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PubMed2001

Comparison of elderly nonfallers and fallers on performance measures of functional reach, sensory organization, and limits of stability.

BACKGROUND: Previous literature indicates that balance impairment is a primary risk factor in the occurrence of falls, which has led clinicians to develop gross standardized balance assessment tests to distinguish elderly nonfallers from fallers. The purpose of this study was to compare functional reach (FR), limits of stability (LOS), and sensory organization among elderly nonfallers and fallers. METHODS: FR was examined in 15 elderly nonfallers and 10 idiopathic fallers who were at least 60 years of age. Forceplate measures from the NeuroCom Smart Balance Master system, which included the LOS test and the sensory organization test (SOT), were used to quantify limits of stability and balance. Associations among the three tests were examined. RESULTS: There was no significant difference in mean FR distance between elderly nonfallers and fallers using the functional reach test. FR distance did not correlate with anterior displacement on the LOS test. There was a significant difference in mean composite score on the SOT between nonfallers and fallers as well as a significant positive correlation between the SOT composite score and anterior displacement on the LOS test for fallers. CONCLUSIONS: The results suggest that FR measures do not differentiate nonfallers from fallers. In contrast, this study demonstrates that using the SOT protocol could differentiate elderly nonfallers from fallers for balance impairment. Caution should be used when interpreting information from the FR test in determining a balance-impaired population.

Accidental Falls↗
PubMed1993

Sensory and pain thresholds to orofacial argon laser stimulation in patients with chronic burning mouth syndrome.

OBJECTIVE: Psychophysical assessments of orofacial sensory function were performed in order to investigate neurophysiological aspects of the burning mouth syndrome (BMS). DESIGN: Sensory and pain thresholds to brief argon laser stimulation were determined on six test regions, which included the tip of tongue, the lower lip mucosa and skin, the buccal mucosa, the anterior hard palate, and the dorsum of the hand. SETTING: The experimental examination was performed at the Pain Clinic Unit at the Royal Dental College. PATIENTS: Twenty-three elderly denture-wearing patients diagnosed as suffering from BMS were studied, and a control group included 23 age-, sex-, and denture-matched subjects. The obtained thresholds were compared between groups. RESULTS: Sensory thresholds were significantly higher and ratios between pain and sensory thresholds significantly lower in patients with BMS on all the tested regions. Pain thresholds were significantly elevated on the lower lip skin, the anterior hard palate, and the hand in patients with BMS. At sensory threshold level, a faint pinprick perception was often reported by patients with BMS contrary to a perception of warmth described by control subjects. The intraregional variations in sensory and pain thresholds on the hard palate, the lower lip mucosa, and on the skin were similar in both groups, but differences occurred in sensory thresholds on the tongue in patients with BMS. CONCLUSIONS: The presence of abnormal prepain perceptions and disturbances in the perception of nonnociceptive and nociceptive thermal stimuli applied on both pain-affected and normal regions suggest a perceptual deficit unrelated to specific pathophysiological mechanisms in BMS. However, it appears that a psychological explanation of BMS should be used cautiously, as the present results suggest alterations in sensory function.

Aged↗
PubMed2002

Discontinuous myelotomy: an alternative to standard myelotomy in the surgical treatment of intramedullary spinal cord tumours.

BACKGROUND: Myelotomy is an essential step for the removal of intramedullary tumours. Often, this manoeuvre requires division of large vessels surfacing the midline, contributing to the development of postoperative sensory deficits. We developed a technique of discontinuous myelotomy to preserve the integrity of these large spinal cord vessels. METHODS: Over a three-year period, we approached 20 intramedullary astrocytomas through a posterior myelotomy consisting of two separate incisions one above and the other below the midline vessel. The tumour was removed using the Cavitron ultrasound aspirator (CUSA), through either incision. Tumour underlying the bridging area between the two incisions was successfully removed through an oblique view. FINDINGS: We retrospectively analysed the clinical outcome in terms of sensory function. Follow-up examinations showed that up to 70% of the patients had their sensory function unchaged. 5 (20%) patients experienced a permanent worsening of their deficits, involving superficial and deep sensation in cases 1 and 4, respectively. Two (10%) patients showed significant improvement. INTERPRETATION: Discontinuous myelotomy is a viable technical option whenever the presence of large vessels on the median raphe would make the standard midline myelotomy unsafe.

