Temporal macrodynamics and microdynamics of the postoperative impedance at the tissue-electrode interface in deep brain stimulation patients.

OBJECTIVE: To study the temporal dynamics of tissue impedance after deep brain stimulation (DBS). BACKGROUND: DBS therapy commonly employs a constant voltage approach, and current delivery to the tissue is a function of electrode-tissue impedance. It is presumed that impedance fluctuates early postimplantation, with implications for variations in current delivery and therapeutic efficacy. We hypothesised that the largest variation will be recorded early after surgery, followed by stabilisation. METHODS: Review of impedance checks of implanted DBS systems at standard parameters during the first five months postimplantation. All measurement time points were binned into 1-week periods, and we used repeated measures analysis of variance with Tukey pairwise multiple comparisons correction. The analysis was repeated after normalising impedance values for each subject to that patient's baseline value. RESULTS: There was an initial (non-significant) drop in impedance at week 1, followed by significant increase at week 3 (p=0.0002). There were no further significant differences in impedance values at subsequent time points. Analysis of normalised data showed a significant difference between the initial measurement in postoperative week 1 (normalised value 1) and week 3 (normalised value 1.73, p<0.0001), with no further difference among the subsequent weekly points during the 5-month follow-up. No significant hourly variations were found at any time points. CONCLUSIONS: We found major changes in impedance within the first month postimplantation, with no further variation. This is an important confirmation in patients of this temporal dynamics of the impedance of implanted DBS hardware, with potential therapeutic implications.

[Möbius syndrome]. / Le syndrome de Möbius.

Möbius syndrome is a rare congenital disease characterized by facial and abducens nerve palsy. Children are unable to smile, frown, suck, grimace, blink their eyes, and to move their eyes laterally. The aim of this study was to analyze the diagnosis and treatment of this disease. Maxillofacial examination reveals: facial diplegia, retrognathism, palatine and dental malformations. Möbius syndrome is usually associated with multiple cranial nerve involvement, limb or orofacial malformation, and Poland syndrome. Although the pathogenesis of the syndrome is unclear, a number of mechanisms have been suggested including vascular and genetic hypotheses. Symptomatic treatment is used to manage this syndrome. The diagnosis of Möbius syndrome may be difficult in some patients with atypical signs of facial diplegia and other cranial nerve palsies, it requires a multidisciplinary approach.

Cellular basis for the response to second-order motion cues in Y retinal ganglion cells.

We perceive motion when presented with spatiotemporal changes in contrast (second-order cue). This requires linear signals to be rectified and then summed in temporal order to compute direction. Although both operations have been attributed to cortex, rectification might occur in retina, prior to the ganglion cell. Here we show that the Y ganglion cell does indeed respond to spatiotemporal contrast modulations of a second-order motion stimulus. Responses in an OFF ganglion cell are caused by an EPSP/IPSP sequence evoked from within the dendritic field; in ON cells inhibition is indirect. Inhibitory effects, which are blocked by tetrodotoxin, clamp the response near resting potential thus preventing saturation. Apparently the computation for second-order motion can be initiated by Y cells and completed by cortical cells that sum outputs of multiple Y cells in a directionally selective manner.

Medial temporal lobe functional connectivity predicts stimulation-induced theta power.

Focal electrical stimulation of the brain incites a cascade of neural activity that propagates from the stimulated region to both nearby and remote areas, offering the potential to control the activity of brain networks. Understanding how exogenous electrical signals perturb such networks in humans is key to its clinical translation. To investigate this, we applied electrical stimulation to subregions of the medial temporal lobe in 26 neurosurgical patients fitted with indwelling electrodes. Networks of low-frequency (5-13 Hz) spectral coherence predicted stimulation-evoked increases in theta (5-8 Hz) power, particularly when stimulation was applied in or adjacent to white matter. Stimulation tended to decrease power in the high-frequency broadband (HFB; 50-200 Hz) range, and these modulations were correlated with HFB-based networks in a subset of subjects. Our results demonstrate that functional connectivity is predictive of causal changes in the brain, capturing evoked activity across brain regions and frequency bands.

[Manifestation of congenital rubella syndrome: clinical and epidemiologic aspects]. / Les manifestations ophtalmologiques de la rubéole congénitale: aspects cliniques et épidémiologiques.

