health Stroke Scale (NIHSS) score at admission ( P =0.009), coexisting swallowing dysfunction ( P =0.026), and a stroke of partial anterior circulation subtype (PACS) ( P =0.008). In particular, in hypogeusic patients the lesion was most frequently localized in the frontal lobe ( P =0.009). Follow-up examinations in 14 patients indicated improvement of taste sensitivity.

Conclusion— Taste disorders after stroke are frequent. A significant association was found for male gender, high NIHSS score, swallowing disorder, and PACS, particularly in the frontal lobe. Generally, taste disorders after stroke seem to have a good prognosis.

The central autonomic nervous system: conscious visceral perception and autonomic pattern generation

The overall organization of the peripheral autonomic nervous system has been known for many decades, but the mechanisms by which it is controlled by the central nervous system are just now coming to light. In particular, two major issues have seen considerable progress in the past decade. First, the pathways that provide visceral sensation to conscious perception at a cortical level have been elucidated in both animals and humans. The nociceptive system runs in parallel to the pathways carrying visceral sensation from the cranial nerves and may be considered in itself a component of visceral sensation. Second, structures in the central nervous system that generate patterns of autonomic response have been identified. These pattern generators are located at multiple levels of the central nervous system, and they can be combined in temporal and spatial patterns to subserve a wide range of behavioral needs.

The cytoarchitecture of the adult human parabrachial nucleus: a Nissl and Golgi study

The parabrachial nucleus (PBN) plays important roles in numerous autonomic functions and in pain modulation. In different animal species, three main regions of the PBN have been identified: the m-PB, the l-PB, and the Kolliker-Fuse nucleus (KF). The KF has not been identified in humans. The present study used Nissl and Golgi-Cox material and morphoquantitative methods to investigate the cytoarchitectural organization of the adult human PBN, paying particular attention to neuronal features endowed with functional significance, i. e. the arborization of the neurons. The PBN neuron population is made up of elements which are heterogeneous in size, shape and dendritic arborization, and grouped into two regions, the lateral and medial PBN (l- and m-PB). It has been suggested that some large sized neurons located in the ventral region of the m-PB might be the counterpart of the KF. In the m-PB the fusiform neurons are the most numerous cells; in the l-PB the multipolar neurons prevail, and are particularly numerous in the dorsal l-PB. Since the dendritic arborization is generally the main target of afferent projections to a neuron, it is possible that the l-PB, and in particular its dorsal region, might be the main site for the endings of afferences to the human PBN.

Gustatory disturbance due to cerebrovascular disorder

OBJECTIVES

Review three cases of unilateral gustatory disturbance due to central lesions caused by cerebrovascular disorders, describe clinical findings and the results of taste examinations, and discuss the central gustatory pathways in humans.

STUDY DESIGN

Retrospective review of three gustatory disturbance cases due to cerebrovascular disorders. Additional review of 12 cases with central gustatory disturbance that have been reported.

METHODS

Central lesions of three cases were examined by magnetic resonance imaging or computed tomography scan. Electrogustometry and a filter paper disk assay using taste solutions were performed in these cases for each of the bilateral gustatory nerves.

RESULTS

In one case of pontine infarct, gustatory disturbance ipsilateral to the lesion was found, and in one case of thalamic infarct and one case of internal capsular infarct, gustatory disturbance contralateral to the lesion was observed.

CONCLUSIONS

Fifteen cases of unilateral gustatory disturbance due to central lesions, including the present cases, have been reported to our knowledge. Examination of these cases strongly suggested that the central gustatory pathways in humans ascend ipsilaterally from the solitary nucleus of medulla oblongata to the pons, and from the pons, cross to a higher position in midbrain and reach the thalamus contralaterally.

