BACKGROUND Idiopathic hypertrophic cranial pachymeningitis (IHCP) is a chronic inflammatory disease of unknown origin that is morphologically characterized by a local fibrotic thickening of the dura mater with a sterile lymphocytic infiltrate. Patients usually present with chronic headache, ataxia and cranial nerve palsies. Because of the great diversity of symptoms and the fact that IHCP can be associated with many other disorders, there is often a long time between the occurrence of clinical features and making the diagnosis. During this time symptoms can further increase. In addition, this is the third case report describing bone involvement in this disorder. METHODS In May 2000, a 51-year-old woman presented with reduced visual acuity on both eyes, complete palsies of the fourth and sixth cranial nerve, a partial palsy of the third cranial nerve and numbness and pain concerning the area of the fifth cranial nerve on the left side, painful eye movement on the left side, headache, and numbness and palsies on the left side of her body. Magnetic resonance imaging of the brain showed a focal gadolinium-enhanced small thickening of the dura mater close to the left hemisphere and a homogeneous bone thickening in the same area close to the thickened dura mater. Cerebrospinal fluid analysis revealed an elevated cell count (lymphocytic pleocytosis), routine blood counts and serum chemistry showed an elevated white blood count, an elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Therapy with corticosteroids resulted in a complete remission in November 2000 except for a persistent numbness of the left side of her face and body and reduced visual acuity on both sides. The following three years were characterized by repeated clinical deteriorations followed by a temporary increase of the daily steroid dose. Altogether, daily oral steroid therapy could slow down the progression of disease and improve the visual acuity when compared with the first examination. CONCLUSIONS Chronic headache, ataxia and cranial nerve palsies in combination with inflammation and dural thickening should call to mind idiopathic hypertrophic cranial pachymeningitis. In principle, every ophthalmological or neurological symptom can be associated with IHCP.