[The hypolossal-facial anastomosis in man. A model for studying peripheral and central nervous system plasticity]. / L'anastomose hypoglosso-faciale chez l'homme: un modèle d'etude de la plasticité du système nerveux périphérique et central.

Hypoglossal-facial anastomosis (HFA) is a cross-over between the proximal stump of the hypoglossal nerve (XII) and the distal one of the facial nerve (VII). The hypoglossal axons regrow within the sheaths of facial fibres, allowing the progressive reinnervation of the facial muscles. This model is interesting to study some mechanisms of plasticity of the nervous system for several reasons: 1) It is a quite simple and reproducible model of pathophysiological state. It allows the study of 2) the modifications of the nervous system induced by the HFA, both upwards and downwards to the lesion and 3) the modifications of reflex activities involving intrapontine connections such as the blink reflex. The electrophysiological features of the trigemino-facial (TF) and trigemino-hypoglossal (TG) connections demonstrated that a central reorganisation of the blink reflex (BR) was induced by HFA: the afferent volleys of the TF and TH reflexes elicited by cutaneous and mucosal trigeminal afferents respectively have been shown to project onto common interneurones located within the trigeminal principal sensory nucleus. A long-term prospective study showed: 1) a reinnervation of the facial muscles by the hypoglossal axons is a necessary perequisite for the central reorganisation of BR, 2) a hyperinnervation of the facial muscles by the hypoglossal axons, 3) a transient and regressive cross-innervation of paralyzed face by the healthy contralateral facial nerve.

[Anatomy and physiology of the vestibular system: review of the literature]. / Anatomie et physiologie du système vestibulaire. Revue de la littérature.

The vestibular system is a complex system involving not only posterior labyrinth but also central structures such as cerebellum, striatum, thalamus, frontal and prefrontal cortex to assure balance, movements and walking. Information reaching the vestibular complex are not purely vestibular but also from visual, somatosensory and cerebellar origins. The equilibrium is also a complex physiological function needing concordance of vestibular, visual and somatosensory information or either central compensation after an injury but also an integrity of the central nervous system.

Hypoglossal-facial nerve anastomosis: dynamic insight into the cross-innervation phenomenon.

The authors investigated the evolution of the dynamic features of the cross-innervation process in patients with complete facial palsy due to facial nerve transection during surgery for acoustic neuroma removal followed by a hypoglossal-facial nerve anastomosis (HFA). Clinical and electrophysiologic investigations were carried out before and over a 3-year period after HFA. Cross-innervation had started by the 10th day, progressed to the seventh to eighth month, then decreased and finally disappeared by the 12th month after HFA. Ipsilateral reinnervation was observed by the fourth month, progressed to the 12th to 18th month, and remained stable for the remainder of the follow-up period.

[Treatment of Bell's palsy with acyclovir and methylprednisolone]. / Traitement des paralysies faciales idiopathiques par méthylprednisolone et aciclovir.

OBJECTIVE: An open therapeutic trial was conducted in patients with Bell's palsy. Results were compared with data in the literature. MATERIALS AND METHODS: Between 1997 and 2000, 76 patients with Bell's palsy were treated with intravenous methylprednisolone (2 mg/kg/day) and acyclovir (5-10 mg/kg/8 hours) for 7 days. Treatment was initiated in all patients before the 14th day of illness. Severity of the palsy was scored on the first day of treatment and again one year later using the House and Brackman scale. RESULTS: Grade II or III palsy were observed in 38% of the patients at initial presentation, grades IV to VI in 62%. After treatment, 92% of the patients had reverted to grades I and II (good outcome) and only 8% had sequelae at 1-year follow-up. All patients with initial grade I or II recovered completely. For patients with grade IV, V, or VI complete recovery at 1 year was observed in 94, 86 and 50% respectively. CONCLUSION: Data in the literature suggest that corticosteroids should improve recovery in Bell's plasy. In our study, adjunction of acyclovir did not demonstrate any clear improvement in the cure rate. Benefit could depend on early prescription.

Midbrain deafness with normal brainstem auditory evoked potentials.

