Idiopathic Hypertrophic Patchymeningitis

A 40 yo female with moderate continuous headache not responding to anelgesics. Neurological examination normal. Advised CT study of Brain. 

Findings:

Plain CT study of Brain shows hyper density along inter hemispheric fissure and tentorium.

MRI study of brain Axial Post contrast SPGR T1 w images show dural thickening along inter hemispheric fissure and tenotorium. No significant signal abnormality in rest of the brain parenchyma. MR Venogram of Brain normal. 

Imaging wise : Idiopathic Hypertrophic Patchymeningitis. 

Csf examination normal.

Pt is responding to steroids.

Similar Cases: 
Case 1
Case 2


HYPERTROPHIC PACHYMENINGITIS

Syn : Dural pseudotumor, Idiopathic cranial hypertrophic pachymeningitis (ICHP) is diffuse dural thickening without known etiology like neoplasm or infection.

Imaging wise best diagnostic clue is thickened enhancing meninges "turn the corner" under temporal lobes in continuous line from vertex on coronal sections.
CT often normal. May show hyper density along inter hemispheric dura and tentorial leaflets. Brain parenchyma show normal attenuation pattern.
MRI is the investigation of choice, shows dural thickening often bilateral follows inner calvarium, extends along falx, tentorium may extend into lACs, along spinal cord with enhancement on post contrast T1w.
Dural thickening has to be more than 2 mm, may be more than 1 cm.
Usually smooth, linear, diffusely thickened dura. Less commonly nodular, focal soft tissue mass like lesions.
Signals on MRI are often iso to hyper intense on T2w images. In cases of densely fibrosing pseudotumor may appear profoundly hypointense.
Invasive variety may show encroachment of dural venous sinus with abnormal MR Venogram, dural venous sinuses showing poor flow related signals.

Diffusely thickened dura is nonspecific finding and can be seen in a spectrum of following identifiable disorders:
- Congenital (mucopolysaccharidoses)
- Iatrogenic (surgery, shunti post-LP meningeal enhancement rare & should be diagnosis of exclusion)
- Trauma (chronic SDH)
- Spontaneous intracranial hypotension
- Infection (TB, HTLV- 1, indolent infections such as pseudomonas, syphilis, rhinoscleroma, fungal.
- Inflammatory (rheumatoid, sarcoid, Wegener, pseudotumor)
- Neoplasm (meningiomatosis, lymphoma, mets)
- Hematologic (monoclonal plasma cell hyperplasia, extramedullary hematopoiesis)
- Other causes fibrosing inflammatory pseudotumors, fibrosclerosis)
- Idiopathic.

Histopathological findings of ICHP
Meningeal fibrosis.
+/- Inflammatory cells (lymphocytes, plasma cells)
May have multinucleated giant cells
No bacteria, fungi, neoplastic cells.

DDs
Normal dural enhancement
- Thin less than 2 mm,
- Discontinuous, most prominent at convexity, less intense than cavernous sinus.
Chronic subdural hematoma
- May contain loculated foci of old hemorrhage
- May show calcification.
Neoplasm
- Lesion in adjacent bony calvarium common in metastasis
- Lymphoma often associated with systemic disease.
Infection/inflammation
- Sarcoid often has other lesions, diffuse non focal dural thickening is less common than focal dura based masses
- TB is meningitis lepto meningeal pattern of involvement is more common than patchy meningeal involvement.
- Sinus disease seen in Wegener, Rheumatoid arthritis, SLE, Sjogren
Intracranial hypotension
- Associated finding are sagging midbrain on sagittal sections with tonsillar herniation.
- Dural venous engorgement.
Dural sinus occlusion
- Engorgement of collateral venous channels may thicken dura

Clinical Presentation: 
Any age; peak 3rd-5th decades.
Most common complaint is Headache.
Cranial neuropathy: Progressive sensorineural hearing loss, hoarseness, optic neuropathy, Tolosa-Hunt syndrome.
Uncommonly seizures.

Prognosis and Treatment: 
Variable course.
Some are benign, require no treatment.
Specific diagnosis may require biopsy.
Corticosteroid therapy. Recurrence may occur with steroid tapering
Immunosuppressants (e.g., methotrexate, azathioprine)

Reference : Diagnostic imaging Osborn.