A 50-year-old male with chronic inflammatory demyelination polyneuropathy (CIDP) on treatment with deflazacort for over a year presented with insidious onset headache of 3-month duration. The headache was diffuse and was not aggravated by coughing or straining. He did not have any early morning headache, transient visual obscurations, or tinnitus. He was diagnosed to have CIDP 1-year back and had a good response to deflazacort and was advised to continue the treatment. Physical examination revealed swelling of the superolateral aspect of both eyeballs. There was no proptosis, chemosis, or restriction of extraocular movements. Fundus examination showed bilateral papilledema. The magnetic resonance imaging of brain showed linear tortuous T1 hypointense and T2 hyperintense lesion in both orbits [Figure 1]. The lesion was encapsulated, running parallel to the optic nerve in the extraconal space and was connected to the optic nerve sheath near the orbital apex [Figure 2]. There was also a partial empty sella. A lumbar puncture measured an opening pressure of 240 mm of cerebrospinal fluid (CSF). CSF protein was 84 mg/dl, sugar 68 mg/dl, without any cells, and culture was sterile. The patient had immediate relief of headache after removal of 20 ml of CSF. The usual causes of idiopathic intracranial hypertension (IIH) such as obesity, antibiotic use, autoimmune disorders, and thyroid dysfunction were ruled out. A diagnosis of IIH secondary to chronic steroid use was made.
Figure 1.
(a) Magnetic resonance imaging brain showing linear, tortuous T2 hyperintense lesion which is encapsulated and runs parallel to the optic nerve sheath in the extraconal space. (b) The lesion is present in both orbits
Figure 2.
(a) Magnetic resonance imaging brain T2-weighted image showing the extraconal lesion in both orbits. (b) The lesion is connected to the optic nerve sheath near the orbital apex (arrowheads)
This case describes a novel neuroimaging feature in IIH. Headache, papilledema, high CSF pressure, and partial empty sella support the diagnosis of IIH in our patient. Long-term glucocorticoid use is a well-recognized risk factor for IIH. The extraconal lesion with CSF density arose from the posterior end of the optic nerve sheath. The high intracranial pressure might have caused the CSF around the optic nerve to leak and form an encapsulated collection outside the optic nerve. CSF leaks are well described in IIH. Spontaneous CSF rhinorrhea and otorrhea can occur in IIH.[1,2] Such leaks provide a natural mechanism for reducing intracranial pressure, and papilledema is much less common in such cases. In our case, the leak was not manifested exteriorly but internally into the orbit. Optic nerve fenestration is one of the surgical treatments of IIH to reduce the risk of visual loss.[3] We can consider our case as a natural, spontaneous fenestration where CSF escaped through weak points in the meninges. To conclude, fluid collections in both orbits should alert the clinician to consider spontaneous CSF leak and IIH should be strongly suspected in such cases.
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References
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