Pathogenesis Of Neurological Manifestations Research Articles

Facial nerve palsy: An atypical presentation of dengue fever

Dengue fever is a grave public health concern in tropical countries. The disease spectrum of dengue fever is multi-systemic, although neurologic complications of dengue fever is relatively uncommon. The pathogenesis of neurologic manifestations in dengue fever is not well understood and may be due to the neurotrophic effect of the virus, or related to the systemic effects of dengue infection, and immune mediated. Here in, we discuss the occurrence of isolated 7th cranial nerve lower motor neuron type palsy in a 23-year-old lady suffering from dengue fever. To date, there are very few case reports citing the involvement of facial nerve in dengue fever.

Neurological involvement of COVID-19: from neuroinvasion and neuroimmune crosstalk to long-term consequences.

As the coronavirus disease 2019 (COVID-19) pandemic continues to be a multidimensional threat to humanity, more evidence of neurological involvement associated with it has emerged. Neuroimmune interaction may prove to be important not only in the pathogenesis of neurological manifestations but also to prevent systemic hyperinflammation. In this review, we summarize reports of COVID-19 cases with neurological involvement, followed by discussion of possible routes of entry, immune responses against coronavirus infection in the central nervous system and mechanisms of nerve degeneration due to viral infection and immune responses. Possible mechanisms for neuroprotection and virus-associated neurological consequences are also discussed.

Reader response: Miller Fisher syndrome and polyneuritis cranialis in COVID-19.

We read with interest the report by Gutiérrez-Ortiz et al.1 Starting from the analysis of 2 cases of Miller Fisher syndrome and cranial polyneuritis, the authors propose some hypotheses regarding the pathogenesis of neurologic manifestations during COVID-19. They affirm that there may be a common pathogenesis among all neurologic clinical features of COVID-19, including chemosensitive disorders, which appear frequently in these patients in Europe.

Neurological complications of dengue infection

Dengue infection is endemic in more than 100 countries, mostly in the developing world. Recent observations indicate that the clinical profile of dengue is changing, and that neurological manifestations are being reported more frequently. The exact incidence of various neurological complications is uncertain. The pathogenesis of neurological manifestations is multiple and includes: neurotrophic effect of the dengue virus, related to the systemic effects of dengue infection, and immune mediated. In countries endemic to dengue, it will be prudent to investigate for dengue infection in patients with fever and acute neurological manifestations. There is need for understanding of the pathogenesis of various neurological manifestations.

Hepatic Encephalopathy

Hepatic encephalopathy is a severe complication of cirrhosis that is related to the effects of ammonia. Analysis of interorgan ammonia trafficking has identified an important role of skeletal muscle in ammonia removal and has highlighted the importance of the nutritional status. Ammonia causes neurotransmitter abnormalities and induces injury to astrocytes that is partially mediated by oxidative stress. These disturbances lead to astrocyte swelling and brain edema, which appear to be involved in the pathogenesis of neurological manifestations. Inflammatory mediators worsen brain disturbances. New methods for assessing hepatic encephalopathy include clinical scales, neuropsychological tests, imaging of portal-systemic circulation, and magnetic resonance of the brain. Reappraisal of current therapy indicates the need for performing placebo-controlled trials and the lack of evidence for administering diets with restricted protein content. Liver transplant should be considered in selected patients with hepatic encephalopathy. Future prospects include new drugs that decrease plasma ammonia, measures to reduce brain edema, and liver-support devices.

Acute porphyrias: pathogenesis of neurological manifestations.

Four types of hepatic porphyria (acute intermittent porphyria; hereditary coprophorphyria; variegate porphyria; delta-aminolevulinate dehydratase deficiency porphyria) present clinically with an identical neurological syndrome. Symptoms include severe abdominal pain, vomiting, constipation, hypertension, tachycardia, and bladder dysfunction. These symptoms have been ascribed to autonomic neuropathy. Other symptoms are motor weakness and sensory involvement, which correlate with peripheral axonal neuropathy, and mental symptoms occurring without clear morphological findings in the cerebrum. The pathogenetic mechanisms which lead to the neurological dysfunction have remained poorly understood, partly due to the lack of a suitable animal model of these rare disorders. Two hypotheses, the possible neurotoxicity of delta-aminolevulinate (ALA) and heme deficiency in nervous tissue are discussed and corresponding data from porphobilinogen-deaminase deficient mice are presented. The present evidence suggests that multiple mechanisms interact in causing the varied symptoms, including ALA interaction with GABA receptors, altered tryptophan metabolism, and possibly heme depletion in nerve cells.

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes with special reference to the mechanism of cerebral manifestations

A 29-year-old man with mitochondrial encephalomyopathy caused by partial deficiency of mitochondrial NADH-ubiquinone oxidoreductase (Complex I) is described. Clinical manifestations were characterized by generalized convulsion, dementia and stroke-like episodes consisting of hemianopsia, Gerstmann's syndrome and visual hallucination. Blood and cerebrospinal fluid lactate and pyruvate levels were elevated. Biochemical studies on a muscle biopsy specimen revealed partial deficiency of Complex I activity, and decreases in the 75-kDa and the 20-kDa subunits of Complex I by immunoblotting analysis. Serial brain CT scans revealed multiple low-density areas with fluctuating densities. Single photon emission tomographic study revealed preservation of blood circulation where CT scans showed diminished density in acute stage, suggesting the presence of abnormal cellular metabolism rather than vascular occlusion as the basic mechanism of his stroke-like episodes. Pathogenesis of neurological manifestations in MELAS is discussed with reference to the possible involvement of free radicals in inducing brain damage.