Vascular neurosyphilis may involve any part of the central nervous system. The common denominator is infarction secondary to syphilitic endarteritis. The process is almost invariably a meningovascular one, stemming from the chronic meningitis that underlies all forms of central nervous system syphilis. In the series of Merritt et al., 10% of patients had this form of neurosyphilis. This disease usually occurs 5-12 years after initial syphilitic infection, which is earlier than the occurrence of paresis or tabes, and most patients are 30-50 years of age. Cerebrovascular neurosyphilis may occur concurrently with, or progress to, general paresis or tabes and may be accompanied by Argyll Robertson pupils in the absence of these complications.
Symptoms and signs
The most common manifestation are hemiparesis or hemiplegia (83% of cases), aphasia (31%) and seizures (14%). Among 241 patients with neurosyphilis studied at the Medical College of Virginia, adult-onset seizure disorders were prominent in 24%. The most common involvement , by far, is the territory of the middle cerebral artery, but any other artery on occasion may be occluded.
The onset of symptoms may be abrupt. However, about 50% of patients have premonitory symptoms of headache, dizziness, insomnia, memory loss, or mood disturbances lasting for weeks or months, probably consistent with diffuse arterial involvement. Psychiatric manifestations (personality and behavioral changes and slowing of mentation and speech) may be so prominent as to suggest the diagnosis of general paresis initially, until the onset of a stroke syndrome.
Serum RPP is positive in meningovascular syphilis. The CSF VDRL test is positive in most but not all cases, and there is a lymphocytic pleocytosis in the CSF. Angiographic changes include diffuse irregularity and “beading” of anterior and middle cerebral arteries and segmental dilatation of the pericallosal artery. In contrast to the short, irregular sites of atherosclerotic disease, the areas of arterial narrowing in cerebrovascular syphilis tend to be longer and smoother. Vascular neurosyphilis, rather than atherosclerosis, is also suggested when angiographic changes occur in the supraclinoid portion of the internal carotid artery and the proximal portions of the anterior or middle cerebral arteries, in the absence of stenotic changes at the carotid bifurcation. Computed tomography (CT) shows low density areas with multifocal infarctions. Magnetic resonance imaging shows focal regions of high signal intensity on T2-weighted sequences, compatible with foci of ischemia.
The characteristic histologic changes of the arteritis of cerebrovascular neurosyphilis consist of infiltration by lymphocytes and plasma cells of the vasa vasorum, the adventitia, and, ultimately, the media of large- and medium-sized arteries. Occlusion of the vasa vasorum results in destruction of the smooth muscle and elastic tissue of the media. Concentric proliferation of subintimal fibroblasts narrows the lumen progressively until it is occluded by thrombus formation.
Diagnosis and differential diagnosis
The possibility of meningovascular syphilis should be considered when cerebrovascular accidents occur in a young adult, especially one who has none of the usual risk factors such as uncontrolled hypertension or findings suggestive of embolic cardiac disease. In the older age group, the diagnostic problem is compounded by the greater likelihood of coexisting cerebral atherosclerosis, which may also be responsible for a stroke, even though the patients has, e.g., meningeal (asymptomatic) neurosyphilis.
Differential diagnosis includes other causes of stroke syndromes such as hypertension (lacunar strokes), atherosclerotic vascular disease, cerebral emboli, or various types of cerebral vasculitis. Angiographic changes in cerebral vessels in systemic lupus erythematosus may be indistinguishable from those of syphilitic arteritis, and those in polyarteritis nodosa may be somewhat similar.