Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 55, Num. 4, 2007, pp. 432-433

Neurology India, Vol. 55, No. 4, October-December, 2007, pp. 432-433

Letter To Editor

Complex spontaneous extracranial-intracranial collateralization in progressive systemic atherosclerotic disease

Peter Horn, Johann Scharf*, Peter Schmiedek

Departments of Neurosurgery and *Neuroradiology, Universitätsklinikum Mannheim, University of Heidelberg, Germany
Correspondence Address:Department of Neurosurgery, Universitätsklinikum Mannheim, University of Heidelberg

Date of Acceptance: 12-Feb-2007

Code Number: ni07136

Sir,

Localized progressive intravascular accumulation of atheromatous deposits represents the leading cause of stenosis or occlusion of the brain supplying arteries in adults. These atherosclerotic changes may be found extra- and intracranially within the anterior and the posterior circulation with varying extent. ^[1],[2] Rarely, the spontaneous development of an extensive extracranial-intracranial collateral network that resembles the late stages of Moyamoya disease (MMD), i.e., a Moyamoya-phenomenon, is observed.

A 36-year-old woman presented with a five-year history of intermittent episodes of blurred vision and vertigo. Cranial CT showed mild supratentorial atrophy and borderzone infarctions with right hemispheric accentuation. Diagnostic cerebral panangiography demonstrated a left-sided internal carotid artery (ICA) occlusion. The left external carotid artery (ECA) led to a significant intracranial blood supply using physiological extracranial-intracranial bypasses via the vessels of the mucous membrane of the ethmoidal sinus and the nasal meatus. Transdural anastomoses were observed involving the middle meningeal and the occipital arteries [Figure 1],[Figure 2]. Intracranially, extensive leptomeningeal collaterals were seen between the middle cerebral artery (MCA) and anterior cerebral artery (ACA) vascular territory on the left side. Right-sided injection showed an occlusion of the ICA and revealed multiple extracranial-intracranial anastomoses involving the pharyngeal, meningeal and the occipital branches of the ECA [Figure 2]. This pattern of blood supply led to an atypical and delayed intracranial opacification with leptomeningeal collateralization between the MCA and the ACA vascular territory [Figure 1]. Neither right nor left-sided injection revealed any parts of the circle of Willis, thus being indicative for complete obliteration of the proximal segments of the basal cerebral vasculature. Angiography demonstrated a distal basilar artery (BA) occlusion and a collateral network arising from the right posterior inferior cerebellar artery (PICA) and the left vertebral artery. The paired functional blood flow (rCBF) study using stable Xenon-CT showed a symmetrical rCBF in all vascular territories and a preserved cerebral perfusion reserve.

The stenosis and occlusion of cervicocerebral arteries represents one of the major manifestations of atherosclerosis in adulthood. It affects the extracranial segments of the brain supplying arteries with preference for the carotid fork, leading to stenosis or occlusion of either the ICA or the common carotid artery. ^[2] The extent and the progression of the atherosclerotic changes within the affected vessels trigger the development of collateral pathways as a physiological response, in order to avoid cerebral ischemia. The type of collaterals recruited depends on the topology, the extent of the atherosclerotic lesion, its hemodynamic relevance and the temporal course of the disease progression. ^[3],[4]

The complete functional reconstruction of the ICA through skull base collaterals from the ECA, however, as observed in the present case, represents a rare condition. The functional recruitment of the extracranial circulation as collateral pathway is a well recognized phenomenon in patients with MMD. ^[5] Moyamoya disease, a disease of unknown etiology that mainly affects children and young adults shows the progressive narrowing of the terminal portions of the internal carotid arteries and the development of a network of pathological collaterals in the vicinity of the steno-occlusive lesions. In addition spontaneous extracranial-intracranial collaterals develop using the ECA and vessels of the mucous membrane of the ethmoidal sinus and the nasal meatus. ^[5] The development of the spontaneous collaterals is assumed to be triggered by the chronic hypoperfusion in these patients. Although the etiology of the vascular changes in the present case is known, the angiographic pattern detected here resembles the late stages of MMD rather than the classical collateralization pattern due to atherosclerosis. Therefore, the capability of complex collateral pathway formation as observed here suggests shared mechanisms for the compensation of chronic ischemia in atherosclerotic cerebrovascular disease and MMD.

References

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