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Biomedical subjects

G Lamas

Publications and source records attributed to G Lamas.

At least 37 records · Page 2Linked to original sources
PubMed1995

Partial restoration of blink reflex function after spinal accessory-facial nerve anastomosis.

Functional motor control requires perfect matching of the central connections of motoneurons with their peripheral inputs. It is not known, however, to what extent these central circuits are influenced by target muscles, either during development or after a lesion. Surgical interventions aimed at restoring function after peripheral nerve lesions provide an opportunity for studying this interaction in the mature human nervous system. A patient was studied in whom the spinal accessory nerve was anastomosed into a lesioned facial nerve, allowing voluntary contractions of the previously paralysed muscles. This procedure, in addition to replacing the facial neurons at peripheral synapses, allowed a new short latency trigeminospinal accessory reflex of the R1 blink reflex type to be demonstrated, implying that trigeminal neurons had sprouted towards spinal accessory motoneurons over a distance of at least 1 cm. These results show an unexpected influence of the periphery in remodelling central connectivity in humans. The motoneuronal excitability for this R1 reflex response was therefore studied to compare the convergent properties of facial motoneurons (normal side) with those of the spinal accessory motoneurons (operated side) using a classic double shock technique with variable interstimulus intervals (conditioning test stimulus). On the normal side, conditioning stimuli (to the ipsilateral or contralateral infraliminar supraorbital nerve) produced a clearcut facilitation of the R1 blink reflex when the interstimulus interval was 30-80 ms. By contrast, a similar procedure had no effect on the R1 blink reflex mediated via the trigeminal-spinal accessory reflex arc. These data indicate that despite the heterotopic sprouting of some axons from neurons in the XIth nucleus, motoneurons involved in the newly formed reflex arc remain totally inexcitable by other trigeminal afferents and seem unable to ensure a physiological functioning of the normal blink reflex. Thus the functional relevance of the recovered R1 blink response remains unclear.

Accessory Nerve↗
PubMed1995

[Hiccups in adults].

Hiccoughs are an involuntary spasmodic and coordinated contractions of the inspiratory muscles associated with a delayed and sudden closure of the glottis which is responsible for the characteristic noise. The pathophysiology of hiccoughs have not been elucidated. There have only been a few observations describing the sequence of inspiratory muscle activation and these suggest that the control of hiccoughs is within the central nervous system. The clinical circumstances associated with acute benign hiccoughs are both numerous and disparate. In these cases, when they stop spontaneously or as a result of simple physical manoeuvres hiccoughs do not require any particular medical attention. Chronic hiccoughs, defined as hiccoughs persisting for more than 24 hours or recurring as repetitive attacks are a rare phenomenon. The causes cover the whole of organic pathology. Systematic protocols of complementary examinations most often enable an underlying organic cause to be found. Amongst these, particular attention should be paid to oesophageal causes by the reason of their being the most frequent. An important place should be reserved for the aetiological treatment as is frequently enables a remission of chronic hiccough.

Acute Disease↗
PubMed1994

Treatment of patients with prior exit block using a novel steroid-eluting active fixation lead. Model 4068 Investigators.

An increased interest has developed in active fixation leads for several reasons. Exit block is an uncommon complication that is seen with both active and passive fixation leads. Exit block has not been a significant problem with passive fixation steroid-eluting leads and has been treated with these leads. A new steroid-eluting active fixation lead was examined for its performance in patients in whom exit block had previously occurred. The lead function was evaluated prospectively in 24 patients with a history of exit block (15 ventricular and 9 atrial). The results in patients with atrial exit block are encouraging with an average chronic stimulation threshold of 0.19 msecs at 2.5 volts. Results in the ventricle are less encouraging with 3 occurrences of recurrent exit block in 15 patients; however, the remaining patients had a good mean threshold of 0.21 +/- 0.11 msecs at 2.5 volts. There were a remarkable number of non-lead related complications suggesting that this is a substantially different group than routine implantations.

Cardiac Pacing, Artificial↗
PubMed1994

Risk factors and clinical relevance of nosocomial maxillary sinusitis in the critically ill.

