eMedicine Specialties > Ophthalmology > Phakomatoses

Sturge-Weber Syndrome

Author: Monte A Del Monte, MD, Skillman Professor of Pediatric Ophthalmology, Professor of Ophthalmology, Pediatrics and Communicable Diseases, Director of Pediatric Ophthalmology and Strabismus, W K Kellogg Eye Center, University of Michigan Medical School
Coauthor(s): Maya Eibschitz-Tsimhoni, MD, Assistant Professor of Ophthalmology, Pediatric Ophthalmology and Adult Strabismus, Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical Center
Contributor Information and Disclosures

Updated: Feb 15, 2007

Introduction

Background

Sturge-Weber syndrome (SWS) belongs to a group of disorders collectively known as the phakomatoses ("mother-spot" diseases). It consists of congenital hamartomatous malformations that may affect the eye, skin, and central nervous system at different times.

SWS is classified into complete trisymptomatic SWS when all 3 organ systems are involved, incomplete bisymptomatic SWS when the involvement is either oculocutaneous or neurocutaneous, and incomplete monosymptomatic SWS when there is only neural or cutaneous involvement. Patients with no cutaneous involvement appear to be spared from the ocular manifestations of the syndrome.

Clinically related features include focal or generalized motor seizures in as many as 85% of patients, some degree of mental retardation in approximately 60% of patients, and such neurologic deficits as hemiplegia and homonymous hemianopsia. Focal or generalized motor seizures usually begin in the first year of life, and profound seizure activity sometimes may be observed with resultant further neurologic and developmental deterioration. Therefore, it is desirable to diagnose and treat the disease early, before permanent damage to the brain occurs.

Progressive characteristic calcifications in the external layers of the cerebral cortex underlying the angiomatosis associated with ipsilateral cortical atrophy frequently develop and progress with age, occasionally extending anteriorly to the frontal and temporal lobes.

Pathophysiology

The hallmark of SWS is a facial cutaneous venous dilation, also referred to as nevus flammeus or port-wine stain, which is present in as many as 96% of patients and is visible at birth. The facial venous dilation appears as one or several dull red patches of irregular outline, along, but not limited to, the distribution of one or more divisions of the trigeminal nerve.

A leptomeningeal congenital venous angiomatosis, usually ipsilateral to the facial lesion and located most commonly in the meninges overlying the occipital and posterior parietal lobes, results in involvement of the central nervous system.

Frequency

United States

The incidence of SWS is unknown.

International

SWS occurs in all countries.

Mortality/Morbidity

The glaucoma associated with SWS is a significant cause of morbidity because of its early onset and resistance to conventional forms of treatment. Glaucoma has been estimated to occur in 30-70% of patients with SWS.

Race

SWS occurs in all races.

Sex

No significant sexual predilection exists.

Age

Generally, SWS is diagnosed easily at birth or in early infancy based on the external clinical signs alone. However, the development of morbidity from secondary changes and complications occurs throughout life.

Secondary glaucoma may present at any age, although early onset is the rule, with approximately 60% of glaucomas presenting at birth or early infancy and another 30% presenting during childhood. In addition, the median ages reported for onset of visual symptoms related to secondary retinal changes range from age 8-20 years.

Clinical

History

The 3 forms of SWS generally are diagnosed on clinical grounds by the association of the typical cutaneous, central nervous system, and ocular abnormalities.

When a typical facial vascular skin lesion is found in a newborn, it should alert the physician to perform a complete ophthalmologic and systemic assessment for the potentially serious associated disorders. Children with bisymptomatic or trisymptomatic SWS initially may seem neurologically normal and have no symptoms of glaucoma or other ocular manifestations; thus, in some instances, the diagnosis may not become clear for an extended period of time.

