Abstract
Hypertrophic cranial pachymeningitis is a rare, idiopathic form of granulomatous pachymeningitis. To understand the modes and mechanism of meningeal involvement in various disease processes that affect the different layers of the meninges, one needs to be familiar with the anatomy of the meninges and the pathophysiology of the blood-brain barrier.
The anatomy of the meninges and the pathophysiology of bood-brain barrier justify two distinct patterns of meningeal enhancement: leptomeningeal and pachymeningeal; dural meningeal enhancement is categorised as diffuse, linear only or linear and nodular, and focal.
Diffuse dural enhancement was defined in our patient as an intense and continuous dural enhancement as seen on MR imaging, encompassing at least 75% of the dural surface.
Other causes of dural thickening include epidural abscess, rheumatoid arthritis, lymphoma, neurosyphilis, sarcoidosis, tuberculosis, Wegener's granulomatosis and intracranial fibromatosis. HTLV-1 infection and chronic dialysis have also been reported to cause granulomatous thickening of the pachymeninges. Intense enhancement of the normal dura mater following gadolinium injection has been seen in cases of intracranial hypotension and the marked dural enhancement resolves with treatment of the intracranial hypotension. Pachymeningeal thickening has been reported with orbital pseudotumour and in a case of multifocal fibrosclerosis. Idiopathic hypertrophic pachymeningitis is thus a diagnosis of exclusion. The most common symptoms are headache and cranial nerve palsies. Cerebellar ataxia has been reported in some patients.
The treatment of hypertrophic cranial pachymeningitis is not well defined, owing to the rarity of the disease and uncertainty regarding its aetiology. At present, high-dose corticosteroid therapy is the treatment of choice, followed by immunosuppressive agents, such as azathioprine and cyclophosphamide, if necessary.
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