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Biomedical subjects

P Picciotti

Publications and source records attributed to P Picciotti.

7 recordsLinked to original sources
PubMed2004

SPET assessment of auditory cortex stimulation and tonotopic spatial distribution in auditory brainstem implant.

Activation of the auditory cortex by multifrequency acoustic stimuli has been evaluated using Single Photon Emission Tomography in a case of auditory brainstem implant after activation of 6 and 11 electrodes. Before implantation, no activation of the auditory cortex has been observed after acoustic stimulation. Following auditory brainstem implant, the stimulation of 11 electrodes showed an activation value, in terms of blood flow increase, of the contralateral temporal cortex similar to that obtained with 6 electrodes (47.70 vs. 43.76%), but a significantly stronger activation was present in the contralateral parietal region (29.59 vs. 14.73%), in the homolateral temporal area (22.02 vs. 10.46%) and, especially, in the homolateral parietal zone (16.6 vs. 4.33%). The strongest activation in the contralateral temporal cortex was detected in the sagittal tomogram at 26.25 mm from the midline, that is in the areas where high frequencies are projected, both with 6 and 11 active electrodes. The medio-lateral auditory cortex, where the middle and lower frequencies are projected, showed an overall lower activation which was however significantly lower with 6-electrode stimulation. Stimulation of the surface of cochlear nuclei determines mainly an activation of the high frequency domain, independently of the electrodes number. This finding may explain the better results of cochlear implants in comparison with auditory brainstem implant and could justify the use of needle electrodes in auditory brainstem implant. In conclusion, Single Photon Emission Tomography can be considered useful in evaluating auditory brainstem implant placement and function. It is also able to define the effectiveness of acoustic stimulation, the degree and tonotopic spatial distribution of auditory cortex activation.

Acoustic Stimulation↗
PubMed2003

Can chronic nasal obstruction cause dysfunction of the paratubal muscles and otitis media? An experimental study in developing Wistar rats.

OBJECTIVE: To quantitatively analyze modifications of the paratubal muscles in developing Wistar rats following nasal obstruction. MATERIAL AND METHODS: Twenty-four Wistar rats were used. Twelve were examined at 6, 8 and 12 weeks after birth and were considered normal controls. The nostrils of the remaining 12 rats were bilaterally obstructed by means of a synthetic resin 28 days after birth. The animals were sacrificed at either 2, 4 or 8 weeks after nostril occlusion. Serial sections were made in the dorsoventral plane and stained with hematoxylin-eosin. Four 5 x 5 microm2 areas, selected within the paratubal muscles, were histologically analyzed and the number of muscular fibers was counted manually. RESULTS: The number of tensor veli palatini muscle fibers progressively decreased in the obstructed rats compared with age-matched normal controls and in those that had been obstructed for 4 and 8 weeks these reductions were statistically significant. CONCLUSION: The correct development of the paratubal muscles seems to be linked to physiological nasal breathing and is negatively affected by oral breathing.

Animals↗
PubMed2001

Vestibulo-ocular reflex modification after virtual environment exposure.

Immersion in an illusory world is possible by means of virtual reality (VR), where environmental perception is modified by artificial sensorial stimulation. The application of VR for the assessment and rehabilitation of pathologies affecting the vestibular system, in terms of both diagnosis and care, could represent an interesting new line of research. Our perception of reality is in fact based on static and dynamic spatial information perceived by our senses. During head movements in a virtual environment the images on the display and the labyrinthine information relative to the head angular accelerations differ and therefore a visuo-vestibular conflict is present. It is known that mismatches between visual and labyrinthine information may modify the vestibulo-oculomotor reflex (VOR) gain. We studied the post-immersion modifications in 20 healthy subjects (mean age 25 years) exposed to a virtual environment for 20 min by wearing a head-mounted display. VOR gain and phase were measured by means of harmonic sinusoidal stimulation in the dark before, at the end of and 30 min after VR exposure. A VOR gain reduction was observed in all subjects at the end of VR exposure which disappeared after 30 min. Our data show that exposure to a virtual environment can induce a temporary modification of the VOR gain. This finding can be employed to enable an artificial, instrumental modification of the VOR gain and therefore opens up new perspectives in the assessment and rehabilitation of vestibular diseases.

