Department of Rheumatology, Clinica Puerta de Hierro, San Martin de Porres 4, 28035 Madrid, Spain
SIR, Optic nerve involvement is a known, although seldom reported, complication of Paget's disease of bone. A well-documented response to treatment has not been published. We report a case of severe visual loss with long-lasting recovery after treatment with pamidronate and dexamethasone.
The patient was a 68-yr-old man whose Paget's polyostotic disease was diagnosed in 1990. The skull and a number of other bones were affected. He had been treated with calcitonin and etidronate for 6 yr and had shown an incomplete clinical and biochemical response. In October 1996 he developed progressive weakness and paraesthesias in his lower extremities. MRI showed basilar invagination and stenosis in the cervical and lumbar spine. He was treated with pamidronate intravenously (i.v.), with one dose of 30 mg followed by two doses of 60 mg each. The treatment was halted because a skin reaction occurred after the second and third doses. Neurological function improved. Seven months after the treatment, at a programmed follow-up visit, he complained of slowly progressive visual loss in the right eye. At examination, his best corrected visual acuity was 20/200 in the right eye and 20/25 in the left eye. The intraocular pressure was 18 mmHg in both eyes. The pupils were of equal size, but the reaction to light was sluggish in the right pupil. Generalized constriction in the right eye was evidenced in a visual field study; the left eye study was normal. Slit-lamp biomicroscopic examination of both eyes revealed a normal anterior segment except for mild subcapsular posterior opacification of the lenses. The optic discs were not pale and the optic fundi were both normal. CT scanning, with special attention to the optic canals, showed no signs of narrowing despite the bone surrounding the optic nerve being affected by Paget's disease (Fig. 1).
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Optic neuropathy is an uncommonly reported complication of Paget's disease of bone. In the literature we reviewed, we found six cases reported by Chen et al. [1] and Eretto et al. [2] that showed optic atrophy due to Paget's disease without radiological evidence of optic nerve compression. All these patients were treated with calcitonin without improvement. A vascular rather than a mechanical factor is believed to be involved in the pathogenesis of this neuropathy, as well as in other neurological complications of Paget's disease. Indeed, neurological involvement in Paget's disease may improve rapidly with intensive medical therapy to reduce bone blood flow [3].
This case presented a difficult clinical decision. Apart from the optic neuropathy due to Paget's disease of bone, ischaemic optic neuropathy was also considered as a diagnosis because the patient was old, hypertensive and atherosclerotic. We do not think this was the reason for his condition, because of the progressive onset of the visual loss, the normal appearance of the optic discs and the response to treatment. Pamidronate is a well-known treatment for Paget's disease of bone and has been used successfully in neurological spinal complications [4], which occurred in this case. The retreatment with pamidronate was risky owing to the previous skin reaction. Furthermore, ocular complications have been described after treatment with pamidronate [5, 6]. These include conjunctivitis, uveitis and scleritis, but not optic neuropathy. Thus, the question of whether to retreat with pamidronate was complex and the decision was taken only after the patient had been informed of the potentials risks and benefits. Other bisphosphonates could have been tried, but only etidronate and pamidronate were available for Paget's disease at that time in Spain.
We think that the addition of dexamethasone to the treatment is likely to have been important. Corticosteroids have a well-known inhibitory effect on bone metabolism. Before current treatments for Paget's disease were available, corticosteroids were used to treat Paget's disease with moderate success, being limited by the side-effects of long-term therapy with high doses [79]. Corticosteroids are also used in the treatment of acute spinal injuries, because of their beneficial effects on vascular supply and oedema. Yost et al. [10] have reported a rapid reversal of vascular steal myelopathy in Paget's disease after treatment with i.v. dexamethasone and subcutaneous calcitonin. It makes sense to try corticosteroids in combination with anti-reabsortive agents in Paget's disease with neurological involvement, such as in the case reported by Yost et al. and in the present case. The only case we have found in the literature in which there was improvement of optic neuropathy in Paget's disease was described by Kristensen in 1971 [11], and steroid therapy was used. The patient was hypertensive, and the visual loss was acute. He had presented a previous irreversible acute visual loss in the other eye with headache and an elevated erythrocyte sedimentation rate. Indeed, temporal arteritis was suspected despite a normal arterial biopsy, and low doses of corticosteroids were maintained. Thus, we think the diagnosis of optic neuropathy due to Paget's disease is questionable.
To our knowledge, this is the first report of well-documented successful treatment of optic neuropathy due to Paget's disease of bone. We think the good and sustained response in our patient was due mainly to pamidronate. The possibility of adding a short course of steroids at high doses should be considered.
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