Neuropathies in Systemic Disease.

Most peripheral neuropathies result from systemic disease. In this review, the authors highlight the main clinical features, electrographic abnormalities, histopathological aspects and treatment, as well as the current, but still incomplete understanding of the pathophysiological mechanisms involved. The peripheral neuropathic manifestations of renal failure, gastrointestinal illness, bariatric surgery, thyroid dysfunction, connective tissue disease, certain viral and bacterial infections, and critical illness are emphasized.

Development and Impact of a Progressive Parental Leave Policy in a Neurology Residency.

Appropriate parental leave policies remain an unmet need in graduate medical education. Although legal and institutional guidelines allow for policies that support parental leave, there are many challenges and perceived barriers to consider in developing and implementing a successful policy. In 2018, we revised the parental leave policy for our neurology residency. Here we describe the development of our policy, measure its effects, and offer guidelines for other programs to develop a similar approach. We propose solutions to commonly encountered problems, focusing on training and education, staffing of clinical services, evolving legal requirements, resident well-being and equity, and financial support.

Clinical neurophysiology of demyelinating polyneuropathy.

Demyelinating neuropathies are remarkably varied in their clinical characteristics: In etiology they may be inherited or acquired, in their time course, acute or chronic, and in their distribution, multifocal or generalized. They present with phenotypes that range from an indolent disorder that begins in childhood and progresses slowly over decades (as might be seen in an inherited form) and leads to weakness but preserved ambulation, to a neuropathy with fulminant onset and rapid progression culminating in tetraparesis and respiratory failure (as seen in the Guillain-Barre syndrome). Often demyelinating neuropathies are amenable to treatment that greatly reduces the burden of disease and extent of disability. Thus, electrophysiologic studies are critically important as an investigatory tool in the evaluation of patients with suspected demyelinating neuropathies. In this chapter, we focus our discussion on the manifold electrophysiologic details regarding the demyelinating neuropathies and provide the reader with the clinical context and pathophysiological underpinnings to help appreciate the complex character of these disorders, including the Guillain-Barré syndrome; chronic inflammatory demyelinating polyneuropathy and its variants; the dysimmune demyelinating neuropathies that accompany systemic disease such as paraproteinemia, POEMS syndrome, and multifocal motor neuropathy; diabetic neuropathy; the demyelinating inherited polyneuropathies, and the demyelinating neuropathy from toxic exposures.

Entrapment Neuropathies of the Upper Extremity.

Upper extremity entrapment neuropathies are common and can cause pain, sensory loss, and muscle weakness that lead to functional disability. In this article, the authors review common entrapment neuropathies of the upper extremities, including median neuropathy at the wrist (carpal tunnel syndrome), ulnar neuropathy at the elbow, and radial neuropathy. The authors discuss the pathophysiology of nerve compression and typical etiologies, as well as strategies for differentiating between common mimics such as cervical radiculopathy and for selecting between various treatment modalities.

Entrapment Neuropathies of the Lower Extremity.

Entrapment neuropathies in the lower limbs are a common neurologic problem and may present in any medical setting. Accurate identification and management of these nerve palsies can prevent pain, sensory loss, incoordination, and muscle weakness that may significantly affect a patient's functional mobility. In this article, the authors focus on the cause, signs and symptoms, diagnosis, and treatment of select entrapment neuropathies of the lower extremity, including palsies of the common peroneal, lateral femoral cutaneous, femoral, and posterior tibial nerves.

Microglia activation and phagocytosis: relationship with aging and cognitive impairment in the rhesus monkey.

While cognitive decline is observed in the normal aging monkey, neurons are not lost with age. Instead, frontal white matter is lost as myelin degenerates and both correlate with age-related cognitive decline. As age-related myelin damage increases, there should be an increase in clearance of damaged myelin by microglial phagocytosis. In this study, brains of behaviorally tested rhesus monkeys were assessed using unbiased stereology to quantify the density of activated microglia (LN3 antibody positive) and phagocytic microglia (galectin-3 (Gal-3) antibody positive) in three white matter regions: the corpus callosum, cingulum bundle (CGB), and frontal white matter (FWM). LN3 cell density was significantly increased in the CGB, whereas Gal-3 cell density was significantly increased in all regions. Increases in Gal-3 cell density in the FWM were associated with cognitive impairment. In the FWM of old animals, Gal-3-positive microglia were classified by morphological subtype as ramified, hypertrophic, or amoeboid. The densities of hypertrophic and amoeboid microglia significantly correlated with cognitive impairment. Finally, microglia were double-labeled with LN3 and Gal-3 showing that 91% of Gal-3 cells were also LN3 positive, thus expressing an "activated" phenotype. Furthermore, 15% of all double-labeled cells formed phagocytic cups. Overall, these results suggest that microglia become activated in white matter with age where the majority express a phagocytic phenotype. We hypothesize that age-related phagocytic activation of microglia is a response to accumulating myelin pathology. The association of Gal-3 in the FWM with cognitive impairment may reflect regional differences in damage or dysfunction of normal clearance mechanisms.

Low glial numbers in the amygdala in major depressive disorder.

BACKGROUND: Functional imaging studies implicate the prefrontal cortex and amygdala in major depressive disorder and bipolar disorder, and glial decreases have been reported in the prefrontal cortex. Here, glia and neurons were counted in the amygdala and entorhinal cortex in major depressive disorder, bipolar disorder, and control cases. METHODS: Tissue blocks from major depressive disorder (7), bipolar disorder (10), and control (12) cases, equally divided between right and left, were cut into 50 microm sections and stained with the Nissl method. One major depressive disorder and all but two bipolar disorder cases had been treated with lithium or valproate. Neurons and glia were counted using stereological methods. RESULTS: Glial density and the glia/neuron ratio were substantially reduced in the amygdala in major depressive disorder cases. The reduction was mainly accounted for by counts in the left hemisphere. No change was found in neurons. Average glia measures were not reduced in bipolar disorder cases; however, bipolar disorder cases not treated with lithium or valproate had significant glial reduction. Similar but smaller changes were found in the entorhinal cortex. CONCLUSIONS: Glia are reduced in the amygdala in major depressive disorder, especially on the left side. The results suggest that lithium and valproate may moderate the glial reduction.

Age changes in myelinated nerve fibers of the cingulate bundle and corpus callosum in the rhesus monkey.

Aging is accompanied by deficits in cognitive function, which may be related to the vulnerability of myelinated nerve fibers to the normal process of aging. Loss of nerve fibers, together with age-related alterations in myelin sheath structure, may result in the inefficient and poorly coordinated conduction of neuronal signals. Until now, the ultrastructural analysis of cerebral white matter fiber tracts associated with frontal lobe areas critical in cognitive processing has been limited. In this study we analyzed the morphology and area number density of myelinated nerve fibers in the cingulate bundle and genu of the corpus callosum in behaviorally assessed young, middle aged, and old rhesus monkeys (Macaca mulatta). In both structures, normal aging results in a 20% decrease in the number of myelinated nerve fibers per unit area, while remaining nerve fibers exhibit an increasing frequency of degenerative changes in their myelin sheaths throughout middle and old age. Concomitantly, myelination continues in older monkeys, suggesting ongoing, albeit inadequate, reparative processes. Despite similar patterns of degeneration in both fiber tracts, only the age-related changes in the cingulate bundle correlate with declining cognitive function, underscoring its role as a critical corticocortical pathway linking the medial prefrontal, cingulate, and parahippocampal cortices in processes of working memory, recognition memory, and other higher cognitive faculties. These results further demonstrate the important role myelinated nerve fiber degeneration plays in the pathogenesis of age-related cognitive decline.