Biomedical subjects

B Giannoni

Publications and source records attributed to B Giannoni.

4 recordsLinked to original sources

PubMed1999

Caloric stimulation of ampullar receptors: a new method to produce mechanically-evoked responses in frog semicircular canals.

A microthermistor positioned close to the exposed posterior semicircular canal in isolated labyrinth preparations of the frog was used to stimulate the sensory organ. Our results indicated that, depending on the position of the heater, the induced endolymphatic convection currents may result in either excitatory or inhibitory cupular deflections and thus in a modulation of ampullar receptor resting activity. Other possible thermal-dependent mechanisms, such as a direct action of the stimulus on vestibular sensors or endolymphatic volume changes, had, in the present experimental conditions, a minor role. Caloric stimulation could therefore represent a novel method to stimulate the semicircular canals 'in situ'.

Animals↗

PubMed1999

Effects of caloric stimuli on frog ampullar receptors.

The observation that caloric nystagmus can be evoked even in microgravity conditions argues against Barany's convective theory. To justify this result, gravity-independent mechanisms (mainly endolymphatic volume changes and direct action of the temperature on vestibular sensors) are believed to contribute to caloric-induced activation of vestibular receptors. To define the importance of both gravity-dependent and gravity-independent mechanisms, the posterior semicircular canal of the frog was thermally stimulated by a microthermistor positioned close to the sensory organ. The stimulus produced a gravity-dependent transcupular pressure difference that, depending on the position of the heater, could result in either excitation or inhibition of ampullar receptor sensory discharge. When the heater was positioned on the ampulla, or when the canal rested on the horizontal plane, no responses could be evoked by thermal stimuli. These results suggest that, in our experimental conditions (DeltaT up to 1.5 degrees C), neither a thermally induced expansion of the endolymph nor a direct action of the temperature on vestibular sensors play any major role.

Ampulla of Vater↗

PubMed1998

[Delayed endolymphatic hydrops].

Delayed Endolymphatic Hydrops (DEH) is a disease entity that must be distinguished from idiopathic endolymphatic hydrops (Ménière's disease). Idiopathic hydrops is characterized by the following symptoms: 1) vertigo often accompanied by nausea and vomiting; 2) tinnitus; 3) hearing loss, usually fluctuating; and 4) sensation of pressure or fullness in the affected ear. Idiopathic hydrops most commonly occurs in middle-aged patients, usually between 30 and 50 years. It may involve one or both ears and usually exibits fluctuating hearing loss and episodic vertigo, although one symptom may precede the other by months or years. It is rare for Ménière's disease to present with a severe sensorineural hearing loss. Delayed Endolymphatic Hydrops was first described, under the name of "unilateral deafness with subsequent vertigo", by Wolfson and Lieberman and Nadol et al.; this was later confirmed by other authors. The disease is characterized by a profound sensorineural hearing loss in one ear, found to have been present in most cases from early childhood, due to an unknown cause, trauma or viral infections. After a prolonged period (usually many years) patients with DEH experience the onset of episodic vertigo from the deaf ear (Ipsilateral Delayed Endolymphatic Hydrops) or develop a fluctuating hearing loss and/or episodic vertigo in the opposite ear, previously with normal hearing (Controlateral Delayed Endolymphatic Hydrops). Vestibular symptoms are identical to those of Ménière's disease: in fact there is evidence that endolymphatic hydrops in the previously damaged ear or in the previously normal ear represents at least part of the labyrinthine pathology. Histopathology studies recently conducted on temporal bones of subjects affected with controlateral DEH show pathologic changes in the deaf ears similar to those found in viral labyrinthitis, whereas pathologic changes in the hearing ears resemble those known to occur in Ménière's disease. Medical treatment has not been found to be effective in patients with DEH, but it must be the first choice of treatment especially in controlateral forms of the disease. So far, surgical intervention has been demonstrated to give the best results; either conservative or more radical, depending on the type of DEH. Pharmacological labyrinthectomy with ototoxic drugs could be the therapy of choice in the future. In this paper we review the literature in order to summarize the clinical features and criteria for diagnosing DEH, we also report histopathologic findings and pathogenetic hypotheses formulated for this syndrome. Moreover, we discuss the best therapeutic approach for the ipsilateral and controlateral variants of DEH.

Endolymphatic Hydrops↗

PubMedDate not supplied

Treatment of horizontal semicircular canal benign paroxysmal positional vertigo.

We evaluated a new therapeutic maneuver-Prolonged Position on the healthy side, for Benign Paroxysmal Positional Vertigo (BPPV) of the horizontal semicircular canal. We devised this type of physical treatment in accordance with the "canalolithiasis" theory of BPPV, in order to try to free the horizontal semicircular canal of otoconial debris. We compared the results obtained by Prolonged Position with two other physical therapies by dividing our horizontal canal BPPV patients into three therapeutic groups: 1) 35 patients treated with Prolonged Position; 2) 24 patients treated with head shaking in a supine position; 3) 15 patients for whom therapy was omitted. More than 90% of the patients treated with Prolonged Position recovered within 3 days, although 6 patients out of 35 subsequently developed BPPV of the posterior semicircular canal, which then responded well to a particular repositioning maneuver. The results of Prolonged Position were significantly better than those obtained by performing head shaking or by omitting treatment. Prolonged Position can be applied to patients of all ages and general conditions and does not require hospitalization.

Adult↗