This connection is involved in the tight modulation of motor strategies computed by a cortico-basal ganglia- thalamo-cortical loop.Indeed, based on the canonical anatomofunctional model of basal ganglia, nigrostriatal dopamine is able to modulate the motor loop by acting on dopaminergic receptors located on striatal GABAergic medium spiny neurons.Dysregulation of the nigrostriatal pathway is causative from Parkinson disease (PD) in humans. Toxic and/or genetic ablation of SNpc neurons produces experimental parkinsonism in mice and primates. The common features of PD and PD animal models are motor impairments (hypotonia, bradykinesia, hypokinesia). RTT pathology, in some aspects, overlaps the motor phenotype observed in PD patients. Several neuropathological studies on postmortem brain samples argued for an SNpc alteration evidenced by neuromelanin hypopigmentation, reduction in the structure area, and even controversial, signs of apoptosis. In parallel, an hypometabolism was underlined by a reduction of several catecholamines (dopamine, noradrenaline, adrenaline) and their principal metabolic by-products. Mouse models of RTT are available and the most studied are constitutively deleted Mecp2 mice developed by Adrian Bird or Katelyn McCormick laboratories.In accordance with the motor spectrum of the RTT phenotype, Mecp2-null mice show motor abnormalities from postnatal day 30 that worsen until death. These models offer a crucial substrate to elucidate the molecular and neuroanatomical correlates of an MeCP2-deficiency.
Brachymetatarsia is a condition in which there is one or more abnormally short or overlapping toe bones (metatarsals). This condition may result due to a congenital defect or it may be an acquired condition. It most frequently involves the fourth metatarsal. If it involves the first metatarsal, the condition is known as Mortons syndrome. Treatment is via a number of differing surgical procedures. Diagnosis
Differential diagnosis
Congenital causes include: Aarskog syndrome, Turner syndrome, Albrights hereditary osteodystrophy, maternal ingestion of thalidomide during pregnancy and Apert syndrome. Can be caused by a trauma, although the exact mechanism is not known. Treatment
Symptoms may be treated by wearing wider shoes to relieve pressure, or patient can wear padding around the toes. Surgery is also an option, if the pain and discomfort cannot be treated, or for cosmetic reasons. In this procedure, the short metatarsal is typically cut and a piece of bone is grafted between the two ends. In some cases an external fixator may be attached to the metatarsal with pins. Within the external fixator is an adjustable screw that must be turned (per doctors orders) to lengthen the gap between bone segments, so the bone will regrow to the appropriate shape.Following surgery, crutches or a knee scooter should be used to keep all weight off the surgically repaired foot for 3 months. After this period, orthopedic shoes or boots may be used. Epidemiology
Brachymetatarsia is found to occur more frequently in women than men.