Myotonia Congenita and Myotonic Dystrophy: Surveillance and Management

Myotonia can be treated both pharmacologically and by lifestyle modifications. Cell membrane stabilizers are the medications most commonly used for symptomatic treatment of myotonia. Most patients do not require treatment for the myotonia itself, unless it is severe, but physicians must be aware of anesthesia risks in both myotonia congenita and myotonic dystrophy. A mainstay of management of myotonic dystrophy is the surveillance and treatment of its various systemic complications.     

Tactile suppression of displacement

In vision, the discovery of the phenomenon of saccadic suppression of displacement has made important contributions to the understanding of the stable world problem. Here, we report a similar phenomenon in the tactile modality. When scanning a single Braille dot with two fingers of the same hand, participants were asked to decide whether the dot was stationary or whether it was displaced from one location to another. The stimulus was produced by refreshable Braille devices that have dots that can be swiftly raised and recessed. In some conditions, the dot was stationary. In others, a displacement was created by monitoring the participant’s finger position and by switching the dot activation when it was not touched by either finger. The dot displacement was of either 2.5 mm or 5 mm. We found that in certain cases, displaced dots were felt to be stationary. If the displacement was orthogonal to the finger movements, tactile suppression occurred effectively when it was of 2.5 mm, but when the displacement was of 5 mm, the participants easily detected it. If the displacement was medial–lateral, the suppression effect occurred as well, but less often when the apparent movement of the dot opposed the movement of the finger. In such cases, the stimulus appeared sooner than when the brain could predict it from finger movement, supporting a predictive rather than a postdictive differential processing hypothesis.     

There is something out there: distal attribution in sensory substitution, twenty years later

Sensory substitution constitutes an interesting domain of study to consider the philosopher's classical question of distal attribution: how we can distinguish between a sensation and the perception of an object that causes this sensation. We tested the hypothesis that distal attribution consists of three distinct components: an object, a perceptual space, and a coupling between subjects' movements and stimulation. We equipped sixty participants with a visual-to-auditory substitution device, without any information about it. The device converts the video stream produced by a head-mounted camera into a sound stream. We investigated several experimental conditions: the existence or not of a correlation between movements and resulting stimulation, the direct or indirect manipulation of an object, and the presence of a background environment. Participants were asked to describe their impressions by rating their experiences in terms of seven possible "scenarios". These scenarios were carefully chosen to distinguish the degree to which the participants attributed their sensations to a distal cause. Participants rated the scenarios both before and after they were given the possibility to interrupt the stimulation with an obstacle. We were interested in several questions. Did participants extract laws of co-variation between their movements and resulting stimulation? Did they deduce the existence of a perceptual space originating from this coupling? Did they individuate objects that caused the sensations? Whatever the experimental conditions, participants were able to establish that there was a link between their movements and the resulting auditory stimulation. Detection of the existence of a coupling was more frequent than the inferences of distal space and object.     

Prognostic factors in vascular traumas of the popliteal region

Injuries of the popliteal region remain a serious problem as far as the outcome is concerned. The role and the risks of revascularization have yet to be properly evaluated. It's always difficult to decide on a major amputation. A retrospective study was applied to 37 cases referred to the CHRU d'Angers, between 1976 and 1987. We were then able to establish a prognostic scale with 120 ischaemia, the contusion, the clinical context and the open wound. The scale is used before any decision and allows us to decide whether revascularization or amputation have to be performed. In this series, 2 patients (5%) eventually died; 11 (33%) underwent a major amputation and 24 (65%) were successfully revascularized. The results are analyzed in relation to the prognostic scale and the literature.     

Neuralgic amyotrophy

Opinion statement  Neuralgic amyotrophy has a broad variety of clinical manifestations. Although it was initially thought to be a plexopathy, its diverse presentation can include isolated sensory nerves or even cranial nerves. Although neuralgic amyotrophy is usually a benign condition with a good recovery, pain can be a disabling feature. NSAIDs and short-term narcotics are appropriate treatments. There is lack of evidence whether the use of corticosteroids has an impact on the duration of the disease or the neuropathic pain. However, given the few adverse effects in a selective population and low cost, short-term steroids can be an option for the treatment of these patients.     

