Year : 2007 | Volume
: 10 | Issue : 5 | Page : 55--58
Great Ormond Street Hospital for Children, London and National Centre for Young People with Epilepsy, Lingfield, United Kingdom
Great Ormond Street Hospital for Children, London and National Centre for Young People with Epilepsy, Lingfield
Sturge-Weber syndrome (SWS) is characterized by a facial capillary hemangioma (port wine stain) involving the periorbital area, forehead or scalp, a venous angioma of the leptomeninges and a choroidal angioma. Following normal early development, children with SWS often experience neurological and developmental deterioration in association with the onset of seizures and consequently suffer a high rate of disability. The classical imaging finding in these children is the evidence of calcification in the occipital area. The striking features of the EEG in SWS are the attenuation and the excess of slow activities. Recent advances in the diagnosis and treatment, particularly the surgical options are discussed.
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Aylett S. Sturge-Weber syndrome.Ann Indian Acad Neurol 2007;10:55-58
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Aylett S. Sturge-Weber syndrome. Ann Indian Acad Neurol [serial online] 2007 [cited 2019 Sep 22 ];10:55-58
Available from: http://www.annalsofian.org/text.asp?2007/10/5/55/33497
Schirmer first described the association of a facial port wine stain (PWS) with bupthalmos in 1860. In 1879 Sturge described the association of a PWS with bupthalmos with focal seizures and postulated naevoid involvement of brain. The early radiological features of SWS were first reported by Weber 1922 and Dimitri 1923.
Sturge-Weber syndrome (SWS) is characterized by a facial capillary hemangioma (port wine stain) involving the periorbital area, forehead or scalp, a venous angioma of the leptomeninges and a choroidal angioma. The facial port wine stain (PWS) may be absent in approximately 10% of cases. The leptomeningeal angioma typically involves the parieto-occipital region or the entire hemisphere and is more often unihemispheric but may be bihemispheric. The presence of a choroidal angioma leads to the association of glaucoma. Neither the size or distribution of the PWS appears to correlate with the neurological features.
SWS is a sporadic condition. It is postulated that SWS is a developmental abnormality arising in the first trimester of pregnancy. It has been suggested that SWS arises due to somatic mosaicism. Huq et al. , examined the karyotype of cell lines of tissue from cerebral angiomas and affected and nonaffected skin and blood in four patients with SWS . Affected tissue from two of the patients showed chromosomal abnormalities. Comi et al. , on the basis of studies of affected skin and brain tissue of patients with SWS, suggested that increased gene expression of fibronectin may have a role in blood vessel proliferation. Comati et al. , found evidence of dysregulation of hypoxia-inducible factor-alpha expression and enhanced endothelial turnover in SWS vessels, suggesting that continuing changes may occur within the angioma.
The angioma and associated vascular abnormaility
The leptomeningeal angioma involves the pia mater, most commonly in the occipito-parietal region but may involve the entire cerebral hemisphere. The angioma consists of tortuous folds of capillaries and veins in the subarachnoid space. In addition, there is either absence or decreased numbers of cortical veins, prominent deep medullary veins and enlargement of the choroid plexus. Calcification is seen within the superficial layers of cerebral cortex with gliosis. Although calcification and focal or generalized atrophy are well demonstrated by computed tomography (CT) [Figure 1], gadolinium enhanced magnetic resonance imaging (MRI), is a superior technique both for detection of the extent of the pial angioma, the associated vascular anomalies and recent ischemic damage [Figure 2],[Figure 3]. MRI is well-established as the imaging modality of choice in SWS, as the technique is more sensitive than CT in demonstrating the extent of the pial angioma at an early and often presymptomatic, stage.,
Abnormalities of diffusion weighted imaging in a small series of infants and children, showed a reduction of the apparent diffusion coefficient. Whether there is a possible relationship of these changes with developmental outcome is not yet known.
Progressive calcification and gliosis may occur, with associated cortical atrophy. In addition to the above venous abnormalities, conventional angiography has shown stasis and slowing of the venous circulation. Magnetic resonance angiography has also shown reduced flow in transverse sinuses/jugular veins. Thus, there is evidence to support the hypothesis that the primary abnormality in SWS is one of venous stasis. Studies of cerebral blood flow and those of glucose utilization have shown a reduction in blood flow and glucose metabolism respectively. This would be consistent with an ischemic process involving the affected hemisphere. There is evidence of an impairment of regulation of cerebral blood flow in response to Co2 and acetazolamide., Middle cerebral artery Doppler recordings suggest there is an impairment of the expected physiological increase in cerebral blood flow of affected/ and contralateral hemisphere during seizures in infants with SWS. Since the arterial tree is anatomically normal in the majority of cases and there is a major venous abnormality, it seems likely that the pathophysiological mechanism involves either poor venous drainage and/or venous hypertension. The progressive gliosis and atrophy seen in SWS are consistent with an ischemic process involving the cortical and subcortical regions of the brain underlying the venous angioma.
