A patient with idiopathic hypertrophic spinal pachymeningitis (HSP) with predominant involvement of the cervical and thoracic dura is reported. Serial magnetic resonance (MR) images detected isolated thickening and ridges of the dura mater. There has been no report describing the serial changes of MR images in idiopathic HSP. According to a review of the English and Japanese literature on idiopathic HSP, the prognosis of patients with positive inflammatory signs is worse than that of those with no inflammatory signs. Idiopathic HSP is a rarely reported disease that can resemble other disorders associated with dural compression. MR imaging can help to differentiate it from other disorders, and enables the diagnosis of the disease in its early stage. The prognosis of idiopathic HSP with positive inflammatory signs may be worse; the authors stress the significance of early surgical treatment.