====== Hypertrophic pachymeningitis ======

Hypertrophic [[pachymeningitis]] is a chronic [[Inflammation disease]], manifesting as a fibrous thickening of the [[dura mater]]. 

Hypertrophic pachymeningitis is a rare disorder of diverse etiology. It was first described by Charcot and later by Naffziger and Stern
((Mamelak AN, Kelly WM, Davis RL, Rosenblum ML. Idiopathic hypertrophic cranial 
pachymeningitis. Report of three cases. J Neurosurg. 1993 Aug;79(2):270-6.
Review. PubMed PMID: 8331412.
))

It can involve the cranial or the spinal dura or both.

===== Classification =====
The condition can be broadly divided into two forms:

Primary or [[Idiopathic hypertrophic pachymeningitis]] where no identifiable cause is found

Secondary where identifiable causes co-exist, although their definite relationship to the development of this condition may be debatable.

[[IgG4-related hypertrophic pachymeningitis]]
----
see [[Idiopathic hypertrophic cranial pachymeningitis]].

===== Etiology =====

see [[IgG4-related hypertrophic pachymeningitis]]
----
Early reports were in relationship to tuberculosis or syphilis. Exact etiopathogenesis of this entity is still unknown, but it is speculated to be an autoimmune phenomenon or occur as a direct result of infectious or infiltrative pathology
((Goyal M, Malik A, Mishra NK, Gaikwad SB. Idiopathic hypertrophic
pachymeningitis: spectrum of the disease. Neuroradiology. 1997 Sep;39(9):619-23. 
PubMed PMID: 9335058.
)).

===== Diagnosis =====

HP can appear as a vanishing tumor, and pathological evaluation is essential for a precise diagnosis. If spontaneous disappearance of tumefactive intracranial lesions is encountered, the possibility of HP should be considered
((Hoshino R, Furuta M, Shibata M, Wakamatsu I, Nagashima K, Yamaguchi R, Ikeda Y. Vanishing tumefactive ANCA-associated hypertrophic pachymeningitis: A case report. Clin Neurol Neurosurg. 2021 Nov 25;212:107070. doi: 10.1016/j.clineuro.2021.107070. Epub ahead of print. PMID: 34894573.)).
===== Treatment =====
A 68-year-old man presented at a nearby hospital with a [[headache]] and a low-grade [[fever]]. A blood test revealed [[inflammation]], as well as elevation of [[IgG4]] level. [[Magnetic resonance imaging]](MRI)revealed diffuse thickening of the [[dura mater]], dominantly in the [[posterior fossa]] and cerebellar [[tentorium]]. The lesion was enhanced significantly with [[gadolinium]](Gd). An open [[biopsy]] was performed to determine pathological diagnosis. [[Hematoxylin]] and [[eosin]] staining showed infiltration of inflammatory cells, including [[plasma]] cells. The infiltrating cells were positive for the IgG4. Post-operatively, the patient was treated with [[glucocorticoid]], and both the inflammation and patient symptoms were improved. In conclusion, IgG4 is related to the etiology of hypertrophic pachymeningitis and glucocorticoid therapy is effective for this disease
((Hayashi K, Somagawa C, Hayashi Y, Iwanaga M. [A Case of IgG4-related
Hypertrophic Pachymeningitis]. No Shinkei Geka. 2018 Dec;46(12):1103-1109. doi:
10.11477/mf.1436203876. Japanese. PubMed PMID: 30572308.
)).

===== Case reports =====
A 59-year-old man with [[hypertrophic pachymeningitis]] (HP), initially presenting as a tumefactive [[lesion]] that disappeared spontaneously. He developed [[headache]] and left [[abducens nerve palsy]] 2 years before [[admission]], and [[brain magnetic resonance imaging]] (MRI) revealed a round mass lesion. [[Meningioma]] was initially considered, but the lesion disappeared spontaneously along with the symptoms. However, 6 months before admission, left abducens nerve palsy reappeared. Repeated MRI revealed multiple intracranial tumefactive lesions. HP was diagnosed based on the pathological analysis of the biopsied specimen. HP can appear as a vanishing tumor, and pathological evaluation is essential for a precise diagnosis. If spontaneous disappearance of tumefactive intracranial lesions is encountered, the possibility of HP should be considered
((Hoshino R, Furuta M, Shibata M, Wakamatsu I, Nagashima K, Yamaguchi R, Ikeda Y. Vanishing tumefactive ANCA-associated hypertrophic pachymeningitis: A case report. Clin Neurol Neurosurg. 2021 Nov 25;212:107070. doi: 10.1016/j.clineuro.2021.107070. Epub ahead of print. PMID: 34894573.)).