Sturge-Weber syndrome (SWS) is a rare disorder characterized by the association of a facial birthmark called a port-wine birthmark, neurological abnormalities, and eye abnormalities such as glaucoma. SWS can be thought of as a spectrum of disease in which individuals may have abnormalities affecting all three of these systems (i.e. brain, skin and eyes), or only two, or only one. Consequently, the specific symptoms and severity of the disorder can vary dramatically from one person to another. Symptoms are usually present at birth (congenital), yet the disorder is not inherited and does not run in families. Some symptoms may not develop until adulthood. SWS is caused by a somatic mutation in the GNAQ gene. This mutation occurs randomly (sporadically) for no known reason.
SWS may be classified as a neurocutaneous syndrome or one of the phakomatoses. Neurocutaneous syndromes or phakomatoses are broad terms for groups of disorders in which growths develop in the skin, brain, spinal cord, bones and sometimes other organs of the body. These growths consist of abnormal blood vessels.
Some publications break down SWS into three main subtypes. Type 1 consists of skin and neurological symptoms. These individuals may or may not have glaucoma. Type 2 consists of skin symptoms and possibly glaucoma, but there is no evidence of neurological involvement. Type 3 consists of neurological involvement, but without skin abnormalities. Glaucoma is usually not present. Type 3 may also be known as the isolated neurological variant.
SWS is a highly variable disorder. Some individuals may develop characteristic skin abnormalities, but no neurological abnormalities. Less often, individuals develop neurological abnormalities without the characteristic skin issues. Therefore, it is important to note that affected individuals may not have all of the symptoms discussed below and that every individual case is unique. Parents should talk to their child’s physician and medical team about their specific case, associated symptoms and overall prognosis.
A congenital facial birthmark known as a port-wine birthmark or nevus flammeus is often the most notable initial symptom. This birthmark can range from light pink to reddish to dark purple in color. The size of a port-wine birthmark can vary. Usually, at least one eyelid and/or the forehead of one side of the face are affected, but both sides of the face have been affected less often. In some cases, the entire half of one side of the face may be affected. Sometimes, the discoloration may extend slightly onto the other side of the face or both sides of the face may be extensively involved. In rare cases, a port-wine birthmark extends all the way to the trunk and/or arms. The port-wine birthmark that characterizes SWS is caused by an overabundance of capillaries just below the surface of the skin in the distribution of the trigeminal nerve. Capillaries are tiny blood vessels that form a fine network throughout the body connecting arteries and veins and are responsible for the exchange of various substances such as oxygen between cells and tissue. If untreated, port-wine birthmarks may deepen in color with age, thicken, and potentially develop blood blisters (blebs) that can burst causing spontaneously bleeding (blebbing).
The abnormal blood vessels that make up a port-wine birthmark will vary in size, diameter, distribution, and depth from one individual to another and even within the same person in different affected areas. This means that a port-wine birthmark in each individual is unique and can be quite dissimilar from one person to another.
Individuals with SWS may also experience a variety of neurological abnormalities. The extent of neurological involvement can vary dramatically from one person to another. Neurological symptoms are caused by the abnormal growth of blood vessels on the surface of the brain (leptomeningeal angiomas). Seizures, which often begin in infancy or childhood, are a common finding. Seizures usually affect the opposite side of the body as the port-wine birthmark, but sometimes affect both sides of the body. Seizures may vary in frequency and intensity and sometimes may worsen in severity and frequency with age. Affected individuals may also experience muscle weakness or paralysis on one side of the body (hemiparesis), usually on the side opposite the port-wine birthmark. Developmental delays and intellectual disability ranging from mild learning disabilities to severe cognitive deficits may occur in some cases; in other cases, intelligence and cognition are unaffected.
