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Dirk De Ridder

Publications and source records attributed to Dirk De Ridder.

27 records · Page 2Linked to original sources
PubMed2004

Identification of kit positive cells in the human urinary tract.

PURPOSE: Analogous to interstitial cells of Cajal in the bowel, functional important networks of interstitial cells could have a role in the complex mechanism of central and peripheral control of urinary tract function. Recently various reports mentioned the presence of interstitial cells in different parts of the urinary tract and in different species. Since important differences among species exist, we performed immunohistochemistry on fresh frozen human tissue to study the presence of interstitial cells in the human urinary tract. MATERIALS AND METHODS: A total of 65 tissue pieces from all levels of the urinary tract were obtained from 44 patients treated at our institution. Tissue was processed for immunohistochemistry immediately after removal. We performed immunohistochemistry for kit, connexin 43 and VRL1/TRPV2. RESULTS: Interstitial cells immunopositive for all 3 antibodies were seen beneath the urothelium and between smooth muscle cells in all tissue pieces with slight topographical differences. CONCLUSIONS: Together with morphological and functional data from other experiments these morphological data suggest that, as in the bowel, networks of interstitial cells might have an important role in the physiology and pathology of the urinary tract. They could be involved in pacemaking or have an integrating role through the modulation of neurotransmission and conduction of electrical impulses. Functional experiments are the next step to study these hypotheses.

Adolescent↗
PubMed2004

Functional anatomy of the human cochlear nerve and its role in microvascular decompressions for tinnitus.

OBJECTIVE: The functional anatomy (i.e., tonotopy) of the human cochlear nerve is unknown. A better understanding of the tonotopy of the central nervous system segment of the cochlear nerve and of the pathophysiology of tinnitus might help to ameliorate the disappointing results obtained with microvascular decompressions in patients with tinnitus. METHODS: We assume that vascular compression of the cochlear nerve can induce a frequency-specific form of hearing loss and that when the nerve is successfully decompressed, this hearing loss can recuperate. Thirty-one patients underwent a microvascular decompression of the vestibulocochlear nerve for vertigo or tinnitus. Preoperative audiograms were subtracted from postoperative audiograms, regardless of the surgical result with regard to the tinnitus and vertigo, because the hearing improvement could be the only sign of the vascular compression. The frequency of maximal improvement was then correlated to the site of vascular compression. A tonotopy of the cochlear nerve was thus obtained. RESULTS: A total of 18 correlations can be made between the site of compression and postoperative maximal hearing improvement frequency when 5-dB hearing improvement is used as threshold, 13 when 10-dB improvement is used as threshold. A clear distribution can be seen, with clustering of low frequencies at the posterior and inferior side of the cochlear nerve, close to the brainstem, and close to the root exit zone of the facial nerve. High frequencies are distributed closer to the internal acoustic meatus and more superiorly along the posterior aspect of the cochlear nerve. CONCLUSION: The tonotopic organization of the cisternal segment of the cochlear nerve has an oblique rotatory structure as a result of the rotatory course of the cochlear nerve in the posterior fossa. Knowledge of this tonotopic organization of the auditory nerve in its cisternal course might benefit surgeons who perform microvascular decompression operations for the vestibulocochlear compression syndrome, especially in the treatment of unilateral severe tinnitus.

Adult↗
PubMed2004

Magnetic and electrical stimulation of the auditory cortex for intractable tinnitus. Case report.

Tinnitus is a distressing symptom that affects up to 15% of the population for whom no satisfactory treatment exists. The authors present a novel surgical approach for the treatment of intractable tinnitus, based on cortical stimulation of the auditory cortex. Tinnitus can be considered an auditory phantom phenomenon similar to deafferentation pain, which is observed in the somatosensory system. Tinnitus is accompanied by a change in the tonotopic map of the auditory cortex. Furthermore, there is a highly positive association between the subjective intensity of the tinnitus and the amount of shift in tinnitus frequency in the auditory cortex, that is, the amount of cortical reorganization. This cortical reorganization can be demonstrated by functional magnetic resonance (fMR) imaging. Transcranial magnetic stimulation (TMS) is a noninvasive method of activating or deactivating focal areas of the human brain. Linked to a navigation system that is guided by fMR images of the auditory system, TMS can suppress areas of cortical plasticity. If it is successful in suppressing a patient's tinnitus, this focal and temporary effect can be perpetualized by implanting a cortical electrode. A neuronavigation-based auditory fMR imaging-guided TMS session was performed in a patient who suffered from tinnitus due to a cochlear nerve lesion. Complete suppression of the tinnitus was obtained. At a later time an extradural electrode was implanted with the guidance of auditory fMR imaging navigation. Postoperatively, the patient's tinnitus disappeared and remains absent 10 months later. Focal extradural electrical stimulation of the primary auditory cortex at the area of cortical plasticity is capable of suppressing contralateral tinnitus completely. Transcranial magnetic stimulation may be an ideal method for noninvasive studies of surgical candidates in whom stimulating electrodes might be implanted for tinnitus suppression.

Adult↗
PubMed2003

Interstitial cells in the human prostate: a new therapeutic target?

