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The best treatment of optic nerve sheath meningiomas remains controversial. Recent reports have emphasised the efficacy of fractionated stereotactic or conformal radiotherapy, and some clinicians favour this approach instead of surgery or observation.1,2 On the other hand, a beneficial effect of hydroxyurea on unresectable, residual, and recurrent meningiomas has been reported in various series.3–5 We report a patient with a meningioma of the optic nerve sheath and nearly complete visual loss who was successfully treated with hydroxyurea alone.
A 46 year old woman presented with painless and progressive right sided visual failure for two years. On admittance, visual acuity of the right eye was 0.05. In addition, there was an afferent pupillary defect, and swelling of the optic disc. Otherwise, the neurological examination was normal. Cranial magnetic resonance imaging (MRI) revealed a homogeneously enhancing, fusiform tumour (5 × 10 × 6 mm; volume 0.15 cm3) originating from the upper part of the right optic nerve sheath and compressing the optic nerve. The tumour showed an isointense signal to grey matter on T1 and T2 weighted images, and was diagnosed as a meningioma (fig 1A). Latency of the P100 wave of visual evoked potentials of the right eye was increased to > 200 ms, and computed perimetric examination showed a severe restriction of the peripheral visual field of the right eye (fig 2A). There were no clinical or radiological features of neurofibromatosis type 1 or 2. The patient was not on regular medication.
Treatment was initiated with hydroxyurea, 20 mg/kg body weight/day orally. Four months after initiation of treatment the patient reported a considerable improvement of vision. No adverse events were noted apart from mild hair loss. Visual acuity improved to 0.5. After seven months of continuous treatment, visual acuity was 0.7, and after 10 months, 0.8. At this time, P100 latency of visual evoked potentials was normal and computed perimetric examination showed a significant recovery of visual field (fig 2B). However, cranial MRI showed no detectable change in tumour size (volume 0.15 cm3; fig 1B). At the time of writing the disease had remained stable for a further 18 months now.
This case shows the clinical value of hydroxyurea in the management of optic nerve sheath meningiomas, although there was no detectable decrease in tumour size. There is increasing evidence for the benefit of radiotherapy in optic nerve sheath meningiomas. Andrews et al reported an improvement in vision in 10 of 24 cases (42%) after treatment with fractionated stereotactic radiotherapy alone.1 A comparison of long term visual outcome by Turbin et al showed better results for patients treated by conventional multiport or conformal planned delivery of radiotherapy than by surgery plus radiation, surgery alone, or observation during the follow up period.2
However, radiotherapy is associated with relevant treatment related morbidity (13% and 33.3% in two studies1,2). As follow up of the available case series is limited and these tumours may pursue a stable course for many years,6 the appropriate time for therapeutic intervention is unclear. In the present case, a profound deterioration of visual acuity led to the initiation of treatment. Hydroxyurea may be a reasonable therapeutic alternative to radiotherapy. Side effects of hydroxyurea such as myelosuppression, raised liver enzymes, and rashes are generally mild, easy to monitor, and reversible.4
As the neuroradiological characteristics were unequivocal in our case, and as histological verification of optic nerve sheath meningiomas carries a high risk of irreversible damage to the optic nerve, the diagnosis was made purely by radiological means. This approach is in accordance with current standard of diagnostic measures of optic nerve sheath meningiomas based on clinical details and high quality neuroimaging without pathological confirmation.1,2,6
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