The authors report two cases of patients with word deafness. The word deafness occurred after a head injury for the first patient and after an arterio venous malformation embolization for the second patient. MRI demonstrated bilateral lesions of the inferior colliculi but brainstem auditory-evoked potentials (BAEP) were within normal limits. These cases demonstrated that lesions involving the two inferior colliculi induced pure word deafness but do not affect BAEP.

[The encephalon. Notions of neuroanatomy]. / A propos de l'encéphale. Notions de Neuroanatomie.

A good knowledge of the brain anatomy is necessary for all physicists interested in neurologic pathology, and especially for the radiologists. The aim of this paper is to summarize the important data in morphological but also in functional brain anatomy. The main neurologic pathways are represented on MR standard slices for practical application. The international anatomica nomenclatura (french terms) is used.

Activation of the hippocampal formation by vestibular stimulation: a functional magnetic resonance imaging study.

Functional MRI (f-MRI) is a non-invasive technique developed to permit functional mapping of the brain with a better temporal and spatial resolution than that offered by PET techniques. In our study, f-MRI was performed using blood oxygenation level dependent (BOLD) contrast imaging based on the magnetic properties of hemoglobin. This method relies on changes in the blood supply to the brain that accompany sensory stimulation or changes in cognitive state. All the images were obtained at 1.5 T on a Signa GEMS without ultrafast imaging. The vestibular stimulation was cold irrigation of the external auditory meatus (caloric stimulation). A population of normal healthy volunteers without a history of vestibular dysfunction was studied. The hippocampal formation as well as the retrosplenial cortex and the subiculum were activated by vestibular stimulation, suggesting that this activation may be related to spatial disorientation and a sensation of self-rotation experienced by the subjects during vestibular stimulation. The other results are similar to those obtained using PET.

Assessment of vestibular function by videonystagmoscopy.

Videonystagmoscopy has been used to subjectively observe the responses of the vestibular system in a population of patients with vestibular deficits. These results were compared with those of a control group of healthy, age-matched volunteers. The videonystagmoscopy device is made of one or two CCD cameras mounted on lightproof goggles, allowing a subjective observation of ocular movements on a video monitor. The eye movements, as well as the position of the head in space, can be recorded on videotape. The eyes are illuminated by infrared light emitting diodes placed on each side of the camera lens. The subjects are seated on a manually driven Barany chair. Subjects went through a protocol of passive roll head tilt on each side, followed by a slow, whole body rotation of 180 degrees amplitude, clockwise and counterclockwise, and then a head shaking test (HST). The eyes were subjectively observed, and we focussed on: torsional eye movements during head tilt, nystagmus when the rotation had stopped, and nystagmus induced by HST. With this simple and noninvasive examining procedure, screening of vestibular function at the bedside or during E.N.T. clinical investigations is possible.

Modification of parameters in vertical optokinetic nystagmus after repeated vertical optokinetic stimulation in patients with vestibular lesions.

Eye movements were recorded in patients with unilateral and bilateral vestibular lesions after upward and downward optokinetic (OK) stimulation before and following 6 weeks' repeated exposure to OK stimulation. In control subjects there was no asymmetry between upward and downward slow-phase velocity (SPV). Before training, less subjects showed that upward and downward SPV was significantly lower than that of controls. There was no asymmetry between upward and downward SPV. After training, in unilateral cases, the values of both upward and downward SPV recovered to the control range. In bilateral cases, the downward SPV values returned to the control range, whereas the values of upward SPV exceeded the control range. The frequencies of both upward and downward OKN in controls were about 3.0 Hz. In unilateral and bilateral cases, before and after training, the OKN frequencies approximated 3.0 Hz, showing no significant differences. The recovery of the SPV in unilateral and bilateral cases after training suggests that OK stimulation acts to stabilize the body and consequently to provoke pronounced OKN, due to eye-head-body co-ordination. The asymmetry of SPV after training in bilateral cases might be a result of the lack of otolith function.

Videonystagmoscopy: its use in the clinical vestibular laboratory.

Vestibular function of a population including labyrinthine-defective patients and a control group of age-matched normal healthy volunteers was evaluated using videonystagmoscopy. This device is made of one or two CCD infra-red cameras mounted on diving glasses and allows observation of ocular movements on a video monitor and/or recording on a videotape. Eye movements are observed after rotations in a Bárány chair and during passive head tilts. With this simple and non-invasive test, a screening of vestibular function at bedside or during ENT clinical investigations can be performed. A further study with videonystagmography to quantify these results being prepared.

