Sturge-Weber syndrome
Sturge-Weber syndrome (Encephalofacial or encephalotrigeminal angiomatosis)
In a report in 1879 of a patient with hemiplegia, epilepsy and a facial naevus flammeus, Sturge suggested that the neurological features would prove to be due to a similar naevoid condition affecting the brain. This was confirmed later when leptomeningeal angiomatosis and cortical calcification were shown radiologically and at operation. Weber, whose name is included in the eponymous title, suggested the descriptive term 'encephalofacial angiomatosis'.
The Sturge-Weber syndrome is a rare disorder, usually occurring sporadically, although dominant and recessively inherited cases are recorded. Both sexes and all races are affected, though cases are more easily overlooked in coloured patients and probably under-reported.
The naevus is congenital and allows the diagnosis to be made at birth. It affects the face, invariably involving its upper part over the forehead and usually also the cheek, side of the nose and upper lip in a distribution corresponding partially, but not completely, to that of the first and second divisions of the trigeminal nerve (Fig. 21.13, Plate 10A and 10B). It is usually unilateral but bilateral distribution is commoner than is realized; it was present in one-third of 22 cases seen at the Hospital for Sick Children, London (Boltshauser et al 1976). The medial border of the naevus may fall short of or cross the midline of the face. The philtrum of the upper lip is often spared. The eye and lip may be involved on the affected side. The naevus is flat and red, being sometimes described as port-wine in colour. It is usually easily distinguished by its distribution from other commoner types of red naevus. One theory explains it as due to a persistence of the primordial vascular plexus of the embryo, an arrangement of primitive blood vessels which is the earliest stage in the development of the arteries and veins of the head. At the stage of development when the primordial plexus appears the ectodern which will later form the skin of the upper face overlies that part of the neural tube destined to form the occipital and adjacent parts of the cerebral cortex, the areas most often involved in the angiomatosis. Separation of the cutaneous and deep elements of the vascular malformation occurs as a result of later growth of the cerebral hemispheres. Occasionally flame-like naevi are present over the trunk and limbs as well as the face and an overlap exists in rare cases with the Klippel-Trenaunay syndrome. Rarely cases are seen with the typical radiological and neurological features of the syndrome, but without a facial naevus: in my experience these cases of 'Sturge-Weber syndrome sine naevus' are usually clinically milder than classical cases. Gobbi and his colleagues (1992) have suggested that such cases may be examples of the syndrome of coeliac disease, epilepsy and cerebral calcifications.
Neurological features
The main neurological features are those common to all cerebral abnormalities of early onset - seizures, developmental retardation and cerebral palsy, in the form of a spastic hemiplegia. Convulsions are usually the earliest neurological symptom, and are rarely absent. They commonly begin in the first year of life, often in the newborn period, and seldom later than 2 years of age. They are often abrupt and catastrophic in onset and the child may suffer a severe setback in his development after the first episode. A hemiplegia may be detected for the first time after the onset of seizures and may progressively worsen after each subsequent bout. The fits are commonly unilateral and contralateral to the naevus but may become generalized. A visual aura is surprisingly rare, despite the frequent involvement of the occipital lobe and the common finding of a hemianopia. The seizures may prove intractable, with frequent status epilepticus, and progressive deterioration is common in such cases. Mental retardation becomes more obvious as time passes and as fits recur, and the hemiplegia may also become more severe. The reasons for this worsening are not absolutely clear but may be due in part to the effects of the seizures themselves. The cyanosed appearance of the angiomatous vessels noted at operation in one child (Alexander & Norman 1960) suggests that the greatly increased oxygen and energy requirements of discharging neurons during seizures cannot be met. Localized hypoxia may explain the necrosis of laminar distribution found in the cortex. Areas of electrical silence may be shown by the EEG over the affected lobe or lobes, and electrocorticography shows circumscribed areas of low potential. Decreased regional cerebral blood flow was found in four Sturge-Weber patients, aged 8-26 years, in the area of their lesions, and impaired vasomotor react- ivity was noted in two patients examined (Riela et al 1985).
