Microglial cells are the resident macrophages in the central nervous system. These cells of mesodermal/mesenchymal origin migrate into all regions of the central nervous system, disseminate through the brain parenchyma, and acquire a specific ramified morphological phenotype termed "resting microglia." Recent studies indicate that even in the normal brain, microglia have highly motile processes by which they scan their territorial domains. By a large number of signaling pathways they can communicate with macroglial cells and neurons and with cells of the immune system. Likewise, microglial cells express receptors classically described for brain-specific communication such as neurotransmitter receptors and those first discovered as immune cell-specific such as for cytokines. Microglial cells are considered the most susceptible sensors of brain pathology. Upon any detection of signs for brain lesions or nervous system dysfunction, microglial cells undergo a complex, multistage activation process that converts them into the "activated microglial cell." This cell form has the capacity to release a large number of substances that can act detrimental or beneficial for the surrounding cells. Activated microglial cells can migrate to the site of injury, proliferate, and phagocytose cells and cellular compartments.

Physiology of Microglia

The blood-brain barrier (BBB) prevents neurotoxic plasma components, blood cells, and pathogens from entering the brain. At the same time, the BBB regulates transport of molecules into and out of t...

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Blood-Brain Barrier: From Physiology to Disease and Back

Measuring neurophysiological signals in aircraft pilots and car drivers for the assessment of mental workload, fatigue and drowsiness.

Rasmussen encephalitis (RE) is a rare but severe immune-mediated brain disorder leading to unilateral hemispheric atrophy, associated progressive neurological dysfunction and intractable seizures. Recent data on the pathogenesis of the disease, its clinical and paraclinical presentation, and therapeutic approaches are summarized. Based on these data, we propose formal diagnostic criteria and a therapeutic pathway for the management of RE patients.

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Pathogenesis, diagnosis and treatment of Rasmussen encephalitis A European consensus statement

We studied 46 patients with paroxysmal dyskinesia and classified them according to phenomenology, duration of attacks, and etiology. There were 13 patients, 7 females, who had paroxysmal kinesigenic dyskinesia (PKD), 10 with attacks lasting 5 minutes or less (short lasting) and 3 with attacks lasting longer than 5 minutes (long lasting). Twentysix patients, 18 females, had paroxysmal nonkinesigenic dyskinesia (PNKD), 9 with short-lasting and 17 with longlasting PNKD. Five patients, 3 females, had paroxysmal exertion-induced dyskinesia (PED), 3 with short-lasting PED and the other 2 with long-lasting PED. In addition, there was 1 patient with paroxysmal hypnogenic dyskinesia (PhD) and 1 with paroxysmal superior oblique myokymia. Only 2 patients, 1 with PKD and 1 with PhD, had family history of paroxysmal dyskinesias. No specific cause could be identified in 21 patients; in the other 23 patients the etiologies included the following: psychogenic (9 patients), cerebrovascular diseases (4), multiple sclerosis (2), encephalitis (2), cerebral trauma (2), peripheral trauma (2), migraine (1), and kernicterus (1). Nine of 10 (90%) patients with PKD improved with medications, mostly anticonvulsants, compared with only 7 of 19 (37%) with PNKD. This new classification, based chiefly on precipitating events, allowed appropriate categorization of the attacks in all our patients with paroxysmal dyskinesias.

Paroxysmal dyskinesias: Clinical features and classification

PURPOSE: To determine whether decreased signal intensity of the motor cortex (T2 shortening) at magnetic resonance (MR) imaging is a useful finding for supporting the diagnosis of amyotrophic lateral sclerosis (ALS). MATERIALS AND METHODS: High-field-strength (1.5-T) MR images of 15 patients (seven men and eight women, aged 28-80 years) and 49 neurologically normal age-matched control patients were examined for T2 shortening in the motor cortex. In addition, brains of patients with ALS were examined at autopsy. RESULTS: The MR images of 14 of the 15 patients showed T2 shortening in precentral cortices, while the images of all but one of the control patients showed no such finding. In three of eight brains at autopsy, sections from the precentral cortex showed sparsely distributed, intensely stained astrocytes and macrophages. CONCLUSION: Abnormal iron deposition associated with the degenerative process could be the source of T2 shortening, which is a useful MR imaging finding in the diagnosis of ALS.

Amyotrophic lateral sclerosis: T2 shortening in motor cortex at MR imaging.

Increased sympathetic outflow to muscles in patients with amyotrophic lateral sclerosis: a comparison with other neuromuscular patients.

We conducted overnight polysomnographic sleep studies of 16 patients (5 men and 11 women) with clinically well-controlled myasthenia gravis (MG). The subtypes of MG were IIA (3 patients), IIB (11 patients), IV (1 patient) and V (1 patient). Twelve patients were found on polysomnography to have obstructive and/or central types of the sleep apnoeas (SA). Their mean age was 42.4, SD 16.4 years, and the mean duration of MG was 7.4, SD 6.96 years. SA was not detected in 4 patients whose mean age was 30.8, SD 10.71 years and who had manifested MG for a mean duration of only 0.9, SD 0.65 years. Thus, patients with a longer duration of MG tended to have more SA. In 9 of the 12 SA patients, polysomnographic studies were repeated following thymectomy. SA had resolved in 6 patients, but persisted in 3. These findings suggest that SA is a possible clinical manifestiation of MG and that nocturnal dysfunction of both peripheral and central colinergic systems may be involved.

Sleep apnoea in well-controlled myasthenia gravis and the effect of thymectomy

Muscle sympathetic nerve activity by (microneurograph) blood pressure and heart rate has been studied in patients with amyotrophic lateral sclerosis and in age-matched normal subjects (controls) at rest and during head-up tilt. Muscle sympathetic nerve activity in amyotrophic lateral sclerosis patients was significantly increased at rest unlike controls. There was no correlation between muscle sympathetic nerve activity and age in the patients with amyotrophic lateral sclerosis. Elevated muscle sympathetic nerve activity was present mainly in younger patients. There were no differences between blood pressure or heart rate in either group at rest or during head-up tilt in amyotrophic lateral sclerosis. The increase in muscle sympathetic nerve activity following tilt in the amyotrophic lateral sclerosis patients was less than in the controls, but they had no postural hypotension. The possible reasons for this observation of increased muscle sympathetic nerve activity at rest in amyotrophic lateral sclerosis are discussed.

Zenji Shiozawa

Papers

Amyotrophic lateral sclerosis: T2 shortening in motor cortex at MR imaging.

Increased sympathetic outflow to muscles in patients with amyotrophic lateral sclerosis: a comparison with other neuromuscular patients.

Sleep apnoea in well-controlled myasthenia gravis and the effect of thymectomy

Microneurographic analysis of muscle sympathetic nerve activity in amyotrophic lateral sclerosis.

Superior sagittal sinus thrombosis and systemic lupus erythematosus.