[Instrumental study of vertigo: when and how?]. / Exploration instrumentale des vertiges: quand et comment?

Any case of vertigo and equilibrium disorder for which an origin is not rapidly determined requires exploration for diagnosis. This exploration comprises two parts: first, that of peripheral components, including a standard audiometric examination, completed by study of the evoked auditory potentials. This is followed by vestibular examination comprising at least caloric tests of both ears, usually associated with rotation tests; second, exploration of the central pathways, by electro-oculography, study of pursuit and saccadic movements. The techniques of posturography, especially dynamic posturography by the equi-test, allow determination of the role of the vestibular apparatus in equilibrium and to define the respective roles of the labyrinth, vision and sensitivity in equilibrium. The technique is rapidly developing and will no doubt include the study of coordination of head and eye movements, study of stabilisation of vision and the head, and in particular study of otolithic function.

Goal-directed linear locomotion in normal and labyrinthine-defective subjects.

When a subject is walking blindfolded straight ahead towards a previously seen target, the brain must update an internal representation with respect to the environment. This study examines whether the information given by the vestibular system is necessary for this simple path integration task and gives a quantitative description of locomotor behaviour during the walk by comparing ten normal and seven bilateral labyrinthine-defective (LD) subjects. Each subject performed 20 blindfolded walks (EC) and ten walks with eyes open (EO) towards a target attached to the floor 4 m in front of them; these walks were made at different velocities. The positions of head, trunk and feet were recorded using a 3D motion analysis system. No significant difference was found between normal and LD groups in terms of the distance error of reaching the target, while LD subjects showed a larger lateral error. Path curvature, expressed as the standard deviation of the angle between the direction of one step and straight ahead, was found to be significantly larger for LD subjects in the EC condition, demonstrating their instability when walking without vision. Mean walking velocity was lower for LD subjects than for normal subjects in both EC and EO conditions. Both groups walked faster with eyes open; LD subjects increased their velocity by increasing step length, normal subjects by increasing step frequency. Head stabilisation in the frontal plane during locomotion was not significantly different between LD and normal subjects, whereas both head and trunk rotation were slightly larger in LD subjects during blindfolded walking. The results show that bilateral LD subjects are able to perform linear goal-directed locomotion towards memorised targets. Thus, the vestibular system does not appear to be necessary for active linear path integration.

Repeated optokinetic stimulation in conditions of active standing facilitates recovery from vestibular deficits.

Successful results obtained by training sessions using optokinetic (OK) stimulations in order to rehabilitate patients with balance disorders motivated this study. The purpose of the study was to measure eye movement parameters and body stabilization during OK stimulation before and after the rehabilitation program. Two populations of patients were studied: bilateral and unilateral labyrinthine-defective patients. Before training, the OK nystagmus (OKN) showed irregularities of the slow-phase velocity (SPV) as well as a reduced number of beats (frequency) when compared with a control group of age-matched healthy volunteers. After training, the SPV became more regular (decrease in SD) and the frequency was similar to the control group's (3 Hz). Body stabilization was measured by dynamic posturography (Equitest) at the beginning and at the end of the training program. At the end of the training program, the patients were asymptomatic and there was a significant correlation between the Equitest results and the modification of the OKN parameters.

[Physiological and clinical recall on equilibrium disorders]. / Rappels physiologiques et cliniques sur les troubles de l'équilibre.

Static and dynamic equilibrium (posture and gait) is indispensable for a normal behavior in human. Its mechanisms are nearly the same in superior species and in man, but humans are the only ones to have acquired exclusively biped upright position and gait. Equilibrium is a sensory function involving 3 sub systems: visual, vestibular and sensori-motor (proprioceptive), controlled by cerebellum and cerebral structures. Information coming from those 3 sub systems must be concordant. In case of discordance, the patient is in a state of sensory conflict. This conflict can induce disequilibrium or true vertigo. After a recall on equilibrium, the authors report the results of an epidemiologic study upon 5298 patients suffering of balance disorders and treated by an alpha-blocker: nicergoline (30 mg/day during 6 months).