Headaches, including migraines, and visual field defects such as the loss of vision in half the visual field in one or both eyes (hemaniopsia) may also occur. There is a risk of stroke, stroke-like episodes or mini-strokes (transient ischemic attacks). Stroke-like episodes can be associated with temporary (transient) weakness or paralysis of half of the body and visual field defects. Behavioral problems such as attention deficit disorder, mood disorders, and poorer social skills have also been seen in some children, particularly those with lower cognitive function and a greater frequency of seizures.
Some children are born with glaucoma, a condition marked by increased pressure within the eye. Glaucoma usually affects the eye on the same side of the face as the port-wine birthmark. Glaucoma can potentially damage the optic nerve, the main nerve that transmits signals from the eye to the brain, ultimately resulting in progressive vision loss. The same eye also may become enlarged so that appears to bulge out of its socket (buphthalmos).
Other eye abnormalities can occur including the development of angiomas in the membranes that line the inner surface of the eyelids (conjunctiva), the layer of blood vessels and connective tissue (choroid) between the white of the eye and the retina, and the clear, transparent membrane covering the membrane (cornea). An affected individual’s eyes can be two different colors (e.g. one brown and one blue eye). Additional ocular symptoms can include an abnormal accumulation of fluid inside the eyeball causing enlargement of the eyeball (hydrophthalmos); degeneration of the cranial nerve that transmit lights signals to the brain (optic atrophy); clouding or displacement of the lenses; retinal detachment; streaks resembling blood vessels in the retina (angioid streaks); and/or loss of vision due to an organic lesion in the visual cortex (cortical blindness). Individuals who have neurological abnormalities, but do not have a port-wine birthmark generally do not develop eye problems.
Endocrine disorders have also been reported in some individuals including central hypothyroidism and an increased risk of growth hormone deficiency. Central hypothyroidism is characterized by underactivity of the thyroid gland due to insufficient stimulation of thyroid stimulating hormone in an otherwise healthy thyroid. Central hypothyroidism in SWS may be due to anti-seizure medication.
Additional symptoms may occur including an abnormally large head (macrocephaly), overgrowth (hypertrophy) of the certain soft tissues underlying the port-wine birthmark, and lymphatic malformations, which are non-malignant masses consisting of fluid-filled channels or spaces thought to be caused by abnormal development of the lymphatic system. These symptoms are consistent with a related rare disorder known as Klippel-Trenaunay syndrome (KTS) and most children with these findings are classified as having KTS. Researchers are not sure whether SWS and KTS are related disorders that overlap or whether they are similar, yet distinct, rare disorders.
SWS is caused by a mutation in the GNAQ gene. This genetic mutation is a somatic mutation because it occurs after fertilization of the embryo; in the case of SWS, most likely at an early stage of embryonic development. By definition, a somatic mutation can occur in any cell of the body except the sex cells (sperm and egg). Affected individuals will have some cells with a normal copy of the gene and some cells with the abnormal gene (mosaic pattern). This may be referred to as having two distinct cells lines in the body. The variability of symptoms associated with SWS is due, in part, to the ratio of healthy cells to abnormal cells in the body and the types of cells that are affected. Somatic mutations are not inherited and are not passed on to children. Researchers believe that somatic mutations of the GNAQ gene occur randomly for no apparent reason (sporadically).
Genes provide instructions for creating proteins that play a critical role in many functions of the body. When a mutation of a gene occurs, the protein product may be faulty, inefficient, or absent. Depending upon the functions of the particular protein, this can affect many organ systems of the body. The GNAQ gene creates a protein known as Gaq that plays an important role in cell function, including the regulation of blood vessels. The specific underlying manner in which Gaq function is disrupted in individuals with SWS is not fully understood. More research is necessary to determine the exact underlying mechanisms that cause the varied symptoms of SWS.
As discussed above, symptoms are caused, in part, by the abnormal development, growth, and proliferation of certain blood vessels. These blood vessel abnormalities often result in secondary effects to the affected tissue including lack of oxygen in affected body tissue (hypoxia), inadequate blood supply to affected areas (ischemia), obstruction of affected veins (venous occlusion), the formation of blood clots (thrombosis), and/or tissue death cause by lack of oxygen (infarction). Calcification of affected areas of the brain may also occur.