Adult↗
PubMed2001

Postural control and glycerol test in Ménière's disease.

Ménière's disease is a clinical disorder, characterized by fluctuating hearing loss, recurrent spontaneous episodic vertigo, tinnitus and aural fullness, which may be defined as the idiopathic syndrome of endolymphatic hydrops. The most important test for diagnosis of Ménière's disease is the glycerol test. This is a simple and rapid method and several authors have confirmed its efficiency for identifying endolymphatic hydrops. This test provides information on the cochlear response to the osmotic changes produced by glycerol in the inner ear, whereas modifications in the vestibular labyrinth are usually not evaluated. The aim of this study was to evaluate the effects of glycerol on postural control during attacks of Ménière's disease, and to correlate this data with data on cochlear function. After the glycerol test, an improvement in postural control was recorded in 70% of patients, with all patients reporting a recovery of vertigo. The impairment of postural control during endolymphatic hydrops could be related to a pressure increase in the labyrinth, which interferes with the normal dynamics of the endolymph, and a rapid functional recovery could occur during an osmotic depletion. Dynamic posturography improves the sensitivity of the glycerol test and may therefore be useful in the diagnosis and staging of Ménière's disease.

Adult↗
PubMed2000

Postural control in horizontal benign paroxysmal positional vertigo.

Sixteen patients affected by benign paroxysmal positional vertigo of the horizontal semicircular canal (BPPV-HSC) were investigated by means of dynamic posturography (DP) and during bithermal caloric stimulation. Data were compared to data from 40 patients with benign paroxysmal positional vertigo of the posterior semicircular canal (BPPV-PSC) and 20 healthy controls. No postural deficit was observed before or after a liberative Lempert's manoeuvre when patients were compared to control subjects. BPPV-PSC postural scores were significantly impaired compared to scores from the BPPV-HSC group. A residual significant postural impairment was also observed after a successful liberative manoeuvre in the BPPV-PSC group. Electronystagmographic recordings before recovery revealed significant hypoexcitability of the affected ear in 8/16 patients of the BPPV-HSC group. After the liberative manoeuvre, a symmetric bilateral response to caloric stimulation was recorded in all patients. Three main conclusions can be drawn from the present data. First, disorders of the horizontal semicircular canal do not change postural control. Second, dynamic posturography can detect the postural imbalance due to posterior semicircular canal dysfunction even after resolution of paroxysmal vertigo attacks. Third, utricular dysfunction can be ruled out as a cause of the residual postural deficit observed in BPPV-PSC patients. Therefore the recovery delay observed even 1 month after the liberative manoeuvre in the BPPV-PSC-group might be due to the persistence of small amounts of residual debris in the canal, to paralysis of ampullar receptors, or to the time needed for central vestibular re-adaptation.

Caloric Tests↗
PubMedDate not supplied

Age-related histopathological changes of the stria vascularis: an experimental model.

The stria vascularis (SV) of 3-, 8- and 18-month-old C57 mice was examined with a fluorescence microscope in order to evaluate the capillary density and vessel diameter. The capillary density was significantly reduced in 18-month-old mice compared to 3-month-old (P<0.001) and to 8-month-old (P<0.001) mice. The difference between 3- and 18-month-old mice was significant for the basal, middle and apical cochlear turns, while the difference between 8- and 18-month-old mice was significant only for the middle and basal turns. Vessel diameter within the whole SV was significantly reduced in all turns in 18-month-old mice (P<0.01) versus 3-month-old animals, while vessel diameter was reduced only in the basal turn in 8-month-old versus 3-month-old mice. The results suggest that previously described histopathological changes in the organ of Corti of C57 mice may be related to modifications of strial capillaries.

Age Factors↗