[Vestibular studies: current status, prospects]. / Explorations vestibulaires: actualités--perspectives.

Equilibrium is based on gaze stabilization. Clinical examinations currently test, individually the three components involved in equilibrium: vestibular, visual and proprioception. New investigations are being developed to test equilibrium dynamic conditions. After briefly reviewing vestibular physiology, under the authors discuss the various tests of vestibular function and equilibrium.

Anatomic and radiologic bases of surgery of the thoracic aorta.

Lesions of the thoracic aorta create problems related to their site and relations with the main aortic branches. The aim of surgery must be to treat the lesion while ensuring perfusion of the tissues excluded by clamping during the operation. Anatomic study of the aortic lesions is based on imaging. Angiography is still often the basic examination though it shows only the lumen and course of the aorta. However, CT and MRI visualise the aortic wall and especially the relations of the aorta to the mediastinal structures. A comparison of anatomic and imaging studies was made on 10 fresh subjects coming from the anatomy department of the Saints-Pères and from the school of surgery of Fer à Moulin. Sections were made every 3 to 5 mm in 3 planes (sagittal, coronal and axial) after CT localisation of the plane of section. This anatomic study was correlated with CT and MR images made on healthy volunteers. The choice of surgical management of a lesion of the thoracic aorta is based on preoperative anatomic assessment by imaging applied not only to the aorta but also to its branches and the territory supplied.

The commissuro-mamillary plane in MRI of the brain (preliminary communication).

MRI sections of the brain in the coronal plane through the line joining the anterior commissure and the mamillary bodies display the constituent parts of the basal forebrain. The visualisation of the septal nuclei and the anterior columns of the fornix show the importance of this plane in the study of behaviour disorders and amnesic syndromes.

Head stabilization during locomotion. Perturbations induced by vestibular disorders.

Head kinematics was studied in 10 normal subjects (NS) and 7 patients (P) with bilateral vestibular deficit while they executed various locomotor tasks. The movement of the body was recorded with a video system which allowed a computer reconstruction of the motion of joint articulations and other selected points on the body in three dimensions. Analyses focus on head translation along the vertical axis and rotation in the sagittal plane. Two conditions were studied: free walking (W) and hopping (H). The subjects were tested in light and in darkness. In NS, while walking in darkness, mean head position was tilted downward. In contrast, this flexion was not systematic in P. Darkness did not significantly influence the amplitude and velocity of head angular displacement during W, but, during H the amplitude decreased by 37% for NS. During H in darkness, head stabilization decreased for P. These results suggest that head kinematics, during natural locomotor tasks, could be used to evaluate vestibular deficiencies.

The thoracic esophagus: sectional anatomy and radiosurgical applications.

The relationships of a tumor of the thoracic esophagus to the adjacent mediastinal structures are currently studied by means of computed tomography (CT), magnetic resonance imaging (MRI) and, more recently, by echoendoscopy. However, the assessment of axial mediastinal CT and of MRI in the coronal and sagittal planes calls for some degree of experience. To further this training a sectional anatomy is proposed in correlation with imaging of the thoracic esophagus and the posterior mediastinum. Ten fresh subjects whose vascular networks had been previously injected with colored resin were sectioned along the three planes of space after positioning under CT monitoring. The axial sections were compared with the CT images made with a GE 9800 Quick scanner. Three frontal and sagittal sections were compared with the MRI images made with a GE Signa apparatus using a high magnetic field. The relations of the esophagus were studied at three levels: the supra-azygo-aortic segment, where it is related to the left subclavian artery; the inter-azygo-aortic segment, where access to the esophagus is barred on the left by the aortic arch and on the right by the arch of the azygos vein, section of which provides ample access; and the sub-azygo-aortic segment, where the esophagus passes behind the left main bronchus and to the right of the descending aorta, two organs whose invasion contraindicates excision of a tumor of the esophagus but is difficult to assess by current thoracic imaging techniques. The esophagus then descends behind the left atrium; the investigation of the kinetics of the heart cavities by transesophageal echocardiography is an application of this anatomic relationship.(ABSTRACT TRUNCATED AT 250 WORDS)