In the spring of 1991, Graham Poll* was looking forward to the new baseball season. He had taken a week off work to watch some preseason games in Florida. As he waited for his outbound flight, he noticed darks spots in his right eye. This was disconcerting, but he resolved not to let it spoil his vacation.

One week later, Mr. Poll—who was 24 years old and Caucasian—was back at work and was still seeing spots. During the next 12 months he experienced transient visual obscurations on a daily basis. Finally, he visited a doctor in April 1992.

The Initial Diagnosis
An MRI scan of Mr. Poll’s head showed an extracranial asymptomatic focal skull (a scalp area of increased signal), which was interpreted as a possible artifact. A spinal tap showed an elevated opening pressure of 35 centimeters of water but was otherwise normal. He was diagnosed with idiopathic intracranial hypertension (IIH) and was started on 500 milli-grams of acetazolamide twice daily.

Spring of 1993 rolled around and there had been no resolution of his symptoms. In April, an ocular exam showed that Mr. Poll had a slightly enlarged blind spot in the right eye and marked papilledema in the left eye greater than in the right eye. The acetazolamide was increased to 500 mg four times a day for IIH. The transient visual obscurations and papilledema im-proved but did not completely resolve.

In the summer of 1998, Mr. Poll presented with a painless lump on the posterior and parietal midline aspect of his scalp. Another 18 months elapsed before Mr. Poll returned. During this time, his scalp mass progressed and became increasingly warm to the touch. In December 1999, a cranial computed tomography (CT) scan now showed parietal bone thickening with an associated soft tissue mass (Fig. 1). A neurosurgeon excised the exophytic skull and soft tissue lesion.

What’s Your Diagnosis?

Caption: Figure 1: A CT scan showed parietal bone thickening with an associated soft tissue mass.

A New Diagnosis
Pathology of the excised lesion showed atypical meningioma, with increased cellularity and pleomorphism. Subsequent MRI scan and magnetic resonance venography (MRV) showed significant extracranial and intracranial growth of the tumor, thrombosis of the superior sagittal sinus, transverse sinus and sigmoid sinus, and extensive collaterals from the cortical veins (Fig. 2).

In February 2000, Mr. Poll underwent embolization and resection of the tumor. Residual gross tumor was treated with one-month radiation therapy (total dose of 6,000 cGy).

Five years later, Mr. Poll has had no recurrence of his symptoms and only mild temporal atrophy of both optic nerves, with the left eye greater than the right eye. Serial MRI scans show no progression or recurrence of the disease.

The Patient Undergoes Further Imaging

Caption: Figure 2: Axial T1-weighted gadolinium-enhanced MRI shows marked bone thickening with enhancing region in the area of the posterior superior sagittal sinus.

Discussion
Cerebral venous sinus thrombosis can mimic the presentation of IIH.¹ While some older references suggest that either a CT or an MRI scan is sufficient to exclude alternative intracranial causes for IIH, we believe that an MRI with a contrast MRV should be considered in diagnosing patients with IIH, especially if atypical features are present. Unfortunately, many patients present with either a CT or an MRI scan that has been performed prior to neuro-ophthalmic evaluation. In typical cases of IIH (e.g., obese young females with classic signs and symptoms), this imaging alone may be sufficient. But in atypical cases of presumed IIH (e.g., children, men and elderly or thin women), a more extensive workup, including post-contrast MRV to exclude sinus thrombosis, is recommended. In addition, although many cases of cerebral venous thrombosis are idiopathic, some have an underlying tumor as the cause. Our case demonstrates that repeated, serial, contrast MRI and MRV may be necessary in patients with presumed IIH who are atypical in presentation, course or response to treatment.

Although there have been a few prior cases of cerebral venous sinus thrombosis due to tumor, ^2–4 our case is interesting in the following ways: 1) The presentation was mistaken for IIH; 2) the patient presented with an extracranial scalp lesion that proved to be meningioma; and 3) he had intracranial involvement by the meningioma of the cerebral venous sinus causing thrombosis and secondary papilledema that did not resolve until after the tumor was resected. This case shows the need for contrast MRI scan and MRV in atypical IIH (i.e., those who are thin, male or elderly) or patients with progressive or unresponsive course. Patients with IIH and a scalp lesion over the sagittal sinus, even if presumed to be extracranial, should be evaluated for sinus thrombosis.

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* Patient name is fictitious.

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1 Biousse, V. et al. Neurology 1999;53:1537– 1542.
2 Kim, A. W. and J. D. Trobe Am J Ophthalmol 2000;129:254–256.
3 Marr, W. G. and J. W. Chambers Am J Ophthalmol 1966;61:45–49.
4 Soma, M. et al. No Shinkei Geka 1996;24: 165–168 (English abstract).

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Dr. Lee is professor of ophthalmology, neurology and neurosurgery at the H. Stanley Thompson Neuro-Ophthalmology clinic at the University of Iowa. Dr. Moritz is a recent graduate of the University of Iowa Carver School of Medicine.