Idiopathic hypertrophic pachymeningitis presenting with occipital neuralgia

Background: Although occipital neuralgia is usually caused by degenerative arthropathy, nearly 20 other aetiologies may lead to this condition. Methods: We present the first case report of hypertrophic pachymeningitis revealed by isolated occipital neuralgia. Results and conclusions: Idiopathic hypertrophic pachymeningitis is a plausible cause of occipital neuralgia and may present without cranial-nerve palsy. There is no consensus on the treatment for idiopathic hypertrophic pachymeningitis, but the usual approach is to start corticotherapy and then to add immunosuppressants. When occipital neuralgia is not clinically isolated or when a first-line treatment fails, another disease diagnosis should be considered. However, the cost effectiveness of extended investigations needs to be considered.


Case report
A 56-year-old man was admitted with moderate-intensity pain that originated at the base of the skull and radiated to the left side of the occipital scalp.Left occipital neuralgia was diagnosed.A few weeks later, the patient was admitted again, this time for an intense headache that required opioid painkillers.Magnetic-resonance imaging (MRI) and computed tomography (CT) scans showed thickening of the dura mater, ranging from the cerebellar tentorium (see arrow, Figure 1) to the meninges of the second cervical vertebra (see arrow, Figure 2).Cerebrospinal-fluid analysis (CSF) showed hyperproteinorachia (0.86 g/L) with normal glycorrhachia, 64 leukocytes/mm 3 with 93% activated non-clonal lymphocytes, mostly CD4+.A PCR assay to detect Mycobacterium tuberculosis DNA was negative.An examination and culture of the CSF was negative which allowed eliminating bacterial causes, especially tuberculosis.There were no abnormal cells in the CSF.Serological testing for HIV 1 and 2 was negative.A body CT scan revealed no carcinoma or other disease except for the cerebral anomaly (described above).We did not find any evidence of lymphomatous or systemic disorders (granulomatosis with polyangiitis, Sjögren's syndrome, rheumatoid arthritis, mixed connective-tissue disease).Therefore, a meningeal biopsy was performed and revealed lymphoplasmocytic infiltration with no abnormal cells.Accordingly, we diagnosed idiopathic hypertrophic cranial pachymeningitis (IHP).

African
During our investigations, a nerve block was performed to reduce the pain, and was repeated, but the results were insufficient.Slight asymmetry in the muscles of the neck suggested damage to the 12 th left cranial nerve.
After this diagnosis, we initiated corticosteroid therapy.However, the patient was still cortico-dependent (at 15 mg/day) at 2 years after starting therapy.Consequently, we decided to introduce cyclophosphamide therapy.The patient received six pulses of cyclophosphamide at 0.7 g/m2 per month.A MRI scan then showed significant improvement, in particular next to the median parietal cortex.
Cyclophosphamide therapy was followed by a maintenance treatment.Our patient remains clinically stable under methotrexate therapy (17.5 mg/week and prednisone 5mg/day).The patient no longer needs pain killers.

Discussion
Although occipital neuralgia is relatively common and is predominantly caused by osteoarthritis, the literature provides no formal evidence on its prevalence and incidence, probably because of its frequent ambulatory management 1 4 reported similar proportions when they reviewed treatment of IHP cases published between 1990 and 2008.They identified 60 patients: 93% were given a corticotherapy, of which 65% were monotherapies: this led to 46% relapse rate.Some patients required radiotherapy or surgery when their condition became too serious (e.g., hydrocephalus).
Herein, we have described, for the first time to our knowledge, a case of idiopathic pachymeningitis revealed by isolated occipital neuralgia.We found one similar case reported in the literature, but occipital neuralgia was not isolated as the patient also presented with tinnitus and deafness at admission.Corticosteroids did not improve the clinical situation and, similar to our patient, a sparing treatment had to be introduced 5 .

Conclusion
IHP is a possible cause of occipital neuralgia and may present without cranial-nerve palsy at the beginning.
There is no consensus on IHP treatment, but the most common approach is to initiate corticotherapy and African Health Sciences Vol 15 Issue 1, March 2015 African Health Sciences Vol 15 Issue 1, March 2015 304 then to add immunosuppressants.We suggest that additional exploration of occipital neuralgia is warranted when conventional treatments fail.However, the cost-effectiveness of extended investigations needs to be considered.

Figure 1 :
Figure 1: MRI T1 axial image showing thickening of the left cerebellar tentorium.

Figure 2 :
Figure 2: CT-scan axial image showing thickening of the meninges between the C1-C2 vertebrae.
2 Its diagnosis is based on cri-teria from the current International Classification of Headache Disorder-2 (ICHD-2)2.The principal causes of occipital neuralgia are summarized in Table1.A clinical examination, a complete blood count, sedimentation rate, C-reactive protein, viral and bacteriological tests and/or serologies, in addition to imagery from a CT-scan or MRI, are required to exclude most secondary causes.
of cases.Immunosuppressants were added when there was a suboptimal response to corticosteroids: this led to remission in 21.4% of these cases.Bosman et al.