Idiopathic hypertrophic pachymeningitis
Idiopathic hypertrophic pachymeningitis (IHP) consists of an inflammatory process with fibrosis and consequent thickening of dura mater, sometimes with pseudotumoral lesions, without secondary cause. According to the site of involvement, it can be classified into cranial, spinal or craniospinal (1, 4). IPH can only be diagnosed after exclusion of infection, neoplasia and other inflammatory diseases, including autoimmune diseases and sarcoidosis. In the present case, histopathological findings favored the diagnosis of IHP since other causes of pachymeningitis were excluded. Inflammatory pseudotumor, which has also been considered as a differential diagnosis, was discarded by the immunohistochemical results.
Clinical features include headache, cranial nerve impairment, paraparesis or tetraparesis, ataxia, hydrocephalus, papilledema, hemorrhage or secondary vascular occlusions (5). Clinical presentation with hearing loss and later tetraparesis suggests cranial-caudal involvement. Cranial localization is the most common, responsible for about 79% of cases, followed by spinal cord (15%) and finally craniospinal (5.5%) (1). Our patient presented severe and extensive craniospinal involvement, including nerve roots.
CSF analysis reveals high protein levels generally proportional to the extent of involvement, as observed in this case, and mild pleocytosis. The high cell count and low glucose levels could be related to a spinal fluid collection in a confined space as the spinal fluid did not circulate in subarachnoid space.
IHP may mimic lymphoplasmacytic meningioma. There are reports of IHP that were initially diagnosed as lymphocytic meningioma and only after histopathologic revision, the correct diagnosis was established, indicating that the differential diagnosis in some cases may be difficult (3).
Magnetic resonance imaging (MRI) is essential for the diagnosis. T1-weighted images shows isointense meningeal thickening with contrast enhancement and T2-weighted images demonstrates hypointense lesions (4).
Pathologic examination generally reveals chronic inflammatory infiltrate with lymphocytes and plasma cells, sometimes with participation of histiocytes, eosinophils and granulocytes. Less commonly (10%), granulomas, necrosis and vasculitis are also seen (1, 3).
Response to treatment is closely related to early diagnosis and the extension of involvement. The treatment consists of surgery (decompression and removal of as much meninges affected as possible) and drugs such as prednisone, azathioprine, cyclophosphamide and methotrexate (1, 2, 4). The scheme most commonly used is steroids (prednisone 1 mg / kg / day). When no response is observed, immunosuppressors such as azathioprine and cyclophosphamide can be used (1, 4). For refractory cases there are some studies demonstrating benefits with methylprednisolone 1 g / day for 3 days associated with methotrexate 12.5 mg per week as maintenance (2). In addition to clinical response, other exams used to follow response to treatment are erythrocyte sedimentation rate, C-reactive protein and MRI (1, 4). The treatment should be continued for at least 1 year followed by slow withdrawal of medications but in the case of worsening of the symptoms, it should be returned to the previous dose (1, 2, 4).
In the present case, surgical decompression was performed followed by methylprednisolone. However there was no response, possibly because of the advanced stage of disease, with severe neurologic impairment, at presentation. The patient developed dysautonomia just after surgery and then refractory sepsis and death.
Contributed by Luiz Felipe R. Vasconcellos; Alexandre M. Cunha; Victor Hugo R. Marussi; Nathalie H. Silva Canedo; Leila M. C. Chimelli