The incidence of infectious maxillary sinusitis (IMS) and its clinical relevance was prospectively studied in 162 consecutive critically ill patients who were mechanically ventilated for a period longer than 7 d. All had a paranasal computed tomographic (CT) scan within 48 h of admission and were divided into three groups according to the radiologic aspect of their maxillary sinuses: Group 1 = normal maxillary sinuses (n = 40), Group 2 = maxillary mucosal thickening (n = 26), Group 3 = radiologic maxillary sinusitis (RMS) defined as the presence of an air fluid level and/or opacification of maxillary sinuses (n = 96). Group 1 patients were randomized between nasal and oral endotracheal intubation with a gastric intubation performed via the same route and had a second paranasal CT scan 7 d later. Endotracheal and gastric tubes were left in their original position in Group 2 patients and a second paranasal CT scan was performed 7 d later. All patients of Group 3 underwent a transnasal puncture for bacteriologic analysis of maxillary sinus content. Forty-five spontaneously breathing patients served as a control group. In all patients with RMS, the occurrence of bronchopneumonia (BPN) was prospectively assessed for 7 d following the initial CT scan. Upon inclusion, only 25% of the patients had normal maxillary sinuses whereas all patients in the control group had normal paranasal CT scans. After 7 d, 46% of Group 2 patients had evidence of RMS. Risk factors for RMS were nasal placement and duration of endotracheal and gastric intubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Clear cell sarcoma of the pre-parotid region: an initial case report.

An unusual case of clear cell sarcoma (CCS) found in the parotid region of a 75-year-old man with a long history of chronic lymphoid leukemia is reported. Treatment of the patient included a total parotidectomy with preservation of the facial nerve. The tumor was pathologically consistent with a clear cell sarcoma. Since CCS originates from the neural crest and is melanin producing, we suggest that this particular tumor originated from the superficial musculo-aponeurotic system (SMAS). To our knowledge, this is the first case of CCS that has been reported in the parotid region.

Aged↗
PubMed1993

Hypoglossal-facial anastomosis alters excitability of hypoglossal motoneurones in man.

In 6 patients who had undergone a hypoglossal-facial anastomosis, showing clinical signs of recovery, a new short-latency trigemino-hypoglossal reflex of the R1 blink reflex type was demonstrated, implying a heterotopical sprouting of trigeminal neurones towards hypoglossal motoneurones. We therefore studied the motoneuronal excitability for this R1 reflex response in order to compare the convergent properties of facial motoneurones (normal side) with those of the hypoglossal motoneurones (operated side) with the use of the classical double-shock and variable interstimulus delay (conditioning-test stimulus) technique. On normal side, conditioning stimuli (ipsi- or contralateral infraliminar supraorbital nerve) produced a clear-cut facilitation of the R1 blink reflex response within a 30-80 ms interstimulus time interval. By contrast a similar procedure remained without any effect on the R1 blink reflex response mediated via the trigeminal-hypoglossal reflex arc. These data indicate that despite the heterotopical sprouting of some axons of neurones from the principal trigeminal nucleus towards the XIIth nucleus, those hypoglossal motoneurones involved in the neoformated trigemino-hypoglossal reflex arc remain totally inexcitable by other trigeminal afferents and thus appear unable to ensure the physiological function of the normal blink reflex.

Anastomosis, Surgical↗
PubMed1993

[Electrophysiological study of the blink reflex in Wistar rats].

The electrophysiological characteristics of the blink reflex evoked by electrical stimulation of supraorbital nerve (V1) have been studied in the awake and anaesthetized rat. This reflex has two components (R1 and R2). The first one, R1, is of short latency, strictly ipsilateral to the stimulus and exhibits all features of an oligosynaptic reflex response. The second component, R2, of longer latency, is observed bilaterally in awaked but ipsilaterally in lightly anaesthetized and totally depressed in deeply anaesthetized animals. This component possesses all characteristics of a largely multi-synaptic reflex response.

Anesthesia↗
PubMed1993

[Electrophysiological study of hemifacial spasm].

Hemifacial spasm is characterized by intermittent involuntary contractions of one or several groups of muscles innervated by the facial nerve. The possible causal mechanisms have been the subject of numerous publications. The pre-eminent work of Moller and Jannetta implicates the compression of the facial nerve at its point of entry into the central nervous system, the Root Entry Zone, while the physiopathology is poorly understood, two principle hypotheses emerge: 1) ephaptic transmission between injured fibers; 2) hyper excitability of the facial motor nucleus. Using standard electromyographic techniques and blink reflex studies, we were able to demonstrate hyperexcitability of the facial nucleus. The cause of this hyperexcitability remains unexplained. It could be the result of a permanent antidromic stimulation from a peripheral ectopic center of excitation.