Astrocytoma↗
PubMed1988

Avoidable complications of resection of major nerve trunk neurofibromas and schwannomas.

Neurofibromas and schwannomas of major nerve trunks may present with a variety of symptoms and other clinical concerns. These include: (1) the question of malignancy, (2) pain and paresthesias, (3) cosmesis, and (4) symptoms and impending problems related to compression of adjacent structures. For these reasons, patients with neurofibromas and schwannomas may have valid reasons for surgery. Precise delineation of the anatomical relationships of the lesions and their location within peripheral nerve trunks is essential for decision making regarding when and how they should be excised; judgement regarding risks vs. benefits must be made carefully. Microsurgical dissection can be utilized to remove some nerve trunk lesions with preservation of most or all motor and sensory functions. An important goal in resecting benign lesions is to avoid sacrificing major motor and sensory functions. Three cases are presented to illustrate these concepts: 2 cases with significant motor loss following partial resection of large neurofibromas involving peripheral nerve trunks and 1 case with a large femoral nerve neurofibroma excised from the nerve trunk with microsurgical dissection, leading to relief of symptoms and complete preservation of motor function.

Adult↗
PubMed2001

Direct clinical evidence for spinal hyperalgesia in a patient with irritable bowel syndrome.

OBJECTIVE: Our objective was to evaluate GI motor and sensory function and spinal cord testing in a patient with severe irritable bowel syndrome. METHODS: A patient is described who underwent an extensive assessment of GI motor and sensory function including transit studies, colonic and rectal barostat studies, sensory and manometric studies of the small bowel, and colon and anorectal physiology testing. The patient also underwent testing with spinal cord stimulation and spinal drug delivery as part of a pain management assessment. RESULTS: The viscerosomatic referral pain pattern resulting from rectal distention was consistent with spinal hyperalgesia. The patient underwent testing for spinal cord stimulation and spinal drug delivery. CONCLUSION: This novel finding provides direct clinical evidence for the presence of spinal hyperalgesia in a patient with irritable bowel syndrome, consistent with the existing indirect clinical evidence and animal data.

Abdominal Pain↗
PubMed1990

Manovolumetric and sensory characteristics of the ileoanal J pouch compared with healthy rectum.

Pouch volume, motility, sensory function and integrated pouch-anal mechanisms during graded isobaric distension of the pouch were prospectively studied in 67 patients with a J pouch-anal anastomosis. The findings were related to functional outcome. Thirty-six normal controls were studied for comparison. In contrast with normal rectum, the ileal pouch exhibited pronounced motility, and pouch contractions were frequent even at a high distension pressure. The presence of high pressure motility was associated with a poor functional outcome. The threshold pressure and threshold volume for eliciting first sensation of filling and urge to defaecate were significantly higher in the ileal pouch. The pressure threshold levels were not related to the functional outcome. Sphincter inhibition on pouch distension reappeared in 25 per cent of the patients. The distension pressure required to elicit the inhibition was considerably higher than in the control subjects. The functional result was similar irrespective of whether sphincter inhibition was present or not. The motor and sensory function of this artificial setting appear to be controlled by nervous mechanisms that are different from those in the healthy anorectum.

Adenomatous Polyposis Coli↗
PubMed1987

Neurobiological studies of sensory gating in schizophrenia.