INTRODUCTION: Congenital rubella syndrome is an ensemble of congenital malformations which results from a primary viral infection in non-immunised pregnant women. The main ophthalmologic manifestation is cataract. It involves at the same time visual and vital prognosis and can be responsible for multiple handicaps. METHODS: We did a retrospective study of 16 infants (32 eyes) having undergone congenital cataract surgery compatible with congenital rubella syndrome in the Casablanca paediatric ophthalmology department between January 2001 and December 2005. All the patients underwent a complete ophthalmologic examination, otorhinolaryngologic, cardiovascular and neurological examinations, and paraclinic explorations. RESULTS: The results were compared with those reported in the literature. In our series, 25 eyes (78.12%) had a cataract of which 56% were nuclear, 13 eyes (40.62%) had microphthalmia. One case each of corneal dystrophy and iris coloboma were described. Congenital glaucoma was found in only one case. Pigmentary retinopathy was found in 12 eyes (37.5%). Seven patients (43.75%) had associated cardiac anomalies, 6 (37.5%) deafness, 5 (31.25%) psychomotor delay and 2 (12.5%) facial dysmorphy. CONCLUSION: Considering the permanent disabilities caused by congenital rubella syndrome, care should be taken with the follow-up of the pregnancies and an immunization program should be implemented for good control of the circulation of the virus.

[Necrotizing fasciitis caused by pseudomonas aeruginosa (an obervation)]. / Fasciite nécrosante à pseudomonas aeruginosa (à propos d' une observation).

Necrotizing fasciitis is an exceptional and severe form of subcutaneous gangrene which requires early diagnosis and emergency treatment. We report the case of a 24 year old woman presenting with necrotizing fasciitis after pansinusitis resistant to treatment. The germ detected was pseudomonas aeruginosa. The infection was controled with intensive care, antibiotics and surgical resection of necrotic tissues. The aim of this observation is to highlight the clinical characteristics of this disease, and to insist on the necessity to recognize the early symptoms and to start treatment as soon as possible.

Widespread theta synchrony and high-frequency desynchronization underlies enhanced cognition.

The idea that synchronous neural activity underlies cognition has driven an extensive body of research in human and animal neuroscience. Yet, insufficient data on intracranial electrical connectivity has precluded a direct test of this hypothesis in a whole-brain setting. Through the lens of memory encoding and retrieval processes, we construct whole-brain connectivity maps of fast gamma (30-100 Hz) and slow theta (3-8 Hz) spectral neural activity, based on data from 294 neurosurgical patients fitted with indwelling electrodes. Here we report that gamma networks desynchronize and theta networks synchronize during encoding and retrieval. Furthermore, for nearly all brain regions we studied, gamma power rises as that region desynchronizes with gamma activity elsewhere in the brain, establishing gamma as a largely asynchronous phenomenon. The abundant phenomenon of theta synchrony is positively correlated with a brain region's gamma power, suggesting a predominant low-frequency mechanism for inter-regional communication.

[Bilateral optic neuropathy and non-Hodkin's lymphoma]. / Neuropathie optique bilatérale et lymphome non Hodgkinien.

UNLABELLED: While ocular lesion is commonly known in lymphoma, optic neuropathy is very rare : 1,3% of lymphomas affecting the central nervous systems. OBSERVATION: Authors report the case of a 75 year old patient treated in the haematology department for 8 years, for a large cell B phenotype stage IV lymphoma for which he received 7 chemotherapy courses (CHOP protocol). After a 4 year remission period, he presented a relapse with a rapid progressive bilateral impairment of visual acuity observed for a week before his admission. The ophthalmologic exam revealed no light perception and no afferent reflex on the right eye. There was light perception and weak afferent reflex on the left eye. The anterior segment was normal on both eyes and fundus examination revealed a bilateral stage I papillar oedema. The general exam showed a right facial palsy and an impairment of general condition. The orbital CT scan revealed a significant thickening of both optic nerves caused by lymphomatous infiltration. A chemotherapy with highly dosed IV and intrathecal methotrexate was performed. DISCUSSION: the optic neuropathy is usually associated with a generalized lymphoma with central nervous system involvement, but sometimes can precede the systemic spread of the disease. Apart from infiltration, the optic nerve can be compressed by an intracranial or orbital tumor. The optic neuropathy can also be caused by lymphomatous leptomeningitis.

[Primary palpebral tuberculosis (case report)]. / La tuberculose palpebrale primaire (a propos d'un cas).

Cutaneous tuberculosis is an uncommon disease and tuberculosis affecting the eyelid alone is even more rare. The clinical presentation is polymorphous which explains a diagnosis delay. Its treatment is based on antitubercular drugs chemotherapy. Authors report through an observation the case of a child with eyelid tuberculosis and discuss a difficult diagnosis, a physiopathogeny of eyelid tuberculosis, its diagnosis and treatment.

Bipolar cells contribute to nonlinear spatial summation in the brisk-transient (Y) ganglion cell in mammalian retina.