BACKGROUND: Interstitial cells have been described in different human organs, including gut and bladder. In the gut they function as pacemaker cells, generating slow wave potentials. Absence or defects in these cells result in motility disorders. In the bladder these cells express the vanilloid receptor and may contribute to the working mechanism of vanilloid therapy. Recently, slow wave potentials and interstitial cells were described in the guinea-pig prostate. In this study we describe the presence of interstitial cells in the human prostate gland. METHODS: We performed immunohistochemical staining for c-kit, vanilloid receptor (VR1), cannabinoid receptor (CB1) connexin43, and neurofilament on fresh frozen tissue from 14 prostatectomy specimens. RESULTS: A large number of cells with a stellate aspect were noticed under the basal layer of the prostatic duct system and in between the smooth muscle cells. They were immunoreactive for c-kit, VR1, and connexin43 but not to CB1 or neurofilament. CONCLUSIONS: There is evidence for interstitial cells in the human prostate. Taken together their topography and immunohistochemical characterization, the discovery of slow wave potentials in guinea pig prostate and the knowledge of interstitial cells in other organs, interstitial cells are likely to be involved in normal prostate physiology.

Action Potentials↗
PubMed2002

Is the root entry/exit zone important in microvascular compression syndromes?

OBJECTIVE: Microvascular compression syndromes such as trigeminal neuralgia, hemifacial spasm, and disabling positional vertigo involve an artery or vein compressing a cranial nerve. A cranial nerve is composed of a central nervous system (CNS) segment and a peripheral nervous system (PNS) segment separated by the root entry/exit zone (REZ). Although vascular compression can occur at any point along the cranial nerve, it has been generally assumed that only vascular contact at the REZ of the affected cranial nerve can cause symptoms. On the basis of personal surgical experience, we propose that vascular compression of the CNS segment alone causes symptoms. This has important repercussions for the future diagnosis and treatment of microvascular compression syndromes, especially the cochleovestibular compression syndrome. METHODS: For the anatomic study, four autopsy specimens and one surgical biopsy specimen of the vestibulocochlear nerve were microscopically and ultramicroscopically analyzed for structural differences between the CNS and PNS segments. For the clinical study, five patients with the clinical picture of cochleovestibular compression syndrome were treated by microsurgical decompression at the level of the CNS segment and not the REZ. One patient underwent reoperation for recurrent symptoms 4 years later, and a 4-mm vestibular neurectomy was performed at that stage. We performed an epidemiological analysis to demonstrate that the known incidences of trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia are related to the length of their respective CNS segments. RESULTS: Histological differences between the PNS and CNS segments suggest that the PNS segment is more resistant to compression. This was confirmed by neurophysiological data from intraoperative monitoring in posterior fossa surgery and experimental studies. We found a clear epidemiological correlation between the length of the CNS segment, which differed among cranial nerves, and the incidence of the microvascular compression syndrome. Successful decompression of the CNS segment in patients without compression at the REZ of the vestibulocochlear nerve for disabling positional vertigo provides clinical support for this hypothesis. CONCLUSION: The evidence we present supports the hypothesis that vascular compression syndromes arise from vascular contact along the CNS segment of the cranial nerves.

Blood Vessels↗
PubMed2002

Hemilingual spasm: a new neurosurgical entity? Case report.

Hemilingual spasm is a little-known movement disorder, presenting as intermittent paroxysmal involuntary contractions of half of the tongue muscles. The authors report a case of hemilingual spasm caused by an arachnoid cyst. After marsupialization of the cyst, the patient's symptoms immediately resolved. There has been no recurrence of hemilingual spasm during the follow-up period of more than 40 months.

Arachnoid Cysts↗
PubMed2002

Topography of the vanilloid receptor in the human bladder: more than just the nerve fibers.

PURPOSE: We determined the presence and distribution of vanilloid receptor-1 in the human bladder and confirmed or rejected previous findings of other groups that used indirect methods or vanilloid receptor-1 antibodies made by immunizing experimental animals. Also, we tested the reproducibility of results using commercially available antibodies against the N-terminus and C-terminus of the vanilloid receptor. MATERIALS AND METHODS: A total of 11 normal bladder tissue samples were obtained from cystectomy specimens and fresh frozen processed. Specimens were studied by immunohistochemistry and confocal laser microscopy using 3 vanilloid receptor-1 antibodies. Immunohistochemical co-localization studies for neurofilament, neuronal nitric oxide synthase and nerve growth factor were performed. RESULTS: Our results confirm the presence of vanilloid receptor-1 on nonmyelinated and myelinated nerve fibers. There was vanilloid receptor-1 immunoreactivity on smooth muscle cells but different sensitivities for the antibodies. There was immunoreactivity on interstitial cells located in the suburothelium and intermuscular septa of the muscularis. There was co-localization of neuronal nitric oxide synthase with interstitial cells but not with neurofilament. No co-localization was found for nerve growth factor and vanilloid receptor-1. CONCLUSIONS: Vanilloid receptor-1 is located on small unmyelinated and myelinated nerve fibers. In addition, vanilloid receptor-1 is also present on interstitial cells in the suburothelium. There is smooth muscle cell immunoreactivity but a difference in antibodies raised against the C-terminus and N-terminus. These data suggest that the current hypothesis about the mechanism of action of vanilloids is through blocking the afferent reflex arc must be revised and the function of interstitial cells deserves further attention.

Humans↗