Co-existent Optic Nerve Drusen in a Patient with Idiopathic Intracranial Hypertension
Pseudotumor cerebri occurs in about one in 1,000 people, and a “cause” is often difficult to identify.
A 29-year-old woman presents complaining of headaches for the past two months. She describes the headache severity as 5 to 6 on a 10-point scale; she has not had vomiting associated with the headaches. She has noticed occasional tinnitus that seems to be syncopated with her pulse. Upon rising from a seated or lying position, she experiences transient bilateral loss of vision.
Past medical history is unremarkable, and the patient is otherwise healthy. Family history is unremarkable. The patient reports no allergies to medications. The only medication she currently uses is topical retinoic acid for acne.
Blood pressure is normal, as is the general physical exam. At 5 feet 3 inches tall and 225 lbs., she is at least 75 lbs. overweight. Visual acuity is 20/25 in the right eye; 20/20 in the left. She has an increased blindspot and arcuate scotoma on automated perimetry (Figure 1). Pupils are normal; no afferent pupillary defect is evident. Her ocular motility is normal. Her funduscopic exam reveals marked elevation of both optic nerves, suggesting papilledema. Her neurologic exam is otherwise normal.
What would you do next?
Comment: The patient’s current complaints are suggestive of idiopathic intracranial hypertension (IIH), commonly known as pseudotumor cerebri. It is critical to confirm this diagnosis and rule out an actual tumor.
The funduscopic finding of elevation of the optic nerve in both eyes in this clinical setting suggests optic nerve edema from papilledema. Consultation with an ophthalmologist or neuroophthalmologist to assess the presence of papilledema from IIH or other causes is helpful. Note that there is some evidence that neurologists may not identify papilledema as readily as ophthalmologists and neuro-ophthalmologists.1
No cotton wool spots are identified on the optic nerve. The presence of cotton wool would be a potential clue that vision loss may be permanent, as these soft exudates suggest ischemic infarct to the nerve.
CT scan with and without contrast or MRI should be performed to rule out an actual tumor. Additionally, magnetic resonance venography will help to rule out venous sinus obstruction.
The CT scan is normal. A lumbar puncture is ordered to measure intracranial pressure. The pressure is determined to be 300mm of water. CSF analysis reveals that chem panel, white and red blood cell count, protein, and culture are negative or normal.
What would you do next?
Comment: The modified Dandy criterion for increased intracranial pressure (ICP) is an ICP greater than 250mm water. At 300mm water, the patient’s ICP is clearly elevated, suggesting intracranial hypertension. The evaluating physician, if not the person who performed the lumbar puncture, should confirm the reliability of the increased ICP by asking the patient to describe the testing process. The lumbar puncture should begin with the patient in the lateral decubitus position. Once the needle is established in the subarachnoid space, the patient should be instructed to slowly straighten her legs as this provides a more accurate reading of the intracranial pressure. If she remains tightly curled in the fetal position, this will falsely increase the intracranial pressure.
Certain medications are known to induce pseudotumor cerebri, including oral contraceptive pills, tetracycline, sulfa antibiotics, and retinoic acid/vitamin A derivatives. Though not well established, we speculate that application of retinoic acid to the face may permit a higher concentration to enter the bloodstream and brain.
The patient’s history includes current use of topical retinoic acid. The patient should be advised to discontinue retinoic acid immediately. The patient is also overweight, and studies suggest that weight loss can lead to improvement of papilledema.2 Most importantly, one study documented a linear relationship between weight loss and improvement in papilledema, with an average of 6.6 percent weight loss promoting resolution of papilledema and IIH.2 Accordingly, five to 10 percent weight loss is generally recommended. Weight loss appears to be more critical in the treatment of IIH than acetazolamide. Patients who lost 3.3 percent or more weight had reduction in papilledema regardless of their use of acetazolamide. However, patients who used acetazolamide, but who did not lose weight, did not have any reduction in papilledema.
Given the link between excess weight and IIH, the patient is advised to lose 11 to 22 lbs., representing five to 10 percent of her current weight. She is referred for a consultation with a dietician. The clinician acknowledges that weight loss may be difficult and encourages the patient as much as possible. The patient is advised to exercise at least 30 minutes/day and to drink plenty of water.
The patient is instructed to follow up in six weeks. It is essential to follow up since, left untreated, between 10 and 25 percent of patients with IIH have vision loss and blindness.3
Before she leaves, fundus photographs and optical coherence tomography (OCT) studies are obtained. OCT shows classic findings of optic disc edema (papilledema) with elevated optic nerve and “lazy V” internal optic nerve contour. This is in contrast to the “lumpy-bumpy” internal optic nerve contour of optic disc drusen (Figure 2).4
The patient returns in two weeks, having lost 4 lbs (1.7 percent weight loss). She returns six weeks later, eight weeks after her initial visit, having lost 10 lbs (4.3 percent weight loss). She reports that she has no more headaches or tinnitus. Transient obscuration of vision has resolved. On examination, the patient’s visual fields show progressive improvement of the arcuate scotoma. Funduscopic evaluation shows normal optic nerves. The resolution of IIH occurred as a result of weight loss and discontinuation of retinoic acid. Often excess weight gain is the only potential cause of IIH.
Comment: If OCT is unavailable, B-scan ultrasonography could be ordered to show calcification of the optic nerve with disc drusen. Another option is pre-injection fluorescein angiogram. In this instance, the angiogram is not performed, however, barrier filters are put in place as if preparing for the angiogram. The barrier filter reveals auto-flourescence of the drusen.
There is no treatment for drusen. Patients should be counseled about the condition. Typically, the patient must understand that there is no treatment and the condition is not typically progressive, but they should return for regular evaluations.
Given that an estimated one to two percent of the population has optic nerve head drusen and that IIH is estimated to occur in about one on 1,000 people, there is a reasonable probability that some patients will have both conditions. The diagnosis of optic nerve drusen may be overlooked, particularly when it presents independent of other conditions. Failure to identify this condition through simple non-invasive measures may lead to patients being exposed to lumbar punctures, which are generally safe but not without risk, and even in some cases unnecessary surgeries.
1. Johnson LN, Hepler RS, Bartholomew MJ. Accuracy of papilledema and pseudopapilledema detection: a multispecialty study. J Fam Pract. 1991 Oct;33(4):381-6.
2. Johnson LN, Krohel GB, Madsen RW, March GA Jr. The role of weight loss and acetazolamide in the treatment of idiopathic intracranial hypertension (pseudotumor cerebri). Ophthalmology. 1998 Dec;105(12):2313-7.
3. Corbett JJ, Savino PJ, Thompson HS, Kansu T, Schatz NJ, Orr LS, Hopson D. Visual loss in pseudotumor cerebri. Follow-up of 57 patients from five to 41 years and a profile of 14 patients with permanent severe visual loss. Arch Neurol. 1982 Aug;39(8):461-74.
4. Johnson LN, Diehl ML, Hamm CW, Sommerville DN, Petroski GF. Differentiating optic disc edema from optic nerve head drusen on optical coherence tomography. Arch Ophthalmol. 2009 Jan;127(1):45-9.