The receptive field of the Y-ganglion cell comprises two excitatory mechanisms: one integrates linearly over a narrow field, and the other integrates nonlinearly over a wide field. The linear mechanism has been attributed to input from bipolar cells, and the nonlinear mechanism has been attributed to input from a class of amacrine cells whose nonlinear "subunits" extend across the linear receptive field and beyond. However, the central component of the nonlinear mechanism could in theory be driven by bipolar input if that input were rectified. Recording intracellularly from the Y-cell in guinea pig retina, we blocked the peripheral component of the nonlinear mechanism with tetrodotoxin and found the remaining nonlinear receptive field to be precisely co-spatial with the central component of the linear receptive field. Both linear and nonlinear mechanisms were caused by an excitatory postsynaptic potential that reversed near 0 mV. The nonlinear mechanism depended neither on acetylcholine nor on feedback involving GABA or glycine. Thus the central components of the ganglion cell's linear and nonlinear mechanisms are apparently driven by synapses from the same rectifying bipolar cell.

[Apert syndrome: a reported observation]. / Syndrome d'Apert: à propos d'une observation.

Apert syndrome is a type of acrocephalosyndactylia that belongs to the group of craniofacial synostoses. It is characterised by craniofacial dysmorphia and syndactyly of hands and feet. It is an uncommon affection that is often transmitted through an autosomal dominant mode, but sporadic cases are frequent. We report the case of a 2 months old baby brought by his parents to the paediatric emergencies for respiratory distress occurring within the framework of a polymalformative syndrome. The examination showed brachycephaly, bilateral exorbitism, syndactyly of the hands and feet and an anal fistula. Echocardiographic examination showed a cardiovascular malformation (interventricular communication), the whole suggestive of Apert syndrome. The child was admitted in intensive care during five days. He died following a respiratory infection. Through this observation the authors illustrate the clinical and evolutionary aspects as well as the therapeutic difficulties of this affection.

[Non-traumatic corneal perforations: Therapeutic modalities]. / Perforations cornéennes non traumatiques : modalités thérapeutiques.

INTRODUCTION: The treatment of non-traumatic perforations of the cornea is a real challenge for the choice of surgical technique as well as for management of the causal pathology. The goal of our study is to determine the anatomical and functional results of the management of non-traumatic perforation of the cornea in the absence of ready access to a corneal graft. MATERIALS AND METHODS: This is a retrospective, non-comparative monocentric study of 23 consecutive cases diagnosed and treated between January 2011 and January 2013. We included 23 eyes with non-traumatic corneal perforation. Various surgical techniques were used depending on the size and location of the corneal perforation. RESULTS: The predominant etiology of the corneal perforations in our series was corneal abscess, found in 30.4% of cases (7 eyes). A conjunctival flap was performed in 43.5% of cases (10 eyes) followed by tarsorrhaphy in 21.7% of cases (5 eyes), autologous corneal patch in 17.4% of cases (4 eyes), amniotic membrane in 13% of cases (3 eyes) and finally cyanoacrylate glue in one case. Mean follow-up was 12.4 ± 2.1 months. Anatomical closure of the corneal perforation was achieved in 91.3% of cases (21 eyes), while the final visual acuity was not improved due to secondary opacities. DISCUSSION: The choice of surgical technique depends on the size of the corneal perforation, its location, its etiology and the resources available for emergencies. When amniotic membrane and corneal donor tissue are unavailable, conjunctival flap is an easy and effective technique, which is a good alternative to close corneal perforations less than 3mm. It improves ocular surface quality and prepares the eye for later penetrating keratoplasty. CONCLUSION: Conjunctival flap is a good technique that is still relevant today, especially in the absence of corneal donor tissue or amniotic membrane. The anatomical success rate is very satisfactory, but sometimes several interventions are needed to improve the visual prognosis.

Anthrax of the eyelids.

Anthrax is a disease caused by Bacillus anthracis. The disease affects primarily herbivores including sheep, cattle, horses, and other domestic animals. Humans may rarely be affected. We examined one male and two female patients with a localised itchy erythematous papule of the eyelid. A necrotising ulcer formed in each of the three cases resulting in a black lesion. Scraping in each case showed Gram positive rods and culture grew Bacillus anthracis. All three patients responded to the intravenous administration of penicillin G, and the lesion resolved leaving scars in two cases. Anthrax is a rare disease but should be considered in the differential diagnosis of ulcers or pustules of the eyelids.

[Ocular damage during HIV infection at the University Hospital Center of Casablanca. (Apropos of 400 cases)]. / Les atteintes oculaires au cours de l'infection par le VIH au CHU de Casablanca. (A propos de 400 cas).

The objective of this study was to report ocular manifestations in Moroccan patients infected with HIV/AIDS. 400 patients were surveyed retrospectively from 1993 to 1998 as part of a co-operative study undertaken by the departments of infectious diseases and ophtalmology of the Casablanca Teaching Hospital. Of the 400 patients, 127 had an infection of the posterior segment and 7 showed signs of a palpebral infection. We also found 44 cases of opportunist retinal infections, dominated by the Cytomegalovirus (CMV) (18 cases). Our sample study indicates an intermediary position between western countries where the widespread use of the tritherapy has increased the life expectancy of patients and sub-Saharan Africa where epidemiological data are still characterised by high mortality and increasing endemic disease.

