There is direct drainage of CSF from subarachnoid space into spinal epidural veins without the formation of any dural defect. In rare cases, a CSF venous fistula can develop between the subarachnoid space and their adjacent spinal epidural veins.
These events can be as benign as a sudden sneeze, sports activity, a twist, fall, orgasm, sexual intercourse, or some other type of benign trauma. There are different events that can incite a rupture of spinal epidural cysts, a tear of the dural nerve sheath, or the rupture of perineural cysts. They are implicated in the development of CSF leaks, thus making connective tissue disorders an associated disease. Meningeal diverticula are often a finding in patients with Marfan syndrome. The connective tissue abnormality, which includes abnormalities of fibrillin or elastin, can cause dural weakness, which eventually plays a role in causing spontaneous low CSF pressure due to cryptic CSF leaks.
Ĭonnective tissue disorder can also be the underlying cause of the development of spontaneous CSF leaks. Other supporting evidence for this hypothesis is the fact that orthostatic headaches are more common with spinal CSF leakage as compared to cranial CSF leakage (e.g., with CSF otorrhea or CSF rhinorrhea). The lack of equilibrium in the craniospinal elasticity precipitates orthostatic headaches. Īnother hypothesis for the underlying mechanism of precipitation of headache in spontaneous intracranial hypotension is that there is an increase in compliance at the lower end of CSF spinal space whenever there is a spinal CSF leak. This phenomenon causes headaches due to increased brain volume. Low CSF pressure in the cranial vault is compensated by an increase in vasodilation of the cerebral vessels. Postural headache is due to the fact that the traction on the meninges is increased in an upright position leading to increased intensity of headache when standing. This sagging causes traction on the sensory nerves of the meninges and the bridging veins, leading to headaches. When CSF volume decreases due to leaking or other causes, it precipitates the sagging of the brain in the cranial vault. This weight is decreased to about 48 grams in a pool of CSF due to the buoyancy provided by the fluid. Normally, the weight of the brain is nearly 1500 grams in air.
The leakage of CSF from the craniospinal vault is thought to be the cause of spontaneous intracranial hypotension.
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