Multi-electrode sequential versus single electrode stimulation to elicit the stapedial reflex during cochlear implantation: Correlation with maximum comfort level.

OBJECTIVES: To assess whether electrical stimulation sequentially delivered through 4 electrodes located in different cochlear areas may elicit the stapedial reflex at lower levels compared to single electrode stimulation and to correlate the sequentially obtained values with the maximum comfort level (C-level). PATIENTS AND METHODS: A retrospective study was performed on 35 post-verbal adult patients (age 19-80 years) consecutively implanted in 2 cochlear implant centers, evaluating the level of stimulation (pulse width) necessary to electrically evoke the stapedial reflex with two different stimulation modalities: single electrode versus sequential 4 electrode stimulation. Threshold values were compared with C-level obtained at activation. RESULTS: The average differences of pulse width and C-level were significantly smaller (P<0.0001) when the stapedial reflex was obtained with the sequential stimulation modality and reached statistical significance for every single electrode (P<0.0001). CONCLUSIONS: Stapedial reflex thresholds obtained with sequential stimulation through 4 different electrodes significantly correlate to the C-level obtained at the first setting and may be helpful in defining the upper limit of the dynamic field during initial CI mapping.

Long term surgical and hearing outcomes in the management of tympanomastoid paragangliomas.

OBJECTIVE: To analyze the long term outcomes after surgery in tympanomastoid paragangliomas. STUDY DESIGN: Retrospective study. METHODS: The charts of 145 patients with tympanomastoid paragangliomas managed between 1988 and 2013 were reviewed. The clinical features, audiological data, pre- and postoperative notes were noted. The tumors were staged according to the modified Fish and Mattox classification. The surgical approaches for all patients were formulated according to the surgical algorithm developed at our center. RESULTS: 34 (23.5%), 46 (31.7%), 22 (15.2%), 18 (12.4%) and 25 (17.2%) patients were diagnosed to have TMP class A1, A2, B1, B2 and B3 tumors respectively. Gross tumor resection was achieved in 141 (97.2%) patients. The facial nerve was uncovered in four patients and infiltrated in three. The cochlea was found eroded in seven cases. The mean follow-up was 48.4 months. Recurrence was seen in one patient (0.7%). In the cases where the facial nerve was preserved (n=143), the nerve function was graded as HB grade 1 in 138 patients (97%). Postoperatively, the mean AC showed an improvement in all categories except in class B2 and B3, which corresponds to the classes that include patients who underwent subtotal petrosectomy. CONCLUSION: We report the long term surgical outcomes in tympanomastoid paragangliomas in the largest series published till date. It is possible to completely eradicate all types of tympanomastoid paragangliomas with minimum sequelae by choosing the correct surgical approach to achieve adequate exposure for individual tumor classes as described in our classification and algorithm. LEVEL OF EVIDENCE: IIb.

Bilateral cochlear implantation in a patient with petrous bone cholesteatoma in the only hearing ear: case report.

OBJECTIVE: We report a case of successful cochlear implantation in a patient with petrous bone cholesteatoma in the only hearing ear. CASE REPORT: A 63-year-old man presented with a four-year history of right-sided, progressive hearing loss in his only hearing ear. Computed tomography and magnetic resonance imaging revealed a right supralabyrinthine petrous bone cholesteatoma, with erosion of the superior semicircular canal and the roof of the internal auditory canal. Due to the high risk of post-operative right-sided deafness, we decided first to perform left cochlear implantation. Five months later, the patient had a 40 per cent score for open-set two-syllable word recognition and an 85 per cent score for sentence recognition. Given these good performances, we decided to eradicate the cholesteatoma via a translabyrinthine approach, with insertion of a second cochlear implant, as a single-stage procedure. A successful outcome was achieved. CONCLUSION: Cochlear implantation can be an effective method of hearing rehabilitation in patients with petrous bone cholesteatoma, following total eradication of disease, if the cochlea remains intact. To our best knowledge, this is the first English language report of cochlear implantation in a patient with petrous bone cholesteatoma.

The primary role of glutathione against nuclear DNA damage of striatum induced by permethrin in rats.

