Nervous and mental diseases . blood-current of this duralchannel. Here the circulatory conditions are rendered still moreunfavorable by hydrostatic pressure, by the presence of trabecular in thesinuses which impede the flow of blood, and by venous retardationduring inspiration. The cerebellar veins empty mainly into the lateralsinuses. Into the dural sinuses also empty many veins from the faceand scalp. The facial vein communicates with the cavernous sinusthrough the ophthalmic vein. The veins of the nasal vault open intothe anterior extremity of the superior longitudinal sinus. Numerousveins
Nervous and mental diseases . blood-current of this duralchannel. Here the circulatory conditions are rendered still moreunfavorable by hydrostatic pressure, by the presence of trabecular in thesinuses which impede the flow of blood, and by venous retardationduring inspiration. The cerebellar veins empty mainly into the lateralsinuses. Into the dural sinuses also empty many veins from the faceand scalp. The facial vein communicates with the cavernous sinusthrough the ophthalmic vein. The veins of the nasal vault open intothe anterior extremity of the superior longitudinal sinus. Numerousveins of the scalp along the median line have a similar outlet. Veinsfrom the mastoid process and its cutaneous surface enter the lateral and 228 DISEASES OF THE BRAIN PROPER. petrosal sinuses, and the occipital and posterior auricular veins are con-nected with the lateral sinus. In addition, many veins of the cranialdiploe discharge into the sinuses. Finally, the sinuses connect with theveins of the spinal canal. Ant. facial vein. Ext Communication with veinsat back of neck Fig. 89.—Diagram showing the communications existing between the lateral and cavernous sinusesand the external veins, indicated in the figure hy * (Leubej. The cerebral veins are subject to the same lesions that influenceveins elsewhere, but we are only called upon to consider phlebitis andvenous thrombosis. They are usually associated and, practically speak-ing, severe cerebral symptoms are alone produced by thrombi. Throm-bosis may occur in the pial vessels of the convexity and extend intothe longitudinal sinus, or, beginning in the sinus, may invade thecortex and give rise to localized softening and focal entire subject may be conveniently described under the head ofSinus Thrombosis. SINUS THROMBOSIS,Intracranial sinus thrombosis occurs more frequently even thanthrombosis in the pelvic veins, or in those of the lower extremities. It DISEASES OF THE CEREBRAL VEINS AND SINUSES. 22
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