Anomalies in the Cerebrospinal System

Arteriovenous malformation (AVM), Secondary subarachnoid hemorrhage and Venous thrombosis are forms of Cerebrovascular anomalies. The pathogenesis of the first two aforementioned diseases is the occurrence of a cerebral hemorrhage, entering the subarachnoid space through the surface or the ventricles. While in Venous thrombosis, simple cerebral venous occlusion is the main cause.

Arteriovenous malformation (AVM)
These developmental anomalies consist of abnormal communications between the arterial and venous systems resulting in a cluster of dilated vessels. They vary in size from a few millimeters to huge masses lying in the cortex or white matter, usually in the posterior half of the cerebral hemispheres. They usually become symptomatic in the second or third decade. They present initially as subarachnoid hemorrhage, focal epilepsy, vascular headaches, hemiparesis or any focal neurological deficit. The combination of epilepsy with subarachnoid hemorrhage should suggest this possibility. X-ray skull may reveal abnormal venous channels with crescentic linear calcification. Arteriography delineates the abnormal vessels. Surgical treatment includes artificial embolization of the feeding vessels, ligation of feeding arteries, and resection of the AVM.

Secondary subarachnoid hemorrhage
This occurs when blood from cerebral hemorrhage enters the subarachnoid space through the surface of the ventricles. Other less common causes of subarachnoid hemorrhage include malignant tumors, trauma, bleeding disorders like thrombocytopenia, purpura and hemophilia and hemorrhagic meningitis. In these cases, the clinical evidence of the underlying disorder will be evident.

Venous thrombosis
This is either secondary to bacterial thrombophlebitis or due to simple cerebral venous occlusion (Phlebothrombosis). Intracranial thrombophlebitis is usually secondary to infections in the middle ear, paranasal sinuses, mastoids or skin over the face. The lateral sinuses, cavernous sinuses, and superior longitudinal sinus are commonly involved. In lateral sinus are commonly involved. In lateral sinus, thrombosis, the infection spreads to involve the jugular bulb to give rise to the jugular foramen syndrome with paralysis of IX, X, XI cranial nerves. In such patients, compression of the ipsilateral jugular vein fails to produce a rise of CSF pressure while doing the Queckenstedt's test, although the test is normal if the other jugular vein is compressed.

Cavernous sinus thrombosis is usually secondary to infections of the ethmoid or maxillary sinuses or the skin around the eyes and nose. The clinical features include high-grade fever, chemosis of the conjunctiva, proptosis, and edema of the ipsilateral eyelid. Later the fundus shows papilledema with retinal hemorrhage and there is involvement of the third, fourth, sixth and ophthalmic division of the fifth cranial nerves. Within a few days, the infection spreads to the other cavernous sinus through the interconnecting vessels. Sooner or later meningeal infection supervenes and meningitis develops.

In superior longitudinal sinus occlusion, symptoms start with unilateral convulsion and hemiplegia. Subsequently, when the occlusion spreads to involve the superior cerebral veins of the opposite side, it produces paraplegia. In all these instances, high-grade fever and toxemia are present. Treatment consists of a high dose of appropriate antibiotics and general measures to prevent cerebral edema and convulsions. Once the infection is controlled, the focus of infection in the offending ear or sinus should be tackled surgically to prevent a recurrence.

Sometimes, even in the absence of intracranial infection, occlusion of the superior sagittal sinus or lateral sinus develops with the rise of intracranial tension. The predisposing causes include postpartum and postoperative states, congenital cyanotic heart disease, polycythemia vera, and sickle cell disease. A stroke occurring in the background of such a clinical setting is suggestive of venous thrombosis. Venous thrombosis evolves more slowly and it has a greater epileptogenic potential than arterial occlusion. There is a great tendency to develop hemorrhagic infarction. The treatment includes correction of the basic disease, reduction of brain edema, antiepileptic medication, and treatment of infection if present.



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