[Involvement of the optic nerve in the course of Behcet's disease (presentation of 148 cases)]. / Les atteintes du nerf optique au cours de la maladie de Behçet (a propos de 148 cas).

Behçet's disease is a multisystemic vascularitis of still unknown etiopathogeny. Among 400 cases of Behçet disease, 148 cases presented an optic nerve involvement during a period of eight years (1992-1999). The goal of this work is to contribute to the study of optic nerve involvement in Behçet's disease. The involvement is higher in males (64%) with median age of 27 years. The involvement of the optic nerve is noticed in 37% of cases. It's isolated in 7% of cases and occurs on average after 5 years of evolution of the disease. The diagnosis is based on the clinical examination, visual field, visual evoked potentials, retinal angiography and neuro-imaging (TDM and/or MRI). It can be an acute anterior neuropathy, stasis papilledema complicating a benign intracranial hypertension, neuroretinitis or retrobulbar optic neuropathy. The extraocular systemic manifestations were dominated by oral aphthosis (94%), genital aphthosis (70%), joint manifestations (40%) and central nervous system involvement (32.4%). The prognosis is reserved, 44% of patients having vision lower than 1/10 in spite of treatment. The authors insist on the therapeutic emergency that this involvement represents and the interest to consider it in all patients having an unexplained visual loss.

[Oculomotor paralyses in the course of diabetes--concerning 12 cases]. / Les paralysis oculomotrices au cours du diabète--a propos de 12 cas.

PURPOSE: Our purpose is to study the clinical features of the oculomotor paralyses in the course of the diabetes, to assess the risk factors and to show the importance of the diagnosis and the cerebral imaging. MATERIAL AND METHODS: We report a series of 12 diabetic patients with OMP collected at the department of ophthalmology in UHC Ibn Rochd in Casablanca between 1995 and 1998. RESULT: Our study was about 9 men and 3 women, the mean age was 58 years 6 months. The diabetes was type I in 2 cases and type II in 10 cases. All the patients complained of diplopia with headache. The paralysis of VI has been noticed in 8 cases, it was bilateral in 5 cases. Unilateral Ill palsy occurred in 4 cases. Brain computed tomography was normal in 10 cases and pathologic in 2 cases. Treatment consisted in alternating occlusion in all patients. Concomitance was achieved, after 4 to 6 months of treatment. CONCLUSION: The metabolic abnormalities due to hyperglycemia and the ischemic phenomena due to the diabetic macroangiopathy explain these palsies.

[Acquired oculomotor paralysis: a new therapeutic approach. Apropos of 10 cases]. / Les paralysies oculomotrices acquises : nouvelle approche thérapeutique. A propos de 10 cas.

PURPOSE: The aim of this work is to report our rehabilitation scheme and outcome in patients with acquired oculomotor palsy. PATIENTS AND METHODS: We cared for 10 patients with oculomotor palsy between January 1996 and March 1998 at the Casablanca University Hospital. Our orthoptic rehabilitation scheme was based on reinforcing the patient's sensorial potential using a prism dioper and motor capacities by soliciting vergency and version movements. RESULTS: The 10 patients (7 males, 3 females, mean age 39.5 years) had unilateral IV palsy (n =3), bilateral IV palsy (n= 1), unilateral VI palsy (n= 2), bilateral VI palsy (n= 1), partial unilateral III palsy (n= 1) and dissociated bilateral III palsy (n= 2). Mean delay to initiation of rehabilitation was 49 days and mean duration for treatment was 3 months. We achieved total recovery in 50% of the cases and partial recovery in 40%. Intermittent diplopia persisted in 10 per thousand of the cases. These results differ slightly from those in the literature where total regression is reported in about 50% of the patients after therapeutic abstention. CONCLUSION: This small series is insufficient to validate our method. The results obtained do however show that rehabilitation is safe and should be applied more widely in patients with oculomotor palsy.

[Pseudotumorous choroid granuloma in miliary tuberculosis]. / Granulome choroïdien pseudotumoral au cours de la tuberculose miliaire.

Recently, tuberculosis re-emerged as a serious public health problem, in industrialized countries, while remaining it remains a major cause of mortality and morbidity in third world countries. Intraocular localization is rare. The most common manifestation of ocular tuberculosis in patients with miliary is Bouchut tubercules. An atypical feature of ocular tuberculosis is discussed: a pseudotumoral choroid granuloma. The behavior of the lesion and its response to antituberculous therapy was documented clinically by fundus photography on fluorescein angiography.