After a new design of Mercedes Benz notoriously failed a moose test (sudden swerving to avoid an obstacle), some manufacturers enhanced suspension using stability control linked to an anti-lock braking system to reduce the likelihood of rollover. After retrofitting these systems to its models in 1999–2000, Mercedes saw its models involved in fewer crashes.Now, about 40% of new US vehicles, mainly the SUVs, vans and pickup trucks that are more susceptible to rollover, are being produced with a lower center of gravity and enhanced suspension with stability control linked to its anti-lock braking system to reduce the risk of rollover and meet US federal requirements that mandate anti-rollover technology by September 2011. MotorcyclesMotorcyclists and pillion-riders have little protection other than their clothing and helmets. This difference is reflected in the casualty statistics, where they are more than twice as likely to suffer severely after a collision. In 2005, there were 198,735 road crashes with 271,017 reported casualties on roads in Great Britain. This included 3,201 deaths (1.1%) and 28,954 serious injuries (10.7%) overall. Of these casualties 178,302 (66%) were car users and 24,824 (9%) were motorcyclists, of whom 569 were killed (2.3%) and 5,939 seriously injured (24%). Sociological factors
Studies in United States have shown that poor people have a greater risk of dying in a car crash than people who are well-off. Car deaths are also higher in poorer states.Similar studies in France or Israel have shown the same results.
Christianson syndrome is an X linked syndrome associated with intellectual disability, microcephaly, seizures, ataxia and absent speech. Presentation
Onset of symptoms is normally within the first year of life with truncal ataxia and seizures. The head is small (microcephaly). Common facial abnormalities include:
Long narrow face
Prominent nose
Prominent jaw
Large ears
Open mouth
Thick eyebrowsOther common features include:
Uncontrolled drooling
Abnormal eye movementsThe associated intellectual disability is usually in the profound range. Those affected often have a happy demeanor with frequent smiling and spontaneous laughter. Genetics
This condition is caused by mutations in the SLC9A6 gene. This gene is located on the long arm of the X chromosome (Xq26.3). The gene encodes a sodium/hydrogen exchanger located in the endosomes. Mutations in this gene cause a rise in the pH of the endosomes.How this causes the clinical features is not known presently. The inheritance of this condition is X-linked dominant. Diagnosis
The diagnosis may be suspected on clinical grounds.It is made by sequencing the SLC9A6 gene. Differential diagnosis
Angelman syndrome
Spinocerebellar ataxia type 29

Management
There is presently no curative treatment. Management is supportive. Epidemiology
The prevalence is not known but this is considered to be a rare disease. History
This condition was first described in 1999. The causative mutation was discovered in 2008. == References ==