Localization of the gustatory pathway in the human midbrain

The localization of the secondary gustatory pathway in the human brainstem still remains uncertain. Here we report two patients with small vascular lesions in the unilateral midbrain tegmentum who presented with taste disturbance on the ipsilateral side of the tongue. In both cases, the dorsomedial mesencephalic tegmental region lateral to the oculomotor nucleus, including the central tegmental tract and the ventral part of the periaqueductal gray, was involved commonly in the lesions. The secondary gustatory pathway arising from the nucleus of the solitary tract appears to run rostrally, without crossing, to the ipsilateral thalamic nucleus through the dorsomedial part of the tegmental region at the rostral level of the midbrain.

The cytoarchitectural organization of the human parabrachial nuclear complex

The cytoarchitecture of the parabrachial nuclear complex in adult and infant human brain was studied. Lying in the dorsolateral pontine tegmentum, surrounding the superior cerebellar peduncle, this complex in several mammalian species is interconnected with autonomic centers in the medulla oblongata, hypothalamus, thalamus, amygdala, and cortex. Postmortem human brain tissue was stained for Nissl substance and fiber tracts with a modified Klüver-Barrera stain. Examination of the tissue revealed distinct medial and lateral subdivisions, similar to descriptions in other mammals. The organization of the parabrachial complex was more obvious in the infant tissue than the adult, because of less myelination of the large fibers of the adjacent superior cerebellar peduncle and lateral lemniscus. Within the lateral parabrachial nucleus, 7 distinct subgroups of cells were identified on the basis of their location and staining characteristics. These were named according to their location in the parabrachial complex and were the central, superior, interstitial, dorsal, dorsolateral, lateral, and ventrolateral. Two subnuclei were found within the medial parabrachial nucleus, the dorsomedial and ventromedial. Additionally, neurons within the superior cerebellar peduncle were arranged in cellular bridges running between the lateral and medial subdivisions. These data suggest that the parabrachial complex in the human brain is organized cytoarchitecturally, similar to other mammals, however, this organization is obscured with increasing myelination in adulthood.

Neuropeptides are present in projection neurones at all levels in visceral and taste pathways: from periphery to sensory cortex

Using combined immuno-staining and retrograde tracing techniques many of the ascending visceral and taste pathways within the rat central nervous system have been shown to be composed of a variety of neuropeptide and catecholamine synthesizing enzyme containing neurones. The pathway we examined extended from the periphery to sensory cortex and included: the nodose ganglion (periphery)----solitary nucleus (medulla)----parabrachial nucleus (pons)----ventral posterior medial nucleus (thalamus)----visceral and taste sensory areas (cortex). In the solitary nucleus of the medulla many neuronal cell bodies could be shown to be both immuno-positive for one of 6 neuropeptides including avian pancreatic peptide (APP), cholecystokinin (CCK), enkephalin (ENK), neurotensin (NT), somatostatin (SOM) and substance P (SP) or the catecholamine synthesizing enzyme tyrosine hydroxylase (TOH) and to have a projection to the parabrachial nucleus of the pons. In the parabrachial nucleus of the pons many neuronal cell bodies could be shown to be immuno-positive for one of 5 neuropeptides (CCK, ENK, NT, SOM, SP) and have a projection to the ventral posterior medial nucleus of the thalamus. In the ventral posterior medial nucleus of the thalamus several neuronal cell bodies were shown to be immuno-positive for one of 3 neuropeptides (CCK, ENK, SOM) and project to the visceral and taste sensory cortex. This is the first report of neuropeptides being present in the projection neurones of any sensory system in the central nervous system and for the first time describes an entire set of putative neurotransmitters which extends from the periphery to the sensory cortex. From previous studies it also appears that in all cases examined the relevant receptors are present in these visceral and taste relay nuclei in order for the neuropeptide or catecholamine to produce an effect upon release. Comparisons between rat and other animals suggest that a similar organization of these visceral and taste pathways may also be present in other mammals including man. Functionally these neuropeptides containing projection neurones appear to be primarily involved in relaying visceral information rather than taste information. In this capacity activation of these neurones may produce such visceral sensations as malaise, well being, hunger, satiety or thirst.