The sensory disturbance in schizophrenia is often described as an inability to filter out extraneous noise from meaningful sensory inputs. The neurobiological basis of this inability to filter has been examined using auditory evoked potentials, which are computerized averages of the brain's electrical response to sound. The sounds are presented in pairs to test the ability of the brain to inhibit, or gate, its response to a repeated stimulus. Schizophrenic patients lack the ability to gate the neuronal response shown by a particular wave, the P50 wave. The measurement of this deficit in human subjects and the exploration of its neurobiology in animals has produced evidence about several issues in the pathophysiology of schizophrenia: (1) the role of dopamine in improvement of sensory function in schizophrenic patients treated with neuroleptic drugs, (2) the interaction between familial or genetic deficits in sensory functioning in schizophrenic patients and possible abnormalities in dopamine metabolism, and (3) a mechanism by which noradrenergic hyperactivity in mania and other psychiatric illnesses might mimic some pathophysiological deficits in schizophrenia.

Antipsychotic Agents↗
PubMed2005

The C. elegans homologs of nephrocystin-1 and nephrocystin-4 are cilia transition zone proteins involved in chemosensory perception.

Nephronophthisis (NPH) is a cystic kidney disorder that causes end-stage renal failure in children. Five nephrocystin (nephrocystin-1 to nephrocystin-5) genes, whose function is disrupted in NPH patients, have been identified and data indicate they form a complex at cell junctions and focal adhesions. More recently, the nephrocystin proteins have also been identified in cilia, as have multiple other cystic kidney disease related proteins. Significant insights into this cilia and cystic kidney disease connection have come from analyses in simpler eukaryotic organisms such as Caenorhabditis elegans. In this regard, we became interested in the C. elegans homologs of nephrocystin-1 (nph-1) and nephrocystin-4 (nph-4) from a database screen to identify genes coordinately regulated by the ciliogenic transcription factor DAF-19. Here we show that expression of nph-1 and nph-4 is DAF-19 dependent, that their expression is restricted to ciliated sensory neurons, and that both NPH-1 and NPH-4 concentrate at the transition zones at the base of the cilia, but are not found in the cilium axoneme. In addition, NPH-4 is required for the localization of NPH-1 to this domain. Interestingly, nph-1 or nph-4 mutants have no obvious cilia assembly defects; however, they do have abnormalities in cilia-mediated sensory functions as evidenced by abnormal chemotaxis and lifespan regulation. Our data suggest that rather than having a ciliogenic role, the NPH proteins play an important function as part of the sensory or signaling machinery of this organelle. These findings suggest that the defects in human NPH patients may not be the result of aberrant ciliogenesis but abnormal cilia-sensory functions.

Animals↗
PubMed2005

The role of semantic distance in category-specific impairments for living things: evidence from a case of semantic dementia.

In this paper, we describe a patient (LI) suffering from semantic dementia who showed a category-specific naming impairment for living things over and above the effects of several nonsemantic confounding variables. We investigated the characteristics of LI's impairment to address the following three issues raised in three different accounts of category-specific impairments: (i) the role of an imbalance in the loss of sensory compared to nonsensory features (assumed by the Sensory Functional Theory [Warrington, E. K., & Shallice, T. (1984). Category-specific semantic impairments. Brain, 107, 829-859]); (ii) the role of cross domain differences in Feature Correlation (assumed by the Conceptual Structure Account [Moss, H., Tyler, L. K., & Devlin, J. T. (2002). The emergence of category-specific deficits in a distributed semantic system. In: E. M. E. Forde & G. W. Humphreys (Eds.), Category Specificity in Brain and Mind (pp. 115-147). New York: Psychology Press]); (iii) the role of semantic distance (proposed by Cree and McRae [Cree, G. S., & McRae, K. (2003). Analyzing the factors underlying the structure and computation of the meaning of chipmunk, cherry, chisel, cheese, and cello (and many other such concrete nouns). Journal of Experimental Psychology: General, 132, 163-201]). We found that semantic distance was the only factor causally linked to LI's poorer performance on living things. In fact, her naming performance was less accurate on items that had many semantic neighbours, which is typical of living things. On the contrary, a feature listing task revealed that the features available to LI were not predicted by their level of correlation, as expected by the Conceptual Structure Account. Finally, at variance with the Sensory Functional Theory, although LI quoted sensory features less accurately than nonsensory ones, this did not give rise to a disproportionate loss of semantic features in the living domain.

