Several competing hypotheses attempt to explain the underlying cause; the two predominant hypotheses are the amyloid beta (Aβ) hypothesis and the cholinergic hypothesis.The oldest hypothesis, on which most drug therapies are based, is the cholinergic hypothesis, which proposes that Alzheimers disease is caused by reduced synthesis of the neurotransmitter acetylcholine. The loss of cholinergic neurons noted in the limbic system and cerebral cortex, is a key feature in the progression of Alzheimers. The 1991 amyloid hypothesis postulated that extracellular amyloid beta (Aβ) deposits are the fundamental cause of the disease. Support for this postulate comes from the location of the gene for the amyloid precursor protein (APP) on chromosome 21, together with the fact that people with trisomy 21 (Down syndrome) who have an extra gene copy almost universally exhibit at least the earliest symptoms of Alzheimers disease by 40 years of age. A specific isoform of apolipoprotein, APOE4, is a major genetic risk factor for Alzheimers disease. While apolipoproteins enhance the breakdown of beta amyloid, some isoforms are not very effective at this task (such as APOE4), leading to excess amyloid buildup in the brain. Genetic
Only 1–2% of Alzheimers cases are inherited (autosomal dominant). These types are known as early onset familial Alzheimers disease, can have a very early onset, and a faster rate of progression. Early onset familial Alzheimers disease can be attributed to mutations in one of three genes: those encoding amyloid-beta precursor protein (APP) and presenilins PSEN1 and PSEN2.
The birthmark can vary in color from light pink to deep purple and is caused by an overabundance of capillaries around the ophthalmic branch of the trigeminal nerve, just under the surface of the face. There is also malformation of blood vessels in the pia mater overlying the brain on the same side of the head as the birthmark. This causes calcification of tissue and loss of nerve cells in the cerebral cortex.Neurological signs include seizures that begin in infancy and may worsen with age. Convulsions usually happen on the side of the body opposite the birthmark, and vary in severity. There may also be muscle weakness on the side of the body opposite the birthmark.Some children will have developmental delays and cognitive delays; about 50% will have glaucoma (optic neuropathy often associated with increased intraocular pressure), which can be present at birth or develop later. Glaucoma can be expressed as leukocoria, which should suggest further evaluation for retinoblastoma. Increased pressure within the eye can cause the eyeball to enlarge and bulge out of its socket (buphthalmos).Sturge–Weber syndrome rarely affects other body organs. Cause
The blood vessel formations associated with SWS start in the fetal stage. Around the sixth week of development, a network of nerves develops around the area that will become a babys head. Normally, this network goes away in the ninth week of development. In babies with SWS due to mutation of gene GNAQ, this network of nerves doesnt go away.