Pyrethroids are one of the most widely used class of insecticides and their toxicity is dominated by pharmacological actions upon the CNS. This study reports as the subchronic treatment (60 days) with permethrin (PERM) (1/10 of LD(50)) induced nuclear DNA damage in rat striatum cells. Comet assay outcomes showed that PERM produced single- and double-strand breaks in striatum cells, the DNA damage was not related to oxidation at pyrimidine and purine bases. Vitamin E (280 mg/kg body weight/day) and vitamin E+coenzyme Q(10) (10 mg/kg/3 ml) supplementation could protect PERM treated rats against nuclear DNA damage. With the aim to evaluate the cause of nuclear DNA damage observed in striatum of rat treated with PERM, in vitro studies on striatum submitochondrial particles (SMPs) and on striatum cells treated with 10 muM PERM alone or plus 16 or 32 nM GSH were performed. SMPs incubated with PERM showed a decrease in superoxide anion release from the electron transport chain by inhibition of mitochondrial complex I. The effect could be related to the decrease of membrane fluidity measured in the hydrophilic-hydrophobic region of the mitochondrial membrane. This result discarded the involvement of the mitochondrial reactive oxygen species in the nuclear DNA damage. On the contrary, GSH played a crucial role on striatum since it was able to protect the cells against nuclear DNA damage induced by PERM. In conclusion our outcomes suggested that nuclear DNA damage of striatum cells was directly related to GSH depletion due to PERM insecticide.

Brownian motion and diffusion: from stochastic processes to chaos and beyond.

One century after Einstein's work, Brownian motion still remains both a fundamental open issue and a continuous source of inspiration for many areas of natural sciences. We first present a discussion about stochastic and deterministic approaches proposed in the literature to model the Brownian motion and more general diffusive behaviors. Then, we focus on the problems concerning the determination of the microscopic nature of diffusion by means of data analysis. Finally, we discuss the general conditions required for the onset of large scale diffusive motion.

Internal auditory canal metastasis.

This report deals with 3 cases of internal auditory canal metastasis, an extremely rare lesion, few cases having been reported in the international literature. Since pre-operative diagnosis is fundamental in the planning of a correct therapeutic strategy, it is important that the neurotologist be aware of the possibility of their occurrence in this particular area. Metastasis can occur unilaterally as well as bilaterally; the latter being the case in 1 of the patients described herein. Correct pre-operative diagnosis is particularly difficult in patients in whom the primary tumour has not been detected at the time of identification of the lesion in the internal auditory canal. The only characteristic, specific of metastasis, is the presence of multifocal cerebral lesions. However, these were detected in only 1 of the present cases. On the contrary, in cases of a single metastasis, both magnetic resonance imaging and computed tomography usually fail to show any distinctive feature when compared to the most common tumours of the internal auditory canal (vestibular schwannomas and meningiomas). Bilateral metastases can also be misdiagnosed as neurofibromatosis type 2. Clinical data that should alert the clinician are: rapidly progressive sensorineural hearing loss, followed by onset of progressive facial nerve weakness. Radiotherapy and/or chemotherapy are the two main treatment modalities, while surgical removal is reserved for selected cases of a single metastasis. Albeit, due to the paucity of specific radiological and clinical characteristics, surgical removal is often necessary to reach the correct diagnosis, as occurred in 2 of the present patients.

Pulsatile tinnitus as a rare presenting symptom of residual cholesteatoma.

Pulsatile tinnitus is an uncommon otological symptom, which often presents a diagnostic and management dilemma to the otolaryngologist. This symptom always deserves a thorough evaluation to avoid disastrous consequences from potentially life-threatening associated pathology. In most of the patients a treatable underlying aetiology can be identified. Frequent causes mentioned in the literature responsible for pulsatile tinnitus are benign intracranial hypertension syndrome, temporal bone paragangliomas and arteriovenous fistulae. Pulsatile tinnitus as a consequence of sigmoid sinus compression by a cholesteatoma has not been reported previously in the literature. Here a case of residual cholesteatoma with pulsatile tinnitus is presented, nine years after the first surgery.

[Preoperative imaging in chronic otitis surgery]. / Utilità della radiologia preoperatoria nella chirurgia dell'otite media cronica.

High resolution computed tomography (CT) is presently the most accurate technique to study the temporal bone. Nevertheless, there is no general agreement about its usefulness in pre-operative evaluation of chronic otitis media. Indeed, if we rule out some exceptions, CT is not fundamental for diagnosis which can often be obtained through an accurate otomicroscopy. The Otology Group in Piacenza applies the following absolute indications for pre-operative CT in chronic otitis media: 1) difficult otomicroscopy evaluation; 2) suspected petrous bone cholesteatoma; 3) dubious diagnosis; 4) suspect of malformations; 5) review of cases that had previously undergone mastoidectomy; 6) suspected intracranial complications and/or meningoencephalic herniation (in this case also a magnetic resonance imaging must be performed). With the exception of these specific conditions, pre-operative CT is useless in cases of simple chronic otitis. However, when a cholesteatoma is suspected, CT can provide the surgeon, particularly when inexperienced, useful, but not indispensable, informations. Pre-operative knowledge of these informations can allow a more accurate evaluation of the case, with a better planning of the surgical procedure, in order to ensure a more specific informed consent. Finally, the Authors point out the fact that surgeon must be able to interpret by his own the CT data to have a real advantage by this examination.

