Hypotonia

About: Hypotonia is a research topic. Over the lifetime, 4101 publications have been published within this topic receiving 84886 citations. The topic is also known as: Low Muscle Tone & muscular hypotonia.

Neonatal encephalopathy following fetal distress. A clinical and electroencephalographic study.

Abstract: • Twenty-one neonates of over 36 weeks' gestation suffered perinatal asphyxia but not chronic hypoxia. Three clinical stages of postanoxic encephalopathy were distinguished. Stage 1 lasted less than 24 hours and was characterized by hyperalertness, uninhibited Moro and stretch reflexes, sympathetic effects, and a normal electroencephalogram. Stage 2 was marked by obtundation, hypotonia, strong distal flexion, and multifocal seizures. The EEG showed a periodic pattern sometimes preceded by continuous delta activity. Infants in stage 3 were stuporous, flaccid, and brain stem and autonomic functions were suppressed. The EEG was isopotential or had infrequent periodic discharges. Infants who did not enter stage 3 and who had signs of stage 2 for less than five days appeared normal in later infancy. Persistence of stage 2 for more than seven days or failure of the EEG to revert to normal was associated with later neurologic impairment or death.

The neuropsychiatry of the cerebellum - insights from the clinic.

Abstract: A central aspect of the cerebellar cognitive affective syndrome is the dysregulation of affect that occurs when lesions involve the ‘limbic cerebellum’ (vermis and fastigial nucleus). In this case series we describe neuropsychiatric disturbances in adults and children with congenital lesions including cerebellar agenesis, dysplasia, and hypoplasia, and acquired conditions including cerebellar stroke, tumor, cerebellitis, trauma, and neurodegenerative disorders. The behaviors that we witnessed and that were described by patients and families included distractibility and hyperactivity, impulsiveness, disinhibition, anxiety, ritualistic and stereotypical behaviors, illogical thought and lack of empathy, as well as aggression and irritability. Ruminative and obsessive behaviors, dysphoria and depression, tactile defensiveness and sensory overload, apathy, childlike behavior, and inability to appreciate social boundaries and assign ulterior motives were also evident. We grouped these disparate neurobehavioral profiles into five major domains, characterized broadly as disorders of attentional control, emotional control, and social skill set as well as autism spectrum disorders, and psychosis spectrum disorders. Drawing on our dysmetria of thought hypothesis, we conceptualized the symptom complexes within each putative domain as reflecting either exaggeration (overshoot, hypermetria) or diminution (hypotonia, or hypometria) of responses to the internal or external environment. Some patients fluctuated between these two states. We consider the implications of these neurobehavioral observations for the care of patients with ataxia, discuss the broader role of the cerebellum in the pathogenesis of these neuropsychiatric symptoms, and revisit the possibility of using cerebellar stimulation to treat psychiatric disorders by enhancing cerebellar modulation of cognition and emotion.

Mutations in the laminin alpha 2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy.

Abstract: Congenital muscular dystrophies (CMDs), are heterogeneous autosomal recessive disorders. Their severe manifestations consist of early hypotonia and weakness, markedly delayed motor milestones and contractures, often associated with joint deformities. Histological changes seen in muscle biopsies consist of large variations in muscle fibre size, a few necrotic and regenerating fibres and a marked increase in endomysial collagen tissue. Diagnosis is based on clinical features and on morphological changes. In several CMD cases, we have demonstrated an absence of one of the components of the extracellular matrix around muscle fibres, the merosin M chain, now referred to as the alpha 2 chain of laminin-2 (ref.3). We localized this CMD locus to chromosome 6q2 by homozygosity mapping and linkage analysis. The laminin alpha 2 chain gene (LAMA2) maps to the same region on chromosome 6q22-23 (ref. 5). We therefore investigated LAMA2 for the presence of disease-causing mutations in laminin alpha 2 chain-deficient CMD families and now report splice site and nonsense mutations in two families leading presumably to a truncated laminin alpha 2 protein.

Prader–Willi syndrome

Abstract: Prader–Willi syndrome (PWS) is a highly variable genetic disorder affecting multiple body systems whose most consistent major manifestations include hypotonia with poor suck and poor weight gain in infancy; mild mental retardation, hypogonadism, growth hormone insufficiency causing short stature for the family, early childhood-onset hyperphagia and obesity, characteristic appearance, and behavioral and sometimes psychiatric disturbance. Many more minor characteristics can be helpful in diagnosis and important in management. PWS is an example of a genetic condition involving genomic imprinting. It can occur by three main mechanisms, which lead to absence of expression of paternally inherited genes in the 15q11.2–q13 region: paternal microdeletion, maternal uniparental disomy, and imprinting defect.