The underlying cause of spontaneous intracranial hypotension is usually a spontaneous cerebrospinal fluid fistula, however, some cases may be due to low cerebrospinal fluid volume. Evidence supports an underlying weakness of the meninges as a contributing factor; for instance, connective tissue disorders like Marfan syndrome, and Ehlers-Danlos syndrome.
Pneumocephalus occurs in ≈ 20% of patients with Cerebrospinal fluid fistulas 1)
A spinal Cerebrospinal fluid fistula can result in an intracranial subdural hygroma 2).