A mutation in the GNAQ gene can also cause a form of skin cancer (melanoma) that affects the eye (uveal melanoma). GNAQ mutations associated with uveal melanoma affect specific cells known as melanocytes. The mutation in people with uveal melanoma occurs in adulthood as opposed to before birth as it does in people with SWS. Therefore, the specific cells involved and the age of an individual when a mutation in GNAQ occurs is extremely important and can cause different disorders or physical findings.
SWS affects males and females in equal numbers. The exact incidence and prevalence is unknown. One estimate places the incidence at 1 in 20,000-50,000 live births. Approximately 1 in 1,000 babies are born with a port-wine birthmark, but only approximately 6% of individuals with a port-wine birthmark on the face develop the neurological abnormalities associated with SWS. The risk increases to 26% when the ophthalmic branch of the trigeminal nerve is affected. SWS can affect individuals of any race or ethnicity.
A diagnosis of SWS is based upon identification of characteristic symptoms (e.g. port-wine birthmark), a detailed patient history, a thorough clinical evaluation and a variety of specialized tests. A diagnosis may be straightforward in an infant with a port-wine birthmark, glaucoma, evidence of cerebral involvement and neuroimaging findings consistent with a diagnosis of SWS. Diagnosis can be more difficult in infants who have a port-wine birthmark, but no neurological symptoms.
Clinical Testing and Workup
Various imaging techniques can be used to identify and assess neurological complications including x-rays of the skull (skull radiography) or magnetic resonance imaging (MRI) with gadolinium. A head computed tomography (CT) scan can show intracranial calcification in certain areas of the brain. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues. Gadolinium is a contrast agent that is used to enhance the scanning results and supply a more detailed picture of tissues such as the brain or blood vessels.
Newer neuroimaging techniques such as susceptibility-weighted imaging (SWI) have proven useful in evaluating individuals for brain abnormalities potentially associated with SWS. SWI uses a different type of contrast to enhance traditional MRIs and may allow physicians to diagnose brain abnormalities earlier. SWI is particularly effective at evaluating venous structures in the brain.
Computerized tomography (CT) scanning may also be used to aid in diagnosing SWS. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. A single-photon emission computed tomography scan (SPECT), which is a specialized CT scan, can reveal areas of involvement in the brain that may not show in MRI or traditional CT scans. SPECT scanning may be used in conjunction with other scanning techniques to evaluate the brain of individuals suspected of having SWS.
Traditional angiography designed to evaluate the health and function of blood vessels) are not usually recommended for individuals suspected of having SWS, but occasionally may be required to exclude a high flow lesion such as an arterial venous malformation or arterial venous fistula. An electroencephalogram (EEG) can be used to evaluate and localize seizure activity.
A complete ophthalmological exam can reveal glaucoma and other eye abnormalities potentially associated with SWS. Because of the high risk of glaucoma, complete eye examination should be performed regularly, especially in infants and young children. Follow-up examination should continue into adulthood even if results are normal through childhood.
The treatment of SWS is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists. Pediatricians, neurologists, neurosurgeons, dermatologists, ophthalmologists, and other healthcare professionals may need to systematically and comprehensively plan an affect child’s treatment. Psychosocial support for the entire family is essential as well.
Laser therapy can lighten or remove the port-wine birthmark in affected individuals, even infants as young as one month old. However, port-wine birthmarks tend to return or darken again, necessitating multiple laser therapy sessions. Pulse dye laser therapy is the most common technique for treating individuals with SWS. However, because each port-wine birthmark is dissimilar (e.g., they vary in size, diameter, distribution and depth), the most effective therapy for one person will not be the same for another person and no one form of laser therapy is effective for all affected individuals. In fact, different laser therapies may be required for different affected areas of the same individual.