Adult↗
PubMed1993

[Demonstration and electrophysiological analysis of the blinking reflex in the rat. Value of the animal model].

The authors have developed an animal model for the electrophysiological investigation of the blink reflex. The justification for such investigations and the experimental protocol were presented. The authors studied the blick reflex with electromyographic recordings obtained after the stimulation of the supra orbital nerve (V1) in the awake rat and in the anaesthesized rat. Two components of the reflex, R1 and R2 were observed. The early component, R1 was ipsilateral to the stimulus. It was observed whatever the degree of anaesthesia. The R2 component came later and was only observed in awake or weakly anaesthesized rats. It appeared to be isolated and unprecedented by an R1 component when the contralateral supra orbital nerve was stimulated. The R1 responses were facilitated by prior ipsilateral or contralateral stimulation of V1.

Anastomosis, Surgical↗
PubMed1992

Redirection of the hypoglossal nerve to facial muscles alters central connectivity in human brainstem.

Functional motor control requires perfect matching of central connectivity of motoneurones with their peripheral connections. However, it is not known to what extent central circuitry is influenced by target muscles, either during development or following a lesion. Surgical interventions aimed at restoring function following peripheral nerve lesions provide an opportunity for studying this interaction in the mature human nervous system. We have followed 8 patients in whom the hypoglossal nerve was anastomosed into a lesioned facial nerve, allowing voluntary contractions of the previously paralyzed muscles. We show that, in addition to replacing the facial neurons at peripheral synapses, a new short-latency trigemino-hypoglossal reflex, of the R1 blink reflex type, can be demonstrated in patients showing recovery, implying a sprouting of trigeminal neurons towards hypoglossal motoneurones, over a distance of at least 0.5 cm. These surprising results show an unexpected influence of the periphery in remodelling central connectivity in man.

Adult↗
PubMed1992

Centrofacial malignant granulomas. Clinicopathologic study of 40 cases and review of the literature.

An important problem in the treatment of centrofacial ulcerations is to establish a precise diagnosis, since similar clinical and microscopic findings can result from many different causes (as in the centrofacial malignant granuloma syndrome [CFMG]). A comprehensive surgical biopsy protocol (known as SNFMI/GMCF), involving microbiology, parasitology, immunology and pathology laboratories, allowed us to evaluate and to treat 40 cases of CFMG, who form the basis of this report. In 13 of them, specific diagnoses were found and curative treatments could be given. In the remaining 27, the optical microscopy pattern met the criteria for CFMG without identifiable origin or the presence of so-called lethal midline granulomas; however, a more precise evaluation with the help of immunofluorescence studies led to the recognition of malignant lymphoma (ulcerative lymphoma of the midface [ULM]). Most of these lymphomas belonged to the T cell lineage; the others were of B lymphoid origin, or, more rarely, of histiocytic origin. Patients with ULM received radiotherapy and chemotherapy with a response rate of 70.3%; however, the toxicity was significant, with frequent occurrence of chemotherapy-induced neutropenia followed by severe infectious facial cellulitis. Six patients were enrolled in a preliminary open trial of treatment with recombinant alpha-2b interferon with little success. Three patients were treated with radiation therapy only, and survived. Thus, CFMG is a syndrome with specific causes and treatments, requiring multiple extensive biopsies to make the correct diagnosis. The recognition of ULM as the cause of the previously called "lethal midline granulomas" leads logically to the use of chemotherapy with growth factors in order to ameliorate its bad prognosis.

Adolescent↗
PubMed1992

[Long-term follow-up and therapeutic results of the protocol of the National Society of Internal Medicine in centrofacial malignant granuloma. Report of 40 cases].

We have studied 40 cases of mediofacial necrosis with no specific diagnosis on biopsy. After an exhaustive work-up we reached a specific diagnosis in 13 patients (Wegener's granulomatosis in 7, classical malignant lymphoma of the nose in 3, squamous cell carcinoma = "goundou" in 1, syphilis and tuberculosis in 1, aspergillosis in 1). Those patients received the appropriate treatments with good results. The remaining 27 patients, however, had ulcerative lymphomas of the midface (according to the immunofluorescence and molecular biology techniques). Their fate was worse since only 15% remain alive on the long-term, despite intensive treatments with chemotherapy, radiotherapy, interferon, artificial nutrition and antibiotics as needed. We present a new protocol with intensified chemotherapy and growth factor treatment in order to ameliorate the very poor prognosis of these patients.

Adolescent↗