Anomia↗
PubMedDate not supplied

Effect of treatment with losartan on cardiovascular autonomic and large sensory nerve fiber function in individuals with diabetes mellitus: a 1-year randomized, controlled trial.

This study evaluated the effect of losartan, an angiotensin II receptor antagonist, on cardiovascular autonomic function and large sensory nerve fiber function in individuals with diabetes mellitus. In a double-blind placebo-controlled trial, individuals were randomly assigned to treatment with a daily oral dose of 50-mg losartan (n=24) or placebo (n=20) for 12 months. Tests of cardiovascular autonomic function (i.e., RR-variation during deep breathing and the Valsalva maneuver) and of large sensory nerve fiber function (i.e., vibratory thresholds) were measured at baseline and at 12 months. No significant difference at baseline was found for duration of diabetes, glycemic control, blood pressure, or body mass index (BMI) between the two groups. After 12 months, the decline in RR-variation that occurs over time appeared to be less for those taking losartan. There was, however, no statistically significant change in the results for any of the tests of cardiovascular autonomic function or vibratory thresholds between the groups. Multivariate analyses in the losartan study group revealed an independent association of duration of diabetes, change in (reduced) systolic blood pressure (SBP), and improved vibratory thresholds. This association was particularly noted for women. Pharmacologic agents may affect cardiovascular autonomic function by favorable or detrimental changes in the electrophysiology of the heart. The results of this study indicate that, although losartan may have slowed the normal decline in RR-variation, it did not result in any significant improvement in cardiovascular autonomic nerve fiber function. An association of vibratory thresholds and SBP was observed.

Adult↗
PubMed1993

Sudomotor skin responses to brain stimulation do not depend on nerve sensory fiber functionality.

Evaluation of sudomotor innervation to the limbs was performed via electrical stimulation of the median nerve at the wrist and transcranial magnetic stimulation of the brain. Sympathetic skin responses (SSRs) from the palms and the soles were recorded in a patient suffering from a form of predominantly sensory neuropathy. Motor responses to nerve stimulation were present, even if with slower than normal conduction velocity. However, median, ulnar and sural nerve sensory potentials were absent. SSRs to median nerve stimulation at the wrist were missing on palms and soles. By contrast, during brain stimulation of the hand motor area with magnetic impulses, SSRs were reliably identifiable at all recording sites. It is hypothesized that SSRs to mixed nerve stimulation need normal functionality of afferent fibers, while those to brain stimulation can be elicited without any sensory information from the limbs.

Brain↗
PubMed2006

Complete functional characterization of sensory neurons by system identification.

System identification is a growing approach to sensory neurophysiology that facilitates the development of quantitative functional models of sensory processing. This approach provides a clear set of guidelines for combining experimental data with other knowledge about sensory function to obtain a description that optimally predicts the way that neurons process sensory information. This prediction paradigm provides an objective method for evaluating and comparing computational models. In this chapter we review many of the system identification algorithms that have been used in sensory neurophysiology, and we show how they can be viewed as variants of a single statistical inference problem. We then review many of the practical issues that arise when applying these methods to neurophysiological experiments: stimulus selection, behavioral control, model visualization, and validation. Finally we discuss several problems to which system identification has been applied recently, including one important long-term goal of sensory neuroscience: developing models of sensory systems that accurately predict neuronal responses under completely natural conditions.

Animals↗
PubMed2005

Improved tracking of time-varying encoding properties of visual neurons by extended recursive least-squares.

