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Idiopathic cranial hypertrophic pachymeningitis (ICHP) consists of meningeal thickening due to chronic inflammation for which no cause such as infection, specific granulomatous disease, or malignancy is demonstrable.1-3 Although aspecific headache may be one of the first symptoms, it is almost always accompanied by other manifestations such as cranial nerve palsies, epileptic seizures, and gait disturbances.1 2 4 The following case illustrates that aspecific headache may remain the only symptom of ICHP for a long time.
A 37 year old man presented in 1984 with persisting bifrontal headache for one year. He had a history of chronic otitis media and right mastoidectomy in 1977, after which he remained symptom free. Neurological examination in 1984 was normal, as were brain CT, chest radiography, and laboratory studies including erythrocyte sedimentation rate (ESR), complete blood count, and blood chemistry. At lumbar puncture a normal CSF opening pressure was found. Analysis of CSF showed a mononuclear pleocytosis of 168 cells/mm3, mainly lymphocytes, a protein concentration of 65 mg/dl (normal <50), and an IgG index of 1.9 (normal<0.66). The CSF glucose content was 3.2 mmol/l. Search for systemic and primary intracranial infections, systemic disease such as sarcoidosis or vasculitis, and malignancy was negative. Repeated CSF analyses after one and three weeks, six months, and two and three years showed the same polymorphic lymphocytic pleocytosis. As a specific cause remained undetectable, idiopathic chronic lymphocytic meningitis was assumed. Chronic headache with fluctuating intensity persisted.
In 1986 a second brain CT was normal, as was brain MRI performed without gadolinium enhancement. From 1984 until 1996 mild to moderate headache with recurrent exacerbations persisted without additional symptoms or signs. In April 1996 he was admitted for a first complex partial epileptic seizure, followed by three tonic-clonic seizures within a few hours. No seizures recurred after treatment with antiepileptic drugs. Clinical examination was normal. Contrast enhanced axial brain CT images showed a left frontobasal enhancing lesion and two small enhancing lesions in the prepontine cistern, possibly attached to the left and right tentorial margin. There was no evidence of local bony destruction or hyperostosis. T2 weighted brain MRI showed a left subfrontal extra-axial hypointense mass surrounded by a hyperintense signal consistent with oedema. Gadolinium enhanced T1 weighted axial and sagittal (figure) images showed an enhancing extra-axial, subfrontal mass possibly extending to the frontal lobe. The meningeal lesion extended posteriorly into the left prepontine cistern, wherein two small granulomatous-like lesions were seen.
Full blood count, ESR, and blood chemistry were normal. There was no evidence of Wegener’s granulomatosis including absence of circulating antineutrophilic cytoplasmatic antibodies. Chest radiography, opthalmological examination, and the serum angiotensin converting enzyme (ACE) concentration were normal. Tests for autoantibodies were negative as were serological tests for syphilis and borreliosis. CSF analysis showed 42/mm3 cells, mainly lymphocytes; the protein concentration was 62 mg/dl, the IgG index was 0.64, and the CSF glucose content was 3.5 mmol/l. Bacterial (including mycobacteria) and fungal cultures of the CSF remained negative. No malignant cells were found in the CSF.
A biopsy of the left frontobasal meninges showed pronounced thickening of the dura mater; microscopy showed chronic non-specific inflammation, mainly consisting of lymphocytes and plasma cells. Multinucleated giant cells, histiocytes, granulomas, and focal necrosis were not seen. Cytological examination showed no malignant cells. Special stains for acid fast bacilli and fungi were negative. As no specific cause was detectable, a diagnosis of ICHP was made. Treatment with steroids was refused by the patient. So far, the further course after the meningeal biopsy (July 1996) has been uneventful.
Although a long diagnostic delay has been reported in patients with ICHP,2 we found no article in which prolonged aspecific headache remained the only symptom over many years (13 years in our patient). In 1984, negative clinical and additional examinations including a brain CT were followed by CSF analysis to exclude an intracranial infectious or inflammatory process, because drug resistent and persisting headache had started at the age of 37. As repeated CSF analyses between 1984 and 1996 showed the same aspecific lymphocytic pleocytosis, we hypothesise that idiopathic chronic meningitis, diagnosed in 1984, was the first manifestation of a very slowly progressing focal inflammatory meningeal process eventually resulting in ICHP and epileptic seizures 12 years later.
Reports on the association of chronic idiopathic meningitis and ICHP are very rare.5 The list of possible causes of chronic idiopathic meningitis is long but in most cases (80%) there is no detectable aetiology. Although several reports have shown the association of otitis media and ICHP, we have no evidence of a relation between this chronic otitis media in 1978 and ICHP, as during six years after the mastoidectomy our patient was symptom free. The brain MRI of 1986 without contrast was normal but we cannot exclude the possibility that if gadolinium had been administered, focal meningeal inflammation would have been diagnosed 10 years earlier by showing meningeal enhancement on T1 weighted contrast enhanced images. As ICHP may improve after treatment with steroids,4 our patient illustrates that a gadolinium enhanced brain MRI should be considered when unexplained chronic headache is associated with aspecific CSF polymorphic lymphocytosis, even in the absence of clinical signs.
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