Inflammation in the Pathogenesis of Lyme Neuroborreliosis

Lyme neuroborreliosis, caused by the spirochete Borrelia burgdorferi, affects both peripheral and central nervous systems. We assessed a causal role for inflammation in Lyme neuroborreliosis pathogenesis by evaluating the induced inflammatory changes in the central nervous system, spinal nerves, and dorsal root ganglia (DRG) of rhesus macaques that were inoculated intrathecally with live B. burgdorferi and either treated with dexamethasone or meloxicam (anti-inflammatory drugs) or left untreated. ELISA of cerebrospinal fluid showed significantly elevated levels of IL-6, IL-8, chemokine ligand 2, and CXCL13 and pleocytosis in all infected animals, except dexamethasone-treated animals. Cerebrospinal fluid and central nervous system tissues of infected animals were culture positive for B. burgdorferi regardless of treatment. B. burgdorferi antigen was detected in the DRG and dorsal roots by immunofluorescence staining and confocal microscopy. Histopathology revealed leptomeningitis, vasculitis, and focal inflammation in the central nervous system; necrotizing focal myelitis in the cervical spinal cord; radiculitis; neuritis and demyelination in the spinal roots; and inflammation with neurodegeneration in the DRG that was concomitant with significant neuronal and satellite glial cell apoptosis. These changes were absent in the dexamethasone-treated animals. Electromyography revealed persistent abnormalities in F-wave chronodispersion in nerve roots of a few infected animals; which were absent in dexamethasone-treated animals. These results suggest that inflammation has a causal role in the pathogenesis of acute Lyme neuroborreliosis.Lyme disease is caused by infection with the spirochete Borrelia burgdorferi (Bb). The spirochetes enter the host''s skin via the bite of infected Ixodes scapularis ticks, causing an inflammatory response that may result in the appearance of a slowly radiating erythematous rash called erythema migrans, followed commonly, after spirochetal dissemination, by early flu-like symptoms, including headaches, fever, fatigue, malaise, and diffuse aches and pains.¹ The disseminating spirochetes show distinct organotropisms, and manifestations of infection can include arthritis, carditis, and neurologic deficits.^2,3Nervous system involvement in Lyme disease, termed Lyme neuroborreliosis (LNB), is manifest in approximately 15% of Lyme disease patients and may affect both the central (CNS) and peripheral nervous systems (PNS). CNS involvement may result in symptoms such as headache, fatigue, memory loss, learning disability, or depression. LNB of the PNS may result in facial nerve palsy, limb pain, sensory loss, and/or muscle weakness.^4–6Clinical findings of patients with LNB typically show the neurologic triad of meningitis, cranial neuritis, and radiculoneuritis,^1,7 commonly described as meningoradiculitis (also known as Garin-Bujadoux-Bannwarth syndrome). Lyme meningitis presents mostly as leptomeningitis, characterized by lymphocytic pleocytosis in the cerebrospinal fluid (CSF).⁸ LNB patients may experience encephalopathy, encephalitis, and encephalomyelitis concomitant with white matter inflammation in the brain and spinal cord.^9–11Neurogenic pain along the back, radiating into the legs and foot, accompanied with weakness, numbness, and tingling in the legs, described as radiculitis or radiculoneuritis, is the most common starting symptom in patients with peripheral LNB.^12,13 Motor deficits are also common, and pain and motor deficits are classically dermatomal or localized to the limb closest to the tick bite, suggesting a pathology that involves sensory neurons that arise from dorsal root ganglia (DRG) in that area of the spinal cord.¹⁴ Other mononeuropathies and plexopathies that result in pain, loss of motor control, and sensory deficits also occur, with patients exhibiting electrophysiologic abnormalities indicative of widespread axonal damage.^12–16 A few case reports also suggest an association with demyelinating neuropathies whereby nerve conduction studies (NCSs) showed conduction slowing and abnormal temporal dispersion, consistent with demyelinating neuropathy.¹⁷Importantly, pathologic examinations of CNS lesions from cases of human LNB have revealed lymphocyte and plasma cell infiltration in the leptomeninges and perivascular infiltrates of immune cells adjacent to white matter lesions in the brain and transverse myelitis lesions in the spinal cord,^18–25 whereas lesions from patients with PNS Lyme disease have shown inflammation in the nerve roots and DRG and patchy multifocal axonal loss accompanied with epineural perivascular inflammatory infiltrates or perineuritis.^12,26,27The rhesus macaque has proved to be an accurate model of human nervous system Lyme disease.^28–31 In one study, almost all of the experimental animals demonstrated perivascular inflammatory infiltrates, multifocal axonal changes, and NCS results that were consistent with mononeuropathy multiplex.³² Sensory ganglia of rhesus macaques that were infected with Bb showed various degrees of necrosis, and peripheral nerve specimens showed multifocal axonal degeneration and regeneration and occasional perivascular inflammatory cellular infiltrates in which macrophages showed positive immunostaining with a monoclonal antibody against a 7.5-kDa lipoprotein of Bb.³² Infection in nerve roots, DRG, and involvement of the spinal cord was also observed in the rhesus monkey model of LNB.^33–35Previously, we reported that rhesus macaques that were inoculated with live Bb into the cisterna magna showed increased levels of IL-6, IL-8, chemokine ligand 2 (CCL2), and CXCL13 in the CSF within 1 week after inoculation, accompanied by a monocytic/lymphocytic pleocytosis.³⁵ In addition, we observed elevated levels of neuronal and satellite glial cell apoptosis in the DRG of infected rhesus macaques, compared with uninfected controls. Importantly, the acute neurologic manifestations observed histopathologically as leptomeningitis and radiculitis were concomitant with the inflammatory response mounted by the Lyme disease spirochete.³⁵ Our aim was to evaluate whether inflammation as induced by the Lyme disease spirochete has a causal role in mediating the pathogenesis of acute LNB. We hypothesized that Bb induces the production of inflammatory mediators in glial and neuronal cells and that this response has a role in potentiating glial and neuronal apoptosis. We addressed this hypothesis by evaluating the inflammatory changes induced in the CNS, spinal nerves, and DRG of rhesus macaques that were inoculated with live Bb into the cisterna magna and were either left untreated or were given the anti-inflammatory drug dexamethasone (Dex), a steroid that inhibits the expression of several immune mediators,³⁶ or meloxicam (Mel), a nonsteroidal anti-inflammatory drug that inhibits cyclooxygenase-2.³⁷ Rhesus macaques were studied for either 8 or 14 weeks. In accordance with our hypothesis we found that the effective suppression of inflammation by Dex treatment resulted in inhibition of glial and neuronal damage, suggesting that inflammation has a causal role in the pathogenesis of LNB. Here, we report the results of these studies.