Traditional approaches to characterizing the transformation from stimulus to response in sensory systems assume both stationarity of the stimulus and time-invariance of the stimulus/response mapping. However, recent studies of sensory function under natural stimulus conditions have demonstrated important features of neural encoding that are in violation of these assumptions. Many sensory neurons respond to changes in the statistical distribution of the stimulus that are characteristic of the natural environment with corresponding changes in their encoding properties. In this paper, an extended recursive least-squares (ERLS) approach to adaptive estimation from stimulus/response observations is detailed. The ERLS approach improves the tracking ability of standard RLS approaches to adaptive estimation by removing a number of assumptions about the underlying system and the stimulus environment. The ERLS framework also incorporates an adaptive learning rate, so that prior knowledge of the relationship between the stimulus and the adaptive nature of the system under investigation can be used to improve tracking performance. Simulated and experimental neural responses are used to demonstrate the ability of the ERLS approach to track adaptation of encoding properties during a single stimulus/response trial. The ERLS framework lends tremendous flexibility to experimental design, facilitating the investigation of sensory function under naturalistic stimulus conditions.

Action Potentials↗
PubMed2002

Usefulness of somatosensory evoked magnetic field dipole measurements by magnetoencephalography for assessing spinal cord function.

OBJECT: Objective assessment of sensory function disorders is difficult. In the present study, the authors investigated the possibility of assessing cervical myelopathy-induced sensory disorders by using magnetoencephalography (MEG) to measure somatosensory evoked magnetic fields (SSEMFs). METHODS: In 12 patients with cervical myelopathy, SSEMFs were measured before and after surgery by using a 160-channel helmet-type MEG system to stimulate the median nerve, and the intensity and latency of N20m (first response occurring 20 msec after stimulation) were then determined. Additionally, the severity of the sensory disorder was assessed before and after surgery by obtaining sensory scores determined using the Neurosurgical Cervical Spine Scale. Furthermore, in 11 healthy individuals (control group), the intensity and latency of N20m were measured in the same fashion. Analysis of the results showed that the preoperative intensity of N20m in the 12 patients with cervical myelopathy was significantly lower than that demonstrated in the control patients (p < 0.005, Student t-test). In addition, of six patients in whom sensory scores improved postoperatively, there were significant increases in the intensity of N20m (p < 0.005, paired t-test). Furthermore, there was a significant correlation between sensory scores and dipole intensity (p < 0.001, Spearman correlation coefficient by rank test). CONCLUSIONS: Somatosensory evoked magnetic field measurements determined by MEG are useful in objectively and noninvasively assessing sensory disorders caused by cervical myelopathy.

Adult↗
PubMed1999

Excitatory projections from the anterior hypothalamus to periaqueductal gray neurons that project to the medulla: a functional anatomical study.

The present study was designed to investigate the organization of excitatory projections from regions of the anterior hypothalamus that are known to co-ordinate autonomic and sensory functions to medullo-output neurons in the periaqueductal gray. The induction of Fos protein was used to identify neurons in the periaqueductal gray that were activated synaptically by chemical stimulation at sites in the anterior hypothalamus from which either increases or decreases in arterial blood pressure were evoked (pressor sites and depressor sites, respectively). This was combined with retrograde tracing using fluorescent latex microspheres from sites in the medulla. When compared to control animals, neuronal activation at pressor sites in the anterior hypothalamus evoked Fos-like immunoreactivity in significantly more neurons in all but one sub-division of the periaqueductal gray (P at least < 0.05). The majority of Fos-positive neurons following a pressor response were located in the caudal half of the periaqueductal gray where significantly more neurons contained Fos-like immunoreactivity in lateral than in any other sub-division (P < 0.01). In all but two of 14 subdivisions of the periaqueductal gray, the numbers of neurons that expressed Fos-like immunoreactivity following stimulation at depressor sites in the anterior hypothalamus were not significantly different from controls. When neuronal activation at pressor or depressor sites in the anterior hypothalamus was combined with retrograde tracing from the rostral ventrolateral medulla, nucleus raphe magnus and/or nucleus raphe obscurus the majority of double-labelled neurons were located in the caudal half of the periaqueductal gray. Comparisons between the numbers of double-labelled neurons that resulted from different combinations of hypothalamic and medullary injection sites revealed that neuronal activation at pressor sites in the anterior hypothalamus combined with retrograde tracing from the rostral ventrolateral medulla resulted in the greatest numbers of double-labelled neurons. The identification of double-labelled neurons indicates that medullo-output neurons in the periaqueductal gray receive excitatory inputs predominantly from pressor compared to depressor sites in the anterior hypothalamus. These results are discussed in relation to the roles of the different longitudinal columns of the periaqueductal gray, and the organisation of their projections to the medulla, in the co-ordination of autonomic and sensory functions.

