On admission, magnetic resonance imaging (MRI) of the head showed diffuse and uniform dural thickening, predominantly in the posterior falx and the cerebellar curtain. Gadolinium enhancement was abnormal, and non-enhancing line like slightly low signal shadow was seen in each dural septum. Chest X-ray showed increased texture in both lungs. Before treatment, lumbar puncture pressure was 300 mm H2O (1 mm H2O = 0. 0098 kPa), cerebrospinal fluid leukocytes 18 × 106 /L, red blood cells 8 × 106 /L, small lymphocytes 0. 69, general monocytes 0.31, protein 1. 52 g/L, oligoclonal bands (+); cerebrospinal fluid and plasma antibodies to tuberculosis and measles virus (+). After treatment, lumbar puncture pressure was 300 mm H2O, leukocytes 16 × 106 /L, erythrocytes 8 × 106 /L, small lymphocytes 0. 87, general monocytes 0. 13, biochemical, virological and immunological tests were normal. The patient was diagnosed with idiopathic hypertrophic dural meningitis (IHP) and was treated with mannitol 25 g and dexamethasone 5 mg intravenously once/8 h for 10 d, followed by once/12 h for 9 d. The patient was discharged from the hospital with oral prednisone 35 mg/d for 7 d. The symptoms resolved quickly. Hypertrophic duralgia is often secondary to infectious, cancerous or inflammatory diseases, and can coexist with nodular disease and aplastic anemia. The main features are headache, cerebral nerve palsy, and possibly cerebellar ataxia, epilepsy, neuro-ophthalmologic complications, and schizophrenia. The course can be complicated by venous sinus thrombosis and cerebral edema. Other extracranial manifestations include intrapulmonary nodules, granulomatous skin infiltrates, myocarditis, and Wegener’s granulomatosis with the same pathologic changes.The diagnosis of IHP is based on neuroimaging, with the exception of known causes and histopathologic findings.MR is more sensitive than control-enhanced CT and shows various forms of dural enhancement with cerebellar curtain and falx enhancement and extension into the adjacent dura [linear and/or nodular]. The dural sinuses are also frequently involved. The degree of cellular response in the cerebrospinal fluid does not correlate with the extent of the abnormal dura on MR, but patients with elevated abnormal cerebrospinal fluid proteins tend to have more diffuse dural involvement, as shown in this case. Biopsies of thickened dura mater showed inactive chronic inflammation of the dura mater with lymphocytes, fenestrated histiocytes, and opportunistic granulomatous infiltrates, with no or very mild soft meningeal or arachnoid inflammation, and biopsies were consistently negative for tissue culture. Dense fibrosis infiltrated by inflammatory cells, mainly lymphocytes, is more evident on the dural surface. Inflammatory infiltration mediated by cells of unknown origin (T cells) is a possible pathogenesis. Vasculitis is rare. Treatment is virtually ineffective for the fibrotic component. IHP rarely affects the spinal column and low brainstem and skull base with posterior group cerebral neuropathy. If left untreated, the clinical symptoms of IHP often progress. With corticosteroid treatment, most patients experience symptom relief, but symptoms may recur after dose reduction or discontinuation. Dural hypertrophy will persist even if clinical symptoms improve. The combination of azathioprine or methotrexate makes it possible to taper the steroids.