Seizures are treated with anti-seizure (anti-convulsant) medications. The effectiveness of these medications in treating people with SWS is highly variable. Some individuals do not respond to anti-seizure medications (refractory seizures) despite an aggressive treatment regimen. Refractory cases may ultimately require surgery. Surgical techniques that have been used to control seizures in SWS include hemispherectomy, focal cortical resection, and vagal nerve stimulation.
Hemispherectomy involves the surgical removal or disabling of half of the brain, specifically the half of the brain which is repeatedly damaged by chronic seizure activity. This surgical procedure can be associated with significant adverse effects including weakness on one side of the body possibly affecting walking (hemiparetic gait), little use of the affected hand, or hemianopsia. In some cases, such abnormalities may already be present before the surgery as a consequence of SWS. In certain cases, hemispherectomy may be recommended for individuals with repeated stroke-like episodes and progressive neurological deficits.
Focal cortical resection is used when seizure activity arises from one specific area of the brain. This area of the brain can be isolated through brain mapping, a scientific method of studying brainwave activity. A neurosurgeon will remove the affected piece of the brain (focal resection). This procedure requires removing a small piece of the skull in order to gain access to the brain.
Vagus nerve stimulation is a procedure in which a device called a pulse generator is inserted into the chest and a wire is run underneath the skin to the vagus nerve in the neck. The pulse generator is similar to a pacemaker and transmits mild, electrical impulses to the brain via the vagus nerve. These impulses prevent seizures from occurring. This intensity and timing of the nerve impulses are determined based upon each individual’s needs.
The decision to undergo surgery to treat refractory seizures in children with SWS is difficult because of the varied pattern, frequency and severity of seizures in each child. Some children experience clusters of seizures that occur close together only to be followed by a seizure-free period that can last for many months or years. Some physicians advocate earlier surgery for seizures in order to protect against refractory seizures, developmental delays, cognitive dysfunction, and hemiparesis.
Decisions concerning the use of particular drug regimens, surgery, and/or other treatments should be made by physicians and other members of the health care team in careful consultation with parents or a patient based upon the specifics of an individual case; a thorough discussion of the potential benefits and risks, including possible side effects and long-term effects; patient preference; and other appropriate factors.
Preventive (prophylactic) treatment of migraines and headaches may be recommended and may include medications such as propranolol or verapamil. Some anti-seizure medications such as gabapentin, topiramate, and valproic acid may also help to treat migraines or headaches.
Affected infants and children should receive regular ophthalmological exams in order to promptly detect and treat glaucoma and any increase in intraocular pressure. Certain medications usually delivered as eye drops or orally may be used to treat glaucoma. Ultimately, glaucoma often requires surgery with medications used as a follow up (adjunct) therapy. There are several different surgical techniques used to treat glaucoma in individuals with SWS depending upon the individual case.
Additional therapy includes physical therapy for muscle weakness, special education for children with developmental delays or intellectual disability as well as other medical, social or vocational services.
The identification of the GNAQ gene mutation will allow researchers to focus on a specific direction to better understand how SWS develops and to explore novel methods in how to treat the disorder. For example, new therapies such as drugs that specifically target the proteins and pathways associated with the GNAQ gene will be explored (targeted therapies).
Low-dose aspirin has been used to treat individuals with SWS. Low-dose aspirin has led to a reduction in the frequency of seizures and stroke-like episodes. In some cases, the decrease in seizure activity is significant. Complications have included increased bruising and gum or nose bleeding. Most reports in the medical literature suggest low-dose aspirin can safely be used in individuals with SWS and provides benefit. However, studies are needed to determine the long-term safety and effectiveness of low dose aspirin and whether this treatment improves long-term cognitive function and overall quality of life.
The Atkins version of the ketogenic diet has been reported to be successful in reducing the frequency of seizures in five children with SWS. These children had seizures that failed to respond to medical treatment and occurred at least monthly.
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