The recent report of a four-layered microgyric cortex in a hemipherectomy specimen from a child operated on at age 97 days suggests a prenatal effect of the vascular anomaly in that particular case (Simonati et al 1994).
Ophthalmological features
Raised intraocular tension is found in about one-third of cases of the Sturge-Weber syndrome with buphthalmos, probably due to an antenatal rise of tension within the globe, and glaucoma. This aspect of the disease is easily overlooked and needs attention to prevent visual impair- ment. Episcleral haemangioma was found in all patients with glaucoma and the Sturge-Weber syndrome studied by Phelps (1978).
A homonymous hemianopic field defect is very common, though often missed.
Retinitis pigmentosa has been reported in association with the syndrome (Berkow 1966).
Findings on imaging
The pathognomonic feature is intracranial calcification with a double contour, like a railway-line, showing a gyriform distribution. This is commonest in the occipital and parietal regions. It is seldom visible on plain skull X-rays in early life but becomes detectable and denser at later ages (Fig. 21.14). It is shown earlier by CT scan (Fig. 21.15) and has been detected in the neonatal period (Kitihara & Maki 1978). The calcification lies in the outer part of the cortex. It is usually unilateral on the side of the naevus, but 21 cases have now been reported with bilateral calcification. In four reported cases (Boltshauser et al 1976), the naevus was bilateral in two. Microcephaly developed in three of these children, suggesting that this may be a useful sign of bilateral cerebral involvement.
Atrophy of an affected hemisphere may be suggested by the finding of a smaller hemicranium on one side, with an enlarged frontal sinus and mastoid, and confirmed by CT scan (Maki & Semba 1979) or MRI. MRI was found to correlate better than CT with the clinical status in 14 Sturge-Weber patients, detecting white matter changes, the extent of lobar involvement and the degree of parenchymal atrophy (Marti-Bonmati et al 1993). Carotid arteriography may show slowing of circulation in the angiomatous vessels.
Pathological findings
The affected hemisphere is often atrophic and shows areas of leptomeningeal angiomatosis most often over the occipital lobe but sometimes over the temporal and parietal regions. The vessels in these areas are closely packed and thin-walled, and densest in the sulci. Intracerebral calcification is seen with several different patterns: concretions are seen in the outer cortical layers, the larger lumps of calcium being more superficial, and this produces the gyriform calcification seen on X-rays. `Droplet' incrustation of the smaller blood vessels is also seen. The calcium is mainly in the form of phosphate and carbonate. The iron content of affected cortex was not increased in five lobectomy specimens studied by Alexander & Norman (1960).
Treatment
This is largely symptomatic with drug treatment for epi- lepsy, appropriate education and physiotherapy and orthopaedic management for the hemiplegia.
The progressive deterioration, often in association with seizures, makes their prevention a matter of great importance. Unfortunately, they are often very difficult to control. For this reason a surgical approach with lobectomy or hemispherectomy was favoured in the past in the hope of preventing deterioration and this may still be justified in selected cases, but improvements in anticonvulsant drugs and monitoring of drug levels have now rendered it rarely necessary. Surgery should not be considered in cases with bilateral hemisphere involvement. The indications for hemispherectomy in the syndrome are the same as for the surgery of epilepsy in general: seizures refractory to medical treatment and cerebral lesions such that surgical removal of the epileptogenic region is unlikely to worsen intellectual, language or motor deficits (Tonsgard & Huttenlocher 1982). The results of hemispherectomy were reviewed by Hoffman et al (1979) in seven children, six of them under 11 months of age, followed up for 1-13 years. Four had excellent results, two were rendered hemiparetic and one died of recurrent haemorrhage into the operative cavity after multiple shunt procedures. Only one patient had been operated on in the 6 years before publication, and surgery is seldom considered nowadays, although it may occasionally still offer hope of benefit.
Argon laser therapy for the unsightly facial naevus may give good results (Noe et al 1980), but the pulsed dye laser now seems to give far better results, especially in children (Van Gemert et al 1993, Strauss & Resnick 1993). Strauss and Resnick discuss the psychosocial and ethical issues of this treatment.