Electromyographic evaluation of facial nerve damage in acoustic neuroma surgery.

OBJECTIVE: This study aimed to determine whether postoperative facial nerve paralysis or surgical manipulation causing paralysis could be predicted on train responses during intraoperative facial nerve monitoring in acoustic neuroma surgery. STUDY DESIGN AND SETTING: This was a prospective study performed at a tertiary referral center. PATIENTS AND METHODS: Train responses were recorded on a floppy disk and compared with postoperative facial nerve function in 51 patients who underwent enlarged translabyrinthine acoustic neuroma surgery. MAIN OUTCOME MEASURES: The number, duration, frequency, and peak-to-peak amplitude of train responses were analyzed and compared with postoperative facial nerve function. RESULTS: Trains were observed in 42 of 51 patients. Six of seven patients with high-amplitude trains more than 250 microV, and three of five patients with bomber-type high-frequency trains elicited during tumor dissection from the facial nerve or stretching the nerve, showed severe facial nerve dysfunction. On the other hand, seven of the nine patients with no trains also showed severe facial nerve dysfunction. CONCLUSIONS: The presence of high-amplitude or high-frequency trains elicited by surgical manipulation to the facial nerve seems to indicate a critical situation for the facial nerve. However, certain types of mechanical trauma resulting in severe facial nerve paralysis cannot be identified by train responses.

Identification of the facial nerve in the translabyrinthine approach: an alternative technique.

An alternative technique for the identification of the facial nerve at the fundus of the internal auditory canal is described.

Meningiomas intrinsic to the geniculate ganglion.

Geniculate ganglion meningiomas are extremely rare lesions-only 14 cases have been reported in the literature. Two new cases of these tumors are described. On computed tomography and magnetic resonance imaging, both lesions appeared centered on the area of the geniculate ganglion, extending to the tympanic cleft and eroding the middle cranial fossa floor. The first case was treated through a middle cranial fossa approach. Because the tumor was so large in the second case, a subtotal petrosectomy was used. The authors review the literature to clarify the clinical and radiological characteristics of these tumors and their surgical treatment.

[Enlarged translabyrinthine approach in large acoustic neurinomas]. / La via translabirintica allargata nei neurinomi dell'acustico di grandi dimensioni.

The translabyrinthine approach has long been, and in some centers is still, considered inadequate for the removal of large acoustic neuromas (AN). Over the years, with experience, the original technique has been modified, extending the approach to what is now called the enlarged translabyrinthine (ET) approach. Applying these modifications, between April 1987 and February 2000, the Gruppo Otologico in Piacenza, Italy removed 132 ANs, 3 cm or larger, from the cerebello-pontine angle. These tumors accounted for 25.9% of the 510 cases of AN to undergo surgery during that period. Of the 132 cases only one patient died and the percentage of complications was very low, generally lower than analogous series published in the literature. Such complications were progressively reduced in time, leading to a significant reduction in the length of post-operative hospitalization: on the average the 8.8 days were reduced to 5.7 in the last 43 cases. Ipsilateral preoperative hearing, inevitably sacrificed using the ET approach, was already significantly compromised in more than 65% of the cases. On the basis of the present data, it can be asserted that tumor diameter does not in any way preclude the use of the ET approach in AN surgery, rather the reduced morbility and shorter post-operative hospitalization make it the approach of choice for large ANs.

Chaos or noise: difficulties of a distinction

In experiments, the dynamical behavior of systems is reflected in time series. Due to the finiteness of the observational data set, it is not possible to reconstruct the invariant measure up to an arbitrarily fine resolution and an arbitrarily high embedding dimension. These restrictions limit our ability to distinguish between signals generated by different systems, such as regular, chaotic, or stochastic ones, when analyzed from a time series point of view. We propose to classify the signal behavior, without referring to any specific model, as stochastic or deterministic on a certain scale of the resolution epsilon, according to the dependence of the (epsilon,tau) entropy, h(epsilon, tau), and the finite size Lyapunov exponent lambda(epsilon) on epsilon.