Spontaneous intracranial hypotension with spinal myelography imaging findings.

32-year-old male was complaining of one-month severe headache. The symptoms were subsiding in recumbent position and did not respond to common analgesics. At lumbar puncture, the cerebrospinal fluid (CSF) opening pressure was found to be low (<60 mm H2O, normal values: 100-200 mm H2O). CSF cytochemical analysis was normal.

Magnetic resonance imaging (MRI) of the brain performed 2-3 hours before the lumbar puncture and showed diffuse smooth thickening of the dura mater (infra- and supratentorial), extending down to the upper cervical spine. The dura mater showed high signal in T2-weighted and T2-FLAIR images (Fig. 1). After intravenous contrast administration, there was diffuse dura mater enhancement along with the "venous distension sign" around the superior sagittal sinus (Fig.2). Bilateral thin subdural effusions were observed and caudal displacement of the brain with the cerebral aqueduct 4.2 mm below the incisural line (normal values < 2 mm) (Fig. 3). The cerebellar tonsils were in a normal position. An increase of the pituitary gland height at 7.4 mm (normal values: 6.1±0.3mm) was observed (Fig. 4). MR-myelography showed signs of CSF leakage at TH1, TH2 levels and ‘the false localizing C1-C2 sign’ (Fig. 5).

Spontaneous intracranial hypotension (SIH) is a syndrome of postural headaches aggravated by sitting or standing and relieved by recumbence. It is characterized by reduced CSF pressure in the intracranial cavity caused by CSF leaks through small defects of the meninges into the spinal canal without previous lumbar puncture or an interventional procedure or surgery on the neural axis [1-4].
The precise cause of spontaneous spinal CSF leaks remains unknown, but an underlying structural weakness of the spinal meninges generally is suspected. A history of a trivial traumatic event can be elicited in 1/3 of patients, suggesting a role for mechanical factors [4]. The dural weakness predisposes to formation of dural defects that allow CSF to leak into the epidural space [5-7].
According to the Monro-Kellie doctrine, the intracranial volume of CSF is inversely related to the brain blood volume [1]. Thus, in SIH a decrease of the CSF volume leads to an increase of the dural blood volume and venous engorgement. The most common and pronounced MR imaging finding of SIH is the diffuse smooth thickening and intense enhancement of the dura, considered to be the result of venous dilation that follows the decrease of the CSF volume produced by the leakage. The increase in the pituitary gland height observed in this case has also been previously described [1]. A possible mechanism of this increase is the venous engorgement at the level of the dura mater covering the sella turcica. Another morphological MR finding is the downward displacement of the brain with decrease in the size of the ventricles and the basal cisterns and the downward displacement of the cerebral aqueduct.
Spinal imaging findings include epidural fluid collections, dural enhancement, dilated epidural venous plexus, abnormalities around the nerve root sleeve (pointing to a possible CSF leakage site), C1-C2 sign or false localizing sign (refers to fluid signal intensity in the soft tissues between the C1-C2 spinous processes and should not be thought to indicate CSF leakage site). CT or MR-myelography are the best imaging modalities to identify the spinal CSF leak. Epidural blood patch ideally at the site of CSF leak is the treatment of choice [5-7].