**7. Radiological manifestations of SIH**

CNS imaging is key in the differential diagnosis. Essentially no MRI findings are seen in aseptic meningitis and imaging is not needed in most of the cases. Cases with encephali‐ tis have special MRI findings varying due to the etiology, being the temporal lobe in‐ volvement of HSV 1 encephalitis the most common. In contrary, MRI findings are characteristic and imaging with contrast material is preferred in SIH. With the wide‐ spread and increasing use of MRI, SIH is more frequently recognized in recent years as an important cause of new onset persistent, daily, positional headaches. Diffuse pachy‐ meningeal (dural) contrast enhancement is the main feature on cranial MRI. Some other findings of SIH have been described: Enlargement of pituitary, tenting of the optic chiasm, subdural fluid collections, engorged cerebral venous sinuses and findings due to sagging of the brain such as obliteration of subarachnoid cisterns, crowding of posterior fossa and descent of cerebellar tonsils [5].

Results of imaging in patients with encephalitis may or may not demonstrate abnormal ra‐ diographic findings on CT or MRI modalities. CT scanning is useful to rule space-occupying lesions or brain abscess. MRI is sensitive for detecting demyelination, which may be seen in other clinical states presenting with mental status changes (eg. progressive multifocal leu‐

Initial examination of the CSF, although not diagnostic, will usually confirm the presence of inflammatory disease of the CNS. The findings with encephalitis, aseptic meningitis and me‐

The fever seen in SIH cases those mimic meningoencephalitis might be explained by the re‐ lease of pyrogenic cytokines by endothelial cells and astrocytes of blood-brain barrier secon‐ dary to a drop in CSF pressure [10]. These cytokines are the main mediators of inflammatory response in infectious and non-infectious disorders. Another suggested mechanism for fever would be an impaired hypothalamic thermoregulation secondary to mechanical distractions

Hearing changes including disturbed sense of balance, tinnitus and echoing; visual changes including visual blurring and diplopia; various neurological symptoms including photopho‐ bia, phonophobia, amnesia and facial numbness are common [11]. A significantly decreased level of consciousness might be observed in cases with SIH and even they would admit with confusion and syncope [7]. Subtle cognitive deficits are common particularly during epi‐

Symptoms in SIH patients related to the vestibulocochlear system such as disturbed sense of balance, tinnitus and sense of echoing may be explained by direct transmission of the abnor‐ mal CSF pressure to that in the perilymph [21]. Visual impairment was probably due to

CNS imaging is key in the differential diagnosis. Essentially no MRI findings are seen in aseptic meningitis and imaging is not needed in most of the cases. Cases with encephali‐ tis have special MRI findings varying due to the etiology, being the temporal lobe in‐ volvement of HSV 1 encephalitis the most common. In contrary, MRI findings are characteristic and imaging with contrast material is preferred in SIH. With the wide‐

stretching of the cranial nerves due to downward displacement of the brain [12].

koencephalopathy) and typical contrast enhancing (mostly temporal lesions).

and venous engorgement in cavernous sinus and diencephalic region.

ningoencephalitis are generally indistinguishable.

**6. Neurologic manifestations of SIH**

**7. Radiological manifestations of SIH**

**5. SIH and fever**

38 Encephalitis

sodes of headache [2].

**Figure 1.** Thickening in meninges demonstrating pachymeningeal contrast enhancement (arrows) and enlargement of the pituitary gland (arrowhead)in a 36 years old female patient [7], presenting with orthostatic headache, stiff neck and fever. **b.** Axial FLAIR image of the same case showing bilateral thin subdural collection (arrow). **c.** Findings of sag‐ ging brain (arrow) in a 37 year old female (case 1] presenting with fever, severe headache, nausea and vomiting. **d.** Engorgement in cerebral veins (arrows) of a 44 year old male presenting with fever and meningeal irritation signs whose LP revealed a marked lymphocytic pleocytosis[450 / mm3 ]. *(Derived from ref. 7. Photo courtesy of Sait Albayram, with permission)*