Animals↗
PubMedDate not supplied

Functional abnormalities of the cervical cord and lower medulla and their effect on pain: observations in chronic pain patients with incidental mild Chiari I malformation and moderate to severe cervical cord compression.

OBJECTIVE: Abnormalities of central sensory processing may play a role in the pathogenesis of chronic pain. The Chiari I malformation is a congenital hindbrain anomaly characterized by protrusion of the cerebellar tonsils into the upper cervical canal, with variable effects on the lower brain stem and cervical cord. The purpose of this study was to compare sensory function and pain among patients with chronic pain who had these disorders incidentally diagnosed, to assess the effect on pain in these patients in comparison with those without central nervous system disease. DESIGN: Retrospective study in which pain, mood, and sensory function in 32 patients with chronic pain who had mild Chiari I malformation were compared with that in 53 patients with chronic pain who had moderate to severe compression of the cervical spinal cord and 52 patients with chronic pain who had no apparent central nervous system disorder. Data had been collected previously as part of standard clinical assessments, including clinical neurological examinations, quantitative sensory testing, pain drawings, and psychometric testing with the Symptom Checklist 90. PATIENTS: All subjects were patients of a hospital-based pain management practice who had been accepted for treatment over a 5-year period. RESULTS: Both the Chiari I and cervical compression groups had long tract signs evident on clinical neurological examination. Quantitative sensory testing indicated elevations in the trigeminal territory among patients with Chiari I malformation and on the neck, hands, and feet in both the Chiari I and cervical compression groups. The extent of pain and mood disturbance was greatest in the Chiari I group and least in the group with no central nervous system disorder. Complex regional pain syndrome, fibromyalgia, and temporal mandibular joint disorder were more common among the Chiari I malformation group than among the other groups. CONCLUSIONS: Quantitative sensory analysis indicates sensory dysfunction associated with Chiari I malformation and cervical cord compression. The pattern of sensory abnormality is consistent with medullary dysfunction among the patients with Chiari I malformation and cervical cord dysfunction among cord compression patients. There were differences in the types and extent of pain and the associated disorders of mood observed among the cohorts defined above. These differences may be partly due to the presence and location of central sensory dysfunction.

Adult↗
PubMedDate not supplied

Neurosensory testing of the medial calcaneal and medial plantar nerves in patients with plantar heel pain.

Eighty-two patients with a chief complaint of plantar heel pain were evaluated for sensory abnormalities within the cutaneous distribution of both the medial calcaneal nerve and the medial plantar nerve, using quantitative neurosensory testing with a pressure-specified sensory device. The results showed that 22.68% of the patients displayed isolated abnormal sensory function within the distribution of the medial calcaneal nerve, whereas 49.48% of the patients displayed abnormal function within the distribution of both the medial calcaneal and the medial plantar nerves. Thus, 72.17% of the patients displayed abnormal sensory function within the distribution of the medial calcaneal nerve. Statistical analysis of the results, using the Pearson chi-square statistic and odds ratio, indicated that a significant percentage of patients with plantar heel pain, even early in the clinical course of plantar heel pain, display abnormal sensibility within the branches of the posterior tibial nerve, and specifically, within the distribution of the medial calcaneal nerve (P <.0008) and the medial plantar nerve (P <.0001).

Adult↗