Idiopathic intracranial hypertension sine disc edema with rare neuroimaging features of cranial nerve compression.

Idiopathic intracranial hypertension (IIH) without papilledema is a known entity with a prevalence of 5%–14% in patients with chronic headache.[1] There is very limited literature on meningoceles of craniomotor nerves in IIH. We report a rare and an interesting neuroimaging of craniomotor meningoceles in a case of IIH without papilledema.

A 41-year-old woman of African descent, morbidly obese in built presented with a progressive inward deviation of the left eye [Figure 1] for 7 years with occasional diplopia, associated with holocranial tension type of headache and pulsatile tinnitus. She gave no history of transient visual obscurations. Her best-corrected visual acuity was 20/20, N6 in both the eyes. Her color vision was normal. Ocular motility showed marked limitation of abduction in the left eye with large-angle esotropia in the primary gaze [Figure 1]. There was no involvement of other cranial nerves. Pupillary reflexes were normal, and optic discs were healthy [Figure 2] in both eyes. Humphrey's visual fields did not show any neurological field defect on the gray scale. Given long-standing non-resolving left sixth cranial nerve palsy with chronic headache, magnetic resonance imaging (MRI) of the brain and orbit with contrast and MR venogram (MRV) were advised.

Figure 1

Clinical photograph in primary and nine gazes depicting large-angle esotropia (arrow) in the left eye with abduction limitation in the left eye (arrowhead)

Figure 2

Both eyes color fundus photograph depicting healthy optic disc with no evidence of edema

T2-weighted(T2W) MRI showed posterior flattening of globes, enlarged perioptic space, and empty sella, and MRV revealed stenosis of the junction of transverse sigmoid sinus [Figure 3a-d]. To our surprise, the patient also had enlarged cerebrospinal fluid (CSF) spaces around oculomotor [Figure 4c and d] and abducens nerve [Figure 5a-d] on either side. There was also CSF expansion along the glossopharyngeal nerves [Figure 4a] as well as distention of Meckel's cave [Figure 4b]. There was no hyperintensity along the meninges of the cranial nerves or elsewhere [Figure 3e-g]. A lumbar puncture was done which revealed CSF opening pressure of 43 cms of water with normal CSF analysis. Even in the absence of papilledema, our patient fulfilled the criteria of IIH without papilledema proposed by Friedman and Jacobson.[2] The patient was advised weight loss and oral acetazolamide 2 g/day in divided doses with potassium supplements. During the follow-up period of 3 months, our patient subjectively felt better; however, there was no improvement in left-sided sixth cranial nerve palsy.

Figure 3

Axial (a), coronal (b), and sagittal (c) T2-weighted images showing globe flattening (black arrows), distended optic nerve sheaths (white arrows), and empty sella. Magnetic resonance venogram (d) showing either transverse venous sinus stenosis. Contrast-enhanced axial T1-weighted images (e-g) showing normal pachymeningeal enhancement

Figure 4

Axial (a) and coronal (b) T2 images showing enlarged cerebrospinal fluid spaces surrounding the glossopharyngeal nerves and distension of the Meckel's caves, respectively. Oblique sagittal along the bilateral oculomotor nerves (c and d) showing enlarged cerebrospinal fluid spaces (white arrows) surrounding them

Figure 5

Axial (a) and coronal (b) T2 images at the petrous apex and oblique sagittal along the Dorello's canals (c and d) showing enlarged cerebrospinal fluid spaces (white arrows) surrounding the abducens nerves (black arrows)

We believe that the lack of papilledema even in the presence of raised intracranial pressure can be attributed to the size of the optic canal diameter and possibly due to the redistribution of CSF more around craniomotor nerves than optic nerves. Meningoceles and enlargement of Meckel's cave have been reported in the literature as an additional imaging sign in IIH.[3] San Millán and Kohler have reported three cases of IIH with enlarged CSF spaces around oculomotor and abducens nerve and enlargement of Meckel's cave.[34] Similarly, our patient also had enlarged subarachnoid CSF spaces around oculomotor, abducens, and glossopharyngeal nerves. The CSF space around abducens nerve is enlarged throughout its course from cisternal segment to cavernous sinus, more localized on the left side compared to the right side, explaining the compressive left-sided sixth cranial nerve palsy. These findings give one step further insight into our understanding of pathophysiology of IIH. Craniomotor meningoceles in the absence of papilledema should be considered an additional imaging sign in IIH.

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The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.