Physical

• Ocular signs, including a corneal diameter of more than 12 mm during the first year of life, corneal edema, tears in the Descemet membrane (Haab striae), unilateral or bilateral myopic shift, optic nerve cupping greater than 0.3, or any cup asymmetry associated with intraocular pressure above the high teens, may indicate the presence of infantile glaucoma.
• Increased conjunctival vascularity can be seen on slit lamp examination or as a pinkish discoloration seen by the naked eye. The abnormal plexus of episcleral vessels may be hidden by the overlying tissue of the Tenon capsule in infancy and only appreciated clinically in later childhood.
• Prominent tortuous conjunctival and episcleral vascular plexuses affect as many as 70% of patients with SWS and often correlate with increased episcleral venous pressure, probably resulting from arteriovenous shunts within the episcleral hemangiomas. The overlying retinal vessels may be affected, demonstrating dilation and tortuosity as well as peripheral arteriovenous communications.
• Iris heterochromia occurs in approximately 10% of patients with SWS. The more deeply pigmented iris usually is ipsilateral to the port-wine stain, signifying an increase in melanocytes number or activity.
• The diagnosis of diffuse choroidal hemangioma is based on tumor appearance on indirect binocular ophthalmoscopy.
• Ocular involvement may include eyelid hemangiomalike superficial changes (which on histology demonstrate only venous dilation), glaucoma, conjunctival and episcleral hemangiomas, diffuse choroidal hemangiomas, and heterochromia of the irides. Tortuous retinal vessels with occasional arteriovenous communications may be found.
• The facial cutaneous venous lesion usually is the first component of the syndrome to be observed, since it is visible at birth. It may be very pale at first. Although it does not increase in extent, it usually becomes darker with age. Although not a medically threatening condition in and of itself, the cosmetic deformity that the port-wine stain imposes may carry a psychological impact.
• Several possible mechanisms exist for decrease in visual function in patients with SWS.
  • As soon as SWS is first suspected or documented, a complete ophthalmologic evaluation is essential to rule out glaucoma, since the infant's eye is damaged quickly by increased intraocular pressure. The earlier glaucoma is documented and the more effectively it is controlled, the less likely secondary glaucomatous changes will occur, including buphthalmos, increased corneal diameter, tears in the Descemet membrane, corneal edema, and optic nerve damage resulting in myopia, anisometropia, amblyopia, strabismus, and visual field defects.
  • Amblyopia is an important cause of poor vision in patients with infantile glaucoma. Amblyopia usually is anisometropic from glaucoma-induced myopia or secondary to unilateral or bilateral pattern deprivation caused by cloudy corneas. Even when glaucomatous optic nerve damage is present, amblyopia may be superimposed upon the organic damage. Therefore, a trial of amblyopia therapy is indicated.
  • Diffuse choroidal hemangioma, characteristically seen in patients with SWS, is present in as many as 40-50% of patients. (A circumscribed, isolated form occurs in otherwise normal adults.) It is almost always unilateral and ipsilateral to the port-wine stain, but bilateral cases associated with bilateral nevus flammeus have been described.
    • The choroidal hemangiomas are flat, commonly covering over one half of the fundus, involving the posterior pole, and extending into the equatorial zone.
    • Diffuse involvement of the entire uvea may be seen.
    • In some cases, the extent and character of the pathognomonic choroidal vascular lesion results in a striking reddish glow to which the descriptive term tomato-catsup fundus has been applied.
    • Some patients have a focal, often paramacular area where the angioma is more thickened and elevated.
    • The choroidal angiomatosis grows slowly and usually remains asymptomatic in childhood. During adolescence or adulthood, marked thickening of the choroid sometimes becomes evident with secondary changes to overlying ocular structures.
  • Changes in the overlying retinal pigment epithelium range from mild atrophy to focal proliferation with drusen formation to severe fibrous transformation and focal ossification. The retina over the hemangioma may be attached and well preserved, attached and degenerated, or detached.
  • Degenerative changes in the overlying retina include focal chorioretinal adhesions, loss of photoreceptors, severe cystoid degeneration of the outer layers, and marked gliosis. Widespread serous detachment, retinal leakage, and edema may occur. In its early stages, the choroidal thickening and elevation of the retina may produce an increasing ipsilateral hyperopia. With progression of secondary changes, visual loss and visual field defects may develop. Subretinal fibrosis in the macular area and cystoid macular edema are associated with the most severe visual loss.
  • The glaucoma is almost always unilateral and ipsilateral to the port-wine stain, although contralateral or bilateral glaucoma with unilateral cutaneous lesions have been reported. The occurrence of glaucoma has been noted, especially when the facial skin changes involve the upper and lower eyelids. Numerous mechanisms have been postulated to explain the pathogenesis of glaucoma in SWS. At present, the most accepted explanation for the elevated intraocular pressure is a combination of developmental angle anomalies, which have a dominant role in infantile onset glaucoma and elevated episcleral venous pressure, which is more important in later onset glaucoma.
  • Glaucomatous damage, as well as degenerative changes in the outer retinal layers and vascular abnormalities in the occipital lobe may cause visual field defects. Careful visual field perimetry is indicated.

Causes

The clinical manifestations of SWS have a common embryological basis. The primary defect is a developmental insult affecting precursors of tissues that originate in the promesencephalic and mesencephalic neural crest. Then, these affected precursors give rise to vascular and other tissue malformations in the meninges, eye, and dermis.

Although the exact nature of the insult is unknown, it has been postulated that a somatic mutation in these precursors may lead to overproduction of an angiogenic factor. Others have suggested that SWS may be due to a lethal gene surviving by mosaicism.

Incomplete SWS results from the same developmental defect, affecting only those cells whose clonal progeny are destined for the affected tissues. In contrast with the other phakomatoses in which clear-cut hereditary patterns are often evident, the influence of heredity in SWS has not been documented. To date, no gene defect has been associated with the syndrome. Several types of chromosomal abnormalities have been reported, but most patients with SWS have normal karyotypes. Most patients with SWS have a sporadic, nonfamilial disease.

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