Episodes of Acute Encephalopathy
Following normal early development, children with SWS often experience neurological and developmental deterioration in association with the onset of seizures and consequently suffer a high rate of disability.,, Children with SWS also frequently develop glaucoma and a homonymous hemianopia. Although a bihemispheric angioma appears to be associated with a poor outcome, global cognitive impairment is seen in cases with unilateral leptomeningeal involvement.,,,,
The majority of children with SWS appear to develop seizures in the first two years of life, with the onset of seizures below the age of six months being associated with intractability and a poor outcome. Frequently, the onset of seizures is followed by the appearance for the first time of a hemiplegia and a homonymous hemianopia. Clinically, acute episodes of encephalopathy occur with altered consciousness associated with recurrent seizures. Neurological deficits often become more severe after each episode of encephalopathy.
Typically, the onset of seizures is with simple partial seizures. Seizures often cluster over a period of one to seven days (personal observation). Complex partial seizures and multiple seizure types may also occur. In a retrospective series, the mean age of onset of seizures was 31 months. Status epilepticus was reported in 50%. Resistance to anticonvulsant treatment was seen in 65% of this series.
Electroencephalographic (EEG) abnormalities may be both nonepileptiform, with asymmetry of the background amplitude or frankly epileptic with focal or generalized discharges. The striking features of the EEG in SWS are the attenuation and the excess of slow activities; bilateral polymorphic delta activity, which is often an EEG marker for ischemia, appears to be related to severe mental retardation, even if the lesion is unilateral. The absence of interictal spiking and the occurrence of EEG seizure discharges only in the periphery of the lesion are compatible with focal ischemia underlying the pial angioma itself. Bilateral interictal EEG abnormalities have been found to be associated with greater number seizures and lower IQ.
Cognitive and Developmental Outcome
Retrospective studies suggest that there is a spectrum of neurological and cognitve disability in children with unihemispheric SWS. In one series 30% were found to fall within the normal ability range, whilst 60% showed cognitive impairment which varied from mild (12.5%), to severe (32.5%). Although a bihemispheric angioma appears to be associated with a poorer outcome than a unihemispheric one, it is noteworthy that in cases with unilateral leptomeningeal involvement, global cognitive impairment is also common.
Whilst the onset of epilepsy in the first year of life is associated with a high rate of developmental delay,, global delay is seen infants with no or relatively well controlled seizures (personal observation). Chugani et al using positron emission studies (PET) found hypometabolism extending beyond the imaging abnormality on CT in two patients with learning disability, suggesting that the physiological abnormality may be more widespread than the area of the hemangioma.
Headache and episodes of acute hemiplegia
Episodes of migraine like headache are described in SWS. These may be accompanied by transient hemiparesis. Flunarazine has reportedly been helpful in some cases. Acute transient hemiplegia following a minor blow to the head has been observed in children with SWS. In the latter series there was resolution of the hemiplegia or improvement to the same level prior to the episode in all cases.
Medical Treatment of SWS
The current approach of medical treatment is anticonvulsant treatment and anti-platelet treatment with prophylactic low dose aspirin. In view of the possibility of neurological deficit with seizure clusters, episodes of seizures should be treated aggressively and prolonged seizures avoided where possible. Maintenance anticonvulsant treatment is indicated in infants and children with seizures and should be considered after one seizure episode. At present, there is no evidence base to suggest one particular anti-epileptic drug above another, thus use of local clinical guidelines is recommended. Acute rescue treatment of seizures with benzodiazepines or if ineffective, intravenous phenytoin or phenobarbitone is recommended.
The rationale for the use of low dose aspirin is that venous stasis may lead to the potential for thrombus formation. Maria et al. reported fewer stroke like episodes in a retrospective series of children with SWS treated with aspirin prophylaxis compared to those not receiving treatment. In this series aspirin was well-tolerated.
Surgical Treatment in SWS
Surgical treatments for SWS have been used for over 30 years. The rationale behind their use has been the traditional epilepsy surgery model of removal or disconnection of the epileptogenic tissue, which in most cases requires hemispherectomy. Lobar or multilobar resection can however be successful in appropriately selected children. Seizures often reduce in frequency, the progressive cognitive decline may be halted or show some recovery. Acquired motor deficits in infants or children with an established hemiplegia following hemispherectomy are often minimal., The timing of such surgery appears to be crucial. Treatment very early in life, often before one year, appears to be more successful in abolishing seizures and ensuring more normal development.,, The difficulty with advocating early surgery for children with SWS, is predicting those that will follow a course with severe episodes of encephalopathy order to select those children who might benefit from early hemispherectomy. In those children where involvement is more localized, lobar or multilobar excision may be associated with improvement in seizures and may minimize post-operative deficits. In a recent series of 14 operated cases, in seven where the angioma could be entirely removed complete and lasting seizure control was obtained. In the remaining cases, only one achieved complete seizure control.
Corpus callosotomy may lead to improvement for children who have drop seizures as the major seizure type. Epilepsy surgery has not generally been used for those with bilateral angiomas. However, Tuxhorn and Pannek report hemispherectomy with improvement in seizure control and improved function in three cases with bilateral angiomas. It is recommended that infants and children with SWS are evaluated at a center with expertise in pediatric neurosurgery if seizures occur or if seizures are associated with developmental delay or progressive neurological deficit.
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